Human Exploration of Mars The Reference Mission of the NASA Mars

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					                        NASA Special Publication 6107




 Human Exploration of Mars:
The Reference Mission of the
     NASA Mars Exploration
               Study Team




                    Stephen J. Hoffman, Editor
                        David I. Kaplan, Editor



               Lyndon B. Johnson Space Center
                               Houston, Texas

                                        July 1997
NASA Special Publication 6107




Human Exploration of Mars:
The Reference Mission of the NASA Mars Exploration Study Team



Stephen J. Hoffman, Editor
Science Applications International Corporation
Houston, Texas




David I. Kaplan, Editor
Lyndon B. Johnson Space Center
Houston, Texas




July 1997
This publication is available from the NASA Center for AeroSpace Information, 800 Elkridge Landing Road, Linthicum Heights,
                                              MD 21090-2934 (301) 621-0390.
Foreword
       Mars has long beckoned to humankind               interest in this fellow traveler of the solar
from its travels high in the night sky. The              system, adding impetus for exploration.
ancients assumed this rust-red wanderer was
                                                                 Over the past several years studies
the god of war and christened it with the
                                                         have been conducted on various approaches
name we still use today.
                                                         to exploring Earth’s sister planet Mars. Much
       Early explorers armed with newly                  has been learned, and each study brings us
invented telescopes discovered that this                 closer to realizing the goal of sending humans
planet exhibited seasonal changes in color,              to conduct science on the Red Planet and
was subjected to dust storms that encircled              explore its mysteries. The approach described
the globe, and may have even had channels                in this publication represents a culmination of
that crisscrossed its surface.                           these efforts but should not be considered the
                                                         final solution. It is our intent that this
       Recent explorers, using robotic
                                                         document serve as a reference from which we
surrogates to extend their reach, have
                                                         can continuously compare and contrast other
discovered that Mars is even more complex
                                                         new innovative approaches to achieve our
and fascinating—a planet peppered with
                                                         long-term goal. A key element of future
craters, cut by canyons deep enough to
                                                         improvements to this document will be the
swallow the Earth’s Grand Canyon, and
                                                         incorporation of an integrated robotic/human
shouldering the largest known volcano in the
                                                         exploration strategy currently under
solar system. They found intriguing evidence
                                                         development.
that water played an important role on Mars
with channels that bear a striking                              We will continue to develop alternative
resemblance to stream beds and clouds of                 approaches, technologies, precursor missions,
crystalline ice that still traverse its red sky.         and flight demonstrations that collectively
But they also found that Mars was cold and               move us forward. Inputs have been, and will
dry, and believed to be devoid of life.                  always be, encouraged from all sources—
                                                         NASA centers, industry, research
       Now present day explorers have
                                                         organizations, entrepreneurs, government
announced that pieces of Mars have arrived
                                                         agencies, international partners, and the
on Earth as meteorites, and that these bits of
                                                         public at large—which will improve our
the red planet contain evidence pointing to
                                                         understanding and current planning. We
the possible existence of life early in Mars
                                                         plan to use the results of these assessments to
history. This has resulted in renewed public
                                                         shape our investments in technology, and to




                                                   III
look for high leverage, innovative, break-           must search for alternatives to substantially
through approaches to the most cost effective        reduce the cost of exploration, while
exploration. These data will also help us            increasing the inherent value to humankind.
understand the required infrastructure, as           This Reference Mission provides a viable
well as provide important insights into how          starting point for NASA’s continuing efforts
we can use the International Space Station to        to develop the technologies and systems, as
validate key assumptions and technologies.           well as the international partnerships, needed
                                                     for the grand adventure of sending humans to
      To achieve our goal, we must
                                                     explore another planet in our solar system—
fundamentally change the way in which we
                                                     one that may have once, and may yet again,
explore with both humans and robots. We
                                                     harbor life.




                                                IV
Acknowledgments
        Sending people to Mars has been a            will be added to and improved upon by
long-held dream of humankind, and many               others in the future. This report has benefited
have approached the task of turning the              from the contributions and advice of many
dream into reality. This document is another         individuals from the government and private
chapter in the ongoing process of melding            sectors. The individuals listed on the
new and existing technologies, practical             following page assisted in preparing the
operations, fiscal reality, and common sense         concepts described in this report and in
into a feasible and viable human mission to          compiling the words, images, and data used
Mars. However, this is not the last chapter in       for that description.
the process, but marks a snapshot in time that




                                                                    Stephen J. Hoffman

                                                                    David I. Kaplan




                                                 V
Contributing Authors                  Los Alamos National Laboratory:
                                          Dr. Paul Keaton
Ames Research Center:
  Roger Arno                          Marshall Space Flight Center:
  Dr. Geoff Briggs                       William Huber
  Dr. Yvonne Clearwater
                                      General Contributors
  Dr. Marc Cohen
  Andy Gonzales                       Ames Research Center:
                                        Betsy Dunsky
Johnson Space Center:
                                        Paul Espinosa
    Dr. Michael Duke
                                        Vladimir Garin
    David Kaplan
                                        Lynn Harper
    Catherine Larson
                                        Butler Hine
    David Weaver
                                        Larry Lemke
    Laurie Weaver
                                        Doug O’Handley
Lewis Research Center:                  Nelson Schlater
   Robert Cataldo                       Michael Sims
   Dr. Stanley Borowski
                                      Boeing:
SAIC:                                     Brent Sherwood
   Dr. Stephen Hoffman
                                      Lewis Research Center:
   Paul Phillips
                                         Dr. Stanley Borowski
Study Team Members
                                      Rockwell International:
Ames Research Center:                    Robert Raasch
  Dr. Geoff Briggs (co-lead)             Lisa Rockoff
Johnson Space Center:                 Reviewers and Commenters
    Jeri Brown
                                      Johnson Space Center:
    Nancy Ann Budden
                                          Nancy Ann Budden
    Beth Caplan
                                          John Connolly
    John Connolly
    Dr. Michael Duke (co-lead)        Other Support and Contributions
    Dallas Evans
    Dr. Steve Hawley                  Ames Research Center:
    Kent Joosten                        Dr. Chris McKay
    David Kaplan                        Jeff Moore
    Darrell Kendrick                    Dr. Carol Stoker
    Barbara Pearson                     Anthony Gross
    Barney Roberts                    Editorial and Graphics Support
    Ed Svrcek
    David Weaver                      J. Frassanito and Associates:
                                           J. Frassanito
Lewis Research Center:
   Dr. Stanley Borowski               SAIC:
   Robert Cataldo                        R. Patrick Rawlings




                                 VI
       There is a set of supplemental technical reports which
provide greater depth into many of the design features of the
Mars Reference Mission than is given in section 3 of this
document. Had those papers been included as appendices, the
size of this document would have greatly expanded.
Consequently, we decided to make those supplemental
materials available through the world wide web. We intend to
post new materials as to the web as they are produced and hope
to maintain a site with the latest information which describes
key technologies and design features of a human mission to
Mars.

      The site for the Mars Reference Mission is

         http://www_sn.jsc.nasa.gov/marsref/contents.html




                              VII
VIII
Contents
Section                                                                                                                                                      Page

      Acronyms .................................................................................................................................................... xv

1.    OVERVIEW AND EXECUTIVE SUMMARY ..................................................................................... 1-1
1.1   INTRODUCTION ..................................................................................................................................... 1-3
1.2   BACKGROUND ........................................................................................................................................ 1-5
1.3   REFERENCE MISSION EXECUTIVE SUMMARY .............................................................................. 1-6
      1.3.1 Objectives ...................................................................................................................................... 1-6
      1.3.2 Groundrules and Assumptions .................................................................................................. 1-7
      1.3.3 Mission and Systems ................................................................................................................... 1-8
            1.3.3.1 Mission Design ............................................................................................................. 1-8
            1.3.3.2 In Situ Resource Production ..................................................................................... 1-16
            1.3.3.3 Flight Crew ................................................................................................................. 1-16
            1.3.3.4 Robotic Precursors ..................................................................................................... 1-17
            1.3.3.5 Launch Systems .......................................................................................................... 1-18
            1.3.3.6 Interplanetary Transportation Systems .................................................................. 1-18
            1.3.3.7 Surface Systems .......................................................................................................... 1-22
            1.3.3.8 Operations ................................................................................................................... 1-24
            1.3.3.9 Mission and Systems Summary ............................................................................... 1-27
1.4   TESTING PRINCIPAL ASSUMPTIONS AND CHOICES ................................................................ 1-28
            1.4.1    Robust Surface Infrastructure .................................................................................. 1-28
            1.4.2    Split Mission Strategy ................................................................................................ 1-28
            1.4.3    Nuclear Thermal Propulsion .................................................................................... 1-30
            1.4.4    In Situ Resource Utilization ...................................................................................... 1-30
            1.4.5    Common Habitat Design .......................................................................................... 1-31
            1.4.6    Nuclear Surface Power .............................................................................................. 1-31
            1.4.7    Abort to the Surface ................................................................................................... 1-32
            1.4.8    Design for the Most Difficult Opportunity ............................................................ 1-33
1.5   CONCLUSIONS AND RECOMMENDATIONS ............................................................................... 1-33
            1.5.1    Mission and Systems ................................................................................................. 1-33
            1.5.2    Technology Development ......................................................................................... 1-34
            1.5.3    Environmental Protection ......................................................................................... 1-37
            1.5.4    Program Cost .............................................................................................................. 1-38
            1.5.5    International Participation ........................................................................................ 1-39
            1.5.6    Program Management and Organization ............................................................... 1-41
1.6   REFERENCES .......................................................................................................................................... 1-44




                                                                                 IX
Section                                                                                                                                                  Page
2.    SCIENCE AND EXPLORATION RATIONALE ................................................................................ 2-1
2.1   INTRODUCTION ..................................................................................................................................... 2-3
2.2   THE “WHY MARS” WORKSHOP ......................................................................................................... 2-3
2.3   SCIENCE RATIONALE ........................................................................................................................... 2-6
2.4   EXPLORATION RATIONALE .............................................................................................................. 2-13
      2.4.1 Inhabiting Another Planet ......................................................................................................... 2-13
      2.4.2 International Cooperation ......................................................................................................... 2-15
      2.4.3 Technological Advancement ..................................................................................................... 2-16
      2.4.4 Inspiration ................................................................................................................................... 2-18
      2.4.5 Investment ................................................................................................................................... 2-19
2.5   WHY NOT MARS? ................................................................................................................................. 2-19
      2.5.1 Human Performance .................................................................................................................. 2-19
      2.5.2 System Reliability and Lifetime ............................................................................................... 2-21
      2.5.3 Political Viability and Social Concerns ................................................................................... 2-22
2.6   SUMMARY .............................................................................................................................................. 2-23
2.7   REFERENCES .......................................................................................................................................... 2-23
3.    MISSION AND SYSTEM OVERVIEW ............................................................................................... 3-1
3.1   INTRODUCTION ..................................................................................................................................... 3-3
      3.1.1 Mission Objectives ....................................................................................................................... 3-3
      3.1.2 Surface Mission Implementation Requirements ...................................................................... 3-4
            3.1.2.1 Conduct Human Missions to Mars ........................................................................... 3-4
            3.1.2.2 Conduct Applied Science Research ........................................................................... 3-5
            3.1.2.3 Conduct Basic Science Research ................................................................................ 3-6
            3.1.2.4 Surface Operations Philosophy .................................................................................. 3-7
      3.1.3 Groundrules and Assumptions ................................................................................................. 3-11
3.2   RISKS AND RISK MITIGATION STRATEGY .................................................................................... 3-12
      3.2.1 Risks to Human Life .................................................................................................................. 3-13
      3.2.2 Risks to Mission Success ........................................................................................................... 3-14
      3.2.3 Risks to Program Success .......................................................................................................... 3-14
      3.2.4 Risk Mitigation Strategy ............................................................................................................ 3-14
3.3   FLIGHT CREW ....................................................................................................................................... 3-16
      3.3.1 Crew Composition ..................................................................................................................... 3-16
      3.3.2 Crew Systems Requirements .................................................................................................... 3-20
3.4   MISSION OPERATIONS ....................................................................................................................... 3-21
      3.4.1 Training Guidelines .................................................................................................................... 3-22
      3.4.2 Science and Exploration ............................................................................................................ 3-24
      3.4.3 System Operations and Maintenance ...................................................................................... 3-24
      3.4.4 Programmatic Activities ............................................................................................................ 3-25
      3.4.5 Activity Planning ....................................................................................................................... 3-26
            3.4.5.1 Pre-Launch Phase ....................................................................................................... 3-27
            3.4.5.2 Earth Launch Phase ................................................................................................... 3-28
            3.4.5.3 Trans-Mars Phase ....................................................................................................... 3-29
            3.4.5.4 Mars Landing Phase .................................................................................................. 3-30
            3.4.5.5 Mars Surface Phase .................................................................................................... 3-31
            3.4.5.6 Mars Launch Phase .................................................................................................... 3-33
            3.4.5.7 Trans Earth Phase ....................................................................................................... 3-34
            3.4.5.8 Earth Entry and Landing .......................................................................................... 3-35
            3.4.5.9 Post Landing ............................................................................................................... 3-35




                                                                               X
Section                                                                                                                                                     Page

3.5   MISSION DESIGN .................................................................................................................................. 3-36
      3.5.1 Trajectory Options ...................................................................................................................... 3-36
      3.5.2 Trajectory Selection Factors ...................................................................................................... 3-37
            3.5.2.1 Satisfying Reference Mission Goals and Objectives ............................................. 3-38
            3.5.2.2 Satisfying Reference Mission Risk Strategy ........................................................... 3-38
            3.5.2.3 Satisfying Reference Mission Program Flexibility ................................................ 3-41
      3.5.3 Mission Design Strategy ............................................................................................................ 3-42
            3.5.3.1 Trajectory Type ........................................................................................................... 3-42
            3.5.3.2 Split Mission Strategy ................................................................................................ 3-42
            3.5.3.3 Aerocapture ................................................................................................................ 3-43
            3.5.3.4 Surface Rendezvous ................................................................................................... 3-43
            3.5.3.5 Use of Indigenous Resources ................................................................................... 3-44
            3.5.3.6 Mars Orbit Rendezvous and Direct Entry at Earth ............................................... 3-44
      3.5.4 Mission Sequence ....................................................................................................................... 3-44
            3.5.4.1 First Mission: 2007 Opportunity .............................................................................. 3-45
            3.5.4.2 Second Mission: First Flight Crew, 2009 Opportunity .......................................... 3-46
            3.5.4.3 Third Mission: Second Flight Crew, 2011 Opportunity ........................................ 3-54
            3.5.4.4 Fourth Mission: Third Flight Crew, 2014 Opportunity ........................................ 3-55
            3.5.4.5 Mission Summary ...................................................................................................... 3-59
3.6   SYSTEMS .................................................................................................................................................. 3-60
      3.6.1 Operational Design Considerations ........................................................................................ 3-61
      3.6.2 Launch Vehicles .......................................................................................................................... 3-62
      3.6.3 Interplanetary Transportation .................................................................................................. 3-72
            3.6.3.1 Trans-Mars Injection Stage ........................................................................................ 3-72
            3.6.3.2 Biconic Aeroshell ........................................................................................................ 3-73
            3.6.3.3 Transit/Surface Habitat ............................................................................................ 3-77
            3.6.3.4 Mars Surface Lander .................................................................................................. 3-79
            3.6.3.5 Mars Ascent Vehicle ................................................................................................... 3-82
            3.6.3.6 Earth-Return Vehicle .................................................................................................. 3-86
            3.6.3.7 Interplanetary Transportation Power Systems ...................................................... 3-90
      3.6.4 Surface Systems .......................................................................................................................... 3-95
            3.6.4.1 Surface Habitat/Laboratory ..................................................................................... 3-95
            3.6.4.2 Life Support System .................................................................................................. 3-97
            3.6.4.3 In-Situ Resource Utilization .................................................................................... 3-101
            3.6.4.4 Surface Mobility ....................................................................................................... 3-105
            3.6.4.5 Extra Vehicular Activity Systems ............................................................................ 3-110
            3.6.4.6 Surface Power Systems ............................................................................................ 3-111
3.7   PRECURSORS ..................................................................................................................................... 3-116
      3.7.1 Current Robotic Program Plans .............................................................................................. 3-116
      3.7.2 Mars Sample Return With ISRU ............................................................................................. 3-116
      3.7.3 Human Exploration Precursor Needs .................................................................................... 3-117
      3.7.4 Autonomous Deployment of Surface and Orbital Elements .............................................. 3-117
3.8   GROUND SUPPORT AND FACILITIES OPERATIONS ................................................................. 3-118
      3.8.1 Systems Operations .................................................................................................................. 3-120
      3.8.2 Science Operations ................................................................................................................... 3-121




                                                                                 XI
Section                                                                                                                                                    Page

3.9  PROGRAMMATIC ISSUES .................................................................................................................                 3-122
     3.9.1 Cost Analysis ............................................................................................................................      3-122
           3.9.1.1 Organizational Culture and Cost ...........................................................................                             3-123
           3.9.1.2 The Cost Model ........................................................................................................                 3-124
     3.9.2 Management and Organizational Structure .........................................................................                               3-132
     3.9.3 Technology Development .......................................................................................................                  3-136
3.10 REFERENCES ........................................................................................................................................   3-144


                                                                           TABLES

Table                                                                                                                                                      Page

1-1               Pricipal Discriminators of Short- and Long-Stay Mission Scenarios .................................... 1-29
1-2               Key Elements of Lower-Cost Programs .................................................................................... 1-42

2-1               Mars Exploration Consultant Team ............................................................................................. 2-4
2-2               Mars Study Team ........................................................................................................................... 2-5

3-1               Capabilities and Demonstrations for Surface Mission Activities ........................................... 3-5
3-2               Surface Mission Skills .................................................................................................................. 3-18
3-3               General Launch Manifest: 2007 Launch Opportunity ............................................................ 3-47
3-4               General Launch Manifest: 2009 Launch Opportunity ............................................................ 3-49
3-5               Surface Science Payload for First Flight Crew ......................................................................... 3-52
3-6               General Launch Manifest: 2011 Launch Opportunity ............................................................ 3-55
3-7               Surface Science Payload for Second Flight Crew .................................................................... 3-57
3-8               General Launch Manifest: 2014 Launch Opportunity ............................................................ 3-59
3-9               Surface Science Payload for Third Flight Crew ....................................................................... 3-60
3-10              Launch Vehicle Concepts for the Mars Reference Mission .................................................... 3-63
3-11              Mass Estimates for TMI Stage Alternatives ............................................................................. 3-75
3-12              Mass and Size Estimates for Biconic Aeroshell Family .......................................................... 3-77
3-13              Mars Transit/Surface Habitation Element ............................................................................... 3-82
3-14              Earth Return Habitation Element Mass Breakdown .............................................................. 3-92
3-15              Estimated Power Profile for Outbound and Return Transits ................................................ 3-93
3-16              30kWe Power System With Fuel Cells and Solar Arrays ........................................................ 3-96
3-17              5kWe Power System With Fuel Cells and Solar Arrays .......................................................... 3-96
3-18              Mars Surface Laboratory/Habitat Element Mass Breakdown .............................................. 3-98
3-19              LSS Mass, Volume, Power Comparison .................................................................................. 3-100
3-20              Mass and Power Estimates for the First ISRU Plant ............................................................. 3-105
3-21              Mass and Power Estimates for the Second ISRU Plant ........................................................ 3-106
3-22              Characteristics for Fixed Surface Power System Options ..................................................... 3-113
3-23              Rover Power System Characteristics ........................................................................................ 3-115
3-24              Program Environment Effects on Program Management Style .......................................... 3-126
3-25              A Comparison of Development Culture Parameters for Commercial
                  Aircraft and NASA Manned Programs ................................................................................... 3-127
3-26              Key Elements of Lower-Cost Programs .................................................................................. 3-134
3-27              Dual Use Technologies: Propulsion ......................................................................................... 3-139
3-28              Dual Use Technologies: Communications/Information Systems ....................................... 3-139




                                                                                XII
Table                                                                                                                                          Page

3-29     Dual Use Technologies: In Situ Resource Utilization ............................................................                     3-140
3-30     Dual Use Technologies: Surface Mobility - Suits ...................................................................                  3-141
3-31     Dual Use Technologies: Surface Mobility - Vehicles .............................................................                     3-141
3-32     Dual Use Technologies: Human Support ...............................................................................                 3-142
3-33     Dual Use Technologies: Power .................................................................................................       3-142
3-34     Dual Use Technologies: Structures and Materials .................................................................                    3-143
3-35     Dual Use Technologies: Science and Science Equipment .....................................................                           3-143
3-36     Dual Use Technologies: Operations and Maintenance .........................................................                          3-144


                                                                FIGURES

Figure                                                                                                                                          Page

1-1      Typical fast-transit trajectory ........................................................................................................ 1-9
1-2      Mars Reference Mission Sequence ............................................................................................. 1-10
1-3      General sequence of events associated with first mission to Mars ........................................ 1-11
1-4      Possible time line for first Mars surface mission ..................................................................... 1-15
1-5      Reference Mars cargo and piloted vehicles .............................................................................. 1-20
1-6      Distribution of Reference Mission costs ................................................................................... 1-39
1-7      Relationship between program cost and program culture .................................................... 1-41

2-1      Orbital image taken by Mariner 4 (1965) .................................................................................... 2-7
2-2      Olympus Mons v (Mariner 9 image), the largest volcano in the solar system ...................... 2-8
2-3      Across the middle is Valles Marineris, a huge canyon as long as the United States ............ 2-9
2-4      Dense tributary networks indicative of past presence of liquid water on Mars ................. 2-11

3-1      A regional map illustrating potential locations for a Mars outpost ....................................... 3-8
3-2      Typical short-stay mission profile .............................................................................................. 3-37
3-3      Typical long-stay mission profile ............................................................................................... 3-37
3-4      Fast-Transit mission profile ........................................................................................................ 3-38
3-5      Round-trip mission duration comparisons .............................................................................. 3-39
3-6      Microgravity comparisons for various mission classes .......................................................... 3-41
3-7      Mars reference mission sequence .............................................................................................. 3-45
3-8      Mars surface outpost after deployment of payloads from
         first two cargo landers ................................................................................................................. 3-48
3-9      Mars surface outpost at the end of first flight crew’s stay ..................................................... 3-51
3-10     Possible surface mission time line ............................................................................................. 3-53
3-11     Mars surface outpost at the end of second flight crew’s stay ................................................ 3-56
3-12     Mars surface outpost at the end of third flight crew’s stay ................................................... 3-58
3-13     Mars Energia-derived HLLV with eight Zenit-type boosters ................................................ 3-64
3-14     STS External Tank-derived HLLV with seven LOX/RP boosters ......................................... 3-65
3-15     STS External Tank-derived HLLV with four strap-on boosters, each
         having two F-1 engines ............................................................................................................... 3-67
3-16     Saturn V-derived Mars HLLV with F-1A/J-2S propulsion .................................................... 3-68
3-17     Saturn V-based Mars HLLV concepts ....................................................................................... 3-69
3-18     Energia launch vehicle adapted to Mars mission profile ....................................................... 3-70




                                                                      XIII
Figure                                                                                                                                       Page

3-19     Mars mission launch vehicle with two external tank boosters and kick stage ................... 3-71
3-20     Reference Mars cargo and piloted vehicles .............................................................................. 3-73
3-21     Biconic aeroshell dimensions for Mars lander and surface habitat modules ...................... 3-76
3-22     Transit habitat attached to International Space Station .......................................................... 3-78
3-23     The crew exercise facility component of the countermeasures system
         designed to inhibit crew degradation from exposure to reduced
         gravity environments .................................................................................................................. 3-80
3-24     EVA suit storage locations are critical in a robust crew safety system ................................. 3-80
3-25     Conceptual Mars habitation module-wardroom design ........................................................ 3-81
3-26     Habitat and surface laboratory joined on Mars surface ......................................................... 3-83
3-27     Mars surface lander descending on parachutes ...................................................................... 3-84
3-28     Mars surface lander just prior to landing illustrating landing legs
         and surface mobility system ....................................................................................................... 3-85
3-29     Mars surface lander and biconic aeroshell ............................................................................... 3-87
3-30     Crew ascent capsule just after launch from Mars surface ...................................................... 3-87
3-31     Methane/LOX ascent stage configuration2 ............................................................................. 3-88
3-32     ECCV returning to Earth on a steerable parafoil ..................................................................... 3-91
3-33     Solar array power source for interplanetary spacecraft ......................................................... 3-94
3-34     Nominal power profile for the transit/surface habitat .......................................................... 3-95
3-35     Hybrid LSS process distribution .............................................................................................. 3-100
3-36     Schematic of the first ISRU plant ............................................................................................. 3-104
3-37     Concepts for the unpressurized and automated surface rovers ......................................... 3-108
3-38     Concept for the large pressurized surface rover ................................................................... 3-109
3-39     Conceptual airlock and EVA suit maintenance facility ......................................................... 3-111
3-40     Mars surface power profile ........................................................................................................ 3-112
3-41     The relative cost of programs using different management approaches ........................... 3-125
3-42     A comparison of the relative costs for Reference Mission elements ................................... 3-129




                                                                    XIV
Acronyms
AMCM     Advanced Missions Cost Model      MTV     Mars transfer vehicle

COSPAR   Committee on Space Research       NASA    National Aeronautics and
CPAF     cost plus award fee                       Space Administration
                                           ND      NERVA derived
CPFF     cost plus fixed fee
                                           NDR     NERVA derivative reactor
DIPS     Dynamic Isotope Power System      NERVA   nuclear engine for rocket vehicle
                                                   application
ECCV     Earth crew capture vehicle        NTR     nuclear thermal rocket
ERV      Earth return vehicle
                                           PI      principal investigator
ETO      Earth-to-orbit
                                           PVA     photovoltaic array
EVA      extravehicular activity

                                           RFC     regenerative fuel cell
GCR      galactic cosmic radiation
                                           RTG     radioisotope thermoelectric generator
HMF      health maintenance facility
                                           SPE     solar proton event
HLLV     heavy-lift launch vehicle
                                           SSME    Space Shuttle Main Engine
IAA      International Academy of          STS     Space Transportation System
         Astronautics
                                           TEI     trans-Earth injection
IMLEO    intial mass to low Earth orbit
                                           TCS     Thermal Contract System
ISRU     in-situ resource utilization
                                           TMI     trans-Mars injection
LEO      low Earth orbit                   TROVs   telerobotic rovers
LMO      low Mars orbit
LOX      liquid oxygen
LSS      life support system

MAV      Mars-ascent vehicle
MGS      Mars Global Surveyor
MOI      Mars Orbit Insertion




                                          XV
      1. Overview




1-1
1-2
1.1 Introduction                                       Reference Mission, choices have been made.
                                                       In this report, the rationale for each choice is
     The human exploration of Mars will be a
                                                       documented; however, unanticipated
complex undertaking. It is an enterprise that
                                                       technology advances or political decisions
will confirm the potential for humans to leave
                                                       might change the choices in the future.
our home planet and make our way outward
into the cosmos. Though just a small step on a              One principal use of the Reference
cosmic scale, it will be a significant one for         Mission is to lay the basis for comparing
humans, because it will require leaving Earth          different approaches and criteria in order to
with very limited return capability. The               select better ones. Even though the Reference
commitment to launch is a commitment to                Mission appears to have better technical
several years away from Earth, and there is a          feasibility, less risk, and lower cost than
very narrow window within which return is              previous approaches, improvement is still
possible. This is the most radical difference          needed in these areas to make the first piloted
between Mars exploration and previous lunar            Mars mission a feasible undertaking for the
explorations.                                          spacefaring nations of Earth. The Reference
                                                       Mission is not implementable in its present
     Personnel representing several NASA
                                                       form. It involves assumptions and
field centers have formulated a “Reference
                                                       projections, and it cannot be accomplished
Mission” addressing human exploration of
                                                       without further research, development, and
Mars. This report summarizes their work and
                                                       technology demonstrations. It is also not
describes a plan for the first human missions
                                                       developed in the detail necessary for
to Mars, using approaches that are technically
                                                       implementation, which would require a
feasible, have reasonable risks, and have
                                                       systematic development of requirements
relatively low costs. The architecture for the
                                                       through the system engineering process. With
Mars Reference Mission builds on previous
                                                       this in mind, the Reference Mission may be
work, principally on the work of the
                                                       used to:
Synthesis Group (1991) and Zubrin’s (1991)
concepts for the use of propellants derived                •Derive technology research and
from the martian atmosphere. In defining the                development plans.




                                                 1-3
   •Define and prioritize requirements for               •The architectural level involves
    precursor robotic missions.                           assembly of all elements into an
                                                          integrated whole. The principal features
   •Define and prioritize flight experiments
                                                          to be addressed in a new architecture
    for precursor human missions, such as
                                                          that will improve on the Reference
    those involving the Space Shuttle, Mir, or
                                                          Mission appear to be simplification
    the International Space Station.
                                                          (particularly the number of separate
   •Understand requirements for human                     elements that must be developed) and
    exploration of Mars in the context of                 integration with other programs.
    other space missions and research and                 Simplification by reduction of system
    development programs, as they are                     elements can lower life-cycle costs and
    defined.                                              diminish both programmatic and
   •Open discussion with international                    technical risk. For example, the
    partners in a manner that allows                      development of higher performance
    identification of potential interests of the          space propulsion systems can lead to
    participants in specialized aspects of the            simplification, particularly if one vehicle
    missions.                                             can be used for transit to and from Mars.
                                                          Integration opportunities to link the
   •Provide educational materials at all
                                                          Mars program with other development
    levels that can be used to explain various
                                                          programs could reduce total cost
    aspects of human interplanetary
                                                          through sharing of developmental costs.
    exploration.
                                                          The Reference Mission did not assume
   •Describe to the public, media, and                    integration with a lunar exploration
    political system the feasible, long-term              program. The development of a major
    visions for space exploration.                        Earth-orbiting operations center in
                                                          another program could lead to major
   •Establish an end-to-end mission baseline
                                                          changes in the Reference Mission
    against which other proposals can be
                                                          architectural approach.
    compared.
                                                         •At the mission level, it may be possible
     However, the primary purpose of the
                                                          to reduce the number of separate
Reference Mission is to stimulate further
                                                          launches from Earth. Reducing the total
thought and development of alternative
                                                          number of launches required to
approaches which can improve effectiveness,
                                                          implement the Reference Mission
reduce risks, and reduce cost. Improvements
                                                          objectives could potentially reduce
can be made at several levels; for example, in
                                                          program and technical risk as well as
the architectural, mission, and system levels.
                                                          cost. Focusing and streamlining mission




                                                   1-4
     objectives and improving technology                programmatic and technical requirements
     that will lower mass and power                     that would be placed on existing and planned
     requirements can improve the mission               Agency programs.
     level.
                                                             In August 1992, the first workshop of the
   •At the system level, the performance of             Mars Study Team held at the Lunar and
    individual systems and subsystems can               Planetary Institute in Houston, Texas,
    be improved through research and                    addressed the “whys” of Mars exploration to
    development programs. The                           provide the top-level requirements from
    programmatic and technical risks can be             which the Mars exploration program could be
    reduced by demonstrations of ground,                built (Duke and Budden 1992). The workshop
    Earth-orbit, or planet surface (including           attendees identified the major elements of a
    the Moon) technology. Criteria for                  potential rationale for a Mars exploration
    improved systems are principally                    program as:
    technical—reduced mass, reduced
                                                           •Human Evolution – Mars is the most
    power, increased reliability.
                                                            accessible planet beyond the Earth-Moon
      The current section of this report                    system where sustained human presence
provides a brief overview of the origins of the             is believed to be possible. The technical
study and the Reference Mission design,                     objectives of Mars exploration should be
specifically discussing key issues, findings,               to understand what would be required
and recommendations. Section 2 of this report               to sustain a permanent human presence
addresses what can be learned by                            beyond Earth.
undertaking the Reference Mission and
                                                           •Comparative Planetology – The scientific
describes the scientific and technical
                                                            objectives of Mars exploration should be
objectives of Mars exploration. Section 3
                                                            to understand the planet and its history,
provides a detailed discussion of the mission
                                                            and therefore to better understand Earth.
life cycle, the systems needed to carry it out,
and the management challenges and                          •International Cooperation – The political
opportunities that are inherent in a program                environment at the end of the Cold War
to explore Mars with humans.                                may be conducive to a concerted
                                                            international effort that is appropriate to,
1.2 Background                                              and may be required for, a sustained
                                                            Mars program.
     The Mars Exploration Study Project was
undertaken to establish a vision for the                   •Technology Advancement – The human
human exploration of Mars that would serve                  exploration of Mars currently lies at the
as a mechanism for understanding the                        ragged edge of achievability. The




                                                  1-5
     necessary technical capabilities are either            •Basic science research to gain new
     just available or on the horizon.                       knowledge about the solar system’s
     Commitment to the program will both                     origin and history.
     effectively exploit previous investments
                                                               The human missions to Mars, which are
     and contribute to advances in
                                                         required to accomplish the exploration and
     technology.
                                                         research activities, also contain requirements
   •Inspiration – The goals of Mars                      for safe transportation, maintenance on the
    exploration are grand; they will motivate            surface of Mars, and return of a healthy crew
    our youth, benefit technical education               to Earth. The surface exploration mission
    goals, and excite the people and nations             envisions approximately equal priority for
    of the world.                                        applied science research (that is, learning
                                                         about the environment, resources, and
     The study team of personnel from NASA
                                                         operational constraints that would allow
field centers used these inputs to construct
                                                         humans eventually to inhabit the planet) and
the Reference Mission, and then translated the
                                                         basic science research (that is, exploring the
inputs into a set of goals and objectives.
                                                         planet for insights into the nature of planets,
Ground rules and assumptions were agreed
                                                         the nature of Mars’ atmosphere and its
upon and reflect the lessons learned from
                                                         evolution, and the possible past existence of
previous study efforts. From this work, a
                                                         life). These more detailed objectives form the
mission and a set of systems were developed.
                                                         basis for defining the required elements and
                                                         operations for the Reference Mission.
1.3 Reference Mission Summary
                                                              In addition, past mission studies have
1.3.1 Objectives                                         yielded results that have characterized piloted
     Reflecting the conclusions of the August            Mars missions as being inherently difficult
1992 workshop, three objectives were adopted             and exorbitantly expensive. To confront these
for the analysis of a Mars exploration                   commonly accepted beliefs that are
program and the first piloted missions in that           unfortunately tied to Mars missions, this
program. They are to conduct:                            study added objectives to:

   •Human missions to Mars and verify a                     •Challenge the notion that the human
    way that people can ultimately inhabit                   exploration of Mars is a 30-year program
    Mars.                                                    that will cost hundreds of billions of
                                                             dollars. Although the nations of the
   •Applied science research to use Mars                     world could afford such expenditures in
    resources to augment life-sustaining                     comparison to, for example, military
    systems.                                                 budgets, the smaller the total cost, the




                                                   1-6
     more likely it is that the program will be         •Define a robust planetary surface
     implemented.                                        exploration capacity capable of safely
                                                         and productively supporting crews on
   •Challenge the traditional technical
                                                         the surface of Mars for 500 to 600 days
    obstacles associated with sending
                                                         each mission.
    humans to Mars.
                                                        •Define a capability to be able to live off
   •Identify relevant technology
                                                         the land.
    development and investment
    opportunities that benefit both Mars                •Rely on advances in automation to
    exploration and Earth-bound endeavors.               perform a significant amount of the
                                                         routine activities throughout the
     From these basic objectives, a Reference
                                                         mission.
Mission was crafted by drawing on lessons
learned from many past studies and by                   •Ensure that management techniques are
adding new insights to various aspects of the            available and can be designed into a
mission. This approach substantially                     program implementation that can
improved the yield from piloted missions                 substantially reduce costs.
while also reducing risk and cost.
                                                        •Use the Earth-Mars launch opportunities
                                                         occurring from 2007 through 2014. A
1.3.2 Ground Rules and Assumptions
                                                         2009 launch represents the most difficult
    Translating these objectives into specific           opportunity in the 15-year Earth-Mars
missions and systems for the Reference                   cycle. By designing the space
Mission required adopting a number of                    transportation systems for this
ground rules and assumptions. These were to:             opportunity, particularly those systems
   •Balance technical, programmatic,                     associated with human flights, they can
    mission, and safety risks.                           be flown in any opportunity with either
                                                         faster transit times for the crew or
   •Provide an operationally simple mission              increased payload delivery capacity.
    approach emphasizing the judicious use
    of common systems.                                  •Examine three human missions to Mars.
                                                         The initial investment to send a human
   •Provide a flexible implementation                    crew to Mars is sufficient to warrant
    strategy.                                            more than one or two missions. Each
   •Limit the length of time that the crew is            mission will return to the site of the
    continuously exposed to the                          initial mission thus permitting an
    interplanetary space environment.                    evolutionary establishment of
                                                         capabilities on the Mars surface.




                                                  1-7
     Although it is arguable that scientific             significantly challenge the management and
     data return could be enhanced by a                  operations systems to support the crew in the
     strategy where each human mission                   new situations.
     went to a different surface site, the goal
     of understanding how humans can                     1.3.3.1 Mission Design
     inhabit Mars seems more logically                        The crew will travel to and from Mars on
     directed toward a single outpost                    relatively fast transits (4 to 6 months) and will
     approach.                                           spend long periods of time (18 to 20 months;
                                                         600 days nominal) on the surface, rather than
1.3.3 Mission and Systems                                alternative approaches which require longer
     Previous studies of human exploration of            times in space and reduce time on the surface.
Mars have tended to focus on spacecraft and              Figure 1-1 illustrates a typical trajectory.
flight, rather than on what the crew would do            Designed to the worst-case mission
on the surface. The Reference Mission takes              opportunity (2007-2009) of the next two
the point of view that surface exploration is            decades, the transit legs are less than 180 days
the key to the mission, both for science and             in both directions. For easier Mars mission
for evaluation of the potential for settlement.          opportunities (for example, 2016-2018), the
As a consequence, the Reference Mission                  transit legs are on the order of 130 days.
architecture allows for a robust surface                 Shorter transit times reduce the time spent by
capability with significant performance                  the crew in zero g to the length of typical
margins: Crews will explore in the vicinity of           tours of duty for the International Space
the outpost out to a few hundred kilometers,             Station. (Thus, the Mars Study Team chose
will be able to study materials in situ and in a         not to use artificial gravity spacecraft designs
surface laboratory, and will be allowed to               for the Reference Mission.) In addition,
update and modify the exploration plan to                relatively fast transits will reduce the
take advantage of their discoveries.                     exposure to galactic cosmic radiation and the
                                                         probability of encountering solar particle
     In addition, key technologies will be
                                                         events. Reducing the exposure to zero g and
developed and demonstrated to test
                                                         radiation events helps reduce the risk to the
settlement issues, potentially imposing a
                                                         crew.
substantial workload on the Mars exploration
crew. To improve the effectiveness of surface                 The strategy chosen for the Reference
operations, supporting systems must be                   Mission, generally known as a “split mission”
highly reliable, highly autonomous, and                  strategy, breaks mission elements into pieces
highly responsive to the needs of the crew.              that can be launched directly from Earth with
Some needs may not be anticipated during                 launch vehicles of the Saturn V or Energia
crew preparation and training, which will                class, without rendezvous or assembly in low




                                                   1-8
Earth orbit (LEO). The strategy has these
                                                                                                       MISSION TIMES
pieces rendezvous on the surface of Mars,                                                        OUTBOUND       150 days
                                                                             Earth Launch        STAY          619 days
which will require both accurate landing and                                   2/1/2014          RETURN        110 days
                                                               Depart Mars
mobility of major elements on the surface to                    3/11/2016                        TOTAL MISSION 879 days

allow them to be connected or to be moved
into close proximity. Another attribute of the                                                                         γ
split mission strategy is that it allows cargo to
                                                             Nominal
be sent to Mars without a crew during the                   Departure                       Earth Return
                                                            3/11/2016                        6/29/2016
same launch opportunity or even one or more
opportunities prior to crew departure. This                              Arrive Mars
                                                                          7/1/2014
allows cargo to be transferred on low energy,
longer transit time trajectories and the crew to
be sent on a required higher energy, shorter                      Figure 1-1 Typical fast-transit
transit time trajectory. Breaking the mission                               trajectory.
into two launch windows allows much of the
infrastructure to be emplaced and checked
                                                          sequence gradually builds up assets on the
out before committing a crew to the mission,
                                                          martian surface so that at the end of the third
and also allows for a robust capability, with
                                                          crew’s tour of duty, the basic infrastructure
duplicate launches on subsequent missions
                                                          could be in place to support a permanent
providing either backup for the earlier
                                                          presence on Mars.
launches or growth of initial capability.
                                                               The six launches used to support the
     Figure 1-2 illustrates the mission
                                                          activities of the first crew will be discussed in
sequence analyzed for the Reference Mission.
                                                          more detail here to illustrate what will
In this sequence, three vehicles will be
                                                          typically occur for all three crews. (Note: For
launched from Earth to Mars in each of four
                                                          the nominal mission, launches 1 through 4 are
launch opportunities which, for reasons
                                                          required to support the first crew; launches 5
presented earlier, start in 2007. The first three
                                                          and 6 provide backup systems for the first
launches will not involve a crew but will send
                                                          crew and, if not used, are available for the
infrastructure elements to low Mars orbit and
                                                          second crew.) Figure 1-3 illustrates the
to the surface for later use. Each of the
                                                          general sequence of events associated with
remaining opportunities analyzed for the
                                                          the first crew’s mission to Mars as discussed
Reference Mission will send one crew and
                                                          in the following paragraphs.
two cargo missions to Mars. These cargo
missions will consist of an Earth-return                       In the first launch opportunity, three
vehicle (ERV) on one flight and a lander                  cargo missions are sent on minimum energy
carrying a Mars-ascent vehicle (MAV) and                  trajectories direct to Mars (that is, without
additional supplies on the second. This                   assembly or fueling in LEO). Launch 1




                                                    1-9
delivers a fully fueled ERV to Mars orbit. (The                              approximately 40 tonnes of additional
crew will rendezvous with this stage and use                                 payload to the surface. After the descent stage
it to return to Earth after completion of their                              lands on the surface, the nuclear reactor
surface exploration mission.) Launch 2                                       autonomously deploys itself several hundred
delivers an unfueled MAV, a propellant                                       meters from the ascent vehicle. Using the
production module, a nuclear power plant,                                    Mars atmosphere as feedstock, the propellant
liquid hydrogen (to be used as a reactant to                                 production module begins to manufacture the
produce the ascent vehicle propellant), and                                  nearly 30 tonnes of oxygen and methane that


     ETO
    FLIGHT   2007    2008       2009        2010         2011       2012        2013       2014       2015         2016         2017    2018
                                    ERV loiter                  ∆ Crew 1 TEI
      1
                       ∆ ERV-1 parks in LMO                            ∆ Crew 1 Earth return
      2
                        ∆ MAV-1 landing

      3                  ∆ Initial Habitat landing

      6
                      Crew 1: launch ∆        ∆ Landing         ∆ Crew 1 ascent
                                                                ERV loiter              ∆ Crew 2 TEI
      4
                                                ∆ ERV-2 parks in LMO                         ∆ Crew 2 Earth return

      5                                              ∆ MAV-2 landing

      9                                              Crew 2 launch ∆       ∆ Landing    ∆ Crew 2 ascent
                                                                                       ERV loiter                ∆ Crew 3 TEI
      7
                                                                            ∆ ERV-3 parks in LMO                       ∆ Crew 3 Earth return
      8                                                                     ∆ MAV 3 landing

     12                                                                    Crew 3 launch ∆        ∆ Landing  ∆ Ascent
                                                                                                           ERV loiter
     10
                                                                                                    ∆ ERV 4 LMO
     11
                                                                                                     ∆ MAV 4 landing



                    Interplanetary transit                                                                ERV:            Earth Return Vehicle
    10987654321
    10987654321     Unoccupied wait in Mars orbit                                                         MAV:            Mars Ascent Vehicle
   87654321                                                                                               TEI:            Trans Earth Injection
                    Propellant production and on Mars surface
                                                                                                          LMO:            Low Mars Orbit
                    Crew surface operations



                            Figure 1-2 Mars Reference Mission sequence.




                                                                       1-10
Figure 1-3 General sequence of events associated with first mission to Mars.




                                    1-11
Figure 1-3 General sequence of events continued.




                      1-12
will be required to eventually deliver the crew   similarly mirrors Launch 2 of the previous
to Mars orbit. This production is completed       opportunity, delivering a second unfueled
within approximately one year—several             ascent vehicle and propellant production
months prior to the first crew’s scheduled        module. These systems provide backup or
departure from Earth. Launch 3 lands in the       extensions of the previously deployed
vicinity of the first descent vehicle and         capabilities. For example, the second MAV
delivers a surface habitat/laboratory,            and second ERV provide the first crew with
nonperishable consumables for a safe-haven,       two redundant means for each leg of the
and a second nuclear power plant to the           return trip. If, for some reason, either the first
planetary surface. The second nuclear power       ascent vehicle or the first return vehicle
plant autonomously deploys itself near the        becomes inoperable after the first crew
first power plant. Each power plant can           departs Earth, this crew can use either of the
provide sufficient power (160 kWe) for the        systems launched in the second opportunity
entire mature surface outpost, thereby            instead. If the first ascent and return vehicles
providing complete redundancy within the          operate as expected, then the systems
power production function.                        delivered in the second opportunity will
                                                  support the second crew that will launch to
      During the second launch opportunity,
                                                  Mars in the third opportunity.
two additional cargo missions and the first
crew are launched. All assets previously               The first crew of six departs for Mars in
delivered to Mars have been checked out and       the second opportunity. They leave Earth
the MAV, already on the martian surface, is       after the two cargo missions have been
verified to be fully fueled before either the     launched, but because they are sent on a fast
crew or the additional cargo missions are         transfer trajectory of only 180 days, they will
launched from Earth. (Should any element of       arrive in Mars orbit approximately 2 months
the surface system required for crew safety or    before the cargo missions. The crew lands on
critical for mission success not check out        Mars in a surface habitat substantially
adequately, the surface systems will be placed    identical to the habitat/laboratory previously
in standby mode and the crew mission              deployed on the martian surface. After
delayed until the systems can be replaced or      capturing into a highly elliptic Mars orbit, the
their functions restored. Some systems can be     crew descends in the transit habitat to
replaced using hardware originally intended       rendezvous on the surface with the other
for subsequent missions; others may be            elements of the surface outpost. (The crew
functionally replaced by other systems.) The      carries sufficient provisions for the entire
first cargo launch of this second opportunity     surface stay in the unlikely event that they are
is a duplicate of Launch 1 from the first         unable to rendezvous on the surface with the
opportunity, delivering a second fully fueled     assets previously deployed.)
ERV to Mars orbit. The second cargo launch




                                              1-13
    Surface exploration by robotic vehicles           Mars. The purpose of these studies would be
and human explorers will include a wide               to support the field investigations, answer
range of activities.                                  “sharper” questions, and allow the human
                                                      explorers to narrow their focus to the sites of
   •Observing and analyzing the surface and
                                                      optimum sample collection. As hypotheses
    subsurface geology.
                                                      evolve, crews will be able to return to sample
   •Observing and analyzing the                       sites and gather specific samples to test the
    composition and structure of the                  hypotheses. Ultimately, selected samples will
    atmosphere.                                       be returned to Earth for more detailed
   •Collecting samples and examining them             analysis.
    in the outpost laboratory.                             As experience grows, the range of human
   •Performing experiments designed to                exploration will grow from the local to the
    gauge the ability of humans to inhabit            regional. Regional expeditions, lasting
    Mars.                                             perhaps 2 weeks and using mobile facilities,
                                                      may be conducted at intervals of a few
     Prior to the arrival of the first human
                                                      months. Between these explorations, analysis
crew, telerobotic rovers (TROVs) may be
                                                      in the laboratory will continue. The crew will
delivered to the surface. (These rovers are
                                                      also spend a significant portion of its time
assumed to be intelligent enough to perform
                                                      performing maintenance and housekeeping
broadly stated objectives without human
                                                      tasks (system design requirements addressing
assistance. But humans will continue to
                                                      enhanced reliability and maintainability will
monitor progress and be available to
                                                      help keep these activities to a minimum).
“supervise” the TROV if it cannot solve a
                                                      Figure 1-4 provides a possible time line for
particular problem.) When the crew arrives,
                                                      the first surface mission.
the rovers will be available for teleoperation
by the crew. The TROVs may be designed to                  The deployment of a bioregenerative life
provide global access and may be able to              support capability will be an early activity
return samples to the outpost from hundreds           after crew landing. Although this system is
of kilometers distance from the site if they are      not required to maintain the health and
deployed 2 years before the crew arrives.             vitality of the crew, it will improve the
                                                      robustness of the life support system and is
     The outpost laboratory will be outfitted
                                                      important to the early objectives of the
to provide mineralogical and chemical
                                                      outpost.
analyses of rocks, soils, and atmospheric
samples; and depending on technical                       Crew activities related to living on
development, it may be possible to undertake          another planet should be viewed as
simple kinds of geochronologic analysis on            experiments. With minor modifications in




                                                   1-14
                                                                                                                                   Mars Surface Mission Time Allocation

                                      (Total Time = 8 crew X 24 hr/day X 600 days = 115,200 hr)

                                                                                                                                                                                                                8 crew X 24 hr day = 200)


                                                                                    Personal                                                                                                                                                                                                                                       Hr/Over
                                                                                       14 hr                                                                                                                                                                                                                                        head                                                                                                                                                                     Production
                                                                                (total 67,200 hr)                                                                                                                                                                                                                                                                                                                                                                                                                7 hr
                                                                                                                                                                                                                                                                                                                                     3 hr                                                                                                                                                                  (33,600 hr total)
                                                                                                                                                                                                                                                                                                                                  (14,400 hr)

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Site Prep,
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Construction        90 days




                                                                                                                                                                                                                                                                                                                                      Group Socialization, Meetings, Life Sciences Subject, Health Monitoring, Health Care: 1 hr
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Verification
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days




                                                                                                                                                                                                                                                                                                                                                                                                                                   System Monitoring, Inspection, Calibration, Maintenance, Repair: 1 hr
                                                                                                                                                                                                                                                          General Planning, Reporting, Documentation, Earth Communication: 1 hr
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Local Excursions

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           100 days
                                                                                 Hygiene, Cleaning, Personal Communication: 1 hr




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion   10 days
                                                                                                                                   Recreation, Exercise, Relaxation: 1 hr
                                      Sleep, Sleep Prep, Dress, Undress: 8 hr




                                                                                                                                                                                                                   One Day Off Per Week: 3 hr (per day)
600 day (or 20 months, or 86 weeks)




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis            40 days
                                                                                                                                                                            Eating, Meal Prep, Clean-up: 1 hr




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Charge Fuel Cells
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Check Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Load Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Plan Excursion
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Drive Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Navigate
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Don Suits (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off                         Pre-breathe (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Egress (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion   100 days     Unload Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Set up Drill (X 10)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Operate Drill
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Collect Samples
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         In Situ Analysis
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Take Photos
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Flare Retreat       15 days      Communicate
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days       Disassemble Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Load Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Ingress (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Clean Suit (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Stow Suit, Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion   100 days     Inspect Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Secure for night
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            (Sleep, eat, cleanup
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days       hygiene, etc.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Sys Shutdown                     covered)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Departure Prep      60 days

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          3 Crew X 7 hr X 10 Day =
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                210 hrs total


                                                                                Figure 1-4 Possible time line for first Mars surface mission.




                                                                                                                                                                                                                                                                                                                                                                                                                                               1-15
hardware and software, ordinary experiences           emplaced, checked out, and operated to
can be used to provide objective databases for        produce the required propellant prior to
understanding the requirements for human              launching the crew from Earth.
settlement.
                                                            In addition to spacecraft propulsion, the
     The first crew will stay at the outpost for      production capability on Mars can provide
18 to 20 months. Part of their duties will be to      fuel for surface transportation, reactants for
prepare the outpost site for the receipt of           fuel cells, and backup caches of consumables
additional elements launched on subsequent            (water, oxygen, nitrogen, and argon) for the
mission opportunities. Since the first crew           life support system.
will have to depart before the second crew
arrives, some systems will have to be placed          1.3.3.3 Flight Crew
in standby mode.                                           Humans are the most valuable mission
     After their stay on Mars, each crew will         asset for Mars exploration and must not
use the previously landed and in situ-                become the weak link. The objective for
resource-utilization fueled ascent vehicle to         humans to spend up to 600 days on the
return to orbit where they will rendezvous            martian surface places unprecedented
with the waiting ERV. The crew will return to         requirements on the people and their
Earth in a habitat similar to the one used for        supporting systems. Once committed to the
the outbound transit leg. This habitat, which         mission on launch from LEO, the crew must
is part of the ERV deployed in a previous             be prepared to complete the full mission
opportunity by one of the cargo flights,              without further resupply from Earth.
typically will have been in an untended mode          Unlimited resources cannot be provided
for nearly 4 years prior to the crew arrival.         within the constraints of budgets and mission
                                                      performance. Their resources will either be
1.3.3.2 In Situ Resource Production                   with them or will have already been delivered
                                                      to or produced on Mars. So trade-offs must be
     The highly automated production of
                                                      made between cost and comfort, as well as
propellant from martian resources is another
                                                      performance and risk. Crew self-sufficiency is
defining attribute of the Reference Mission.
                                                      required because of the long duration of their
The technology for producing methane and
                                                      mission and the fact that their distance from
liquid oxygen from the martian atmosphere
                                                      Earth impedes or makes impossible the
and some nominal hydrogen feedstock from
                                                      traditional level of communications and
Earth is an effective performance
                                                      support by controllers on Earth. The crews
enhancement and appears to be
                                                      will need their own skills and training and
technologically feasible within the next few
                                                      specialized support systems to meet the new
years. The split mission strategy allows the
                                                      challenges of the missions.
propellant production capability to be




                                                   1-16
     The nominal crew size for this mission is      Mission objectives. The site must be
six. This number is believed to be reasonable       consistent with operational considerations,
from the point of view of past studies and          such as landing and surface operational
experience and is a starting point for study.       safety. Detailed maps of candidate landing
Considerable effort will be required to             sites built from data gathered by precursor
determine absolute requirements for crew            robotic missions will define the safety and
size and composition. This determination will       operational hazards of the sites, as well as
have to consider the tasks required of the          confirm whether access to scientifically
crew, safety and risk considerations, and the       interesting locations is possible by humans or
dynamics of an international crew. Crew             robotic vehicles. Robotic surface missions,
members should be selected in part based on         including missions to return samples, may be
their ability to relate their experiences back to   required to confirm remotely sensed data
Earth in an articulate and interesting manner,      from orbit and to satisfy planetary protection
and they should be given enough free time to        issues. To satisfy the human habitation
appreciate the experience and the opportunity       objectives in particular, it would be highly
to be the first explorers of another planet.        desirable to locate the outpost site where
Significant crew training will be required to       water can be readily extracted from minerals
ensure that the crew remains productive             or from subsurface ice deposits. Such a
throughout the mission.                             determination may only be possible from data
                                                    collected by a robotic surface mission.
1.3.3.4 Robotic Precursors
                                                         To accomplish the Reference Mission, key
     Robotic precursor missions will play a         advances in certain critical technologies will
significant role in three important areas of the    need to occur. The robotic precursor missions
Reference Mission. The first area is to gather      offer an opportunity to demonstrate the
information about Mars that will be used to         operation of many of those technologies, such
determine what specific crew activities will be     as in situ resource utilization, aerocapture,
performed and where they will be performed.         precision landing, etc. The information and
The second area is to demonstrate the               experience gained from the demonstration of
operation of key techonologies required for         these technologies will add immeasurable
the Reference Mission. The third is to land,        confidence for their use in the human
deploy, operate, and maintain a significant         mission.
portion of the surface systems prior to the
                                                         The first phase of human exploration is
arrival of the crew.
                                                    the automated landing of surface
     For optimum mission performance, it            infrastructure elements, including a system to
will be necessary to pick a landing site based      produce propellant and life support
primarily on its ability to achieve Reference       consumables, the first of two habitats, power




                                                 1-17
systems, and surface transportation elements.         depart for Mars. To avoid the boiloff loss of
All of these systems will be delivered, set up,       cryogenic propellants in the departure stages,
and checked out using robotic systems                 all elements must be launched from Earth in
operated or supervised from Earth. The                quick succession. This places a strain on a
propellant required for the MAV will be               single launch facility and its ground
produced and stored as will oxygen and                operations crews or requires the close
water caches for the habitat. The overall site        coordination of two or more launch facilities.
will be prepared for receipt of the second            Assembling the Mars vehicles in orbit and
habitat.                                              loading them with propellants from an
                                                      orbiting depot just prior to departure may
1.3.3.5 Launch Systems                                alleviate the strain on the launch facilities, but
    The scale of the required Earth-to-orbit          the best Earth orbit for a Mars mission is
(ETO) launch capability is determined by the          different for each launch opportunity.
mass of the largest payload intended for the          Therefore, a permanent construction or
martian surface. The nominal design mass for          propellant storage facility in a single Earth
individual packages to be landed on Mars in           orbit is not an optimal solution.
the Reference Mission is 50 tonnes for a crew             The choice of a launch vehicle remains a
habitat sized for six people that is transferred      significant issue for any Mars mission. For the
on a high-energy orbit. This requires the             Reference Mission, however, the larger, 200-
capability for a single launch vehicle to be          ton-class launch vehicle has been assumed
from about 200 to 225 tonnes to LEO.                  without specifying a particular configuration.
     Because 200-ton-class launch vehicles
                                                      1.3.3.6 Interplanetary Transportation System
raise development cost issues, consideration
was given to the option of launching pieces to             The interplanetary transportation system
LEO using smaller vehicles and assembling             consists of a trans-Mars injection (TMI) stage,
(attaching) them in space prior to launching          a biconic aeroshell for Mars orbit capture and
them to Mars. This smaller launch vehicle             Mars entry, a descent stage for surface
(110 to 120 tonnes) would have the advantage          delivery, an ascent stage for crew return to
of more modest development costs and is               Mars orbit, an Earth-return stage for
within the capability of the Russian Energia          departure from the Mars system, and a crew
program. However, the smaller launch vehicle          capsule (similar to an Apollo Command
introduces several potential difficulties to the      Module) for Earth entry and landing. As
Reference Mission scenario. The simplest,             mentioned earlier, the Reference Mission
most desirable implementation using this              splits the delivery of elements to Mars into
smaller launch vehicle is to simply dock the          cargo missions and human missions, all of
two elements in Earth orbit and immediately           which are targeted to the same locale on the




                                                   1-18
surface and must be landed in close proximity       between the NDR engine assembly and the
to one another. The transportation strategy         LH2 tank to protect the crew from radiation
adopted in the Reference Mission eliminates         that builds up in the engines during the TMI
the need for assembly or rendezvous of              burns. Although it may seem wasteful to
vehicle elements in LEO, but it does require a      discard the nuclear stage after one use, the
rendezvous in Mars orbit for the crew leaving       complexity of Mars orbit insertion and
Mars. The transportation strategy also              rendezvous operations for the return flight
emphasizes the use of common elements to            are avoided.
avoid excessive development costs and to
                                                         As shown in Figure 1-5, the same TMI
provide operational simplicity.
                                                    stage is used in all cargo missions, which
      The TMI stage (used to propel the             allows the transportation system to deliver
spacecraft from LEO onto a trans-Mars               approximately 65 tonnes of useful cargo to the
trajectory) employs nuclear thermal                 surface of Mars or nearly 100 tonnes to Mars
propulsion. Nuclear thermal propulsion was          orbit (250 × 33,793 km) on a single launch
adopted for the TMI burn because of its             from Earth. The TMI stage for cargo delivery
performance advantages; its advanced,               requires the use of only three NDR engines,
previously demonstrated state of technology         so one NDR engine and the shadow shield are
development; its operational flexibility; and       removed from the TMI stage, which reduces
its inherent mission enhancements. A single         cost and improves performance.
TMI stage was developed for both piloted
                                                         Mars orbit capture and the majority of
and cargo missions. The stage is designed for
                                                    the Mars descent maneuver is performed
the more energetically demanding 2009 fast
                                                    using a single biconic aeroshell. The decision
transit trajectory and then used in the
                                                    to perform the Mars orbit capture maneuver
minimum energy cargo missions to carry the
                                                    was based on the facts that (1) an aeroshell
maximum payload possible to Mars. In the
                                                    will be required to perform the Mars descent
human missions, the TMI stage uses four
                                                    maneuver no matter what method is used to
15,000 lb. thrust NERVA (Nuclear Engine for
                                                    capture into Mars orbit, (2) the additional
Rocket Vehicle Application)-derivative reactor
                                                    demands on a descent aeroshell to meet the
(NDR) engines (Isp = 900 seconds) to deliver
                                                    Mars capture requirements were determined
the crew and the surface habitat/descent
                                                    to be modest, and (3) a single aeroshell
stage onto the trans-Mars trajectory
                                                    eliminated one staging event, and thus one
(Borowski, et al., 1993). After completion of
                                                    more potential failure mode, prior to landing
the two-perigee-burn Earth departure, the
                                                    on the surface.
TMI stage is inserted into a trajectory that will
not reencounter Earth or Mars over the course           The crew is transported to Mars in a
of one million years. The TMI stage used with       habitat that is fundamentally identical to the
the crew incorporates a shadow shield




                                                1-19
               2007 Cargo Mission 1                  2007 Cargo Mission 2            2007 Cargo Mission 3           2009 Piloted Mission 1
            "Dry" Ascent Stage & Lander              Hab Module & Lander             LOX/CH4 TEIS & Hab       Surface Hab with Crew and Lander




                                                                            19.0 m         7.6 m
        15.0 m                              16.3 m
                                                                                                            16.3 m
1-20




       20.6 m*
                    86.0 t LH 2                         86.0 t LH 2                       86.0 t LH 2                  86.0 t LH 2
                    (@ 100%)                            (@ 100%)                         (@ 192.9%)                    (@ 100%)
                       10 m                                10 m                             10 m                         10 m


        4.7 m




       IMEO =        216.6T                              216.6T                           204.7T                       212.1T



                   "Expandabe TMI Stage LH 2 (@ 18.2 m length) sized
                   by 2009 Mars Piloted Mission




                                     Figure 1-5 Reference Mars cargo and piloted vehicles.
surface habitat deployed robotically on a            been assumed to reduce the descent vehicle’s
previous cargo mission. By designing the             speed after the aeroshell has ceased to be
habitat so that it can be used during transit        effective and prior to the final propulsive
and on the surface, a number of advantages to        maneuver. The selection of LOX/CH4 allows
the overall mission are obtained.                    a common engine to be developed for use by
                                                     both the descent stage and the ascent stage,
   •Two habitats provide redundancy on the
                                                     the latter of which is constrained by the
    surface during the longest phase of the
                                                     propellant that is manufactured on the
    mission.
                                                     surface using indigenous materials.
   •By landing in a fully functional habitat,
                                                         The ascent vehicle is delivered to the
    the crew does not need to transfer from a
                                                     Mars surface atop a cargo descent stage. It is
    “space-only” habitat to the surface
                                                     composed of an ascent stage and an ascent
    habitat immediately after landing, which
                                                     crew capsule. The ascent stage is delivered to
    allows the crew to readapt to a gravity
                                                     Mars with its propellant tanks empty.
    environment at their own pace.
                                                     However, the descent stage delivering the
   •The program is required to develop only          ascent vehicle includes several tanks of seed
    one habitat system. The habitat design is        hydrogen for use in producing the
    based on its requirement for surface             approximately 30 tonnes of LOX/CH4
    utilization. Modifications needed to             propellant for the nearly 5,600 meters per
    adapt it to a zero-g environment must be         second delta-V required for ascent to orbit
    minimized.                                       and rendezvous with the ERV. The ascent
     A common descent stage has been                 vehicle uses two RL10-class engines modified
assumed for the delivery of the transit/             to burn LOX/CH4.
surface habitats, the ascent vehicle, and other            The ERV is composed of the trans-Earth
surface cargo. The descent vehicle is capable        injection (TEI) stage, the Earth-return transit
of landing approximately 65 tonnes of cargo          habitat, and a capsule the crew will use to
on the Mars surface. The landing vehicle is          reenter the Earth’s atmosphere. The TEI stage
somewhat oversized to deliver crew;                  is delivered to Mars orbit fully fueled, where
however, design of a scaled-down lander and          it waits for nearly 4 years before the crew uses
the additional associated costs are avoided To       it to return to Earth. It uses two RL10-class
perform the postaerocapture circularization          engines modified to burn LOX/CH4. These
burn and the final approximately 500 meters          are the same engines developed for the ascent
per second of descent prior to landing on the        and descent stages, thereby reducing engine
Mars surface, the common descent stage               development costs and improving
employs four RL10-class engines modified to          maintainability. The return habitat is a
burn LOX/CH4. The use of parachutes has              duplicate of the outbound transit/surface




                                                  1-21
habitat used by the crew to go to Mars, but        approximately 30 percent of the power
contains consumables for the return trip only      generated in space. For emergency situations,
and minimizes crew accommodations                  the pressurized rover’s Dynamic Isotope
required for the surface mission.                  Power System can supply 10 kWe of
                                                   continuous power.
1.3.3.7 Surface Systems
                                                        From a series of volume, mass, and
     The provision of adequate amounts of          mission analyses, a common habitat structural
electrical power is fundamental to a               cylinder, 7.5 meters in diameter, bilevel, and
successful exploration program. For the            vertically oriented, was derived for the
transit phase, the need for power is less          Reference Mission. The three habitation
severe than on the martian surface. Solar          element types identified for the Reference
energy is available for crew needs throughout      Mission (the surface laboratory, the transit/
the cruise phase (the transit phase both to and    surface habitation element, and the Earth-
from Mars).                                        return habitation element) will contain
     The selection of a power systems strategy     substantially identical primary and secondary
for surface operations is guided by risk           structures, windows, hatches, docking
considerations, which require two-level            mechanisms, power distribution systems, life
redundancy for mission-critical functions and      support, environmental control, safety
three-level redundancy for life-critical           features, stowage, waste management,
functions. The surface power systems should        communications, airlock function, and crew
have 15+ year lifetimes to allow them to serve     egress routes. The following are brief
the three mission opportunities with good          descriptions of the unique aspects of the three
safety margins. Surface transportation power       primary habitation elements developed for
systems should have 6+ year lifetimes to           the Reference Mission analysis.
minimize the need for replacement over the             •The Mars surface laboratory, sent out,
program lifetime.                                       landed, and verified prior to the launch
     The strategy adopted for the Reference             of any crew members, will operate only
Mission includes a primary and backup                   in 3/8 gravity. It contains a large,
nuclear reactor with dynamic energy                     nonsensitive (that is, no special
conversion. Each system is capable of                   environmental control required) stowage
producing 160 kWe. Additionally, each habitat           area with crew support elements on one
retains the solar arrays used during transit,           level and the primary science and
and they can also be operated on the martian            research lab on the second level. Future
surface. Due to several factors (for example,           development of this element includes
the presence of an atmosphere, a day-night              possible retrofitting of the stowage level
cycle, etc.) each power system can produce              into a greenhouse as consumables and




                                                1-22
     resources are consumed and free volume         field work, sample collection, and
     is created.                                    deployment, operation, and maintenance of
                                                    instruments.
   •The Mars transit/surface habitats
    contain the required consumables for the             Mobility on several scales is required by
    Mars transit and surface duration of            people operating from the Mars outpost.
    approximately 800 days (180 days in             Crew members outside the habitat will be in
    transit and 600 days on the surface) as         pressure suits and will be able to operate at
    well as all the required equipment for          some distance from the habitat, determined
    the crew during the 180-day transfer            by their capability to walk back to the
    trip. This is the critical element that must    outpost. They may be served by a variety of
    effectively operate in both zero and            tools, including rovers, carts, and wagons. On
    partial gravity. Once on the surface of         a local scale, perhaps 1 to 10 kilometers from
    Mars, this element will be physically           the outpost, exploration will be implemented
    connected with the previously landed            by unpressurized wheeled vehicles. Beyond
    surface lab thereby doubling the                the safe range for exploration on foot,
    pressurized volume for the crew.                exploration will be in pressurized rovers,
    Eventually, all four habitation elements        allowing explorers to operate for the most
    (the surface laboratory and three transit/      part in a shirtsleeve environment.
    surface habitats) will be interconnected.
                                                         The requirements for long-range surface
   •The Earth-return habitat, functioning           rovers include having a radius of operation of
    only in zero g and requiring the least          up to 500 km in exploration sorties that allow
    amount of volume for consumables, will          10 workdays to be spent at a particular
    be volume rich but must be mass                 remote site, and having sufficient speed to
    constrained to meet the limitations of the      ensure that less than half of the excursion
    TEI stage. Since little activity (other than    time is used for travel. Each day, up to 16
    conditioning for the one-g environment          person-hours would be available for EVAs.
    on Earth and training for the Earth-            The rover is assumed to have a nominal crew
    return maneuvers) is projected for the          of two people, but be capable of carrying four
    crew during this phase of the mission,          in an emergency. Normally, the rover would
    mass and radiation protection were the          be operated (maneuvering from site to site,
    key concerns in the internal architecture       transmitting high data rate communications,
    concepts created.                               supporting EVA activities, etc.) only in the
                                                    daytime, but could conduct selected
    Extravehicular activity (EVA) tasks
                                                    investigations at night.
consist of maintaining the habitats and
surface facilities and conducting a scientific
exploration program encompassing geologic




                                                 1-23
1.3.3.8 Operations                                  flight crews can execute all activities which
                                                    lead to the accomplishment of mission
      Previous space missions have generally
                                                    objectives. All crew activities throughout each
cost more to operate than to design and
                                                    mission, from prelaunch through postlanding,
construct. This phenomenon was caused
                                                    constitute crew operations and as such are
partly by the fact that systems were designed
                                                    essential to the overall program. To enhance
first and operations were developed to fit the
                                                    program success, they must be factored into
designs. The Reference Mission attempts to
                                                    all aspects of program planning. The majority
bring operational considerations into the
                                                    of crew activities fall into one of four
process early to better balance the cost of
                                                    categories: training, science and exploration,
design and development with the cost of
                                                    systems operations and maintenance, and
operations.
                                                    programmatics.
1.3.3.8.1 Crew Operations                               •Training includes activities such as
     The principal difference between Mars               development of training programs,
exploration and previous space ventures is               development of training facilities and
the requirement for crew operations in an                hardware, prelaunch survival training
environment where on-call communications,                for all critical life support systems,
assistance, and advice from ground                       operational and maintenance training on
controllers is not available in emergencies due          mission-critical hardware, prelaunch and
to the communications delay. This leads to a             in-flight proficiency training for critical
set of operations requirements that:                     mission phases, and science and research
                                                         training for accomplishing primary
   •The crew be able to perform
                                                         science and exploration objectives.
    autonomously for time-critical portions
    of the mission.                                     •The majority of science and exploration
                                                         activities will be accomplished on the
   •Highly reliable, autonomous system
                                                         surface of Mars and will include, but not
    operations be possible without intensive
                                                         be limited to, operating TROVs,
    crew participation.
                                                         habitability exercises, local and regional
   •A balance be struck between ground                   sorties, and planetary science
    control and the crew on Mars which                   investigations. Supplemental science
    optimizes the crew’s time and                        objectives may be accomplished during
    effectiveness yet maintains their                    other phases of the mission as well but
    independence and motivation to attain                will be limited by the mass available for
    mission objectives.                                  onboard science equipment. Those
                                                         activities required for crew health and
    Thus, the Reference Mission will be
                                                         safety (such as medical checks during
successful to the degree that ground and




                                                 1-24
 transit phases, monitoring solar activities         before each crew leaves Earth. However,
 for flares, etc.) will be performed.                once on the surface of Mars, the very
                                                     nature of the work done by the crews
•During the first mission, a substantial
                                                     will require real-time activity planning
 amount of crew time will be devoted to
                                                     to take advantage of discoveries made as
 the operation and maintenance of
                                                     the mission progresses.
 vehicle systems. This time is expected to
 decrease during subsequent missions as              No specific conclusions regarding
 both the systems and operational               hardware requirements, facilities
 experience bases mature. However,              requirements, training programs, and the like
 maximizing the crew’s useful science           were derived for this study. But a number of
 and exploration time will increase             recommendations and guidelines regarding
 overall mission effectiveness, and the         these areas have been developed and tailored
 systems or procedures which contribute         to the various mission phases that will be
 to increasing this time and decreasing         experienced by each crew sent to Mars. While
 routine operations and maintenance will        these and other crew activities may not be
 be incorporated wherever possible.             seen as directly affecting program success, all
                                                areas contribute to the successful execution of
•Lastly, programmatic activities for flight
                                                each mission and, therefore, are essential to
 crews will include public relations,
                                                the overall success of the Reference Mission.
 documentation, reporting, and real-time
 activity planning. Public relations
                                                1.3.3.8.2 Earth-Based Support
 activities have been and always will be
 an integral part of crew activities. While          The overall goal of Earth-based support
 these activities absorb resources, the         operations is to provide a framework for
 most significant of which is time, they        planning, managing, and conducting
 also bring public and political support to     activities which achieve mission objectives.
 the program and provide some of the            Achieving this operational goal requires
 return on investment of the program.           successful accomplishment of the following
 Throughout all mission phases,                 functions.
 documentation of activities and feedback           •Safe and efficient operation of all
 on training effectiveness will be required          resources. This includes, but is not
 of all crews. This will be essential to             limited to, vehicles, support facilities,
 make effective use of the follow-on                 training facilities, scientific and systems
 crew’s training time and the program’s              data, and personnel knowledge and
 training hardware and facilities. Many of           experience bases.
 the mission-critical activities will be
 planned and rehearsed in great detail




                                             1-25
   •Provision of the facilities and an              managing and monitoring operations
    environment which allow users (such as          planning and execution while crew members
    scientists, payload specialists, and to an      will be assigned the actual responsibility for
    extent crew members) to conduct                 operations planning and execution. Crew
    activities that will enhance the mission        members will be told what tasks to do or
    objectives.                                     what objectives to accomplish, but not how to
                                                    do it. This has the benefit of involving system
   •Successful management and operation of
                                                    and payloads experts in the overall planning,
    the overall program and supporting
                                                    yet giving crews the flexibility to execute the
    organizations. This requires defining
                                                    tasks. The proposed method for the Reference
    roles and responsibilities and
                                                    Mission would take advantage of the unique
    establishing a path of authority. Program
                                                    perspective of crew members in a new
    and mission goals and objectives must
                                                    environment but would not restrict their
    be outlined so that management
                                                    activities because of the mission’s remote
    responsibilities are clear and direct.
                                                    nature. Additionally, it places the
    Confusing or conflicting objectives can
                                                    responsibility of mission success with the
    result in loss of resources, the most
                                                    crew, while the overall responsibility for
    important of which are time and money.
                                                    prioritizing activities in support of mission
    In addition, minimizing the number of
                                                    objectives resides with Earth-based support.
    layers of authority will help to prevent
    operational decision-making activities                After dividing functional responsibilities
    from being prolonged.                           between Earth-based support and crew, the
                                                    support may be structured to manage the
    The Reference Mission, while large and
                                                    appropriate functions. To accomplish mission
complex, has the added complication of being
                                                    objectives while maintaining the first
a program with mission phases which cannot
                                                    operational objective of safe and efficient
be supported with near real-time operations.
                                                    operation of all resources, Earth-based
Planetary surface operations pose unique
                                                    support can be organizationally separated
operational considerations on the
                                                    into systems operations and science
organization of ground support and facilities.
                                                    operations provided a well-defined interface
A move toward autonomy in vehicle
                                                    exists between the two. The systems
operations, failure recognition and resolution,
                                                    operations team would be responsible for
and mission planning is needed. And ground
                                                    conducting the safe and efficient operation of
support must be structured to support these
                                                    all resources, while the science operations
needs.
                                                    team would be responsible for conducting
    In general, due to the uniqueness of            activities which support scientific research.
planetary surface operations, Earth-based           Such an organizational structure would
support should be assigned the role of




                                                 1-26
dictate two separate operations teams with            the overall operations manager should reside
distinct priorities and responsibilities yet the      within systems operations. A science
same operational goal.                                operations manager, who heads the science
                                                      operations team, should organizationally be
     Systems operations are those tasks which
                                                      in support of the operations manager. Various
keep elements of the program in operational
                                                      levels of interfaces between systems engineers
condition and support productive utilization
                                                      and science team members must exist to
of program resources. Thus, the systems
                                                      maximize the amount of science and mission
operations team has responsibility for
                                                      objectives that can be accomplished.
conducting the safe and efficient operation of
all such resources. The systems operations
                                                      1.3.3.9 Mission and Systems Summary
team consists of representatives from each of
the primary systems (power, propulsion,                    To summarize, the major distinguishing
environmental, electrical, etc.) which are used       characteristics of the Reference Mission
throughout the various mission phases.                include:

     The science operations team’s sole                   •No extended LEO operations, assembly,
function is to recommend, organize, and aid                or fueling.
in conducting all activities which support                •No rendezvous in Mars orbit prior to
scientific research within the guidelines of the           landing.
mission objectives. The team will consist of
                                                          •Short crew transit times to and from
representatives from the various science
                                                           Mars (180 days or less) and long surface
disciplines (biology, medicine, astronomy,
                                                           stay-times (500 to 600 days) for the first
geology, atmospherics, etc.) which support
                                                           and all subsequent crews exploring
the science and mission objectives. Each
                                                           Mars.
scientific discipline will have an appropriate
support team of personnel from government,                •A heavy lift launch vehicle capable of
industry, and academia who have expertise in               transporting either crew or cargo direct
that field. The science operations team will act           to Mars, and capable of delivering in
as the decision-making body for all science                four launches all needed payload for the
activities—from determining which activities               first human mission and in three
have highest priority to handling and                      launches for each subsequent
disseminating scientific data.                             opportunity.
     Crew and vehicle safety are always of                •Exploitation of indigenous resources
primary concern. When those are ensured,                   from the beginning of the program, with
science activities become the highest priority.            important performance benefits and
To accommodate this hierarchy of priorities                reduction of mission risk.
within the operations management structure,




                                                   1-27
   •Availability of abort-to-Mars surface                  Two different approaches have been
    strategies, based on the robustness of the        proposed in the past. The first is comparable
    Mars surface capabilities and the cost of         to the Reference Mission by the long stay-time
    trajectory aborts.                                on the martian surface. The second involves a
                                                      short stay-time (<30 days on the martian
   •Common transit/surface habitat design.
                                                      surface) mission. Table 1-1 characterizes
   •Maintenance of a robust, safe                     principal discriminators of the two scenarios.
    environment for crews throughout their
                                                          In most studies, the short stay-time
    exploration.
                                                      missions have only been invoked for the first
   •Substantial autonomy of crew and                  mission; to develop long stay-time capability
    system operations from ground control.            would require close to total mission redesign
                                                      and much higher cost for a continued
1.4 Testing Principal Assumptions                     program.
and Choices
                                                            The second alternative is to land each
     A number of assumptions and choices              crew at a different location. This scenario
were made in constructing this Reference              would be permitted by the capability defined
Mission. For each assumption, this section            in the Reference Mission. The principal trade-
provides a top-level trade analysis, the              off is between the additional exploration that
rationale for the choice, and guidance to             might be accomplished by exploring three
further research and development which                distant sites versus the benefits of building up
could strengthen, improve, or change the              the capability to test settlement technologies
choice.                                               (such as closed life support systems) and the
                                                      reduced risk provided by accumulating
1.4.1 Robust Surface Infrastructure                   surface assets at one site. As the range of
     The principal payoff from Mars                   exploration provided in the single location
exploration lies in surface capability—stay-          Mars outpost is high (hundreds of
time, crew safety, exploration range, and             kilometers), the advantages of exploring
other factors that characterize the crew’s            several landing sites were considered of lower
performance environment. All dictate a                priority for the Reference Mission.
robust infrastructure. The choice to land all of
the payloads and crews at the same site on            1.4.2 Split Mission Strategy
four different opportunities was based on the             The split mission strategy takes
assumption that the marginal cost of                  advantage of the currently available
additional surface capability would be a cost-        capability to successfully fly and land
effective way to substantially increase the           automated spacecraft on another planet. Such
accomplishment of the program.                        capability can be used to deliver supplies and




                                                   1-28
     Table 1-1 Principal Discriminators of Short and Long Stay-Time Mission Scenarios

                             Long Stay-Times            Short Stay-Times            Key
                                                                            Discriminating Factor

        Surface                   High                        Low              Difference in time
    Accomplishment                                                                 on surface
         Surface                  Low                        High              Robust vs. limited
        risk/day                                                               surface capability
         Surface                  Low                         Low              Difference of time
    risk/cumulative                                                             vs. robustness
   Interplanetary risk            Low                        High

      Available to                 Yes                        No
      direct launch
      Available to                 Yes                      Difficult
      split mission
     Abort to Mars                 Yes                        No
       surface
  Availability of Mars             Yes                        No
  at every opportunity




equipment to support human missions                 increased number of transportation elements
without a crew being present. By using this         that must be used.
capability to deliver cargo not absolutely
                                                         The split mission strategy is contrasted
necessary for transporting crews between
                                                    with the “all-up” approach in which a single
Earth and Mars, the size of the transportation
                                                    vehicle, assembled in LEO, is capable of
system (both launch vehicles and upper
                                                    landing the required assets in a single mission
stages) for any one mission becomes smaller
                                                    to the surface. The principal trade-off is
and thus less expensive to develop and
                                                    between rendezvous and assembly in LEO
manufacture. In addition, these cargo
                                                    and rendezvous on the Mars surface. For the
missions can be sent on the absolute
                                                    all-up approach, significant capability is
minimum energy trajectories between Earth
                                                    required in LEO to assemble and fuel the
and Mars because there is no time-critical or
                                                    spacecraft. Previous designs (the 90-Day
life support critical element on board.
                                                    Study; see NASA, 1989) projected very high
However, the total number of launches
                                                    LEO infrastructure costs, which would have
increases under this strategy which offsets at
                                                    to be expended in the early phases of the
least part of the cost savings due to the
                                                    program. For chemically propelled spacecraft,




                                                 1-29
the logistics of transporting, storing, and           propulsion was selected because of its higher
loading propellants was excessive and                 propellant utilization efficiency and because
inevitably high in cost. Because the best             nuclear rockets were developed almost to
departure orbit at Earth is different for each        flight status in the 1960s. For any given
Mars opportunity, the space-based                     velocity change needed to depart from or be
infrastructure would have to be moved or              captured at a planet, a nuclear thermal rocket
reproduced, or additional propulsion                  uses approximately 50 percent less propellant
penalties be taken to modify the vehicle’s            than the theoretical best chemical engine. (The
departure orbit for every launch to Mars. The         Space Shuttle main engine is approaching this
elimination of this element in the architecture       theoretical upper limit.) The vast majority of
provides a significant cost reduction. It has         mass needed for a Mars mission is propellant,
been assumed here that the capability of very         and any option that reduces the need for
precise landing on Mars can be developed              propellant can lower the program life cycle
technically, and that all assets for each flight      cost by reducing the size and number of
can be integrated on Earth and simply joined          launch vehicles. Although such rockets might
on Mars. These capabilities can be                    be expensive to test on Earth (the magnitude
demonstrated on precursor robotic missions.           of which has not been determined) with
                                                      current environmental concerns, their use in
     While the savings resulting from a
                                                      space should not present an environmental
smaller transportation system may not alone
                                                      issue for they are dangerous only after firing
be sufficient to invoke the use of the split
                                                      the engines for a significant period of time.
mission strategy, the strategy does enhance
                                                      Higher performance engines would be better,
another assumed element of the Reference
                                                      but typically require a large source of
Mission—the use of in situ resource
                                                      electrical power (from either a nuclear source
utilization. By splitting the missions into
                                                      or very large solar arrays) which calls for
cargo and crew flights, infrastructure can be
                                                      additional development to reach the same
set up and operated before committing a crew
                                                      level of maturity as nuclear thermal rockets.
to a flight to Mars. Operating this
infrastructure for an extended period prior to
                                                      1.4.4 In Situ Resource Utilization
launching a crew also improves the
confidence of using the Mars surface as a safe             This technology (assumed to be currently
haven for the crew.                                   available) has been developed at breadboard
                                                      level and can be demonstrated on robotic
1.4.3 Nuclear Thermal Propulsion                      missions. It provides significant benefits to
                                                      the mission by reducing launch mass from
    High-performance propulsion is found to
                                                      Earth and increasing robustness of surface
be an enabling technology for a human
                                                      systems where caches of consumables and
exploration program. Nuclear thermal




                                                   1-30
surface vehicle fuels can be maintained. As          planning. Study team members were not
discussed in the previous section, any               unanimous in the choice of a common habitat
technology that can reduce the amount of             for space transit, for landing on the surface,
mass (and propellant is the largest single item      and for surface habitation. Some argued that,
on such a list) can do much to reduce life           due to the different requirements, a common
cycle cost. This is accomplished primarily by        design was not in the best interest of the
reducing the size and number of launches             mission. This is an area for further research.
from Earth and by providing a dual purpose
infrastructure that not only provides                1.4.6 Nuclear Surface Power
propellants for a return trip but also supports           With no known natural resources on
crew activities and helps reduce risk.               Mars that can be used to generate power, a
                                                     crew exploring Mars must rely on either
1.4.5 Common Habitat Design                          converting solar radiation or using a power
     A common habitat was chosen for the             source they have brought with them. With
Reference Mission primarily to save on cost          Mars lying, on average, 50 percent farther
over the life of the program. Because seven          from the Sun as Earth, only 44 percent as
separate habitats will be required to support        much solar radiation reaches that planet. This
the three crews sent to Mars, this item              means a crew must bring 2.25 times as much
becomes a likely candidate for a common              solar energy collecting and converting
approach rather than designing, testing, and         systems to generate the same amount of
building separate systems for the                    power as could be generated on Earth. Add to
interplanetary leg, the surface leg, and the         this a day-night cycle (which requires the
transition between the two. It may not be            addition of an energy charging and storage
feasible to use a common design for all of the       system) as well as martian dust storms (which
components that make up a habitat. However,          significantly diminish the amount of light
some of the significant elements—such as the         reaching the surface over extended periods of
pressure vessel (both primary and secondary          time) and the size of a solar power station on
structure), electrical distribution, hatches, and    Mars becomes both large in area and mass
docking mechanisms—lend themselves to a              and subject to interruption or diminished
common approach. Inasmuch as these major             effectiveness due to the dust storms. Of those
elements of the habitat can be defined and           sources of energy that can be brought with
their cost estimated, a common design for the        the crews, only a nuclear power source can
habitats has been adopted for the Reference          concentrate sufficient energy in a reasonable
Mission. A significant amount of work still          mass and volume. However, other concerns—
remains on definition and design of interior         environmental on Earth, operational on Mars,
details of the habitats which will become part       to name a few—are added to any mission that
of future efforts associated with Mars mission       considers the use of a nuclear power source.




                                                  1-31
     Given these kinds of considerations, a         to a small habitable space for an extended
choice was made to rely primarily on nuclear        duration can lead to cabin fever. Zero g has
power for systems operating on the martian          known debilitating effects on the human body
surface. Power provided by the solar arrays         that must be addressed. Radiation from a
used during the transit to Mars will be             constant background and the threat of solar
available for backup and emergency                  flares require that protection be adequate for
situations. However, the solar arrays will not      background sources and that a safe haven be
be sufficient to power the propellant               provided for extreme events. All of these
manufacturing plants that are also a key            threats have engineering solutions that can
feature of this mission architecture.               make the extended stay in interplanetary
                                                    space a viable prospect for the crew. But the
1.4.7 Abort to the Surface                          solutions typically require increases in size,
      Mars missions differ from Space Shuttle       mass, and complexity of the vehicle and the
and lunar missions in that once the crew is         transportation elements that are used to move
committed to launch, orbit mechanics force          it from planet to planet.
the crew to remain away from Earth for                   An alternate strategy, and one that was
approximately 2 to 3 years. This imposes on         selected for this Reference Mission, is to take
all of the systems the need for a higher degree     advantage of the martian surface as a safe
of reliability and maintainability or for           haven where open space, gravity, and
multiple independent means of providing             radiation protection are naturally available.
life-critical functions (collectively referred to   This strategy, referred to as “abort to the
as robustness).                                     surface,” builds on these naturally available
     There has been a tendency to view the          resources and breaks from the previous
martian surface as the most hostile location        viewpoint of Mars as the most hostile
for a crew during a Mars mission. However,          environment encountered on the mission. The
of the three environments that a crew will          reliability and maintainability of the systems
encounter—Earth, interplanetary space, and          needed to keep the crew alive on the surface
the martian surface—interplanetary space            is no greater than that imposed on space-
offers the highest potential for debilitating       based systems. In fact, the buildup of an
effects on the crew. Practicality dictates a        infrastructure at a single site on the surface
relatively small habitable space for the crew       enhances the safe haven character of the
during transit. To do otherwise causes a            martian surface. This approach places a
corresponding increase in the size and cost of      greater burden on the entry, landing, and
the systems, primarily launch vehicles and          martian-based launch systems. However, the
transfer stages, associated with the                trade-off of making these systems a viable
transportation system. But to confine the crew      part of the abort strategy through increased




                                                 1-32
redundancy and reliability versus the              1.5 Conclusions and Recommendations
enhancements needed to sustain a crew                  Based on both mission and programmatic
through a 2- to 3-year interplanetary abort        points of view, a number of conclusions and
have tended to favor the abort to the surface      recommendations are made in the following
strategy. The enhancements that will be made       areas: mission and systems, technology
to various systems to allow an abort to the        development, environmental protection,
surface also work to the advantage of the          program cost, international participation, and
overall mission by improving the chances of        program management and organization.
the crews to successfully reach the surface
and perform their exploration activities.          1.5.1 Mission and Systems

1.4.8 Design for the Most Difficult                Conclusions
Opportunity
                                                        A feasible mission scenario and suite of
     The design of the Reference Mission was       vehicles and other systems have been
based on the premise that a series of closely      integrated to meet the objectives initially set
spaced missions would result in costs              out for this study. In addition, the Reference
significantly lower than the sum of an             Mission addresses a long-standing issue
equivalent number of single missions. To           regarding extended-duration flights and crew
achieve this cost savings requires that a single   safety by adopting a view that the surface of
set of systems be designed which can               Mars is a safe haven and that equipment and
accomplish the mission under the most              procedures should be developed with this in
difficult circumstances of any single              mind.
opportunity. The most significant of these
                                                        The Reference Mission includes
variations results from trajectory differences
                                                   technology assumptions which require
that occur during sequential mission
                                                   further development and which contribute to
opportunities. As a result, some systems may
                                                   an estimated development cost that is higher
have excess capability during some years.
                                                   than can currently be supported. Both
However, this allows the advantage of either
                                                   technology and cost must be addressed and
launching more payload mass in those years
                                                   the alternative missions and systems could
with more favorable trajectories or reducing
                                                   result in a better program for human
mission durations by flying shorter trajectory
                                                   exploration of Mars. However, the mission
legs, but at the expense of greater fuel
                                                   and systems described here substantially
consumption. For example, in the 2009
                                                   reduce the program cost and at the same time
opportunity, transit times for piloted missions
                                                   present a more robust approach than in
are approximately 6 months; using the same
                                                   previous studies of this subject.
systems in the 2018 opportunity reduces
transit times to just 4 months.




                                                1-33
Recommendations                                     the assumed technologies can be started now
                                                    and, to a certain degree, may be required for
   •Use this study as an informal baseline
                                                    such a program to progress. In the current
    against which future alternatives should
                                                    political environment, investment in
    be compared.
                                                    technology is seen as a means of improving
   •Continue investigating alternative              the general quality of life for people on Earth,
    mission scenarios and systems to                and multiple use of technologies is
    improve this Reference Mission, or              emphasized to obtain the best return on the
    suggest a better alternative.                   resources invested in their development. The
                                                    following is a list of twelve technologies
1.5.2 Technology Development                        which are important to space transportation,
                                                    humans living in space or on a planetary
Conclusions
                                                    surface, or the utilization of extraterrestrial
     The Reference Mission was developed            resources.
assuming advances in certain technology
                                                    Resource Utilization
areas thought to be necessary to send people
to Mars for a reasonable investment in time             •Extraterrestrial mining techniques
and resources. The Reference Mission is not             •Resource extraction process and
intended to lock in these assumed                        chemistry
technologies. The purpose of identifying
technologies at this time is to characterize            •Material preparation and handling in
those areas that can either significantly reduce         reduced gravity
the required mass or cost of the program or             •Extraterrestrial manufacturing
significantly reduce its risks (for example, in
                                                    Transportation and Propulsion
the area of fire safety). Alternative means of
satisfying these requirements may be                    •Advanced chemical systems that provide
identified and, if promising, should be                  high performance and are compatible
supported. The alternatives could be the                 with the resources available on the Moon
result of a dual use development, spin off               and Mars
from other programs, or a fortunate “spill              •Nuclear propulsion to enable short trip
over” from some unexpected area.                         times to Mars
     At this particular stage in developing             •Aerocapture/aerobraking at the Earth
human exploration missions to Mars, it is                and at Mars for propulsive efficiency
difficult to do more than speculate about spin           and reusable systems
off and spill over technologies that could
result from or be useful to this endeavor.              •Lightweight/advanced structures
However, identifying dual uses for some of              • Reduced-g combustors




                                                 1-34
Cryogenic Fluid Management                             •Health care at remote locations

   •Long-term (years) storage in space                 •Radiation protection in transit and on
                                                        surface
   •Lightweight and high efficiency
    cryogenic liquefaction                         Power Generation and Storage

   •Zero g and microgravity acquisition,               •Long life, lighter weight, and less costly
    transfer, and gauging                               regenerative fuel cells

EVA Systems                                            •Surface nuclear power of the order of
                                                        100kw
   •Lightweight, reserviceable, and
    maintainable suit and PLSS                         •High efficiency solar arrays

   •Durable, lightweight, high mobility suits      Teleoperations/Telerobotics
    and gloves
                                                       •Remote operations with long time delays
Regenerative Life Support Systems
                                                       •Fine control manipulators to support
   •Contamination and particle control                  wide range of surface activities

   •Loop closure                                       •Telepresence sensors and displays

   •Introduction of locally produced               Planetary Rovers
    consumables
                                                       •Long range (hundreds of km) rovers
   •Food production
                                                       •Motor lubricants (long-term use)
   •Trash and waste collection and
                                                       •Dust control
    processing
                                                       •High efficiency lightweight power
   •High efficiency and lighter weight active
                                                        generation and storage
    thermal control systems
                                                   Advanced Operations
Surface Habitation and Construction
                                                       •Automated systems control
   •Lightweight structures
                                                       •Systems management and scheduling
   •Seal materials and mechanisms
                                                       •Simulations and training at remote
   •Construction techniques using local
                                                        locations
    materials
                                                   Fire Safety
Human Health and Performance
                                                       •Fire prevention
   •Zero-g adaptation and countermeasures
                                                       •Fire detection
   •Human factors
                                                       •Fire suppression




                                                1-35
      Some of these technologies (such as           Recommendations
nuclear thermal propulsion, Mars surface
                                                       •Establish a Mars Program Office
space suits, and in situ resource extraction), at
                                                        (discussed further under International
the system level, are unique to the Reference
                                                        Participation and Management and
Mission or to human space exploration in
                                                        Organization) early in the process (now,
general. It is likely that NASA or cooperating
                                                        probably) at a low level to lay the
international partners will have to bear the
                                                        foundation for technology requirements
burden for support of this research and
                                                        to be undertaken by NASA or other
development. The Reference Mission, as it is
                                                        government agencies with similar
described here, will fail if these systems are
                                                        requirements. Formal organizational
not advanced to a usable state. Other areas,
                                                        agreements should exist between these
such as medical countermeasures, closed-loop
                                                        offices if the technology development is
life support systems, autonomous operations
                                                        not formally assigned to the Program
systems, surface power systems, and surface
                                                        Office.
mobility, may be of more general interest and
may provide opportunities for government               •Rank technology investments according
and industry to develop shared programs. In             to their return to the Program, as either
still other areas, such as long-lived electronics       cost or risk reductions.
and materials research, where the underlying           •Prior to initiation of the Reference
research will probably be done by industry to           Mission, take critical technologies to a
address general problems of technology                  demonstration stage. NASA should
development, NASA or the international                  ensure that experimental work in
partners should focus on infusing that                  support of the Reference Mission is
technology. The exchange of information                 incorporated into the International Space
should be continuous between NASA and the               Station program at the earliest
commercial sector particularly concerning the           reasonable time.
needs of future missions, so that industry can
                                                       •Create a database (in the Program Office)
incorporate research into its privately funded
                                                        of available technologies that can be
programs where it is justified. In all areas,
                                                        used in design studies, and track the
subsystem or component technologies may be
                                                        progress of these technologies. The
developed by industry to meet commercial
                                                        database should include domestic and
requirements, and the Mars Program will
                                                        international capabilities.
need to have processes that allow the element
designers to use the most advanced
capabilities available.




                                                1-36
1.5.3 Environmental Protection                     extraterrestrial life. NASA itself has
                                                   contributed to this perception by supporting
Conclusions                                        legitimate scientific research in this area.
     Fundamental principles of planetary           Because it is not possible to prove that Mars is
environmental protection have been                 completely devoid of life, there is the
developed since the first planetary                potential for misinterpretation or
exploration missions began in the 1960s. With      misunderstanding when martian materials
respect to Mars, the principles adopted by the     and human crews are brought back to Earth.
international scientific community are             For example, an ailment (regardless of the
straightforward: Mars should be protected          source) among a returning human crew could
from biological contamination from Earth that      give rise to speculation that the crew has
would interfere with or confound the search        some unknown Mars “bug” and is about to
for natural martian organisms, and Earth           expose the rest of the human population to its
must be protected from contamination by            effects.
martian organisms harmful to the terrestrial
biosphere. The United States is signatory to a     Recommendations
treaty under the auspices of the Committee on          •Develop adequate and acceptable
Space Research (COSPAR) which provides the              human quarantine and sample handling
basic framework for its Planetary Protection            protocols early in a Mars exploration
policy and program (COSPAR 1964 and                     program. The protocols must address
United Nations 1967).                                   not only the purely scientific concerns to
     Planetary protection will be an ongoing            maintain the pristine nature of samples
discussion at an international level. The               but also the societal concerns, real or
policy principles stated here and those that            imagined, that are likely to arise.
evolve in the future must be carried along as          •Include the protocols as program-level
significant requirements for mission planning           requirements for mission and system
and system design.                                      development.
     A further political concern is                    •Publicly release for review (by
unfortunately tied to the planet Mars. A                independent authoritative bodies) the
significant portion of the popular press and            principles and practices of
the entertainment industry is devoted to                contamination control in effect for Mars
speculation about life, intelligent and                 missions.
otherwise, that may exist beyond the planet
Earth. Percival Lowell, H. G. Wells, Orsen
Wells, and others have placed Mars in the
forefront of possible locations for




                                                1-37
1.5.4 Program Cost                                  managing and running this type of program,
                                                    estimating the cost for this phase of the
Conclusions                                         program was deferred until an approach is
     The cost of the Reference Mission was          better defined. Similarly, the issue of
estimated using standard models. Input for          management reserve was not addressed until
these models was derived from previous              a better understanding of the management
experience and information provided by              approach and controls has been developed.
members of the Study Team. Included in the               When compared to earlier estimates of a
estimate were the development and                   similar scale (NASA, 1989), the cost for the
production costs for all of the systems needed      Reference Mission is approximately an order
to support three human crews as they explore        of magnitude lower. A distribution of these
Mars. In addition, ground rules and                 costs is shown in Figure 1-6. It can be seen
assumptions were adopted that incorporated          from this figure that the major cost drivers are
some new management paradigms, as                   those associated with the transportation
discussed later in the Program Management           elements: the ETO launch vehicles, the TMI
and Organization section. The management            stages, and the Earth-return systems.
costs captured program level management,
integration, and a Level II function. Typical           The Mars Study Team recognizes that,
pre-production costs, such as Phase A and B         even with the significant reduction in the
studies, were also included.                        program cost achieved by this Team, the
                                                    Reference Mission is probably still too
     Not included in the cost estimate were         expensive in today’s fiscal environment. More
selected hardware elements, operations, and         work to further reduce these costs is needed.
management reserve. Hardware costs not
estimated include science equipment and EVA         Recommendation
systems, for which data were not available at
                                                        •Seek alternative solutions or effective
the time estimates were prepared; however,
                                                         approaches to cost reduction in each of
these are not expected to add significantly to
                                                         the areas cited above. The efforts may
the total. No robotic precursor missions are
                                                         require revolutionary changes
included in the cost estimate although their
                                                         throughout NASA, the aerospace
need is acknowledged as part of the overall
                                                         industry, the United States, and the
approach to the Reference Mission.
                                                         world.
Operations costs have historically been as
high as 20 percent of the development cost.
However, due to the extended operational
period of the Reference Mission and the
recognized need for new approaches to




                                                 1-38
  1.5.5 International Participation                    Study (IAA 1993) describes in more detail the
                                                       rationale and possible organizational
  Conclusions                                          approaches to an international Mars
       The human exploration of Mars should            exploration program.
  be inherently an international, indeed a                 The Reference Mission is rich in
  global, undertaking. Just as the U. S. landing       possibilities for multinational or even global
  on the Moon excited and amazed the world at          participation. Many major elements, systems,
  U. S. technological skills and organizational        and subsystems will have to be developed
  accomplishment, the human exploration of             and produced, precursor missions must be
  Mars can excite and amaze the people of the          developed and flown, and operations
  world with a commonly sought level of                capabilities must be developed; and the
  technological prowess and organizational             mission operations can be designed to be
  capability. The International Academy of             undertaken on an international basis. Three
  Astronautics’ International Mars Exploration         types of international participants may




                                                      Phase A & B     Cost of
                                    Surface Systems       2%         Facilities
                         Habitats         8%                            8%        Mgmt, Adv. Devel.,
                          12%                                                     Program Support
                                                                                        12%
Mars to Earth
  Vehicle
    11%




           Descent Vehicle
                6%                                                                Earth to Orbit Vehicle
                                             Earth to Mars Vehicle                         26%
                                                      18%




                       Figure 1-6 Distribution of Reference Mission costs.




                                                  1-39
contribute based on the ability to provide               The ranges of opportunities and interests
resources and participate technically in the        are large and must be well understood before
program.                                            an international program is constructed. The
                                                    discussions may be iterative with respect to
   •Countries with limited resources and
                                                    initial design in order to optimize the
    technical base. Their participation could
                                                    collective returns to all nations in the
    be linked to technology transfer to their
                                                    program, and it is not unlikely that 10 years
    countries, which could improve the level
                                                    would be needed to formulate the principles
    of technical education and take
                                                    and agreements needed to undertake the
    advantage of technical internship in the
                                                    program. It is important that these
    endeavor. These relationships might be
                                                    discussions lead to a set of basic principles
    similar to the participation of Cuba or
                                                    under which the program will be designed
    Viet Nam in the Russian space program.
                                                    and implemented.
   •Countries with greater amounts of
    resources and technical base. Their             Recommendations
    participation would reflect technical
                                                        •Make the human exploration of Mars
    interest in limited areas targeted for
                                                         program international from its inception,
    technical or industrial growth in their
                                                         and take as a basic principle that all
    economies. The participation of Canada
                                                         partners will have a voice in all phases of
    in the International Space Station
                                                         the program in proportion to the
    program is an example.
                                                         resources contributed to the program.
   •Countries with substantial resources and
                                                        •Do not exclude any nation even though
    technical base. Their participation would
                                                         their participation might be small in
    reflect a desire to demonstrate world
                                                         economic terms.
    leadership, retain broad technological
    skills, and promote aerospace industry.             •Create a forum in the near future for
    The major contributors to the                        discussion of the elements of an
    International Space Station program fall             international program to lay the basis for
    into this category.                                  international participation.

     All participating countries should expect          •Create an International Program Office
to gain in proportion to their investment in             (sensitive to political and technical
the enterprise; richer countries might view              issues) to lead the design effort. Just as it
the program as an opportunity to help poorer             is important to have all of the design
countries improve their standards of living              requirements understood prior to
through stimulation and transfer of modern               development, all of the political
technology and technological training.                   requirements must also be understood
                                                         early in the process.




                                                 1-40
1.5.6 Program Management and                   Space Station Freedom programs. To manage a
Organization                                   Mars exploration program to a lowest possible
                                               cost, several recommendations are proposed.
Conclusions

     Organization and management is one of Recommendations
the principal determinants of program cost.     •In subsequent studies of the Reference
This is a rather wide-ranging topic, which is    Mission, investigate the design of the
not entirely divisible from the technical        organization and management system.
content of the program, because it includes
                                                •Reach a formal philosophical and budgetary
program level decision-making that is
                                                 agreement (between all parties) as to the
intimately tied to the system engineering
                                                 objectives and requirements imposed on the
decision-making process. The relationship
                                                 mission before development is initiated, and
between program cost and program culture
                                                 agree to fund the project to its completion. In
(Figure 1-7) is an indication of that
                                                 the U. S., this would include multiyear
relationship.
                                                 budgetary authority. This should be
     The relationship between cost and           accompanied by a management process that
management style and organizational culture      would protect against program overruns
is rather well-known in a general manner,        through appropriate incentives.
through a large number of “lessons learned”
                                                •Prepare a risk management plan. The human
analyses made postprogram. The list of key
                                                 exploration of Mars will have risks that are
elements of lower-cost programs (shown in
                                                 quite different from any space mission
Table 1-2) have been pointed out in a series of
                                                 previously undertaken. Two general types of
analyses, but have not commonly been
applied at the critical stage of developing
program organization and management
approaches. The organizational and                Relative Cost                           Spacecraft
management style has been determined
rather late in the program, generally because
                                                                                      D ifficulty




the program content and final design was                                          Aircraft
typically delayed through redesign, changing
                                                                                              +
requirements, and funding irregularities. For
                                                                       Ships
                                                                Trucks               +
example, the International Space Station
program went through several redesigns, and
                                                                        Specifications
some of the hardware was actually in
production when the program architecture
was modified to integrate the Russian and         Figure 1-7 Relationship between
                                                    program cost and program culture.




                                               1-41
 risk seem to be most critical: risks to the          •Establish a clear demarcation between
 safety of the crew and accomplishment                 the design phase and the development
 of the mission (primarily technical risks)            and production phase of the project, and
 and risks of not meeting cost and                     do not allow development to begin
 schedule objectives. Maintaining launch               before the design phase is ended. Prove
 schedule is important due to the                      all technologies prior to initiating
 dependency on several successful                      production of program elements. Do not
 launches for mission success and the                  change requirements after they are
 high cost of missed launch windows.                   established unless they can be relaxed.
 Failure to maintain the launch schedule               Ensure that a system to document the
 implies a 2-year program delay at a                   relationship and interaction of all
 potentially high program cost.                        requirements exists and is available for

                    Table 1-2 Key Elements of Lower-Cost Programs

•Use government only to define requirements.

•Keep requirements fixed: once requirements are stated, only relax them; never add new
 ones.

•Place product responsibility in a competitive private sector.

•Specify end results (performance) of products, not how to achieve the results.

•Minimize government involvement (small program offices).

•Ensure that all technologies are proven prior to the end of competition.

•Use the private sector reporting system: reduce or eliminate specific government
 reports.

•Don’t start a program until cost estimates and budget availability match.

•Minimize or eliminate government-imposed changes.

•Reduce development time: any program development can be accomplished in 3 to 4
 years once uncertainties are resolved.

•Force people off of development programs when development is complete.

•Incentivize the contractor to keep costs low (as opposed to CPAF, CPFF of NASA).

•Use geographic proximity of contractor organizations when possible.

•Use the major prime contractor as the integrating contrator.




                                               1-42
 use prior to the beginning of production.        multinational activity). The Program
 The Reference Mission requires a                 Office will be in place to manage
 number of elements, many of which are            technical requirements, provide
 technically alike but serve somewhat             decisions that require consultation and
 different functions over the duration of         trade-offs (both technical and political),
 the program. For example, the surface            and manage development contracts. The
 habitat may be the basis for the transit         Program Office should establish
 habitat; each of the habitats delivered to       functional requirements for the design
 the surface will have a different                phase and conduct a competitive
 complement of equipment and supplies,            procurement for the design phase, with
 according to its position in the delivery        the selection of a prime contractor.
 sequence. The elements will be
                                                 •Prepare a specific construction sequence
 developed over a period of several years,
                                                  and plan to accompany each production
 and there will be a temptation to
                                                  element of the program. Once
 improve the equipment and supply
                                                  committed to development, the
 manifest. To maintain cost control for the
                                                  development time should be strictly
 program, requirements must be fixed at
                                                  limited if costs are to be contained. This
 the time of initial development.
                                                  will be difficult in the Mars program,
•Provide clear requirements for the               where it probably will be effective to
 design phase, describing the                     produce common elements sequentially
 performance expected and a clear set of          rather than all at one time, although
 criteria for completeness of design as a         there may be a high enough production
 function of resources expended in                rate that costs will drop as experience is
 design. Use a significant design cost            gained. A new approach will be needed
 margin to manage the design resources.           to ensure that the development time for
 Terminate the project if a satisfactory          each individual element is strictly
 design cannot be accomplished within             limited.
 the available resources. Further, select
                                                 •Make the two levels of integration,
 the successful prime contractor as
                                                  program and launch package, the
 integration contractor for the
                                                  responsibility of a single organization—a
 development phase, and exclude the
                                                  prime contractor to the Program Office.
 prime contractor as a development
                                                  The program will require two levels of
 contractor. The design phase of the
                                                  integration, similar to that of the
 program is critical to successful cost
                                                  International Space Station program: a
 control, and should be based on a set of
                                                  program level which ensures that overall
 functional requirements established by
                                                  mission requirements are met at each
 the Program Office (which may well be a




                                          1-43
 stage of the mission, that is, for the       1.6 References
 packages assembled for each launch
                                                  Borowski, S. K., R. R. Corban, M. L.
 opportunity; and a launch package level
                                                  McGuire, and E. G. Beke, “Nuclear
 integration, in which all required
                                                  Thermal Rocket/Vehicle Design Options
 elements of each launch to Mars are
                                                  for Future NASA Missions to the Moon
 packaged and their performance
                                                  and Mars,” NASA Technical
 ensured.
                                                  Memorandum 107071, 1993.
•Include operational considerations in the
                                                  Committee on Space Research (COSPAR),
 design and development phases of the
                                                  “Statement on the Potentially Harmful
 program, and use life cycle costs for
                                                  Effects of Space Experiments Concerning
 program design and development
                                                  the Contamination of Planets,” COSPAR
 decisions. The operational phase of the
                                                  Information Bulletin No. 20, pp. 25-26,
 Mars program must be represented in
                                                  Geneva, Switzerland, 1964.
 the design and development phase. This
 will require a concurrent engineering            Duke, M. and N. Budden, “Results,
 approach which considers the                     Proceedings and Analysis of the Mars
 operational costs as well as the                 Exploration Workshop,” JSC-26001,
 development costs in a life cycle cost           NASA, Johnson Space Center, Houston,
 approach to the program. If the                  Texas, August 1992.
 approaches identified above to separate          International Academy of Astronautics
 design and development and to obtain             (IAA), “International Exploration of Mars:
 prior commitments for funding for the            A Mission Whose Time Has Come,” Acta
 entire program are successful, there             Astronautica, Vol. 31, pp. 1-101, New York,
 should be less of a problem maintaining          USA, October 1993.
 the life cycle cost approach to
                                                  United Nations, “Treaty on Principles
 minimizing program costs.
                                                  Governing the Activities of States in the
•Put into place positive incentives to            Exploration and Use of Outer Space,
 maintain program costs within approved           Including the Moon and Other Celestial
 levels at all stages of design,                  Bodies,” U.N Document A/RES/2222/
 development, production, and                     (XXI), TIAS #6347, New York, USA,
 operations, and to reduce costs of each          January 1967.
 phase of the program.
                                                  NASA, "Report of the 90-Day Study on
                                                  Human Exploration of the Moon and
                                                  Mars," NASA Headquarters, Washington,
                                                  DC, November 1989.




                                           1-44
Synthesis Group, “America at the
Threshold: Report of the Synthesis Group
on America’s Space Exploration
Initiative,” U.S. Government Printing
Office, Washington DC, May 1991.

Zubrin, Robert, “Mars Direct: A Simple,
Robust, and Cost Effective Architecture
for the Space Exploration Initiative,”29th
Aerospace Sciences Meeting, AIAA 91-
0326, held in Reno, Nevada, January 7-10,
1991.




                                             1-45
     2. Science and
Exploration Rationale




       2-1
2-2
2.1 Introduction                                        autonomous manner with only general
                                                        support from Earth. From the rationale
      Mars is an intriguing and exciting planet
                                                        generated by the Mars Study Team for
with many adventures and discoveries
                                                        sending human crews to Mars, goals and
awaiting planetary explorers. But before we
                                                        objectives are derived to provide guidance for
go, we must provide the tools the explorers
                                                        the exploration crews during their extended
will use, anticipate as much as possible the
                                                        stay on the martian surface. This section will
situations they will encounter, and prepare
                                                        discuss that Study Team rationale.
them for the unexpected. For the first time in
a space exploration mission, it will be up to
the crew and supporting personnel on Earth
                                                        2.2 The “Why Mars” Workshop
to create specific activities as the mission                  In August 1992, a workshop was held at
progresses and discoveries are made. The                the Lunar and Planetary Institute in Houston,
length of time spent on the martian surface, as         Texas, to address the “whys” of Mars
presented in the Reference Mission, will                exploration. This workshop brought together
preclude development of the detailed, highly            a group of experts (listed in Table 2-1) familiar
choreographed mission plans typical of                  with the key issues and past efforts associated
today’s space missions. The crew will have              with piloted Mars missions in an effort to
general goals and objectives to meet within             provide the top-level rationale and
their other time constraints (for example,              requirements from which the Mars
exercise for health maintenance, regular                exploration program could be built (Duke
medical checks, routine systems maintenance,            and Budden, 1992). This group was asked to
etc.). Based on knowledge gained from                   generate three key products: a Mars mission
precursor robotic missions, the crew will land          rationale, Mars exploration objectives, and a
in an area that has a high probability of               list of key issues and constraints, to be used
satisfying the pre-set mission objectives.              by the Mars Study Team (members listed in
However, due to the extended                            Table 2-2) to define the technical details of a
communications time lag between Earth and               Reference Mission. The workshop attendees
Mars, the crews and their systems must be               identified six major elements of the rationale
able to accomplish objectives in a highly               for a Mars exploration program.




                                                  2-3
                 Table 2-1 Mars Exploration Consultant Team

Dr. David Black                           Dr. George Morgenthaler
Director                                  University of Colorado
Lunar and Planetary Institute             Boulder, Colorado
Houston, Texas
                                          Dr. Robert Moser
Dr. Michael Carr                          Chama, New Mexico
U.S. Geological Survey
Menlo Park, California                    Dr. Bruce Murray
                                          California Institute of Technology
Dr. Ron Greeley                           Pasadena, California
Dept. of Geology
Arizona State University                  Mr. John Niehoff
Tempe, Arizona                            Science Applications International
                                          Corporation
Dr. Noel Hinners                          Schaumburg, Illinois
Lockheed Martin
Denver, Colorado                          Dr. Carl Sagan
                                          Center for Radiophysics and Space
Dr. Joseph Kerwin                         Research
Skylab Astronaut                          Cornell University
Lockheed Martin                           Ithica, New York
Houston, Texas
                                          Dr. Harrison Schmitt
Mr. Gentry Lee                            Apollo 17 Astronaut
Frisco, Texas                             Albuquerque, New Mexico

Dr. Roger Malina                          Dr. Steven Squyers
Center for EUV Astrophysics               Cornell University
University of California                  Ithica, New York
Berkeley, California
                                          Mr. Gordon Woodcock
Dr. Christopher McKay                     Boeing Defense and Space Group
NASA Ames Research Center                 Huntsville, Alabama
Moffett Field, California




                                    2-4
                              Table 2-2 Mars Study Team

   Dr. Geoff Briggs                                 Mr. Kent Joosten
   NASA Ames Research Center                        NASA Johnson Space Center
   Moffett Field, California                        Houston, Texas

   Ms. Jeri Brown                                   Mr. David Kaplan
   NASA Johnson Space Center                        NASA Johnson Space Center
   Houston, Texas                                   Houston, Texas

   Ms. Nancy Ann Budden                             Dr. Paul Keaton
   NASA Johnson Space Center                        Los Alamos National Laboratory
   Houston, Texas                                   Los Alamos, New Mexico

   Ms. Beth Caplan                                  Mr. Darrell Kendrick
   NASA Johnson Space Center                        NASA Johnson Space Center
   Houston, Texas                                   Houston, Texas

   Mr. John Connolly                                Ms. Barbara Pearson
   NASA Johnson Space Center                        NASA Johnson Space Center
   Houston, Texas                                   Houston, Texas

   Dr. Michael Duke                                 Mr. Barney Roberts
   NASA Johnson Space Center                        NASA Johnson Space Center
   Houston, Texas                                   Houston, Texas

   Dr. Steve Hawley                                 Mr. Ed Svrcek
   NASA Johnson Space Center                        NASA Johnson Space Center
   Houston, Texas                                   Houston, Texas

   Mr. William Huber                                Mr. David Weaver
   NASA Marshall Space Flight Center                NASA Johnson Space Center
   Huntsville, Alabama                              Houston, Texas



•Human Evolution – Mars is the most                     permanent human presence beyond
 accessible planetary body beyond the                   Earth. However, it is not an objective of
 Earth-Moon system where sustained                      the Reference Mission to settle Mars but
 human presence is believed to be                       to establish the feasibility of, and the
 possible. The technical objectives of Mars             technological basis for, human
 exploration should be to understand                    settlement of that planet.
 what would be required to sustain a




                                              2-5
•Comparative Planetology – The scientific               The workshop attendees then translated
 objectives of Mars exploration should be           these elements into two specific mission
 to understand the planet and its history           objectives. For the first human exploration of
 to better understand Earth.                        Mars:
•International Cooperation – The political                •A better understanding is needed of
 environment at the end of the Cold War                    Mars—the planet, its history, and its
 may be conducive to a concerted                           current state. And to answer, as best as
 international effort that is appropriate,                 possible, the scientific questions that
 and may be required, for a sustained                      exist at the time of the exploration, a
 program.                                                  better understanding of the evolution of
•Technology Advancement – The human                        Mars’ climate and the search for past life
 exploration of Mars currently lies at the                 are pressing issues.
 ragged edge of achievability. Some of the                •It is important to demonstrate that Mars
 technology required to achieve this                       is a suitable location for longer term
 mission is either available or on the                     human exploration and settlement.
 horizon. Other technologies will be
                                                         The following sections discuss the details
 pulled into being by the needs of this
                                                    of the science and exploration rationale as
 mission. The new technologies or the
                                                    applied to the Reference Mission.
 new uses of existing technologies will
                                                    Implementation details are in Section 3.
 not only benefit humans exploring Mars
 but will also enhance the lives of people
                                                    2.3      Science Rationale
 on Earth.
                                                         Mars is an intriguing planet in part for
•Inspiration – The goals of Mars
                                                    what it can tell us about the origin and history
 exploration are bold, are grand, and
                                                    of planets and of life. Visible to the ancients
 stretch the imagination. Such goals will
                                                    and distinctly reddish in the night sky, it has
 challenge the collective skill of the
                                                    always been an attractive subject for
 populace mobilized to accomplish this
                                                    imaginative science fiction. As the capability
 feat, will motivate our youth, will drive
                                                    for space exploration grew in the 1960s, it
 technical education goals, and will excite
                                                    became clear that, unlike Earth, Mars is not a
 the people and nations of the world.
                                                    planet teeming with life and has a harsh
•Investment – In comparison with other              environment. The images of Mariner 4
 classes of societal expenditures, the cost         showed a Moon-like terrain dominated by
 of a Mars exploration program is                   large impact craters (Figure 2-1).
 modest.




                                              2-6
Figure 2-1 Orbital image of Mars.




               2-7
     This terrain now is believed to represent          exhibits later volcanic and tectonic features.
ancient crust, similar to the Moon’s, formed in         Large volcanoes of relatively recent activity
an initial period of planetary differentiation.         (Figure 2-2) and large crustal rifts due to
Mariner 9 showed for the first time that Mars           tensional forces (Figure 2-3) demonstrate the
was not totally Moon-like, but actually                 working of internal forces.




                     Figure 2-2 Olympus Mons, the largest volcano
                                   in the solar system.



                                                  2-8
Figure 2-3 Across the middle is Valles Marineris, a huge canyon
                  as long as the United States.



                              2-9
     The absolute time scale is not accurately          •What are the implications of such
calibrated; however, by analogy with the                 changes for environmental changes on
Moon, the initial crustal formation may have             Earth?
occurred between 4 billion and 4.5 billion
                                                        •Were the conditions on early Mars
years ago, and the apparent freshness of the
                                                         enough like those of early Earth to guide
large martian volcanoes suggests their
                                                         a search for past life?
formation within the last billion years.
                                                         These questions are part of the Mars
     Many scientific questions exist regarding
                                                    scientific exploration addressed by the
Mars and its history and will continue to exist
                                                    Reference Mission, and these questions can be
long after the first human missions to the
                                                    answered only by understanding the
planet have been achieved. Two key areas of
                                                    geological attributes of the planet: the types of
scientific interest are the evolution of martian
                                                    rocks present, the absolute and relative ages
climate and the possible existence of past life.
                                                    of the rocks, the distribution of subsurface
     Mars’ atmosphere now consists largely of       water, the history of volcanic activity, the
carbon dioxide with a typical surface pressure      distribution of life-forming elements and
of about 0.01 of Earth’s atmosphere                 compounds, and other geologic features.
(comparable to Earth’s atmospheric pressure         These attributes all have to be understood in
at an altitude of approximately 30,000 meters       the context of what we know about the Earth,
or 100,000 feet) and surface temperatures that      the Moon, and other bodies of our solar
may reach 25°C (77°F) at the equator in             system.
midsummer, but are generally much colder.
                                                         Addressing the question of whether life
At these pressures and temperatures, water
                                                    ever arose on Mars can provide a
cannot exist in liquid form on the surface.
                                                    fundamental framework for an exploration
However, Mariner 9 and the subsequent
                                                    strategy because, in principle, the search for
Viking missions observed features which
                                                    past life includes investigating the geological
indicate that liquid water has been present on
                                                    and atmospheric evolution of the planet. It is
Mars in past epochs (Figure 2-4).
                                                    generally understood that the search for
    Evidence for the past existence of              evidence of past life cannot be conducted
running water and standing water has been           simply by a hit-and-miss landing-and-looking
noted, and the interpretation is that the           strategy, but must be undertaken in a step-
atmosphere of Mars was thicker and                  wise manner in which geological provenances
warmer—perhaps much like Earth’s early              that might be suitable are characterized,
atmosphere before the appearance of oxygen.         located, and studied (Exobiology Program
Three questions arise:                              Office, 1995). The characteristics of suitable
                                                    exploration sites are highly correlated with
   •What was the reason for the change of
                                                    the search for past or present water on the
    atmospheric conditions on Mars?




                                                 2-10
Figure 2-4 Dense tributary networks indicative of past presence
                    of liquid water on Mars.




                             2-11
planet. Within the geological framework,                aqueous fluids, as found in the SNC
strategic questions related to the search for           meteorites) is of major interest. Can the
evidence of life can be posed.                          channels apparently formed by water
                                                        erosion be demonstrated to have
   •What is the absolute time scale for
                                                        experienced running water? Is there
    development of the major features on
                                                        verifiable evidence for the existence of
    Mars? This would include determining
                                                        ponds of water? What is the distribution
    the time of formation of the martian
                                                        of subsurface permafrost, and can the
    crust, a range of formation ages for
                                                        features interpreted as permafrost
    volcanic plains, and the age of the
                                                        collapse be verified?
    youngest volcanoes. With this
    information as a guide, the age of                 •What are the distribution and
    formation of water-formed channels                  characteristics of carbon and nitrogen—
    should be boundable, and the                        the organogenic elements? Where do
    organogenic element content of martian              they exist in reduced form? In what
    materials as a function of time may be              environments are they preserved in their
    obtainable. As is inferred from the SNC             original state? Is there chemical, isotopic
    meteorites which are believed to have               (hydrogen, carbon, nitrogen isotopes), or
    originated on Mars (Bogard, et al., 1983            morphological evidence that will link
    and McSween, 1994), impacts on Mars                 concentrations of organogenic elements
    have preserved samples of the martian               to the past existence of life?
    atmosphere in shock-produced glasses.
                                                       •If organic remains can be found, how
    Thus, it may be possible to characterize
                                                        extensive are they in space and time?
    the evolution of the atmosphere from
                                                        What are their characteristics, variety
    carefully selected samples of impact
                                                        and complexity? How are they similar or
    glass.
                                                        different to biological materials on
   •What is the evidence for the distribution           Earth?
    in space and time of water on the
                                                        Answers to these questions may be
    surface? This would include water
                                                   sought through orbital mapping (for example,
    combined in widely distributed igneous
                                                   to determine the distribution of hydrothermal
    or clay minerals, in localized deposits
                                                   mineral deposits), in situ studies (surface
    such as hydrothermal vents, in
                                                   mineralogy, distribution of volatile elements),
    subsurface permafrost, in the polar caps,
                                                   sample return (age of rock units, detailed
    and in the atmosphere. The distribution,
                                                   chemistry, mineralogy, and isotopic
    age, composition, and mode of
                                                   composition), and human exploration with
    formation (minerals formed by reaction
                                                   sample return (similar but with more highly
    with or deposition from heated or cool
                                                   intelligent sample collection). The scientific




                                                2-12
community debates the precise order of                modes of exploration that cannot be achieved
investigative means used to achieve this              robotically, then the human mission will be
strategy, but generally concludes that the            cost effective on scientific grounds.
question of distribution of past life will be of
such a difficult nature that sample return will       2.4      Exploration Rationale
be required and that humans will ultimately
                                                          Aside from purely scientific benefits, the
choose to carry out the exploration in person.
                                                      human exploration of Mars brings with it
     Given the assumption that humans will            many tangible and intangible near-term
take on the bulk of this type of exploration,         benefits such as:
the key questions become:
                                                            •New associations between groups or
   •What is the appropriate role and place in                disciplines which previously have not
    the exploration strategy of robotic                      interacted, but because of common
    sample return missions?                                  objectives in exploration find new
                                                             strengths and opportunities (for
   •Scientifically, where is the appropriate
                                                             example, new international cooperation).
    transition from robotic missions,
    conducted routinely, and human                          •New technologies which may be used
    exploration missions, which may be                       for practical application on Earth or in
    singular, large, and not reproducible?                   other space enterprises (dual-use
                                                             technologies).
     General guidelines are needed to answer
these questions. Sample return missions                     •Education of a new generation of
should be favored when they can be used to                   engineers and scientists spurred by the
significantly reduce the number of                           dream of Mars exploration.
subsequent missions to address the geological
                                                           In the long term, the biggest benefit of
modeling of the planet. Sample return
                                                      the human exploration of Mars may well be
missions are likely to be more expensive than
                                                      the philosophical and practical implications
one-way missions, so to be cost effective, they
                                                      of settling another planet.
must reduce the need for a proportionally
larger number of subsequent missions or               2.4.1    Inhabiting Another Planet
garner otherwise unobtainable information if
their justification is purely scientific. From a           The dream of human exploration of Mars
scientific perspective, the guidelines for            is intimately tied to the belief that new lands
human exploration are similar. If a human             create new opportunities and prosperity. In
exploration mission promises to answer the            human history, migrations of people have
major strategic questions better than a larger        been stimulated by overcrowding, exhaustion
number of robotic explorers, or opens new             of resources, the search for religious or




                                                   2-13
economic freedom, competitive advantage,          The fact that, once on Mars, humans cannot
and other human concerns. Rarely have             easily return to the Earth (and then only at
humans entered new territory and then             specified times approximately 26 months
completely abandoned it. A few people have        apart) makes it necessary to develop systems
always been adventurous enough to adopt a         with high reliability and robustness.
newly found territory as their home. Most of
                                                        At the present level of human
the settlements have eventually become
                                                  technological capability, a self-sufficient
economically self-sufficient and have
                                                  settlement on Mars stretches our technical
enlarged the genetic and economic diversity
                                                  limits and is not economically justifiable, but
of humanity. The technological revolution of
                                                  it is imaginable. If, however, transportation
the twentieth century, with high speed
                                                  costs were to be reduced by two orders of
communication and transportation and
                                                  magnitude, such settlements might become
integrated economic activity, may have
                                                  economically feasible. What kind of strategy
reversed the trend toward human diversity;
                                                  should be followed to explore the concept of
however, settlement of the planets can once
                                                  humans permanently inhabiting Mars? Three
again enlarge the sphere of human action and
                                                  considerations are important.
life.
                                                      •Demonstrating the potential for self-
     Outside the area of fundamental science,
                                                       sufficiency. This would include
the possibility that Mars might someday be a
                                                       understanding the potential to obtain all
home for humans is at the core of much of the
                                                       important materials to support human
popular interest in Mars exploration. A
                                                       habitation from the natural materials of
human settlement on Mars, which would
                                                       Mars. It is most important that humans
have to be self-sufficient to be sustainable,
                                                       be able to capture energy for driving
would satisfy human urges to challenge the
                                                       processes and have access to natural
limits of human capability, create the
                                                       resources (such as water, oxygen,
potential for saving human civilization from
                                                       agricultural raw materials, building
an ecological disaster on Earth (for example, a
                                                       materials, and industrial materials) from
giant asteroid impact or a nuclear incident),
                                                       martian rocks and soil. Demonstrating
and potentially lead to a new range of human
                                                       self-sufficiency requires that resources be
endeavors that are not attainable on Earth.
                                                       located and technology and experience
     The settlement of Mars presents new               be developed to efficiently extract them
problems and challenges. The absence of a              from the in situ materials. Much can be
natural environment that humans and most               done robotically to locate resources prior
terrestrial fauna and flora would find livable         to arrival of the first human crew.
and the current high cost of transportation are        Extraction technology depends on a
the main barriers to human expansion there.            more detailed understanding of the




                                               2-14
 specific materials present on Mars and                    International Space Station program to
 requires the detailed mineralogical and                   be conducted in the late 1990s. Some of
 chemical analyses generally associated                    these concerns can also be addressed on
 with sample return missions. An                           the first human exploration missions to
 exception is the production of water,                     Mars, in which greater risks may be
 methane, and oxygen from the martian                      taken than are appropriate for later
 atmosphere, which is now known well                       settlement.
 enough to design extraction technology
                                                       •Demonstrating that the risks to survival
 (Sullivan, et al., 1995). In addition to the
                                                        faced in the daily life of settlers on Mars
 extraction and use of martian resources,
                                                        are compatible with the benefits
 self-sufficiency undoubtedly requires
                                                        perceived by the settlers. Risks to
 highly advanced life support systems in
                                                        survival can be quantified through the
 which most of the waste product from
                                                        Mars exploration program. However, the
 human activity is recovered and reused,
                                                        benefits will be those perceived by
 and food is grown on the planet.
                                                        future generations and cannot be
•Demonstrating that human beings can                    addressed here.
 survive and flourish on Mars. This will
 likely be first explored by long-duration         2.4.2     International Cooperation
 missions in Earth orbit and may be                     The space age gained its start in a period
 continued in the 1/6-g environment of             of intense technical and social competition
 the Moon (Synthesis Group, 1991). Two             between East and West, represented by the
 types of needs—physical and                       Soviet Union and the United States.
 psychological—must be met for humans              Competition during the International
 to survive and flourish on Mars. Physical         Geophysical Year resulted in the Soviet Union
 needs will be met through advanced life           being the first to launch a satellite into Earth
 support systems, preventive medical               orbit, which served to challenge and remind
 sciences (nutrition, exercise,                    the United States that technological
 environmental control, etc.), and the             supremacy was not solely the province of the
 capability of medical support for people          United States.
 on Mars. Psychological needs will be
 met through the design of systems,                     The start of the Apollo program was a
 identification and selection of work for          political decision based more on the
 crews, communications with Earth, and             perception of the political and technological
 a better understanding of human                   rewards to be gained by attacking a truly
 interactions in small communities. Many           difficult objective in a constrained time
 of these can be addressed through a               period. The space race began, the United
 lunar outpost program or in the                   States won it, and a relatively few years later,




                                                2-15
the Soviet Union collapsed. Fortunately, the         Section 3 of this report will illustrate that
Russians did not view Apollo success as a            much of the technology needed for a Mars
reason to terminate their space exploration          mission is either currently available or within
program, and they continued to develop               the experience base of the spacefaring nations
capabilities that are in many areas on a par         of the Earth. No fundamental breakthroughs
with United States capabilities. Also, during        are required to accomplish the mission.
the post-Apollo time frame, space capability         However, an extended period of advanced
grew in Europe (with the formation of the            development will be required to prepare the
European Space Agency), Japan, Canada,               systems needed to travel to and from Mars or
China, and other countries. With these               to operate on the surface of Mars; specifically,
developments, the basis has been laid for a          high efficiency propulsion systems, life
truly international approach to Mars                 support systems, and an advanced degree of
exploration—an objective in which all                automation to operate, and if necessary
humanity can share.                                  repair, processing equipment. At a general
                                                     level, perhaps two of the most important
     The exploration of Mars will derive
                                                     ways in which the Reference Mission will
significant nontechnical benefits from
                                                     help advance technology that will benefit
structuring this undertaking as an
                                                     more than just this program is to provide the
international enterprise. It is unnecessary for
                                                     programmatic “pull” to bring technologies to
any country to undertake human exploration
                                                     a usable state and the “drive” to make
of Mars alone, particularly when others, who
                                                     systems smaller, lighter, and more efficient for
may not now have the required magnitude of
                                                     a reasonable cost.
capability or financial resources, do have the
technological know-how. An underlying                     For any of the technology areas
requirement for the Reference Mission is that        mentioned above (as well as others not
it be implemented by a multinational group           mentioned), this program will require
of nations and explorers. This would allow           systems using these technologies to meet
for a continuation of the cooperative effort         performance specifications and be delivered
that is being made to develop, launch, and           on schedule, all at a pace perhaps not
operate the International Space Station.             otherwise required. This applies to any
                                                     development effort. But for the Reference
2.4.3   Technological Advancement                    Mission, many technologies will need to be
    From the outset, the Reference Mission           ready at once, causing many of these systems
was not envisioned to be a technology                to advance in maturity much faster than
development program. The Mars Study Team             might have otherwise been possible. These
made a deliberate effort to use either               mature systems and related technologies will
technology concepts that are in use today or         then be available to the marketplace to be
basic concepts that are well understood.




                                                  2-16
used in applications limited only by the            necessary to be used on the Reference
imagination of entrepreneurs.                       Mission. Once developed, these technologies
                                                    become available for use, perhaps on reusable
     The matured systems and the
                                                    vehicles, for the ever-increasing traffic in LEO
technologies behind them will be attractive
                                                    up to geosynchronous altitude.
to entrepreneurs in part because of the effort
to make them smaller, lighter, and more                  Another area of tremendous leverage for
efficient. A kilogram of mass saved in any of       a mission to other planets is the ability to use
these systems saves many tens of kilograms          resources already there rather than burdening
of mass at launch from Earth (depending on          the transportation system by bringing them
the propulsion system used) simply because          from Earth. Focusing on understanding what
less propellant is required to move the             is required for eventual settlement on Mars
systems from Earth to Mars. Smaller, lighter,       leads quickly to those technologies that allow
or more efficient each translate into a             the crew to live off the land. Of the known
competitive advantage in the marketplace            raw materials available on Mars, the
for those who use these technologies.               atmosphere can be found everywhere and can
                                                    be used as feedstock to produce propellants
     Among the specific areas of desirable
                                                    and life support resources. Other raw
technology advancement is propulsion
                                                    materials (such as water) will eventually be
systems. Even the earliest studies for sending
                                                    found and used, but sufficient detail is not
people to the Moon or Mars recognized that
                                                    currently known about their locations and
propulsion system efficiency improvements
                                                    quantities. This is an objective for initial
have tremendous leverage in reducing the
                                                    exploration.
size of the complete transportation system
needed to move people and supplies.                      Much of the processing technology
Chemical propulsion systems are reaching            needed to produce propellants from
the theoretical limits of efficiency in the         atmospheric gases already exists and is in use
rocket engines now being produced. Further          on Earth. However, integrating these
improvements in efficiency will require the         technologies into a production plant that can
use of nuclear or electrical propulsion             operate unattended for a period of years,
concepts which have the potential of                including self-repair, is an area where
improving propulsion efficiencies by a factor       additional development effort will be
of up to 10, with corresponding reductions in       required. (Chemical processing plants on
the amount of propellant needed to move             Earth are making significant progress toward
payload from one place to another. Both of          autonomous operation even now.) In this
these propulsion technologies have matured          area, the Reference Mission will adapt the
to a relatively high state of readiness in the      existing technologies at the time of the
past, but neither has reached the level             Reference Mission rather than pull those




                                                 2-17
technologies up to the levels needed by the          Reference Mission possible. Equal with this is
program. Regardless of how this technology           instilling an attitude of cost consciousness in
is developed, the advantages in                      the engineering community that will design
manufacturing and materials processing will          and produce these systems. The importance
be significant.                                      of cost as a design consideration and
                                                     providing the tools to accurately forecast cost
     Life support systems is another specific
                                                     should be incorporated in the educational
area where advancing the state of the art can
                                                     system that trains these engineers.
significantly reduce the overall size of the
systems launched from Earth. The same
                                                     2.4.4   Inspiration
technologies that produce propellants can
also produce water and breathable gases for              It can be argued that one role of
human crews. These resources can be used as          government is to serve as a focusing agent for
makeup for losses in a closed or partially           those events in history that motivate and
closed life support system, and can also serve       unify groups of people to achieve a common
as an emergency cache should primary life            purpose. Reacting to conflicts quickly comes
support weaken or fail. Life support for this        to mind as an example. For the United States,
Reference Mission can take advantage of              World War II and the Persian Gulf War are
developments already made for International          examples of how a nation was unified in a
Space Station and submarine use.                     positive sense; the Viet Nam War is an
Developments in support of the Reference             example of how the opposite occurred.
Mission are likely to return technologies that            It can also be argued that a role of
are smaller, more efficient, and perhaps less        government is to undertake technical and
costly than those available at the time.             engineering projects that can inspire and
     Important in all of these areas is a focus      challenge. The great dam building projects in
on ensuring that the cost to manufacture and         the American West during the 1930s is an
operate these systems is affordable in the           example of the government marshaling the
current economic environment. The design-            resources to harness vast river systems for
to-cost concept is not currently well                electrical power and irrigation to allow for
understood in the aerospace industry, and            population growth. The Interstate Highway
any advancements in this area will benefit           System is another example that receives little
development programs well beyond those               fanfare but has changed the way we live. The
connected with the Reference Mission.                government incentives to private entities that
Developing the tools needed to determine             led to the development of the vast
costs that are as easy to use as the tools used      intercontinental rail system in the last century
to predict system performance is one of the          is another example.
key technology areas that will help make the




                                                  2-18
    Few government efforts can collectively         the infrastructure that affects our everyday
motivate, unify, challenge, and inspire. The        life: the use of space for business, commerce,
Apollo program was one such example that            and entertainment. Just as space projects do
focused a national need to compete with             now, the Reference Mission can serve as a
another nation in a very visible and high           focal point for invigorating the scientific,
profile manner; the Reference Mission can           technical, and social elements of the
serve as another. In this instance, the             education system, but with a much longer
undertaking provides a focus for the human          range vision.
need to struggle and compete to achieve a
worthy goal—not by competing against each           2.5     Why Not Mars?
other but rather against the challenges
                                                         Several impediments may severely
presented by a common goal.
                                                    hamper the implementation of a program for
                                                    the human exploration of Mars. Some
2.4.5   Investment
                                                    impediments are due simply to the fact that
     Scientific investigation, human                they have not been evaluated in sufficient
expansion, technology advancement, and              detail to gauge their impact. Others are
inspiration are not attainable free of charge.      simply beyond the control of this or any other
Resources must be devoted to such a project         program and must be taken into account as
for it to succeed; and at a certain level, this     the program advances. The following
can be viewed as denying those resources to         paragraphs discuss some of these
other worthy goals. The Reference Mission           impediments as viewed by the Mars Study
costs are high by current space program             Team and others considering programs of this
standards, and additional effort is needed to       type (Mendell, 1991).
reduce these costs. The total program and
annual costs of the Reference Mission range         2.5.1   Human Performance
from 1 percent to 2 percent of the current
                                                         It is a known fact that the human body
Federal budget—still far below other Federal
                                                    undergoes certain changes when exposed to
programs. If this program expands to an
                                                    extended periods of weightlessness—changes
international undertaking, the costs incurred
                                                    that are most debilitating when the space
by each partner would be reduced even more.
                                                    traveler must readapt to gravity. The most
     A debate must still occur to determine if      serious known changes include
this project is a worthwhile investment of the      cardiovascular deconditioning, decreased
public’s resources. But the use of these            muscle tone, loss of calcium from bone mass,
resources should be viewed as more than just        and suppression of the immune system. A
an effort to send a few people to Mars. This        variety of countermeasures for these
project will be investing in a growing part of      conditions have been suggested, but none




                                                 2-19
have been validated through testing for long-       time required for recovery is particularly
term, zero-g spaceflight. The Russians have         important if the surface stay is short (as has
had some success with long periods of daily         been proposed for “opposition-class”
exercise to maintain cardiovascular capacity        missions).
and muscle tone, but monotonous and time-
                                                         No one knows whether exposure to a
consuming exercise regimes affect the
                                                    gravity field lower than the Earth’s will
efficiency and morale of the crew.
                                                    reverse the deconditioning induced by
     Artificial gravity is often put forward as a   weightless space travel. And if some level of
possible solution. In this case, the entire         gravity does halt the deconditioning effects,
spacecraft, or at least that portion containing     what level is too low? In other words, if a
the living quarters for the crew, would be          crew arrives on Mars in good physical
rotated so that the crew experiences a              condition, what will their condition be after
constant downward acceleration that                 spending an extended period of time under
simulates gravity. It is generally assumed that     martian gravity? Artificial gravity cannot be
the Coriolis effect (the dizziness caused by        provided easily on the martian surface, and
spinning around in circles) will fall below the     Apollo missions to the Moon were too short
threshold of human perception if the                to produce observable differences between
spacecraft is rotated at a slow rate. It is not     the condition of the astronauts who went to
known whether simulation of full terrestrial        the surface and those who remained
gravity is required to counteract all of the        weightless in orbit.
known deconditioning effects of
                                                          The human body’s reaction to Mars
weightlessness, or whether the small residual
                                                    surface conditions, other than gravity, is also
Coriolis effect will cause some disorientation
                                                    not yet known. The Viking missions to Mars
in crew members. No data from a space-based
                                                    found a highly reactive agent in the martian
facility exists, and the space life science
                                                    soil, an explanation for which has not yet
research community is split over the viability
                                                    been agreed to by the scientific community.
of artificial gravity as a solution.
                                                    Without understanding this agent’s chemical
    Deconditioning is a critical issue for Mars     behavior, its impact on human crews cannot
missions because the crew will undergo high         be determined. No matter how carefully the
transient accelerations during descent to the       Mars surface systems are designed and no
martian surface. Depending on the                   matter how carefully the crews handle native
physiological condition of the crew, these          materials, small amounts of the martian
accelerations could be life threatening. Once       atmosphere and soil will be introduced into
on the surface of Mars, the crew must recover       crew living compartments during the course
without external medical support and must           of the mission. It will be necessary to better
perform a series of demanding tasks. The            characterize the Mars environment and assess




                                                2-20
its impact on the crew. Assuring the health        be no opportunity for resupply. Either the
and safety of the crew will be of obvious          systems must work without failure or the
importance.                                        crew must have adequate time and capability
                                                   to repair those elements which fail.
     Psychiatrists and psychologists agree that
piloted missions to Mars may well give rise to          Particularly important to the success of
behavioral aberrations among the crew as           piloted Mars missions will be testing of
have been seen on Earth in conditions of           integrated flight systems under conditions
stress and isolation over long periods of time.    similar to the actual mission for periods of
The probability of occurrence and the level of     time similar to, and preferably much greater
any such anomalous behavior will depend            than, the actual mission. Integrated flight
not only on the crew members individually          testing is truly critical if the flight system is
but also on the group dynamics among the           the first of its kind. Unfortunately, if history is
crew and between the crew and mission              a guide, budget pressures will cause program
support personnel on Earth. In general, the        management to search for substitutions for
probability of behavior extreme enough to          full-up flight testing. (For full-up flight
threaten the mission will decrease with an         testing, hardware identical to that used in
increased crew size. However, the expense of       flight is operated for periods of time equal to
sending large payloads to Mars to support a        or greater than the actual mission which
large crew will limit the number of people in      allows weaknesses or failures to be identified
any one crew. At the present time, little effort   and corrected. This is the most expensive way
has been spent developing techniques for           to test, in terms of time and money.) After all,
crew selection that will adequately guarantee      most of the expense of a mission to Mars is in
psychological stability on a voyage to Mars        launch and operations, two categories of
and back. Russian experience suggests that a       expense for a flight test whose magnitude
crew should train together for many years          would be similar to that of an actual mission.
prior to an extended flight.                       And what possible motivation would there be
                                                   for a crew to spend 2 or 3 years in orbit
2.5.2   System Reliability and Lifetime            pretending to go to Mars?
     The spacecraft and surface elements will           Somewhere in a large, complex program,
likely be the most complex systems                 a manager will take a shortcut under pressure
constructed up to that point in time, and the      from budget or schedule reasons, and the
lives of the crew will depend on the reliability   consequences will not always be obvious to
of those systems for at least 3 years. By          program management. As a result, the
comparison, a Mars mission will be of a            reliability of the product will be
duration at least two orders of magnitude          overestimated. And management always
greater than a Shuttle mission, and there will     expresses a very human tendency to believe




                                               2-21
good news. (This can be illustrated by the           Shortening development time can be
change in the official estimates of the              beneficial if the project remains focused on its
reliability of the Shuttle before and after the      requirements and can avoid changes imposed
Challenger tragedy.) In short, significant risk      by external forces.
is introduced when relying on a product that
                                                          If an institution wishes to be supported
has not been tested in its working
                                                     with public funds for a long-duration project,
environment, whether it is a new car, a
                                                     then the institution must be sophisticated
complex piece of software, or a spacecraft.
                                                     enough to plan visible milestones, which are
                                                     comprehensible to the public, at intervals
2.5.3 Political Viability and Social
                                                     appropriate to the funding review process.
Concerns
                                                     Historically, NASA has been reasonably
     The human exploration of Mars is likely         successful at maintaining funding of decade-
to be undertaken for many of the reasons             long programs in the face of an annual budget
already cited as well as others not presented        review. The vast majority of the programs are
here. To a large degree, the responsibility for      understood by all to have a finite duration.
taking action based on these reasons is in the       After a satellite has been launched and
realm of political decision makers as opposed        operated for a given period of time, it either
to commercial concerns or other spheres of           fails or is shut off. Neither NASA nor the U.S.
influence. Thus, support for this type of            Congress are yet comfortable with open-
program must be sustained in the political           ended programs such as the Shuttle or
environment for a decade or more in the face         International Space Station or human
of competition for the resources needed to           settlement of the solar system.
carry it out.
                                                          The decades-long time frame for human
     Perhaps the closest analogy to a possible       exploration of Mars cannot be supported until
international Mars exploration program is the        the role of the space program is well
International Space Station, which has been          integrated into the national space agenda and
an approved international flight program for         the exploration of space is no longer
over 10 years. During those 10 years, the            considered a subsidy of the aerospace
configuration of the Station has changed             industry. To accomplish this, the space
several times and the number of and level of         program must show concern for national and
commitment from partners has changed                 international needs (visible contributions to
significantly. Also during this time, Russia,        technology, science, environmental studies,
initially a significant competitor, has turned       education, inspiration of youth, etc.) while
into one of the larger partners in the               maintaining a thoughtful and challenging
endeavor. And all of this has taken place prior      agenda of human exploration of space in
to launching the first element of the Station.       which the public can feel a partnership.




                                                  2-22
     Finally there is the political concern of      2.7      References
back-contamination of Earth. This is as much
                                                          Bogard, D. and P. Johnson, “Martian
a social issue as a technical one. Some
                                                          Gases in an Antarctic Meteorite,” Science,
segments of the population will object to any
                                                          Vol. 221, pp. 651-654, 1983.
Mars mission on these grounds. The two
tenets of a successful defense against such               Duke, M. and N. Budden, “Results,
opposition are to ensure that prudent steps               Proceedings and Analysis of the Mars
are taken at all phases of the project to                 Exploration Workshop,” JSC-26001,
minimize risks and to demonstrate that the                NASA, Johnson Space Center, Houston,
value of the mission is high enough to merit              Texas, August 1992.
the residual minuscule risk.                              Exobiology Program Office, “An
                                                          Exobiological Strategy for Mars
2.6    Summary                                            Exploration,” NASA SP-530, NASA
     This section has woven together several              Headquarters, Washington, DC, April
key elements of a rationale for undertaking               1995.
the Reference Mission: human evolution,                   McSween, H., “What We Have Learned
comparative planetology, international                    About Mars From SNC Meteorites,”
cooperation, technology advancement,                      Meteoritics, Vol. 29, pp. 757-779, 1994.
inspiration, and investment. Several
                                                          Mendell, W., “Lunar Base as a Precursor
challenging aspects must be resolved before
                                                          to Mars Exploration and Settlement,” 42nd
the first human crews can be sent to Mars. But
                                                          Congress of the International Astronautical
the Reference Mission has a longer range
                                                          Federation, IAF-91-704, Montreal, Canada,
view and purpose that makes these
                                                          October 5-11, 1991.
challenges worth the effort to overcome. If, at
some future time, a self-sufficient settlement            Sullivan, T., D. Linne, L. Bryant, and K.
is established on Mars, with the capability of            Kennedy, “In Situ-Produced Methane and
internal growth without massive imports                   Methane/Carbon Monoxide Mixtures for
from Earth, the benefit will be to the eventual           Return Propulsion from Mars,” Journal of
descendants of the first settlers, who will have          Propulsion and Power, Vol. 11, No. 5, pp.
totally different lives and perspectives                  1056-1062, 1995.
because of the initial investment made by
                                                          Synthesis Group, “America at the
their ancestors.
                                                          Threshold: Report of the Synthesis Group
                                                          on America’s Space Exploration
                                                          Initiative,” U.S. Government Printing
                                                          Office, Washington, DC, May, 1991.




                                                 2-23
3. Mission and System
             Overview




       3-1
3-2
3.1    Introduction                                          An infinite number of designs are
                                                         possible for a mission of this type. The
     Previous studies of human exploration of
                                                         approach taken here is based on two general
Mars have tended to focus on spacecraft and
                                                         principles.
flight, rather than on what the crew would do
on the surface. The Reference Mission takes                 •A hierarchy of requirements (starting
the point of view that surface exploration is                from mission objectives) is followed,
the key to the mission, both for science and                 which, as they gain greater depth and
for evaluation of the potential for settlement.              definition, merge with the proposed
As a consequence, the Reference Mission                      implementation through a set of system
architecture allows for a robust surface                     specifications (note that the Reference
capability with significant performance                      Mission has followed these requirements
margins: crews will explore in the vicinity of               down to the system level only).
the outpost out to a few hundred kilometers,
                                                            •A reasonable number of alternatives will
will be able to study materials in situ and in a
                                                             be considered, through trade studies at
surface laboratory, and will iterate their
                                                             each level of definition allowing
findings with their exploration plan. In
                                                             comparisons and choices.
addition, the development and demonstration
of the key technologies required to test
                                                         3.1.1   Mission Objectives
settlement issues will provide a substantial
workload. To make surface exploration                         Section 1 of this report discussed a series
effective, the supporting systems (such as               of workshops conducted by NASA to define a
EMU, life support, vehicles, robotics) must be           set of objectives and supporting rationale for
highly reliable, highly autonomous, and                  a Mars exploration program. The workshop
highly responsive to the needs of the crew.              attendees (see Table 2-1) identified and
Some needs may not be anticipated during                 recommended for adoption three objectives
crew preparation and training, which will                for analysis of a Mars exploration program
significantly challenge the management and               and the first piloted missions in that program.
operations systems.




                                                   3-3
They are to conduct:                                  3.1.2 Surface Mission Implementation
                                                      Requirements
   •Human missions to Mars and verify that
    people can ultimately inhabit Mars.                    To satisfy the objectives for the Reference
                                                      Mission, the Mars Study Team developed a
   •Applied scientific research for using
                                                      series of capabilities and demonstrations that
    martian resources to augment life-
                                                      should be accomplished during surface
    sustaining systems.
                                                      mission activities. Table 3.1 defines the
   •Basic scientific research to gain new             activities and capabilities that must exist to
    knowledge about the solar system’s                meet the first three program objectives to the
    origin and history.                               next level of detail. The three objectives added
                                                      by the Study Team are useful in selecting
    A Mars Study Team composed of NASA
                                                      among feasible mission implementation
personnel representing most NASA field
                                                      options that could be put forth to satisfy the
centers (see Table 2-2) used inputs from the
                                                      capabilities and demonstrations listed in the
adopted objectives to construct the Reference
                                                      table.
Mission. In addition, the Study Team
recognized that past mission studies had
                                                      3.1.2.1 Conduct Human Missions to Mars
characterized piloted Mars missions as
inherently difficult and exorbitantly                      From the point of view of the surface
expensive. Therefore, the Mars Study Team             mission, conducting human missions implies
added three objectives. These were to:                that the capability for humans to live and
                                                      work effectively on the surface of Mars must
   •Challenge the notion that human
                                                      be demonstrated. This includes several sub-
    exploration of Mars is a 30-year program
                                                      objectives to:
    that will cost hundreds of billions of
    dollars.                                             •Define a set of tasks of value for humans
                                                          to perform on Mars and provide the
   •Challenge the traditional technical
                                                          tools to carry out the tasks.
    obstacles associated with sending
    humans to Mars.                                      •Support the humans with highly reliable
                                                          systems.
   •Identify relevant technology
    development and investment                           •Provide a risk environment that will
    opportunities.                                        maximize the probability of
                                                          accomplishing mission objectives.

                                                         •Provide both the capability and the
                                                          rationale to continue the surface
                                                          exploration beyond the first mission.




                                                3-4
          Table 3-1 Capabilities and Demonstrations for Surface Mission Activities

    Conduct Human Missions to Mars
    a. Land people on Mars and return them safely to Earth.
    b. Effectively perform useful work on the surface of Mars.
    c. Support people on Mars for 2 years or more without resupply.
    d. Support people away from Earth for periods of time consistent with Mars mission durationss
        (2 to 3 years)
    e. Manage space operations capabilities including communications, data management, and
        operations planning to accommodate both routine and contingency mission operational
        situations; and understand abort modes from surface or space contingencies.
    f. Identify the characteristics of space transportation and surface operations systems consistent
        with sustaining a long-term program at affordable cost.
    Conduct Applied Science Research to Use Mars Resources to Augment Life-Sustaining Systems
    a. Catalog the global distribution of life support, propellant, and construction materials
        (hydrogen, oxygen, nitrogen, phosphorous, potassium, magnesium, iron, etc.) on Mars.
    b. Develop effective system designs and processes for using in situ materials to replace products
        that otherwise would have to be provided from Earth.
    Conduct Basic Science Research to Gain New Knowledge About the Solar System’s Origin and
    History
    a. Using robotic and human investigations, gain significant insights into the history of the
        atmosphere, the planet’s geological evolution, and the possible evolution of life.
    b. Identify suitable venues at Mars, in the martian system, and during Earth-Mars transits for
        other science measurements.




    These then require a set of functional               effective system designs be developed and
capabilities on the surface, including habitats,         demonstrated to extract and use indigenous
surface mobility systems, and supporting                 resources. Opportunities exist to use
systems (such as power and communications                indigenous resources as demonstrations in
systems).                                                the life support subsystem, in energy systems
                                                         as fuel or energy storage, and as propellant
3.1.2.2 Conduct Applied Scientific Research              for spacecraft. These may eventually develop
to Use Mars Resources to Augment Life-                   into essential systems for the preservation of
Sustaining Systems                                       the outpost. In addition, the following
    This objective will require that an                  habitation activities and demonstrations
assessment be made of the location and                   satisfy the first and second objectives.
availability of specific resources (such as                 •Demonstrate that martian habitability
water) that are useful for human habitation or               has no fundamental limitations due to
transportation. It will also require that                    uniquely martian characteristics such as




                                                   3-5
     low gravity, absence of a magnetic field,          additional systems for producing food and
     soil toxicity, or the radiation                    recycling air and water.
     environment.
                                                        3.1.2.3 Conduct Basic Scientific Research to
   •Demonstrate that self-sufficiency can be
                                                        Gain New Knowledge About the Solar
    achieved on the local scale of a Mars
                                                        System’s Origin and History
    base. This includes providing a
    reasonable quality of life and reasonably                This will require that a variety of
    low risk for the crews, and should                  scientific explorations and laboratory
    include operating a bioregenerative life            assessments be carried out on the surface of
    support system capable of producing                 Mars by both humans and robots. The
    food and recycling air and water.                   scientific research will not be conducted
                                                        completely at any one site, which will create a
   •Determine the potential for expansion of
                                                        need for crew member mobility and
    base capabilities using indigenous
                                                        transportation systems to support
    resources. This would include the
                                                        exploration, the specialized tools required
    successful extraction of life support
                                                        outside the outpost to collect and document
    consumables from the martian
                                                        materials, and the facilities inside the outpost
    environment and storage for later use.
                                                        to perform analyses.
   •Investigate the biological adaptation of
                                                            The principal science activities and
    representative plant, animal, and
                                                        demonstrations for Mars exploration include
    microbial species to the martian
                                                        answering the following questions.
    environment over multiple generations.
                                                           •Has Mars been a home for life?
     These activities and demonstrations are
aimed at establishing the feasibility and                    This set of objectives will combine field
approach required to move beyond the                    and laboratory investigations in geology,
exploratory phase toward the development of             paleontology, biology, and chemistry. The
long-term activities on the planet. They                underlying assumption is that this question
influence the selection of elements that are            will not have been answered by previous
included in the surface systems (habitats,              robotic Mars exploration programs, and the
mobility, life support, power, and                      best way to get an answer is through
communications systems).                                judicious use of humans on Mars as field
                                                        geologists and laboratory analysts. Recent
    To the support facilities identified in the
                                                        evidence indicating past life on Mars found in
previous section must be added exploration
                                                        a martian meteorite has placed increased
systems (orbital or surface), resource
                                                        emphasis on this question (McKay, et al.,
extraction and handling systems, and
                                                        1996).




                                                  3-6
   •What are the origin and evolution of                rover sample collectors having accessibility to
    Mars, particularly its atmosphere, and              interesting or significant sites at increasing
    what does it tell us about Earth?                   distances from the outpost. Figure 3-1 shows
                                                        a photomosaic of the Candor region of the
     This set of objectives involves geology
                                                        Valles Marineris in which the location of an
and geophysics, atmospheric science,
                                                        outpost could address fundamental questions
meteorology and climatology, and chemistry.
                                                        of Mars’ origin and history. This region is
Iterative sampling of geological units will be
                                                        located roughly between 70 degrees and 75
required as well as monitoring of a global
                                                        degrees west longitude and between 2.5
network of meteorological stations. (A global
                                                        degrees and 7.5 degrees south latitude. A
network will most likely be established by
                                                        general geological map of the region of the
robotic elements of the program.)
                                                        outpost site should be prepared using data
   •What resources are available on Mars?               gathered by robotic missions prior to selecting
     The resource discovery and verification            and occupying the initial site.
of accessibility will require investigations in              Once the outpost is established,
geology, atmospheric science, and chemistry.            exploration activity will consist of surface
A general strategy for accomplishing this will          observations made by robotic vehicles and
begin with a global mapping (from orbit) of             human explorers, collection of samples, and
selected elemental and mineralogical                    examination of samples in the outpost
abundances. This activity is best suited for a          laboratory. Crews will be given broadly stated
robotic spacecraft sent prior to the flight of          scientific questions or exploration objectives
the first human crew. Robotic missions are              to be addressed in relatively large regions
also likely for verifying the abundances and            near the outpost site. Operations will not be
making an initial assessment of accessibility           as highly choreographed over the 600-day
of the resources. The data gathered will also           surface stay-time as they are for current
be important for selecting likely sites for the         spaceflight missions. The crews and Earth-
surface outpost to be used by human crews.              based supporting investigators will plan
                                                        campaigns lasting days or weeks, eventually
3.1.2.4 Surface Operations Philosophy
                                                        extending to months, but always with the
    In addition to the facilities and                   assumption that replanning may be necessary
equipment mentioned above, the crew must                based on discoveries made. It is likely that a
have a general operating philosophy for                 strategy of general reconnaissance followed
conducting activities, demonstrations, and              by detailed investigations will be followed.
experiments on the surface. The targeted                The outpost laboratory will be outfitted to
investigations to be carried out from the Mars          provide mineralogical and chemical analyses
outpost depend on humans and automated                  and, depending on technical development, it




                                                  3-7
       Desired
       Landing
       Area




Figure 3-1 A regional map illustrating potential locations for a Mars outpost.




                                     3-8
may be possible to perform simple kinds of             Information will be transmitted to
geochronologic analysis. The purpose of these          scientists on Earth so they can
studies will be to support the field                   participate in the replanning activity.
investigations, answer “sharper” questions,            Crews will also emplace geophysical and
and allow human explorers to narrow their              meteorological instruments to measure
focus to the sites of optimum sample                   internal properties and atmospheric
collection. Ultimately, selected samples will          dynamics. Drilling short depths into the
be returned to Earth for more detailed                 surface should be standard capability. At
analysis.                                              some point it will be appropriate to drill
                                                       deeply into the surface to address
     Science equipment, experiments, and
                                                       stratigraphic issues and to locate and tap
tools must be proven in order for the
                                                       into water reservoirs.
exploration and science objectives of the
missions to be accomplished, and their                •The Mars crews will also have the
selection is at the core of the argument that          capability to operate telerobotic systems
humans can effectively perform scientific              conducting even broader exploratory
research on the planet. Failure to equip               tasks using the ability to communicate
humans properly will be a failure to take              with and direct these systems in near
advantage of their unique potential. Over-             real-time. Some teleoperated rovers
equipping them may be counterproductive as             (TROVs) may be emplaced before crews
well, at least from the cost aspect of                 arrive on Mars and may collect samples
transporting unneeded equipment to Mars.               for assembly at the Mars outpost. The
The exploration and science objectives to be           TROVs may be designed to provide
performed on the surface can be broken into            global access and may be able to return
four categories: field work, telerobotic               samples to the outpost from hundreds of
exploration, laboratory and intravehicular             kilometers distance from the site. These
activity experiments, and preparation of               robotic systems may also emplace
materials for return to Earth.                         geophysical monitoring equipment such
                                                       as seismometers and meteorological
   •Observations related to exobiology,
                                                       stations.
    geology, and martian atmosphere studies
    will be made by humans in the field.              •Scientific experiments will also be
    Samples and data will be collected and             conducted that are uniquely suited to
    returned to the outpost laboratory for             being performed on the surface of Mars.
    analysis. The information from the                 These will typically be experiments that
    analyses will be used to plan or replan            make use of the natural martian
    future traverses as scientific and                 environment (including reduced gravity)
    exploration questions are sharpened.               or involve interaction with martian




                                                3-9
     surface materials. Studies will be            weeks and using mobile facilities, may be
     performed on biological systems, best         conducted at intervals of a few months.
     performed in conjunction with an              Between these explorations, analysis in the
     experimental bioregenerative life             laboratory will continue. The crew will also
     support system. The deployment of a           spend a significant portion of time
     bioregenerative life support capability       maintaining and ensuring the continuing
     will be an early activity after crew          functionality of life support and materials
     landing. Although this system is not          processing systems and performing
     required to maintain the health and           maintenance on robotic vehicles and EVA
     vitality of the crew, it will improve the     suits (systems should be designed to help
     robustness of the life support system and     keep these activities to a minimum).
     is important to the early objectives of the
                                                       Crew activities related to living on
     outpost. Field samples will be studied in
                                                   another planet should be viewed not only as
     laboratory facilities shared between the
                                                   experiments but also as activities necessary to
     geosciences, biosciences, and facilities
                                                   carry out the mission. With minor
     support systems. For example, analytical
                                                   modifications in hardware and software,
     systems used to monitor organisms in
                                                   ordinary experiences can be used to provide
     the biological life support system may
                                                   objective databases for understanding the
     also be used to monitor the environment
                                                   requirements for human settlement.
     of the habitat in general. Some analytical
     capabilities (such as gas                          To optimize the performance of the
     chromatographs) find use in both              mission, it will be necessary to pick a landing
     geological and biological analysis. All       site primarily on the basis of satisfying
     samples and data (geological, biological,     mission objectives. However, the landing site
     medical, etc.) will be documented and         must be consistent with landing and surface
     cataloged for later research.                 operational safety. Detailed maps of candidate
                                                   landing sites should be available to define the
   •One crew task will be to select and
                                                   safety and operational hazards of the site, as
    package samples for return to Earth for
                                                   well as to confirm access (by humans or
    more detailed study. This will require the
                                                   robotic vehicles) to scientifically interesting
    creation of a minicuratorial facility and
                                                   locations. Depending on the results of prior
    procedures to ensure that
                                                   missions, it would be desirable to site the
    uncontaminated samples are returned to
                                                   outpost where water can be readily extracted
    Earth.
                                                   from minerals or from subsurface deposits.
    As experience grows, the range of human
exploration will grow from the local to the
regional. Regional expeditions, lasting several




                                               3-10
3.1.3   Ground Rules and Assumptions                   systems can potentially reduce the total
     Translating these goals and objectives            program costs and enhance crew safety
into specific missions and systems required            and system maintainability.
adopting a number of guidelines and                   •Provide a flexible implementation
assumptions.                                           strategy. Mars missions are complex, so
   •Balance technical, programmatic,                   multiple pathways to the desired
    mission, and safety risks. Mars                    objectives have considerable value in
    exploration will not be without risks.             ensuring mission success.
    However, the risk mitigation philosophy           •Limit the length of time the crew is
    as well as the acceptability of the mission        continuously exposed to the
    concept to the public, its elected leaders,        interplanetary space environment. Doing
    and the crews will be critically important         this will reduce the physiological and
    in the technical and fiscal feasibility of         psychological effects on the crew and
    these missions. Mars is not “3 days                enhance their safety and productivity. In
    away,” and overcoming the temptation               addition, the associated life science
    to look back to Earth to resolve each              concerns are partially mitigated. It is
    contingency situation may be the most              assumed that crews will arrive at Mars
    challenging obstacle to overcome in                in good health, that full physical
    embarking upon the human exploration               capability can be achieved within a few
    of Mars.                                           days, and that crew health and
   •Provide an operationally simple mission            performance can be maintained
    approach emphasizing the judicious use             throughout the expedition.
    of common systems. For example, an                •Define a robust planetary surface
    integrated mission in which a single               exploration capacity capable of safely
    spacecraft with all elements needed to             and productively supporting crews on
    carry out the complete mission is                  the surface of Mars for 500 to 600 days
    launched from Earth and lands on Mars              each mission. The provision of a robust
    to conduct the long exploration program            surface capability is a defining
    is not feasible due to launch mass                 characteristic of the Reference Mission
    considerations alone. It is necessary to           philosophy. This is in contrast to
    determine the simplest and most reliable           previous mission studies that have
    set of operations in space or on the               adopted short stay-times for the first or
    surface of Mars to bring all of the                first few human exploration missions
    necessary resources to the surface where           and focused attention principally on
    they are to be used. A strategy                    space transportation.
    emphasizing multiple uses for single




                                               3-11
•Be able to live off the land. The                  transit times for the crew or increased
 capability to manufacture resources at             payload delivery capacity for cargo. This
 Mars, particularly propellants, has long           enhances program flexibility.
 been known to have significant leverage
                                                   •Examine at least three human missions
 in terms of the amount of material that
                                                    to Mars. The initial investment to send a
 must be launched from Earth. It also
                                                    human crew to Mars is sufficient to
 provides a risk reduction mechanism for
                                                    warrant more than one or two missions.
 the crew when viewed as a cache of life
                                                    Each mission will return to the site of the
 support consumables to back up those
                                                    initial mission, with missions two and
 brought from Earth. Additional system
                                                    three launching in the 2012 and 2014
 development effort will be required, but
                                                    launch opportunities, respectively. This
 the advantages outweigh the cost and
                                                    approach permits an evolutionary
 development risk, particularly if the
                                                    establishment of capabilities on the Mars
 infrastructure supports more than one
                                                    surface and is consistent with the stated
 human exploration expedition.
                                                    goals for human exploration of Mars.
•Rely on reasonable advances in                     Although it is arguable that scientific
 automation to perform a significant                data could be enhanced by landing each
 amount of the routine activities                   human mission at a different surface site,
 throughout the mission. This includes a            the goal of understanding how humans
 capability to land, set up, operate, and           could inhabit Mars seems more logically
 maintain many of the Mars surface                  directed toward a single outpost
 systems needed by the crew prior to                approach. This leaves global exploration
 their arrival.                                     to robotic explorers or perhaps later
                                                    human missions.
•Ensure that management techniques are
 available and can be designed into a
                                               3.2   Risks and Risk Mitigation
 program implementation that can
                                               Strategy
 substantially reduce costs.
                                                    Several related but also separable aspects
•Use the Earth-Mars launch opportunities
                                               of risk are associated with a Mars mission and
 occurring from 2007 through 2014. A
                                               must be considered in designing the
 2009 launch represents the most difficult
                                               Reference Mission. Reference Mission
 opportunity in the 15-year Earth-Mars
                                               activities will inevitably be hazardous
 trajectory cycle. By designing the space
                                               because they are conducted far from home in
 transportation systems for this
                                               extreme environments. However, the hazards
 opportunity, particularly those systems
                                               can be reduced by proper design and
 associated with human flights, they can
                                               operational protocols. Before a Mars
 be flown in any opportunity with faster




                                            3-12
exploration program is approved, it will be           However, there are important and potentially
necessary to decide whether the elements of           deadly environmental hazards (such as
risk to the enterprise can be reduced to a level      radiation and meteoroid damage) which must
consistent with the investment in resources           be addressed. Two radiation hazards exist.
and human lives.                                      First and most dangerous is the probability of
                                                      a solar proton event (SPE) which is likely to
3.2.1   Risks to Human Life                           occur during any Mars mission. Solar proton
    Crews undertaking the human                       events can rise to the level where an unshield-
exploration of Mars will encounter the active         ed person can acquire a life threatening
space environment, the in-space environment,          radiation dosage. However, shielding with
and the planetary surface environment.                modest amounts of protective material can
                                                      alleviate this problem. The task becomes one
     The active space environment includes            of monitoring for events and taking shelter at
launch from Earth, maneuvers in near-Earth            the appropriate time. Galactic cosmic rays, the
space, launch on a trajectory to Mars, entry          other radiation hazard, occur in small
and landing on Mars, launch from Mars, Mars           numbers, are very energetic, and can cause
orbital maneuvers, launch on a trajectory to          deleterious effects over a long period of time.
Earth, reentry of Earth’s atmosphere, and             For astronauts in LEO, exposure to cosmic
landing on Earth. Because these are energetic         radiation has been limited to that level which
events, the risk is relatively high. In 100           could induce an additional 3 percent lifetime
launches of United States manned spacecraft           risk of cancer (curable or incurable). Because
and a similar number of Russian spacecraft,           of a policy that radiation hazards should be
the only fatal accidents have occurred in             kept as low as reasonably achievable, space-
launch or landing. Once in space, the                 craft and space operations must be designed
environment has been relatively benign.               to minimize exposure to cosmic rays. The
(Apollo 13 was an exception. En route to the          health risk today from radiation exposure on
moon, it experienced an equipment failure             a trip to Mars cannot be calculated with an
which jeopardized the crew. Because of the            accuracy greater than perhaps a factor of 10.
characteristics of the Earth-Moon trajectories        The biomedical program at NASA has given
and the spacecraft design, it was possible to         high priority to acquiring the necessary health
recover the crew. This type of risk can be            data on HZE radiation, including the design
addressed in part by the Mars exploration             shielding materials, radiation protectant
architecture, and can be different for humans         materials, and SPE monitoring and warning
and cargo.)                                           systems for the Mars crew. (For additional
     The quiescent in-space environment is            discussion and explanation of this topic, see
relatively benign from the point of view of           NASA, 1992; Townsend, et al., 1990; and
explosions and other spacecraft accidents.            Simonsen, et al., 1990.)




                                                   3-13
     The planetary surface is the third               trip to and from Mars, without accomplishing
environment which provides risks to crews.            any surface exploration objectives, would be
Because operational experience on Mars is             only minimally successful. Mission risk is
limited, this environment is the least                related to the integrated capability of the crew
understood. As the objective of human                 and their systems to conduct the mission. For
exploration of Mars will be to spend time on          the crew or the systems to fail to perform puts
the surface of Mars, extensive EVA will be            the mission at risk of failure. On the human
required as part of the mission. EVAs will            side, this requires attention to health, safety,
involve exiting and reentering pressurized            performance, and other attributes of a
habitats and conducting a variety of activities       productive crew. On the system side, this
on the surface in space suits or other                requires that systems have low failure rates,
enclosures (including vehicles). In this area,        have robust backups for systems that may fail
accidents and equipment failures are the              or require repair, and be able to operate
biggest concerns. These risks must be                 successfully for the required period of the
addressed by examining a combination of               mission. Strategies to minimize failure can be
detailed information about the surface                designed at the architecture level or at the
environment, designing and testing                    system level.
hardware, and training the crew. To some
extent, EVA can be reduced or simplified by           3.2.3   Risks to Program Success
using telerobotic aids operated by the crew                Program risk is a term that refers to the
from their habitat. (The risks associated with        programmatic viability of the exploration
the habitat itself are probably similar to those      program—that is, once the program has been
faced in free space, with somewhat more               approved, what are the risks that it will not be
benign radiation and thermal environments.)           completed and the exploration not
Finally, the presence of dust on Mars will            undertaken? These are programmatic issues
present risks, or at least annoyances, to             that in many cases seem less tractable than
surface operations. Robotic missions to Mars          the technical risks. They can be influenced
prior to human expeditions should improve             when management of the enterprise fails to
understanding of the surface hazards crews            meet milestones on schedule and cost, when
will encounter.                                       unforeseen technical difficulties arise, or
                                                      when political or economic conditions
3.2.2   Risks to Mission Success                      change. They can be mitigated by sound
    The risk of a Mars exploration mission is         program management, good planning, and
measured by the degree to which the program           advocacy or constituency building on the
objectives can be accomplished. A successful          political side.




                                                   3-14
3.2.4   Risk Mitigation Strategy                      suitable suite of replacement systems as
     The riskiest part of the first exploration       backups to the prime systems. The following
missions to Mars may well be the risk of              priorities are recommended.
accident on launch from Earth, and the                    •Crew health and safety are top priority
energetic events of launches and landings                  for all mission elements and operations;
during other phases of the mission are likely              life-critical systems are those absolutely
to make up the remaining high risk parts of                required to ensure the crew’s survival.
the mission. Yet, the environment on the                   This implies that life-critical systems will
surface of Mars will be new and untried, the               have two backup levels of functional
missions will be long, and the opportunities               redundancy; if the first two levels fail, the
to make up for error small. Therefore, a                   crew will not be in jeopardy but will not
conscious approach to minimizing risks on                  be able to complete all mission objectives.
the martian surface must be adopted. For a                 At least the first level of backup is
starting point, it is assumed that this risk               automated. (This is a fail operational/fail
must be smaller than the combined risks of all             operational/fail-safe system.)
of the energetic events. Design requirements
                                                          •Completing the defined mission to a
will have been developed with this in mind.
                                                           satisfactory and productive level
     The strategy for reduction of risks on the            (mission-critical) is the second priority.
surface involves four levels of consideration.             This implies that mission-critical
At the top level, the mission architecture                 objectives will have one automated
provides for assurance that all systems will               backup level. (This is a fail operational/
operate before crews are launched from Earth.              fail-safe system.)
The strategy must be flexible in allowing
                                                          •Completing additional, possibly
subsequent robotic missions to replace any
                                                           unpredicted (mission-discretionary),
systems shown not to be functional prior to
                                                           tasks which add to the total productivity
sending crew. This, in turn, places design
                                                           of the mission is third priority. The crew
requirements on the hardware to allow
                                                           will not be in jeopardy if the mission-
problems to be identified, isolated, fixed in
                                                           discretionary systems fail, and a backup
place if possible, and bypassed if necessary
                                                           is not needed. (This is a fail-safe system.)
through the addition of a parallel capability
sent on a subsequent flight.                               The systems contributing to this backup
                                                      strategy were assumed to be provided by
     The second level of risk reduction
                                                      either real redundancy (multiple systems of
involves providing redundancy through the
                                                      the same type) or functional redundancy
overlapping functional capabilities between
                                                      (systems of a different type which provide the
various systems, the ability to repair any life-
                                                      required function). Recoverability or
critical systems, and the provision of a




                                                   3-15
reparability by the crew will provide yet           be prepared to complete the full mission
additional safety margins.                          without further resupply from Earth.
                                                    Unlimited resources cannot be provided
     The third level of risk reduction involves
                                                    within the constraints of budgets and mission
the automation of systems including fault
                                                    performance. Their resources will either be
detection, failure projection, and maintenance
                                                    with them or will have already been delivered
activities, and the provision of data that
                                                    to or produced on Mars. So trade-offs must be
demonstrate current status and predict future
                                                    made between cost and comfort as well as
states. Such systems are not only conservative
                                                    performance and risk. Crew self-sufficiency is
of crew time, but also more effective and
                                                    required because of the long duration of their
precise, particularly on routine monitoring
                                                    mission and the fact that their distance from
and control tasks.
                                                    Earth impedes or makes impossible the
     The fourth level of risk reduction is          traditional level of communications and
related to crew training and proficiency. The       support by controllers on Earth. The crews
biggest concern in this area is that the crew       will need their own skills and training and
will be away from the traditional Earth-based       specialized support systems to meet the new
training environment for years at a time.           challenges of the missions.
Those areas with direct human
                                                         Crews should be selected who will agree
involvement—EVA, life support systems,
                                                    to conduct operational research willingly and
high capacity power systems, propellant
                                                    openly. Crew members should be selected
production and storage, mobile vehicles, and
                                                    who can relate their experiences back to Earth
other complex facilities—all carry a high risk
                                                    in an articulate and interesting manner, and
for accident, particularly if training is not
                                                    they should be given enough free time to
recent or crew members become
                                                    appreciate the experience and the opportunity
overconfident. Crews will most likely be
                                                    to be the first explorers of another planet.
required to participate in continuous task
training for safety awareness requirements.              Because the objectives of the missions are
                                                    to learn about Mars and its capability to
3.3    Flight Crew                                  support humans in the future, there will be a
                                                    minimum level of accomplishment below
    Humans are the most valuable mission
                                                    which a viable program is not possible.
asset for Mars exploration and must not
                                                    Survival of humans on the trip there and back
become the weak link. The objective for
                                                    is not a sufficient program objective.
humans to spend up to 600 days on the
martian surface places unprecedented
                                                    3.3.1   Crew Composition
requirements on the people and their
supporting systems. Once committed to the               The number of crew members to be taken
mission on launch from LEO, the crew must           to Mars is an extremely important parameter




                                                 3-16
for system design, because the scale of the        lists of required skills were developed.
habitats, space transportation system, and         Expertise is required in three principal areas.
other systems supporting the mission are
                                                       •Command, control, and vehicle and
directly related to the number of crew
                                                        facility operations functions. These
members. This, in turn, will have a direct
                                                        functions include command,
relationship to the cost of the first missions.
                                                        management, and routine and
The size of the crew also is probably inversely
                                                        contingency operations (piloting and
proportional to the amount of new
                                                        navigation, system operations,
technology which must be developed to allow
                                                        housekeeping, maintenance, and repair
all tasks to be performed. Because of
                                                        of systems). Maintenance must be
communication time delays between Earth
                                                        accomplished for facility systems,
and Mars, some functions that have
                                                        human support systems (medical
previously been performed by people on
                                                        facilities, exercise equipment, etc.), EVA
Earth will be carried out autonomously or by
                                                        systems, and science equipment.
crew members. Generally, there will be a high
degree of automation required for routine              •Scientific exploration and analysis. This
operations on the Mars journey to allow crew            area includes field and laboratory tasks
members to do specialized tasks.                        in geology, geochemistry, paleontology,
                                                        or other disciplines associated with
      For the Reference Mission study, it was
                                                        answering the principal scientific
assumed that crew health and safety are of
                                                        questions.
first priority in successfully achieving mission
objectives and that the surface system design          •Habitability tasks. These tasks include
requirements for operability, self-monitoring,          providing medical support; operating
maintenance, and repair will be consistent              the bioregenerative life support system
with the identified minimum number of crew              experiment; performing biological,
members. The crew size and composition was              botanical, agronomy, and ecology
determined in a top-down manner (objectives             investigations; and conducting other
¨ functions ¨ skills ¨ number of crew                   experiments directed at the long-term
members + system requirements) as the                   viability of human settlements on Mars.
systems have not been defined in a bottoms-             The types of crew skills needed are
up manner based on an operational analysis         shown in Table 3-2 (Clearwater, 1993). If each
of the system.                                     skill is represented by one crew member, the
    The Mars Study Team workload analysis          crew size would be too large. Personnel will
assumed that the crew would spend available        have to be trained or provided the tools to
time in either scientific endeavors or             perform tasks which are not their specialty.
habitation-related tasks. From that analysis,




                                                3-17
                                 Table 3-2 Surface Mission Skills

      Specialized Operations                       Focused
           and Services                           Objectives                  In-Common

     Mechanical Systems Operations,       Geology                       Management/planning
      Maintenance and Repair              Geochemistry                  Communications
                                          Paleontology                  Computer Sciences
     Tool-Making                          Geophysics including          Database Management
                                           Meteorology and
                                           Atmospheric Science
     Electrical Systems Operations,                                     Food Preparation
      Maintenance and Repair                                            • routine greenhouse
                                          Biology                         operations
     Electronics Systems Operations,
     Maintenance and Repair               Botany                        • plants to ingredients
                                          Ecology                       • ingredients to food
                                          Agronomy
                                          Social Science                Vehicle Control
                                                                        Navigation
                                                                        Teleoperated Rover Control

     General Practice Medicine
     Surgery                              Biomedicine                   Journalism
     Psychology                           Psychology                    Housekeeping




Special skill requirements appear to be in the             procedures under the direction of
areas of medicine, engineering, and                        medical experts on Earth (through
geoscience.                                                telemedicine).

   •Medical treatment. In a 3-year mission, it          •Engineer or technician. A person skilled
    is very likely that an accident or disease           in diagnosing, maintaining, and
    will occur. At least one medically trained           repairing mechanical and electrical
    person will be required as well as a                 equipment will be essential. A high
    backup who is capable of conducting                  degree of system autonomy, self-
                                                         diagnosis, and self-repair is assumed for
                                                         electronic systems; however, the skill to




                                                 3-18
     identify and fix problems, in conjunction           and a minimum number of crew
     with expert personnel on Earth, has been            members will be required by the
     repeatedly demonstrated to be essential             distribution of tasks. For example, EVAs
     for space missions.                                 are likely to require at least two people
                                                         outside the habitat at any one time in
   •Geologist-Biologist. A skilled field
                                                         order to assist each other. A third person
    observer-geologist-biologist is essential
                                                         is likely to be required inside to monitor
    to manage the bioregenerative life
                                                         the EVA activities and assist if necessary.
    support system experiment. All crew
                                                         If other tasks (repair, science,
    members should be trained observers,
                                                         bioregenerative life support system
    should be highly knowledgeable of the
                                                         operation) are required to be done
    mission science objectives, and should be
                                                         simultaneously, the number of crew
    able to contribute to the mission science.
                                                         members may need to be increased.
     Other factors will also contribute to the
                                                        •Specific contingency situations and
final determination of crew size: system
                                                         mission rules have not been established
autonomy, simultaneous operations,
                                                         for the Reference Mission because it is
contingency situations, human factors, and
                                                         too early in the design phase. However,
international participation.
                                                         the choice of what the crew will be
   •Electronic and mechanical equipment                  allowed to do or not do can impact the
    must be highly autonomous, self-                     size of the crew. For example, during
    maintained or crew-maintained, and                   exploration campaigns, mission rules
    possibly self-repairing. The amount of               may require that some portion of the
    time taken to do routine operations must             crew be left in the main habitat while the
    be minimized through system design. In               remainder of the crew is exploring in the
    principle, the operation of supporting               mobile unit. It will be necessary to have
    systems (such as power, life support, in             a backup crew to operate a rescue
    situ resource recovery) should be                    vehicle in case the mobile unit has a
    transparent to the crew. The best                    problem. If the exploration crew requires
    approach in this area is to define the               three people, the requirement to have
    requirement for technological                        one driver for a backup unit and one left
    development based on the mission                     at the outpost implies a crew of not less
    requirements for a given crew size.                  than five.
   •Simultaneous operations will be                     •In terms of human factors
    required during the nominal mission. All             considerations, the psychological
    crew members will be fully occupied                  adjustment is more favorable in larger
    during their assigned working hours,                 crews of six to eight than in smaller




                                                 3-19
     crews of three to five. However, the             success. Therefore, a larger crew may be
     psychological environment may be met             required to address the risk issues. Currently,
     by system and support provisions rather          the Reference Mission is built on the
     than by the crew size itself.                    assumption of a crew of six.

   •It is conceivable that each country that
                                                      3.3.2   Crew Systems Requirements
    makes a major contribution to an
    international Mars exploration mission                 To survive, the crew will need adequate
    will demand representation on the crew.           shelter, including radiation protection;
    Currently, a Mars crew might be                   breathable, controlled, uncontaminated
    patterned after the International Space           atmosphere (in habitats, suits, and
    Station with representatives from the             pressurized rovers); food and water; medical
    United States, Russia, European Space             services; psychological support; and waste
    Agency, and Japan. However, in an                 management. During the 4- to 6-month transit
    enterprise of this magnitude, Third               to Mars, the chief problems will be
    World representatives might also be               maintaining interpersonal relationships
    selected by the United Nations.                   needed for crew productivity and
                                                      maintaining physical and mental
     At a summary level, the five most
                                                      conditioning in preparation for the surface
relevant technical fields required by the
                                                      mission. On the Mars surface, the focus will
exploration and habitation requirements
                                                      turn to productivity in a new and harsh
include mechanical engineer, electrical and
                                                      environment. The transit environment is
electronics engineer, geologist, life scientist,
                                                      likely to be a training and conditioning
and physician-psychologist. These fields
                                                      environment, the surface environment is
should be represented by a specialist, with at
                                                      where the mission-critical tasks will be done.
least one other crew member cross-trained as
a backup. Crew members would also be                       For long-duration missions with
cross-trained for the responsibilities of a wide      inevitably high stress levels, the trade-off
variety of support tasks as well as tasks of          between cost and crew comfort must be
command and communications.                           weighed with special care. High quality
                                                      habitats and environmental design features
    The result of the workload analysis
                                                      are critical to assuaging stress and increasing
indicates that the surface mission can be
                                                      crew performance—conditions that will
conducted with a minimum crew of five,
                                                      greatly increase the likelihood of mission
based on the technical skills required.
                                                      success. Providing little more than the
However, loss or incapacitation of one or
                                                      capability to survive invites mission failure.
more crew members could jeopardize mission
                                                           Not all amenities need be provided on
                                                      the first mission. The program should be




                                                   3-20
viewed as a sequence of steps which, over            member will be from 10 percent to 20 percent
time, will increase the amount of habitable          of the amount of their time on Mars.
space on the surface, increase the amount of         Automated or teleoperated rovers could
time available to the crew to devote to              extend the effective field time by crew
mission objectives and personal activities,          members.
increase the amount of crew autonomy,
improve the quality of food, increase access to      3.4      Mission Operations
privacy, and increase the quality and quantity
                                                          Central to the success of the Reference
of communications with Earth. In addition,
                                                     Mission is the accomplishment of all activities
experience in Mars surface operations may
                                                     associated with mission objectives. To this
reduce some of the stresses associated with
                                                     end, crew operations are an essential part of
the unfamiliarity of the environment.
                                                     ensuring program success and must be
     The quality of life can be enhanced by          factored into all aspects of program planning.
access to and use of indigenous resources. In        All crew activities throughout each mission,
the near term, use of indigenous resources           from prelaunch through postlanding,
reduces some of the mission risks (creation of       constitute crew operations. The majority of
caches, use of local resources for radiation         crew activities fall into four categories:
shielding, etc.). In the long term, use of local     training, science and exploration, systems
resources may allow more rapid expansion of          operation and maintenance, and
usable space. Achieving the capability to            programmatic.
produce water and oxygen from local
                                                           •Training activities include such areas as
resources may have physical and
                                                            prelaunch survival training for all critical
psychological benefits over continued
                                                            life support systems, operational and
recycling (for example, reducing limitations
                                                            maintenance training on mission-critical
on water utilization for hygiene purposes).
                                                            hardware, prelaunch and in-flight
The ability to grow food on site also has an
                                                            proficiency training for critical mission
enhancing psychological effect. The
                                                            phases, and science and research
psychological impacts of these developments
                                                            training for accomplishing primary
is difficult to quantify, however real the effects
                                                            science objectives.
may be.
                                                           •The majority of science and exploration
     Finally, crew support by intelligent robots
                                                            activities will be accomplished on the
and automated systems appears to be a good
                                                            surface of Mars. They include, but are
investment from the point of view of total
                                                            not limited to, teleoperated robotic
mission productivity. The workload analysis
                                                            activities, habitability experiments, local
indicates that the total amount of time spent
                                                            and regional sorties, and planetary
in the field (on foot or in a rover) by a crew




                                                 3-21
        science investigations. Supplemental          Extensive training in these areas will improve
        science objectives may be accomplished        overall mission success as well as contribute
        during other phases of the mission as         to meeting science and exploration objectives.
        well.                                         Several overriding principles must govern the
                                                      way training is conducted for the Reference
   •During the first mission, a substantial
                                                      Mission. Due to time constraints, crew
    amount of crew time will be spent
                                                      training in preparation for the first mission
    operating and maintaining vehicle
                                                      must be done concurrently with vehicle and
    systems. This time allocation is expected
                                                      training facility development. The first crew
    to decrease with subsequent missions as
                                                      and mission controllers will be supplanting
    the systems and operational experience
                                                      operational training with involvement in
    base matures.
                                                      system design and testing. This will provide
   •Lastly, programmatic activities for the           the mission team with the needed system
    crews include publicity, documentation,           familiarity which would otherwise come from
    reporting, and real-time activity                 operational training exercises. Operations
    planning.                                         input on system designs also has the added
     This report does not make specific               benefit of enhancing vehicle functionality and
conclusions regarding hardware                        operability (for example, nominal daily
requirements, facilities requirements, and            operations such as housekeeping, food
training programs, but a number of                    preparation, and system maintenance will
recommendations and guidelines regarding              benefit from input by the actual users).
these areas have been developed and tailored                Additional prelaunch training must
to the various mission phases that will be            emphasize developing a working knowledge
experienced by each crew sent to Mars. While          of life-critical and mission-critical elements.
these and other crew activities may not be            Because reliance on Earth-based ground
seen as directly affecting program success, all       control becomes more difficult and less time-
areas contribute to the successful completion         responsive as the mission progresses toward
of each mission and are, therefore, essential to      Mars, crew self-sufficiency becomes essential.
the overall success of the Reference Mission.         In-depth training on life-critical and mission-
                                                      critical systems will enable crews to become
3.4.1     Training Guidelines                         more self-sufficient. Contingency survival
    The key to successful operations is               training for failures in critical life support
having well prepared, knowledgeable team              systems will also be required as real-time
members. This knowledge and preparation is            ground support will not be possible during
most effectively obtained by training for             Mars surface operations and similar remote
nominal and contingency operations.                   phases of flight.




                                                   3-22
     Extensive preflight and in-flight training      critical events will ensure that crews are
on critical event activities (such as major          adequately prepared for both nominal and
propulsive maneuvers, Mars atmospheric               contingency situations. From Earth launch
entry, surface sorties, and Earth atmospheric        until Mars ascent and TEI is about 2 years
entry) will be required to ensure crew               which necessitates an ongoing training
proficiency during these busy time periods.          regime to maintain proficiency. The Earth-
The need for such training will require              based training the crews received 2 years
preflight development of a well-defined              earlier prior to Earth launch will not be
activity plan for all critical events.               sufficient. Training for the Mars atmospheric
Significantly less preflight training will be        entry and landing phase will be conducted by
required for noncritical, mission-success-           the crew during the transit between Earth and
oriented activities such as surface science          Mars. While on the martian surface and
operations. The initial surface operations           intermixed with other surface activities, the
required for the establishment of the Mars           crew will conduct proficiency training for the
surface base and preliminary surface science         critical Mars ascent phase, subsequent
activities will be well defined before the first     docking with the ERV, and trans-Earth
crew departs. Subsequent exploration and             propulsive maneuver. In-flight and surface
science activities will depend on the findings       training requirements dictate the need for
from the initial scientific investigations. As a     effective training facilities in the habitat
result, training for more than the initial           vehicles or in the ascent vehicles. Design and
science activities will not be feasible. Instead,    development of such facilities will require
it will be necessary to ensure that crews have       further investigation and is beyond the scope
the skills to enable them to plan and prioritize     of this preliminary report.
real-time activities in support of the overall
                                                          Documentation in the form of computer-
mission objectives. Some planning assistance
                                                     based libraries must be available for
and direction will be provided by ground
                                                     operational instruction, maintenance of and
personnel; however, the responsibility for
                                                     troubleshooting systems, and hardware
detailed planning and execution will reside
                                                     failures. Reliable and immediate access to this
with the crew. They are on the surface and
                                                     type of information will supplement crew
have firsthand knowledge of environmental
                                                     training for all types of activities from
and logistical considerations.
                                                     mission-discretionary to life-critical. Extensive
     Due to the length of the mission and            computer-based resources will have the
length of time between critical event                added effect of increasing crew self-
activities, proficiency training will be             sufficiency during remote mission phases.
necessary during all phases of the mission. In
                                                         The final, but by no means least
flight and on the martian surface, training for
                                                     significant, element of crew training will be




                                                  3-23
the feedback provided by the early crews on         objectives as well. Detailed identification of
training applicability and effectiveness related    safety requirements and related activities is
to all mission phases. Feedback from the first      not required until later in the mission
crew in particular will need to be                  planning process and will not be discussed
incorporated into training procedures,              here.
hardware, and facilities to be used by
                                                         Subsequent exploration and science
subsequent crews. An effective channel for
                                                    activities will depend on the findings from
incorporating this feedback into redesign and
                                                    the initial scientific investigations. As a result,
upgrading of systems and procedures will be
                                                    it will be necessary for crews to do real-time
essential for follow-on crew training.
                                                    science activity planning to continue research
                                                    activities. Principal investigators and ground
3.4.2   Science and Exploration
                                                    support personnel will provide the guidelines
     The majority of science and exploration        for use in planning priorities of mission
activities will be accomplished on the surface      objectives. However, the detailed procedures
of Mars. They include, but are not limited to,      for executing science activities must be left, in
teleoperated robotic activities, habitability       general, to the crews who have firsthand
experiments, local and regional sorties, and        knowledge of the unique environmental and
planetary science investigations. Additional        logistical considerations of this mission.
science activities which supplement the             Additionally, eliminating the excessive
primary science objectives may be                   ground planning and replanning activities
accomplished during other phases of the             which have been customary for near real-time
mission as well; however, the largest portion       manned space operations will reduce cost.
of time and activity allocated in support of
                                                         Beyond the initial investigations, several
science and exploration will occur on the
                                                    surface science and exploration activities can
planetary surface.
                                                    be identified preflight as targets for detailed
     Initial surface science activities will be     planning and execution: telerobotic
well defined before each crew departs Earth.        exploration and local and regional surface
Detailed activity planning to maximize the          sorties. Such preflight planning will maximize
crews useful science and exploration time will      the crew’s useful science time, maximize
increase overall mission success and will be        science return, improve crew safety on
necessary to ensure the successful completion       difficult exercises, and increase overall
of many primary science objectives and              mission success.
mission safety requirements. Many
investigative results designed to satisfy safety
requirements (for example, tracking crew
health) will contribute to satisfying science




                                                 3-24
3.4.3 Systems Operations and                            Where applicable, autonomous vehicle
Maintenance                                        health monitoring and testing will enable
     During the first mission, a substantial       crew members to use their time performing
amount of crew time will likely be spent           science and exploration activities. In
operating and maintaining vehicle systems.         conjunction with this automation, access to
This time is expected to decrease with             hardware and software documentation for all
subsequent missions as the systems and             systems can expedite operations and
operational experience base mature.                maintenance activities which require crew
However, until that time, the more familiar        participation. Additionally, due to large
the crews are with all systems, the less time      resource requirements, some of the vehicle
operations and maintenance will take from          operations, such as long-term health
science and exploration activities. To enhance     monitoring, trend development or prediction,
crew familiarity with the numerous vehicle         and failure analysis, may be accomplished by
systems prior to launch, crews should be           ground system support personnel. The
involved in the design and testing of primary      delineation between which system functions
vehicle systems. The resulting intimate            are automated, crew-managed, or ground-
knowledge of the vehicle systems has the           support-managed is not clear and is subject to
added benefit of supplementing crew training       a host of variables. Some of the considerations
on their operational use. Another way to           to be used in making this determination are
facilitate crew familiarity is to ensure that      crew useful time, availability of supporting
system designs are modular and easily              documentation, knowledge of system
repairable. The simpler and more familiar the      performance (that is, are we operating outside
design, the easier it is to repair and maintain.   the envelope?), time criticality of failure
                                                   recognition and recovery, and constraints on
     Due to the nature of the Reference
                                                   development time and cost. General
Mission program design (where vehicles are
                                                   guidelines of responsibility for vehicle
placed in a standby mode and subjected to
                                                   operations are best determined early in the
hostile environments for long durations), in-
                                                   design process as automation of functions
depth vehicle and system checkouts will be
                                                   will affect mission and vehicle design.
required periodically. Crew participation in
these activities should be minimized but may       3.4.4   Programmatic Activities
be necessary due to their access to some of the
system hardware. Such access and                        Programmatic activities for the crews
participation may make the crews uniquely          include publicity, documentation, reporting,
suited for analysis of anomalous results that      and real-time activity planning. These types
might appear in the system testing.                of activities are not usually seen as directly
                                                   affecting program success. They do, however,




                                               3-25
and if properly planned and coordinated, will      political support to programs and contribute
enhance crew performance and interaction.          to program success. Crew resources from
Like vehicle performance, crew performance         preflight through postlanding will have to be
is key to a successful mission.                    allocated in support of this activity.

     Successful team performance and                    Another element which contributes to
interaction depends on having defined roles        program success is the crew feedback on all
and responsibilities and the flexibility to        aspects of the mission. Their input on system
handle real-time events. For complex               designs, operations, science activities (for
programs like the Reference Mission, this is       example, appropriateness, preparedness,
important not only among crew member               required hardware), and training effectiveness
teams, but also among ground support               is necessary for the continued improvement
personnel teams and between ground support         and enhancement of follow-on missions.
and the crews. For the crews, knowing who is       Along these same lines, documentation of all
responsible for what and when makes for            activities (such as procedural changes, lessons
smoother operations and can alleviate some         learned, observations, hardware
of the stress associated with long-term, small     discrepancies) is a time-consuming but
space, personnel interaction. For ground and       necessary crew activity. (Using various
crew interaction, clear rules governing who is     electronic systems rather than similar paper
in charge of what activities and who               systems for documentation preparation will
determines what gets done and when are             provide savings in terms of mass, reliability,
essential for maximizing mission and science       reduced consumables, etc.) Crew records can
objective returns and alleviating confusion        be used to contribute to mission feedback as
especially during remote operations. This will     well as documentation. Documentation and
enhance operational performance when               feedback are important, especially for the first
combined with a flexible operational               crew, to ensure optimal use of the subsequent
architecture allowing crews to create and          crew’s time and to enhance the chances of
optimize the methods required to handle real-      success of future missions of this type.
time events and achieve set objectives and
goals. (Further discussion on ground               3.4.5   Activity Planning
operations and team interaction can be found            The level of crew operations in training,
in Section 3.8.)                                   science and exploration, systems operations
     Public affairs activities have been and       and maintenance, and programmatic
always will be an integral part of crew            activities varies throughout different phases
activities. While they absorb resources            of the mission; however, some characteristics
(mostly time), they also bring public and          are consistent throughout the phases. For
                                                   instance, life-critical or mission-critical




                                                3-26
activities, regardless of mission phase, require    and the success of mission objectives.
detailed planning and precise execution. In         Feedback from the crew will be important
contrast, non-life-critical or mission-critical     during the early phases of this mission, as
science and exploration activities may rely on      both ground support and flight crew
real-time procedures generated by the crew          members adapt to the unique environmental
whose guidelines for planning will be to            and operational challenges of the mission.
achieve set mission objectives and goals.
Guidelines for crew activity planning must          3.4.5.1 Prelaunch Phase
incorporate the flexibility to adapt to the              Crew activities during the prelaunch
crew’s experience as they learn to live and         phase of the mission will concentrate on
work in a new environment.                          training activities for all mission phases. Early
     In general, crew activity planning must        on in the program development, crew
be done using a relatively fixed format and         involvement in design and testing of primary
timeline. This will allow crew members to           systems will help facilitate crew familiarity
readily adapt to the various environments in        with the systems and enhance applicability of
which they will be expected to work and live.       system designs. The resulting intimate
Having regular awake and sleep times,               knowledge of the vehicle systems has the
consistent meal times, etc., from phase to          added benefit of supplementing crew training
phase will help the crew adapt to mission           on their operational use. Extensive training on
phase transitions. Having a consistent length       nominal everyday operations (such as
workday is also important. With the Mars day        housekeeping and food preparation) will also
lasting nearly 25 hours, adhering to an Earth-      make the crew more comfortable in their
based daily schedule of 24 hours would              changing environments. Strong emphasis on
routinely have the crew awake during                critical life support and mission-critical
martian night. A consistent 25-hour day             systems training will also be required.
throughout all phases of flight should be                An important part of crew training
considered.                                         activities in this prelaunch phase will be
     A typical work schedule on the Space           participation in integrated training activities
Shuttle has crew members working                    with scientists and systems engineers.
throughout an entire flight, only getting time      Preflight interaction with the science
off during extremely long flights (those            community, in the form of experimental
approaching 2 weeks in duration). For               exercises (crews learn to conduct scientific
missions that can last a number of years, a         investigations) and exploration exercises
consistent long-term work schedule must be          (crews simulate local and remote sortie
developed that will give crew members               operations) will enhance overall mission
sufficient time off yet maintain productivity       success and scientific return. This will benefit




                                                 3-27
not only the crew but also the ground science        Nominal actions directly associated with the
and systems teams by forcing them to interact        launch are expected to be minimal. Once in
in a way that will be unique to remote               orbit, crew activities will center on a complete
operations.                                          checkout of vehicle systems prior to leaving
                                                     Earth orbit while near real-time
     Crew involvement in integrated training
                                                     communications with ground support are
for critical activities (such as launch, injection
                                                     possible. This checkout will include all life-
phase, Earth orbit systems checkout, Mars
                                                     critical, mission-critical, and mission-
landing phase, return phases) will be needed
                                                     discretionary systems with appropriate
to ensure crew proficiency and performance
                                                     actions being taken for anomalies on each
during these phases. Simulations which stress
                                                     system according to its criticality. Such a
the crew and ground support by introducing
                                                     checkout, which will be as automated as
failures and abort scenarios will help ensure
                                                     possible, will require some crew and ground
crew safety should such instances occur
                                                     support actions either for testing or for
during the mission.
                                                     troubleshooting failures.
     In addition to prelaunch training
                                                          While in Earth orbit but before TMI,
activities, extensive medical testing will be
                                                     limited time or personnel may cause some of
required of the crew during this time. Their
                                                     the less critical pre-TMI testing to be deferred.
long- and short-term health will be critical
                                                     For instance, testing on mission-discretionary
factors in the success of this type of long-
                                                     hardware intended for use only on the
duration mission.
                                                     martian surface may be delayed until later in
3.4.5.2 Earth Launch Phase                           the transit to Mars. Such decisions will be
                                                     more appropriately made when vehicle
     The Earth launch phase is defined as the
                                                     system checkout requirements are identified
crew activities required to support mission
                                                     during the design process. Additionally, such
activities from launch through TMI and
                                                     real-time decisions may be made based on
subsequent powerdown of nonessential
                                                     assessments of other activities during the
hardware. It is expected that some systems
                                                     Earth orbit phase.
used during the launch phase will not be
required until later in the mission. The                  Training activities will not be scheduled
hardware which fits in this category will be         during the Earth launch through TMI phase
placed in a quiescent mode to conserve               of the mission as the crew will have been
resources.                                           trained for these activities prior to launch.
                                                     Additionally, with the exception of those
    During the Earth launch phase of the
                                                     activities related to crew health maintenance
mission, the crew’s primary focus will be to
                                                     and monitoring, planned science activities
ensure a safe launch and Mars injection.
                                                     will not be performed during this high




                                                 3-28
systems activity time frame. Medical testing        be made prior to launch based on time or
and assistance may be required during this          personnel constraints or based on the result of
phase as crew members adapt to the change           earlier failures. Activities for failure analysis
in environment. (The number of crew                 and troubleshooting will be accomplished on
members who typically do not experience             an as needed basis.
space sickness during the first few days of
                                                         The relatively quiescent vehicle system
weightlessness is just one in three based on
                                                    activity during the transit phase makes it
171 Shuttle crew members (Reschke, et al.,
                                                    well-suited for crew training activities.
1994).) Any serious life- or mission-
                                                    During this time, additional training time can
threatening crew illness prior to TMI will be
                                                    be made available for the training above and
reason to abort the mission.
                                                    beyond the preflight training that is required
     Throughout all mission phases,                 to maintain crew proficiency during the
documentation of activities and feedback on         relatively long Mars transit time. The need for
training effectiveness will be required of all      in-flight training will require that training
crew members. This will be essential in order       simulators be available to the crew in the
to make effective use of the training time of       transit-habitat vehicle. Critical events that will
the follow-on crew and the program’s                require training during this time are MOI,
training hardware. Due to the high systems          landing, and Mars launch activities.
activity during this phase, documentation           Additional time may also be made available
and other programmatic activities will be           for training and review of payload and
either minimal or deferred to a later time.         science hardware to be used on the surface.

                                                         During the transit phase, time may be
3.4.5.3 Trans-Mars Phase
                                                    available for limited science activities. The
      The trans-Mars phase of the mission is        primary restriction on conducting
defined as crew activities from post-TMI            interplanetary science activities will likely be
system powerdown through Mars Orbit                 mass related. Interplanetary science
Insertion (MOI) preparation. This                   (astronomy, solar observations) is not the
interplanetary transit phase will be fairly         primary science objective for this type of
homogeneous from the standpoint of                  mission; and, as such, related hardware will
environment and crew activity. Crew                 only be provided for crew use if mass
activities related to vehicle systems are           margins exist at the appropriate point in the
expected to be minimal. Only nominal                design process. However, there may be
operations (housekeeping, food preparation,         opportunities for useful scientific data return
etc.) will be required unless mission-              which can “piggy-back” on instruments
discretionary systems testing has been              provided for crew safety issues. An example
postponed until after TMI. This decision may        would be conducting some solar science




                                                 3-29
experiments as part of meeting requirements          and appropriate time must be allocated
for crew safety (as in solar flare detection).       during the crew schedule for such activities.
Also, medical testing will be required
periodically throughout this phase to verify         3.4.5.4 Mars Landing Phase
crew health. Related studies on crew                      The Mars landing phase is a very
adaptation to the space environment and              dynamic phase of the mission and is defined
other health-related biomedical science              as the time from MOI preparation through
experiments may benefit from such testing.           postlanding crew recovery and surface
     As with all mission phases,                     system activation. Many of the activities
documentation of activities and feedback on          during this time frame will have been
training effectiveness will be required of all       planned in detail before launch and perhaps
crew members in order to make effective use          updated during the interplanetary transit.
of the follow-on crew’s training time.                    Prior to MOI the crew will have to
Additionally, the information will provide           prepare the transit-habitat vehicle for
engineers on Earth with guidelines for               transition from a zero-g to a partial-g surface
upgrading and improving the vehicle systems          vehicle. All peripherals, supplies, and
and training hardware. Transit time is ideal         hardware that have been taken out for use
for documenting current and earlier phases of        during transit will have to be safely stowed.
the mission.                                         Nonessential equipment will be powered
     Due to the high interest in such a              down in exchange for equipment necessary
mission, the crew will be required to                for this phase of flight. During this time, the
participate in numerous public affairs               crew will have to checkout or verify the
activities. International participation in this      operational status of all hardware and
type of mission will only increase press             software required for the upcoming critical
demands on crew time. Press and crew                 MOI and landing activities.
exchanges will be particularly productive                 Pre-MOI activities must be initiated early
during relatively quiescent periods early in         enough to allow sufficient time to
the transit phase when communication lag             troubleshoot any failures or discrepancies
times are short. As communication lag time           prior to the critical phase. Many of the
increases, the necessity for crew autonomy           activities during this phase will, by necessity,
will become evident. However,                        be automated. However, crew intervention
communication with Earth will still have to          and override must be available due to the
be provided for failure assistance and crew          uniqueness and criticality of this phase of the
personal interaction with Earth.                     mission (for example, doing critical activities
Communication activities will be higher              without real-time support in a new and
during the initial and critical mission phases,      unique environment) and in general as a
                                                     backup to the automated systems.



                                                  3-30
    After landing, a thorough vehicle                      On approach and on the surface of Mars,
checkout will be necessary due to the drastic         communication lag time with Earth will be
transition in operational environment from            near or at its maximum. During such a critical
vacuum and zero g to a planetary surface              phase of flight, crew functions will, of
environment. Initially, the only checkout             necessity, be virtually autonomous from
which will be done will be on those systems           Earth-based support. Some communication
required to certify that crew safety and life-        with Earth will still have to be provided for
support systems and their backups are                 failure assistance and vehicle health
operational.                                          monitoring of trend data. Such requirements
                                                      may drive the need for regular, perhaps
     Crew training activities during the latter
                                                      continuous, communications capability with
part of the transit phase and the early part of
                                                      Earth.
the landing phase will intensely focus on
critical activities for the MOI and landing
                                                      3.4.5.5 Mars Surface Phase
phase so that the crew is adequately prepared
for upcoming events. Again, this will require              The Mars surface phase is defined as
that adequate training facilities be available to     postlanding recovery operations to prelaunch
the crew on the transit-habitat vehicle.              operations. In general, this phase of the
                                                      mission will receive a minimal amount of
    Minimal science activities will be done
                                                      mission-specific planning and training prior
during the Mars landing phase. Time may be
                                                      to departing Earth; its focus will be on the
available for limited orbital observations to
                                                      mission’s primary science and exploration
take advantage of the unique opportunity to
                                                      activities which will change over time to
photograph and gather remotely sensed data
                                                      accommodate early discoveries. A general
of Mars on approach and from orbit.
                                                      outline of crew activities for this time period
However, this will depend on the available
                                                      will be provided before launch and updated
mass allocated for this type of equipment, the
                                                      during the interplanetary cruise phase. This
success of the higher priority critical systems,
                                                      outline will contain detailed activities to
and the training activities during this time
                                                      ensure initial crew safety, make basic
frame.
                                                      assumptions as to initial science activities,
     Due to the high systems activity during          schedule periodic vehicle and system
this phase, documentation and other                   checkouts, and plan for a certain number of
programmatic activities will be minimal.              sorties. Much of the detailed activity planning
Those activities necessary to improve the             while on the surface will be based on initial
follow-on crew’s training time and program            findings and therefore cannot be
training hardware will be deferred until the          accomplished before landing on Mars.
crew has time available.                              However, the crew will be provided with




                                                   3-31
extensive, but not mission-specific, training          operations personnel, crew involvement
related to scientific investigation and vehicle        provides the crew with confidence in their
systems. This will assist the crew in planning         return systems, enables visual verification of
specific activities in these areas, as required,       ascent vehicle system integrity, and allows for
while on the martian surface.                          crew interaction or intervention in anomaly
                                                       troubleshooting on surface hardware. Beyond
      Initial postlanding systems activities will
                                                       annual, comprehensive vehicle checkouts,
focus on hardware testing and verification for
                                                       system activities for the crew will consist of
life support, then mission-critical, and finally
                                                       maintenance, housekeeping, consumables
mission-discretionary systems. The initial
                                                       tracking, and repair operations.
phase of these checkouts must be done
without the requirement for EVAs. EVAs will                 Initial science activities during the
be restricted until sufficient data have been          surface phase will concentrate on verifying
collected to fully characterize the immediate          crew health and safety on the martian surface.
martian environment. Once it has been                  Atmospheric, chemical, and biological studies
confirmed that the martian environment is              of the immediate environment surrounding
not a threat to crew health or mission success         the crew habitat will be critical to ensure crew
(assuming this has not been done by prior              safety. Once the immediate environment is
robotic missions), EVAs may then be                    characterized and potential threats well
accomplished to complete required systems              understood, planning for future local and
testing and verification.                              regional sorties may begin. Some general
                                                       planning of these initial science activities may
     During the crew stay-time on the surface
                                                       be done in advance; however, much of the
of Mars, additional full-scale testing and
                                                       crew activity will depend on the initial
verification of some hardware will be
                                                       findings and therefore cannot be prepared
required. After vehicle system checkout of the
                                                       prior to launch. The crew must be provided
crew habitat shortly after crew arrival,
                                                       with enough expertise and applicable
activities for joining the crew habitat with a
                                                       hardware and resources to help them deal
previously landed laboratory may begin.
                                                       with potential unforeseen discoveries and
Complete connection of these two vehicles
                                                       obstacles to their investigations.
will be accomplished after a full verification
of each vehicle’s individual integrity is                  Prior to the first EVA and sortie, robotic
completed. Also during the initial                     exploration may map local areas and allow
postlanding time frame, verification and               investigators to seek out interesting sites for
system status check of the vehicles needed for         regional sorties. Mission preparation will
crew launch and Earth return will be                   have assumed a minimum number and type
required. While much of this activity will be          of EVAs; however, adaptation to real-time
autonomous and supervised by ground




                                                    3-32
discoveries will be necessary for many of                 Time will also be allocated for public
these excursions.                                    affairs events. These types of events will not
                                                     be interactive due to the time lag, but will be
     Additional biomedical health science
                                                     recorded and subsequently transmitted to
activities performed on the crew will be
                                                     Earth. Requests from news media and other
required during the surface phase as well.
                                                     organizations will be reviewed, scheduled,
Safety issues, health examinations,
                                                     and then relayed to the crew through mission
investigations to gather data on low-g
                                                     management personnel on Earth. Activities
adaptation, and long-term physiological
                                                     such as these will require a flexible planning
effects on the crew will also be conducted
                                                     architecture in which crew and ground
during the surface phase.
                                                     support both participate.
     As with other phases of flight, there may
                                                          All of the above mentioned surface
be opportunities for some scientific data
                                                     activities will require some level of
return which can piggy-back on instruments
                                                     communication with mission teams on
provided for crew safety issues. For instance,
                                                     Earth—both science and systems teams.
limited solar science may be provided in part
                                                     Analysis of the communication requirements
for crew safety issues (as part of solar flare
                                                     will result from a combination of system data
detection), thus providing opportunity for
                                                     requirements, crew health data requirements,
additional solar science observations while on
                                                     crew personal communications, and science
the martian surface.
                                                     data requirements.
     Training during surface operations will
be periodic to maintain proficiency for              3.4.5.6 Mars Launch Phase
mission-critical activities (such as launch and
                                                          The Mars launch phase is a very dynamic
Earth return). Additional training activities,
                                                     phase of the mission and is defined as the
on an as needed basis, may be required for
                                                     activities from preparation for launch through
activities such as sorties and EVAs.
                                                     TEI and nonessential hardware powerdown.
     Documentation of activities and feedback        Many of the activities during this time frame
on training effectiveness will be required of        will have been planned in detail prior to
all crew members in order to make effective          launch from Earth.
use of the follow-on crew’s training time. The
                                                          Before committing the crew to Mars
information will provide engineers on Earth
                                                     ascent and Earth return activities, full systems
with guidelines for upgrading and improving
                                                     checkout of the MAV and ERV is required.
the vehicle systems and training hardware.
                                                     Because both vehicles are critical to crew
Additional documentation of scientific
                                                     safety and survival, sufficient time must be
experiments and results will need to be
                                                     provided prior to launch to verify systems
relayed to Earth for use by the science teams
                                                     and troubleshoot any anomalous indications
in analysis and future planning.




                                                  3-33
prior to crew use. Additional crew time will               During this most critical of time frames,
be spent preparing the surface habitat and            other activities such as public affairs events
other facilities for an untended mode. Such           and documentation of activities will be
activities will include stowing any                   minimized. Due to the critical nature of this
nonessential hardware, safing critical systems        mission phase, communication transmissions
and their backups, and performing general             to Earth will be necessary for failure
housekeeping duties which will facilitate use         assistance and vehicle health monitoring.
of the facilities by future crews.                    However, due to the nature of the lag time
                                                      and the criticality of events, vehicle and crew
     Once the crew has prepared all surface
                                                      activities will remain fairly autonomous.
equipment for departure, the actual departure
activities will begin. Detailed activities for this
                                                      3.4.5.7 Trans-Earth Phase
departure will have been prepared and
simulated on Earth, so a detailed plan for                  The trans-Earth phase is defined as the
Mars launch through TEI will be available             post-TEI powerdown through preparation for
and executed at the appropriate time.                 Earth landing. This interplanetary transit
Contingency scenarios will also have been             phase will be fairly homogeneous from an
planned prior to Earth launch, and enough             environment and crew activity standpoint.
time will be allocated during ascent and              The crew activities related to vehicle systems
rendezvous activities to enable successful            are expected to be minimal. Only those
operations within these contingencies. After          activities required for nominal operations will
successful launch, rendezvous with the return         be required (housekeeping, food preparation,
vehicle, and TEI, the crew will again place           etc.).
nonessential hardware in a quiescent mode                  Crew training activities during this time
for the return trip.                                  frame will focus on the critical Earth entry
     In the time period leading up to the Mars        and landing phase of flight. This will drive an
launch phase, the crew will spend an                  ERV hardware requirement to provide the
increasing amount of time training and                crew with adequate simulators and on-board
preparing for this extremely critical phase of        training facilities to maintain proficiency in
the mission. In particular, the rendezvous            vehicle operations. The crew will also begin a
with the ERV will require attention. Sufficient       regime of zero-g countermeasure activities
training facilities must be available on the          (such as exercise, lower body negative
surface to ensure crew proficiency in these           pressure, etc., depending on the best available
activities prior to execution. Also,                  knowledge at the time) to prepare themselves
physiological training for the return to a zero-      physically for return to a one-g environment.
g and eventually a one-g environment will be              Again, due to the relatively quiescent
dramatically increased during prelaunch.              system activity during the transit phase, time




                                                   3-34
may be available for the crew to do limited         currently known how prolonged low-g and
science activities. The restrictions on             zero-g environments will affect the human
interplanetary science activities will be mass      physiology, the main focus of this phase of
related. Medical testing will be required           flight will be the safe return and recovery of
periodically throughout this phase in order to      the crew.
meet biomedical science objectives and verify
                                                         Crew activities related to vehicle systems
crew health for entry.
                                                    will be emphasized prior to entry. System
     During this time frame, documentation          checkout will be required with sufficient time
activity will be extremely important due to         prior to entry to allow for troubleshooting
the fact that the next crew will be launched        any failures and guarantee a safe crew
prior to the return crew’s landing.                 landing. Upon landing, vehicle safing and
Additionally, the information will provide          powerdown will be required. Due to the high
engineers on Earth with guidelines for              probability of lower than normal physical
upgrading and improving the vehicle systems         capability among the crew, many of the
and training hardware. Due to time                  postlanding system activities should be
considerations, some handover                       automated.
documentation for the next crew will have
                                                         No training or science activities will be
been prepared prior to leaving Mars. Final
                                                    planned during this critical phase of flight.
transfer of vehicle status is recommended to
                                                    Crew health monitoring will be conducted for
be direct from crew to crew to prevent
                                                    the purposes of crew health and safety. Also,
confusion and ensure thoroughness. Some
                                                    due to the time-critical nature of this phase,
aspects of the hand over may be filtered
                                                    documentation will be minimal and will
through ground support in order to simplify
                                                    pertain only to crew preparedness and system
communications requirements.
                                                    performance.
     Due to the high interest in such a
mission, the crew will be required to               3.4.5.9 Postlanding
participate in numerous public affairs                  The postlanding phase of crew
activities. Quiescent periods of transit time       operations is defined as the activities
can provide opportunities for press and crew        conducted after vehicle powerdown through
interaction.                                        mission termination. In most instances,
                                                    mission termination will not be a well-defined
3.4.5.8 Earth Entry and Landing
                                                    time and may be different for different
    The Earth entry and landing phase is            members of the crew as crew involvement in
defined as the crew activities which support        additional program activities is subject to
preentry preparation through landing and            various conditions.
crew health recovery. Because it is not




                                                 3-35
     Face-to-face debriefings with the             3.5     Mission Design
engineers responsible for individual systems
                                                        The focus of this section is to describe a
and vehicles will be beneficial after landing.
                                                   feasible sequence of flights on specific
Such meetings can be more productive and
                                                   trajectories with specific systems that
provide more information than written
                                                   accomplish Reference Mission goals and
documentation. Feedback on all training
                                                   objectives. Foremost among the choices that
activities and facilities throughout the mission
                                                   must be made is the type of trajectory to use.
will also be beneficial postlanding as it will
                                                   It must be one that can accomplish mission
facilitate the training of follow-on crews.
                                                   objectives using a reasonable transportation
     Medical testing after landing will            system and at the same time address the risk
continue as part of long-term health               mitigation strategy and still provide for
monitoring. This may be required for an            flexibility within a development and flight
indefinite period of time. Some effects from       program. Other assumptions made that affect
the mission may not appear until months or         the “how” of mission implementation are
even years after the flight phases of the          discussed as part of the overall mission
mission have ended. Therefore, the crew            strategy. With these elements in place, this
members should be subject to periodic              section presents a discussion that includes
medical testing for observation of long-term       such information as launch and arrival dates,
effects of the mission. It may also be necessary   payload manifests, and crew activities for
to satisfy quarantine issues, whether real or      each flight in the set studied for this Reference
political, immediately upon return to Earth.       Mission.
(Quarantine issues will have to be addressed
early in the mission planning phases to            3.5.1   Trajectory Options
ensure that adequate facilities are available           Trajectory options between Earth and
when and if they are needed.)                      Mars are generally characterized by the
     Formal documentation of all aspects of        length of time spent in the Mars system and
the mission will be required of all crew           the total round-trip mission time. The first
members after landing. Additional emphasis         option is typified by short Mars stay-times
will be placed on providing engineers on the       (typically 30 to 90 days) and relatively short
ground with guidelines for upgrading and           round-trip mission times (400 to 650 days).
improving vehicle systems and training             This is often referred to as an opposition-class
hardware.                                          mission, although this report has adopted the
                                                   terminology “short-stay” mission. The
    Due to the high interest in such a
                                                   trajectory profile for a typical short-stay
mission, the crew will be required to
                                                   mission is shown in Figure 3-2. This class has
participate in many public events and
                                                   higher propulsive requirements than the often
debriefings after they return to Earth.




                                               3-36
                                                                                                               MISSION TIMES
                                      MISSION TIMES
                                                                                                         OUTBOUND        224 days
                                OUTBOUND         224 days                                                STAY           458 days
                                STAY              30 days                             Earth Launch       RETURN         237 days
                                RETURN           291 days                               1/17/2014
                                                                        Depart Mars
                                                                                                         TOTAL MISSION 919 days
                                TOTAL MISSION 545 days                   11/30/2015



              DEPART                                                                                                            γ
               EARTH
              1/15/2014
                                      VENUS
                                      FLYBY
                                                                                                      Earth Return
                                     2/23/2015
                                                                                                       7/24/2016



                                                            γ
                                                                                                     Arrive Mars
                                                                                                      8/29/2014
                                 EARTH
                                RETURN
                                7/14/2015

                                                                       Figure 3-3 Typical long-stay mission
                     ARRIVE
                                     DEPART                                          profile.
                                       MARS
                     MARS            9/26/2014
                    8/27/2014
                                                                   conjunction-class, although this report has
                                                                   adopted the terminology “long-stay” mission.
 Figure 3-2 Typical short-stay mission
                                                                   These represent the global minimum-energy
                profile.
                                                                   solutions for a given launch opportunity. The
considered long-stay missions, and typically                       trajectory profile for a typical long-stay
requires a gravity-assisted swingby at Venus                       mission is shown in Figure 3-3.
or the performance of a deep-space                                      Within the long-stay category of
propulsive maneuver to reduce total mission                        missions, the option exists to dramatically
energy and constrain Mars and Earth entry                          decrease the transit times to and from Mars
speeds. Short-stay missions always have one                        through moderate propulsive increases. The
short transit leg, either outbound or inbound,                     total round-trip times remain comparable to
and one long transit leg, that requires close                      those of the minimum-energy, long-stay
passage by the Sun (0.7 AU or less). A                             missions; but the one-way transits are
significant characteristic of this class of                        substantially reduced, in some cases to less
trajectory is that the vast majority of the                        than 100 days, and the Mars stay-times are
round-trip time, typically over 90 percent, is                     increased modestly to as much as 600 days.
spent in interplanetary space. The second                          The round-trip energy requirements of this
mission class consists of long-duration Mars                       class, referred to as a “fast-transit” mission,
stay-times (as much as 500 days) and long                          are similar to the short-stay missions even
total round-trip times (approximately 900                          though the trajectories are radically different.
days). This mission type is often referred to as                   The profile for a typical fast-transit mission is
                                                                   shown in Figure 3-4.




                                                                3-37
                                                MISSION TIMES
                                                                       possible about how humans react in this
                      Earth Launch
                                          OUTBOUND
                                          STAY
                                                         150 days
                                                        619 days
                                                                       environment. Verifying the ability of people
                        2/1/2014          RETURN        110 days
        Depart Mars                                                    to inhabit Mars requires more than a brief
         3/11/2016                        TOTAL MISSION 879 days
                                                                       stay of 30 days at the planet. In addition, the
                                                                       low return on investment associated with a
                                                                γ
                                                                       30-day stay at Mars (of which significantly
    Nominal
   Departure                         Earth Return                      less than 30 days would actually be
   3/11/2016                          6/29/2016
                                                                       productively spent on the Mars surface due to
                  Arrive Mars
                                                                       the crew adaptation to the Mars gravity, crew
                   7/1/2014
                                                                       preparations for Mars departure, etc.) was
                                                                       considered unacceptable. Following the
 Figure 3-4 Fast-transit mission profile.                              August 1992 Workshop (Duke, et al., 1992), it
                                                                       was decided that the “Plant the Flag” mission
3.5.2     Trajectory Selection Factors                                 objective was not a tenable rationale to
                                                                       support the substantial investment involved.
     Three factors make the selection of the
                                                                       Consequently, a long-stay trajectory option
trajectory class critical to the Reference
                                                                       was considered to be best able to satisfy the
Mission. First, the selection must be consistent
                                                                       greatest number of mission goals and
with achieving the Mars exploration goals
                                                                       objectives.
and objectives. Second, the selection must be
consistent with the risk philosophy of the                             3.5.2.2 Satisfying Reference Mission Risk
Reference Mission. And third, for                                      Strategy
programmatic reasons, the trajectory class
selection must provide the flexibility to                                   The applicability of each of the
conduct missions in all opportunities within                           previously discussed mission types to the
the 15-year Earth-Mars trajectory cycle and to                         human exploration of Mars has been the
conduct missions supporting the evolution of                           subject of much debate. The general opinion
Mars exploration objectives and                                        is that the initial flights should be short-stay
implementation strategies.                                             missions performed as fast as possible (so-
                                                                       called “sprint” missions) to minimize crew
3.5.2.1 Satisfying Reference Mission Goals                             exposure to the zero-g and space radiation
and Objectives                                                         environment, to ease requirements on system
                                                                       reliability, and to enhance the probability of
    The goals and objectives of the Reference
                                                                       mission success. However, when considering
Mission focus on allowing human crews to
                                                                       “fast” Mars missions, it is important to
spend the greatest amount of time on the
                                                                       specify whether one is referring to a fast
surface of Mars for the investment made to
                                                                       round-trip or a fast-transit mission. Past
transport them there and to learn as much as




                                                                    3-38
analyses have shown that decreasing round-                                      exceeding long-term cancer risk by more than
trip mission times for the short-stay missions                                  3% above the natural cancer death probability
does not equate to fast-transit times (that is,                                 (which is approximately 20% lifetime risk for
less exposure to the zero-g and space                                           the US population as a whole). At present,
radiation environment) as compared to the                                       the information required to calculate
long-stay missions. Indeed, fast-transit times                                  acceptable risk from radiation exposure
are available only for the long-stay missions.                                  during a Mars mission, especially for the
This point becomes clear when looking at                                        GCR, is not available. Although doses (the
Figure 3-5 which graphically displays the                                       average physical energy deposition by
transit times as a function of the total round-                                 incident particles) can be calculated, the
trip mission duration. Although the short-stay                                  conversion of this information into a
mission has approximately half the total                                        predicted radiation risk cannot be done
duration of either of the long-stay missions,                                   accurately. The National Research Council
over 90 percent of the time is spent in transit,                                recently issued a report estimating the
compared to 30 percent for the fast-transit                                     uncertainty in risk predictions for GCR can be
mission.                                                                        as much as 4-15 times greater than the actual
                                                                                risk, or as much as 4-15 times smaller.
     The interplanetary ionizing radiation of
concern to mission planners consists of two                                          Current knowledge does allow for some
components: galactic cosmic radiation (GCR)                                     qualitative conclusions to be drawn. Radia-
and solar particle events. NASA policy                                          tion risk on the Mars surface, where the GCR
establishes that exposure of crews to radiation                                 fluence is attenuated by 75 percent due to the
in space shall not result in heath effects                                      Mars atmosphere and the planet itself, is
exceeding acceptable risk levels. At present,                                   likely to involve less risk than a comparable
acceptable risk levels are based on not                                         length of exposure in interplanetary space. If
                                                                                the difference in radiation effectiveness
    Long-Stay
    (Minimum                                                                    between the interior of a shielded spacecraft
     Energy)
                                                                                and a habitat on the surface of Mars is not
      Long-Stay
    (Fast-Transit)
                                                                                considered, the GCR fluence to which crews
                                                                                are exposed during a 500 plus day transit to
      Short-Stay
                                                                                Mars is equivalent to approximately 125 days
                     0   100 200 300 400 500 600 700 800 900 1000               of Mars surface exposure. A significant
                                   Mission Duration, Days                       reduction in transit time, to 100 days for the
           Outbound Transit      Time at Destination        Return Transit
                                                                                one-way transit, would result in a radiation
                                                                                exposure comparable to the short-stay
                                                                                mission. Thus, the risk to crews on fast-
      Figure 3-5 Round-trip mission                                             transit missions may be even less than the risk
              comparisons.




                                                                             3-39
to crews on short-stay missions, not only          long surface stays associated with the
because of minimized exposure to GCR but           minimum-energy, fast-transit missions.
also reduced probability of exposure to solar
                                                        Several potential solutions to the
particle events in interplanetary space.
                                                   physiological problems associated with zero-g
     A similar analysis of mission classes is      transits to and from Mars may exist:
involved in considering the crew’s exposure        countermeasures (exercise, body fluid
to the zero-g environment during transits to       management, lower body negative pressure),
and from Mars. Significant physiological           artificial-g spacecraft, and reduced transit
changes occur when zero-g time begins to be        times.
measured in weeks or months. (Bone
                                                        The usefulness of countermeasures to
decalcification, immune and cardiovascular
                                                   reduce some of the zero-g effects is still
system degradation, and muscular atrophy
                                                   unknown. Russian long-duration crews have
are a few of the more unpleasant effects.)
                                                   experienced physiological degradation even
Research on the effects of long-term zero-g on
                                                   when rigorous exercise regimens have been
the human body is in an elementary stage. At
                                                   followed. However, most of these effects seem
the time of the writing of this report, the
                                                   to be quickly ameliorated upon return to a
longest continuous stay in space by a U.S.
                                                   one-g environment, at least when immediate
astronaut is the 181 days of Shannon Lucid
                                                   medical aid is available.
(aboard the Russian MIR Space Station); the
longest stay by a Russian cosmonaut is 366              Rotating the Mars transfer vehicle (MTV)
days. In none of the cases were crews exposed      and ERV is a method of providing an
to zero-g/partial-g/zero-g sequences similar       artificial-g environment for the crew and is
to that projected for Mars missions. Current       most often associated with low-performance
data indicates that recovery in a one-g            propulsion systems, or the short-stay class of
environment can be fairly rapid (a few days),      trajectories (since both require long transit
but development of full productivity could         times). Studies have indicated that the MTV
require significantly more time. Upon arrival      design mass penalties are on the order of 5
on the martian surface, the crew will need to      percent to 20 percent if artificial g is
spend some currently unknown, but probably         incorporated. Depending on the specific
short, time re-adapting to a partial-g field.      configuration, there may also be operational
This may be of concern for the short-stay          complications associated with artificial-g
missions where a substantial portion of the        spacecraft including EVA, maintenance, and
surface stay-time could be consumed by crew        the spin-up/spin-down required for
adaptation to martian gravity. Conversely,         midcourse maneuvering and rendezvous and
ample time will be available for the crew to       docking.
regain stamina and productivity during the




                                                3-40
     Time                                                        Outbound
                                                                                  may prove sufficient to ameliorate the
    (Days)
                                                                 Inbound
                                                                 Total
                                                                                  physiological effects of the relatively short
    600
                                                                                  outbound transit.
    500


    400                                                            Maximum
                                                                    Soviet
                                                                                  3.5.2.3 Satisfying Reference Mission Program
                                                                  Experience
    300
                                                                  (366 Days)      Flexibility
    200
                                                                                       Finally, the selection of trajectory type
                                                                 Maximum US
    100
                                                                  Experience
                                                                  (84 Days)
                                                                                  depends on its allowance for flexibility to
      0
          Minimum Energy *    Fast-transit *     Short Stay **
                                                                                  respond to mission opportunities and
    * Zero-g transits separated by long surface stay (450-600 days)
    ** Zero-g transits separated by short surface stay (30-90 days)
                                                                                  implementation strategies. The higher energy,
                                                                                  short-stay missions significantly vary in both
                                                                                  propulsive requirements and round-trip flight
     Figure 3-6 Microgravity                                                      times across the 15-year Earth-Mars trajectory
  comparisons for various mission                                                 cycle. Additionally, these missions generally
             classes.                                                             require the use of a Venus swingby maneuver
                                                                                  to keep propulsive requirements within
                                                                                  reason. However, these swingbys are not
    Figure 3-6 illustrates some example
                                                                                  always available on the return transit leg and
transit times for minimum-energy, fast-transit,
                                                                                  must be substituted in the outbound transit
and short-stay missions. Note that all one-
                                                                                  leg. Because the transit leg containing the
way transits are within the Russian zero-g
                                                                                  Venus swingby is the longer of the two, the
database.
                                                                                  crew will spend up to 360 days on the trip to
     However, the surface stay-times for                                          Mars, with any associated physiological
short-stay missions are typically 1 to 3                                          degradation occurring at the beginning of the
months. It is unknown whether such a short                                        mission—that is, prior to the crew’s arrival at
time spent in a 0.38-g field will counteract 5                                    Mars. These variations in the trajectory
months of outbound zero-g exposure. In                                            energy requirements can significantly impact
contrast, the one-way trip times of                                               the configuration of the Earth-Mars
representative fast-transit missions are nearly                                   transportation elements for different Earth-
within the current U.S. zero-g database,                                          Mars opportunities. Programmatically, such a
which will certainly be augmented by normal                                       result is unattractive. In contrast, the
International Space Station operations prior to                                   minimum-energy, long-stay missions exhibit
executing human interplanetary missions.                                          very little variation over the 15-year cycle,
Also note that the fast-transit mission’s zero-g                                  while the fast-transit long-stay missions
transfer legs are separated by a substantial                                      reflect only moderate variations across the
period of time in the martian gravitational                                       same 15-year cycle. In addition, neither
field. This long period on the surface of Mars




                                                                               3-41
mission requires a Venus swingby or travel          propulsive capability improvements or would
inside the Earth’s orbit around the Sun.            necessitate much larger interplanetary
                                                    spacecraft launched into LEO for the human
3.5.3   Mission Design Strategy                     missions, thereby requiring assembly and
    Keeping the Reference Mission goals and         docking in LEO and higher ETO launch rates.
objectives in mind, numerous alternatives           Indeed, others have demonstrated that
were considered that could successfully             reductions in trip times reach a point of
accomplish the basic mission. Two major             diminishing returns from the space transfer
considerations that drove many of the               vehicle design perspective (Drake, 1991).
mission design-related selections include:          Thus, a C3 leaving Earth of 20 to 25 km2/sec2
                                                    appears to be appropriate for human
   •Reducing the amount of propellant               missions. This results in maximum Earth-
    needed to move mission hardware from            Mars transit times of approximately 180 days
    one location to another (propellant mass        (2009 opportunity) and minimum transit
    is the single largest element of all            times of approximately 120 days (for the 2018
    components in the Reference Mission)            opportunity, the best case). Similarly, a C3
   •Extending the amount of time spent by           leaving Mars of ~16 km2/sec2 appears to be
    the crew conducting useful                      appropriate for human missions, resulting in
    investigations on the surface of Mars.          similar Mars-Earth transfer times for these
                                                    opportunities. (C3 is a measure of the energy
     The alternatives selected by the Mars
                                                    required to get from Earth to Mars or vice
Study Team that impact mission design
                                                    versa. Specifically, C3 is the square of the
strategy have been grouped into six major
                                                    velocity of departure from a planet. Low C3s
areas and are presented here. Other
                                                    are desirable because there is a direct
alternatives will be discussed in subsequent
                                                    correlation between C3 and the size of the
sections.
                                                    transportation system.)
3.5.3.1 Trajectory Type
                                                    3.5.3.2 Split Mission Strategy
     The discussion presented in the previous
                                                         The split mission approach has been
section led to the selection of the fast-transit,
                                                    adopted for the Reference Mission because it
long-stay class trajectories. However, the
                                                    allows mission elements to be broken into
amount of reduction sought in the Earth-Mars
                                                    manageable pieces rather than trying to
and Mars-Earth transit times must be
                                                    integrate all necessary hardware elements for
balanced with other considerations.
                                                    a single, massive launch. For this mission,
Reductions below 180 days in the one-way
                                                    “manageable” was defined to mean pieces
transit times (for the 2009 opportunity, the
                                                    that can be launched directly from Earth and
worst case) would require either significant
                                                    sent to Mars, using launch vehicles of the




                                                3-42
Saturn V or Energia class, without                   used to capture into orbit about Mars, and
rendezvous or assembly in LEO. A key                 current technology can develop an aeroshell
attribute of the split mission strategy is that it   with a mass that is equal to or less than the
allows cargo to be sent to Mars without a            propulsion system required for capture. Thus,
crew, during the same launch opportunity or          the strategy assumed the development of a
even one or more opportunities prior to the          single aeroshell that can be used for both
crew’s departure. This creates a situation           Mars orbit capture and descent maneuvers.
where cargo can be transferred on low energy,        Given the demands on a descent aeroshell of
longer transit time trajectory, and only the         the Mars entry and landing requirements, the
crews must be sent on a high-energy, fast-           additional capability to permit aerocapture is
transit trajectory. By using a low energy            considered modest.
transfer, the same transportation system can
deliver more payload to the surface of Mars at       3.5.3.4 Surface Rendezvous
the expense of longer flight times. Spacing the           The hardware elements launched as part
launches needed to support a mission across          of the split mission approach must come
two launch windows allows much of the                together on the surface of Mars, which will
infrastructure to be pre-positioned and              require both accurate landing and mobility of
checked out prior to committing crews to             major elements on the surface to allow them
their mission. When combined with the                to be connected or moved into close
decision to focus all Mars surface                   proximity. The alternative was to link major
infrastructure at a single site, this approach       components either in Earth orbit or in Mars
allows for an improved capability to                 orbit prior to entry and landing. Previous
overcome uncertainties and outright failures         studies (NASA, 1989) indicated that the heat
encountered by the crews. Launches of                shields for vehicles with the combined mass
duplicate hardware elements, such as ERVs,           implied by such an orbital rendezvous
on subsequent missions provides either               approach would be exceedingly large and
backup for the earlier launches or growth of         difficult to launch and assemble in orbit.
capability on the surface.                           Precision landing has been demonstrated for
                                                     the Moon (Apollo 12), and studies indicate
3.5.3.3 Aerocapture
                                                     (Barton, et al., 1994) that available guidance
     Mars orbit capture and the majority of          and control systems combined with a simple
the Mars descent maneuver will be performed          beacon transmitting from the surface
using a single biconic aeroshell. The decision       (assumed to be carried by the first element at
to perform the Mars orbit capture maneuver           the site) are sufficient to allow a vehicle to
aerodynamically was based on the fact that an        land at a designated location on Mars with
aeroshell will be required to perform the Mars       uncertainties measured in meters.
descent maneuver no matter what method is




                                                 3-43
3.5.3.5 Use of Indigenous Resources                maneuvers associated with the return:
                                                   departing from the martian surface, departing
     The highly automated production of
                                                   from Mars orbit, and capturing into Earth
propellant from martian resources is another
                                                   orbit. Several alternatives are associated with
defining attribute of the Reference Mission.
                                                   these three events, the proper selection of
The hardware necessary to produce and store
                                                   which can result in a significant savings in
propellants using raw materials available on
                                                   propellant and thus in mass that must be
Mars (in this case, carbon dioxide from the
                                                   launched from Earth. Three key choices
atmosphere) is less massive than the
                                                   affecting this portion of the mission are made
propellant needed to depart the martian
                                                   in the Reference Mission. First, the Earth-
surface for orbit (Ash, et al., 1978). It is now
                                                   return transit habitat used by the crew is left
apparent that the technology for producing
                                                   in Mars orbit. While the outbound habitat
methane and liquid oxygen from the martian
                                                   could have been used for this task, the
atmosphere and some nominal hydrogen
                                                   propellant needed to lift it is significant; and
feedstock from Earth is not only an effective
                                                   it is considered more valuable as part of a
performance enhancement but also appears to
                                                   growing surface infrastructure. The entire
be technologically feasible within the next few
                                                   ERV is composed of the TEI stage and the
years. Splitting the launch of mission
                                                   Earth-return transit habitat. The ERV is
elements allows the propellant production
                                                   delivered to Mars orbit fully fueled, and it
capability to be emplaced, checked out, and
                                                   loiters there for nearly 4 years before being
operated prior to committing the crew to
                                                   used by the crew in returning to Earth.
launch from Earth. In addition to spacecraft
                                                   Second, the crew is not captured into an Earth
propulsion, this production capability on
                                                   orbit at the completion of the mission, but
Mars can provide fuel for surface
                                                   descends directly to the surface much as the
transportation, reactants for fuel cells, and
                                                   Apollo astronauts did when returning from
backup caches of consumables (water,
                                                   the Moon. The Earth crew capture vehicle
oxygen, and trace gases) for the life support
                                                   (ECCV) has the necessary heat shield for
system. All of these features allow for smaller
                                                   Earth reentry. Third, the crew rides into Mars
amounts of consumable material to be
                                                   orbit in a dedicated ascent capsule.
launched from Earth and contributes to the
goal of learning how to live on Mars.
                                                   3.5.4   Mission Sequence
3.5.3.6 Mars Orbit Rendezvous and Direct                Figure 3-7 illustrates the mission
Entry at Earth                                     sequence analyzed for the Reference Mission.
    The last element of mission design is          In this sequence, three vehicles will be
returning the crew to Earth. There are             launched from Earth to Mars in each of four
potentially three significant propulsive           launch opportunities starting in 2007. The




                                               3-44
     ETO
    FLIGHT   2007     2008      2009        2010         2011       2012        2013       2014       2015      2016         2017       2018
                                     ERV loiter                 ∆ Crew 1 TEI
      1
                        ∆ ERV-1 parks in LMO                           ∆ Crew 1 Earth return
      2
                         ∆ MAV-1 landing

      3                  ∆ Initial Habitat landing

      6
                       Crew 1: launch ∆       ∆ Landing         ∆ Crew 1 ascent
                                                                ERV loiter              ∆ Crew 2 TEI
      4
                                                ∆ ERV-2 parks in LMO                         ∆ Crew 2 Earth return

      5                                              ∆ MAV-2 landing

      9                                              Crew 2 launch ∆       ∆ Landing    ∆ Crew 2 ascent
                                                                                       ERV loiter            ∆ Crew 3 TEI
      7
                                                                            ∆ ERV-3 parks in LMO                       ∆ Crew 3 Earth return
      8                                                                     ∆ MAV 3 landing

     12                                                                    Crew 3 launch ∆        ∆ Landing  ∆ Ascent
                                                                                                           ERV loiter
     10
                                                                                                    ∆ ERV 4 LMO
     11
                                                                                                     ∆ MAV 4 landing


    ERV:            Earth Return Vehicle
    MAV:            Mars Ascent Vehicle
    TEI:            Trans Earth Injection
    LMO:            Low Mars Orbit

                             Figure 3-7 Mars Reference Mission sequence.

first three launches will send infrastructure                                  3.5.4.1 First Mission: 2007 Opportunity
elements to both Mars orbit and to the surface
                                                                                     In the first opportunity, September 2007,
for later use. Each remaining opportunity
                                                                               three cargo missions will be launched on
analyzed for the Reference Mission will send
                                                                               minimum energy trajectories direct to Mars
one crew and two cargo missions to Mars.
                                                                               (without assembly or fueling in LEO). The
The cargo missions will consist of an ERV on
                                                                               first launch delivers a fully fueled ERV to
one flight and a lander carrying a habitat and
                                                                               Mars orbit. The crew will rendezvous with
additional supplies on the second. This
                                                                               this stage and return to Earth after completion
sequence will gradually build up assets on the
                                                                               of their surface exploration in October 2011.
martian surface so that at the end of the third
crew’s tour of duty, the basic infrastructure                                      The second launch delivers a vehicle to
could be in place to support a permanent                                       the Mars surface which is comprised of an
presence on Mars.                                                              unfueled MAV, a propellant production




                                                                        3-45
module, a nuclear power plant, liquid              Table 3-3 lists the various payload items
hydrogen (to be used as a reactant to produce      deployed to the surface during the first
the ascent vehicle propellant), and                opportunity. And Figure 3-8 illustrates the
approximately 40 tonnes of additional              surface outpost configuration after
payload to the surface. After this vehicle         deployment of payloads from the first two
lands on the surface in late August 2008, the      cargo landers.
nuclear reactor will be autonomously
deployed approximately 1 kilometer from the        3.5.4.2 Second Mission: First Flight Crew,
ascent vehicle, and the propellant production      2009 Opportunity
facility (using hydrogen brought from Earth             In the second opportunity, opening in
and carbon dioxide from the Mars                   October 2009, two additional cargo missions
atmosphere) will begin to produce the nearly       and the first crew mission will be launched.
30 tonnes of oxygen and methane that will be       Before either the crew or additional cargo
required to launch the crew to Mars orbit in       missions are launched from Earth in 2009, all
October 2011. This production will be              assets previously delivered to Mars are
completed within approximately 1 year—             checked out and the MAV launched in 2007 is
several months before the first crew’s             verified to be fully fueled. Should any
scheduled departure from Earth in mid-             element of the surface system required for
November 2009.                                     crew safety or critical for mission success not
     The third launch in the 2007 opportunity      check out adequately, the surface systems will
will deliver a second lander to the Mars           be placed in standby mode and the crew
surface; it will be comprised of a surface         mission delayed until the systems can be
habitat/laboratory, nonperishable                  replaced or their functions restored. Some of
consumables for a safe haven, and a second         the systems can be replaced using hardware
nuclear power plant. It will descend to the        originally intended for subsequent missions
surface in early September 2008 and land near      and which would have otherwise provided
the first vehicle. The second nuclear power        system enhancement; others may be
plant will be autonomously deployed near           functionally replaced by other systems.
the first plant. Each plant will provide                Table 3-4 lists the manifested payloads
sufficient power (160 kWe) for the entire          for launch in the 2009 opportunity.
mature surface outpost, thereby providing
                                                        The first cargo launch in October 2009 is a
complete redundancy within the power
                                                   duplicate of the first launch from the 2007
function. The outpost laboratory will include
                                                   opportunity, delivering a fully fueled Earth-
tools, spare parts, and teleoperated rovers to
                                                   return stage to Mars orbit. The second cargo
support scientific exploration and will
                                                   launch similarly mirrors the second launch of
provide geological and biological analyses.
                                                   the 2007 opportunity, delivering a second




                                                3-46
                   Table 3-3 General Launch Manifest: 2007 Launch Opportunity

 Flight 1: Cargo                       Flight 2: Cargo                Flight 3: Cargo
                                          Surface Payload
 • None                                • Ascent Capsule               • Surface Habitat/Laboratory
                                       • Empty Ascent Stage           • Nonperishable
                                       • LOX/CH4 Production             Consumables
                                         Plant                        • Power Supply (nuclear-
                                       • LH2 Propellant Seed            160 kW)
                                       • Power Supply (nuclear-       • Utility Truck
                                         160 kW)                      • Spares
                                       • Utility Truck                • Teleoperable Science
                                       • Pressurized Rover              Rover
                                       • Additional Payload

                                         Mars Orbit Payload
 • Earth-Return Vehicle                • None                         • None
   • Fueled (LOX/CH4)
     TEI Stage
   • Transit Habitat
   • Earth-Return Capsule

                                    Space Transportation Vehicles
 • NTR Transfer Stage                  • NTR Transfer Stage           • NTR Transfer Stage
 • LOX/CH4 TEI Stage                   • LOX/CH4 Descent              • LOX/CH4 Descent
   w/Mars Aerobrake                      Stage w/Mars                   Stage w/Mars
                                        Aerobrake                      Aerobrake

TEI:   Trans Earth Injection           LOX:     liquid oxygen          LH2:    liquid hydrogen
NTR:   Nuclear Thermal Rocket          CH4:     methane



unfueled ascent stage and propellant                plenty of time to be available for the crew’s
production module. These systems provide            departure from Mars in October 2011. If the
backup or extensions of the previously              MAV and ERV delivered in 2007 operate as
deployed capabilities. For example, the             expected, then the systems delivered in 2009
second MAV and second ERV provide the               will support the second crew of six that will
2009 crew with two redundant means for each         launch to Mars early in 2012.
leg of the return trip. If, for some reason,
                                                         The first crew of six will depart for Mars
either the first ascent stage or the first ERV
                                                    in mid-November 2009. They leave Earth
become inoperable after the first crew departs
                                                    after the two cargo missions launched in
Earth in 2009, the crew can use the systems
                                                    October 2009, but because they are sent on a
launched in 2009 instead. They will arrive in
                                                    fast transfer trajectory of only 180 days, they




                                                3-47
3-48
                                                                             MAV:    Mars Ascent Vehicle
                                                                             TROV:   teleoperated rover
                                                                                     (unpressurized)
                                                                             ROV:    pressurized rover
                                                                             LSS:    life support system
                                                                             ISRU:   in-situ resource utilization
                                                                             PVA:    photo-voltaic array



       Figure 3-8 Mars surface outpost after deployment of payloads from first two cargo landers.
                   Table 3-4 General Launch Manifest: 2009 Launch Opportunity

 Flight 4: Cargo                       Flight 5: Cargo               Flight 6: First Crew
                                          Surface Payload
 • None                                • Ascent Capsule              • Crew
                                       • Empty Ascent Stage          • Surface Habitat
                                       • LOX/CH4 Production          • Consumables
                                         Plant                       • Spares
                                       • LH2 Propellant Seed         • EVA Equipment
                                       • Bioregenerative Life        • Science Equipment
                                         Support Outfitting
                                         Equipment
                                       • Science: 1 km drill
                                       • Science Equipment
                                       • Additional
                                         Payload /Spares

                                         Mars Orbit Payload
 • Earth-Return Vehicle                • None                        • None
   • Fueled (LOX/CH4)
     TEI Stage
   • Transit Habitat
   • Earth-Return Capsule

                                    Space Transportation Vehicles
 • NTR Transfer Stage                  • NTR Transfer Stage          • NTR Transfer Stage
 • LOX/CH4 TEI Stage                   • LOX/CH4 Descent             • LOX/CH4 Descent
   w/Mars Aerobrake                      Stage w/Mars                  Stage w/Mars
                                        Aerobrake                     Aerobrake

TEI:      Trans Earth Injection         LOX:    liquid oxygen         LH2:    liquid hydrogen
NTR:      Nuclear Thermal Rocket        CH4:    methane


will arrive in Mars orbit approximately 2          Additional time will be available during the
months prior to the cargo missions. Once the       outbound leg to conduct experiments and
TMI burn has been completed, the crew must         continue a dialog with Earth-bound science
reach the surface of Mars. During the              and exploration teams who may revise or
outbound portion of this mission, the crew         refine the initial set of surface activities
will use their time to monitor and maintain        conducted by this crew. The crew carries with
systems on board the transit spacecraft,           them sufficient provisions for the entire 600-
monitor and maintain their own physical            day surface stay in the unlikely event that
condition, and train for those activities          they are unable to rendezvous on the surface
associated with capture and landing at Mars.       with the assets previously deployed.




                                                3-49
     The crew will land on Mars in a surface            investigations and participants in the
habitat almost identical to the habitat/                exploration of Mars.
laboratory previously deployed to the Mars
                                                             Prior to the arrival of the first human
surface. The transit habitat sits atop a descent
                                                        crew, teleoperated rovers (TROV) may be
stage identical to those used in the 2007
                                                        delivered to the surface. When the crew
opportunity. After capturing into a highly
                                                        arrives, these rovers will be available for
elliptic Mars orbit (250 by 33793 km), the crew
                                                        teleoperation by the crew. It is also possible
descends in the transit habitat to rendezvous
                                                        for the rovers to be operated in a supervised
on the surface with the other elements of the
                                                        mode from Earth. If used in this mode, the
surface outpost. There is no required
                                                        TROVs may be designed to provide global
rendezvous in Mars orbit prior to the crew
                                                        access and may be able to return samples to
descent. This is consistent with the risk
                                                        the outpost from hundreds of kilometers
philosophy assumed for the Reference
                                                        distance from the site if they are deployed
Mission.
                                                        with the first set of cargo missions launched
    Figure 3-9 illustrates the surface outpost          more than 2 years before the crew arrives.
configuration at the end of the first crew's stay.
                                                            As experience grows, the range of human
     Surface exploration activity will consist          exploration will grow from the local to the
of diverse observations by robotic vehicles             regional. Regional expeditions lasting
and human explorers, the collection of                  perhaps 2 weeks, using mobile facilities, may
samples and their examination in the outpost            be conducted at intervals of a few months.
laboratory, and experiments designed to                 Between these explorations, analysis in the
gauge the ability of humans to inhabit Mars.            laboratory will continue. Figure 3-10 (Cohen,
Table 3-5 lists a representative set of science         1993) provides a possible surface mission
and exploration equipment that will be                  timeline for the first 600-day mission.
delivered as part of the cargo on Flight 5.
                                                             The deployment of a bioregenerative life
These payloads are simply examples; the
                                                        support capability will be an early activity
selection of specific experimental capability
                                                        following crew landing. This bioregenerative
will depend on the requirements of martian
                                                        system is not required to maintain the health
science at the time that the missions are
                                                        and vitality of the crew; however, it will
defined in detail. There is also a category
                                                        improve the robustness of the life support
listed for “discretionary principal investigator
                                                        system and is important to the early
(PI) science.” This category of experimental
                                                        objectives of the outpost.
equipment will be allocated to investigators
who have competed through a proposal and                     The first crew will stay at the outpost
peer review process and are selected for one            from 16 to 18 months. Part of their duties will
of these flights. This allows a wider range of          be to prepare the outpost site for the receipt of




                                                     3-50
3-51
                                                                     MAV:    Mars Ascent Vehicle
                                                                     TROV:   teleoperated rover
                                                                             (unpressurized)
                                                                     ROV:    pressurized rover
                                                                     LSS:    life support system
                                                                     ISRU:   in-situ resource utilization
                                                                     PVA:    photo-voltaic array


       Figure 3-9 Mars surface outpost at the end of first flight crew's stay.
                    Table 3-5 Surface Science Payload for First Flight Crew
                             Payload Description                    Payload Mass (kg)
             Field Geology Package: geologic hand tools, cameras,         335
               sample containers, documentation tools
             Geoscience lab instruments: microscopes,                     125
               geochemical analysis equipment, camera
             Exobiology laboratory: enclosures, microscopes,               50
               culture media
             Biomedical/bioscience lab                                    500
             Traverse geophysics instruments                              400
             Geophysics/meteorology instruments (8 sets)                  200
             10-meter drill                                               260
             Meteorology balloons                                         200
             Discretionary PI science                                     300
             Total                                                       2370


additional elements launched on subsequent          typically has been in an untended mode for
mission opportunities. Systems associated           nearly 4 years prior to the crew’s arrival.
with the ascent vehicle, although monitored
                                                          During the return portion of the mission,
during the entire stay on the surface, will be
                                                    the crew will again spend a significant
checked and, if necessary, tested in detail to
                                                    portion of their time monitoring and
ensure that they will operate satisfactorily.
                                                    maintaining systems on board the transit
The surface crew will also spend increasing
                                                    spacecraft, monitoring and maintaining their
amounts of time rehearsing the launch and
                                                    physical condition, and training for the
rendezvous phase of the Mars departure to
                                                    activities associated with Earth return. As
sharpen necessary skills that have not been
                                                    mentioned previously, the second crew will
used in over 2 years. Because the first crew
                                                    be in transit to Mars during a portion of the
will have to depart before the second crew
                                                    first crew’s return to Earth. This implies that a
arrives, surface systems will have to be in
                                                    debriefing of the first crew, to gain insight
standby mode for approximately 10 months.
                                                    from lessons learned and suggestions for
     After their stay on Mars, the crew uses        future surface activities, will begin during this
one of the previously landed ascent vehicles        return phase. This debriefing will be relayed
to return to orbit, rendezvous with the ERV,        to the outbound crew so that they can
and return to Earth. Like the outbound transit      participate in the interaction with the
leg, the crew rides in a habitat on the inbound     returning crew and modify their plans to take
transit leg. This habitat is part of the Earth-     advantage of the first crew’s experience.
return stage deployed in a previous
                                                        On landing, the first crew and their
opportunity by one of the cargo flights and
                                                    returned samples will be placed in quarantine




                                                 3-52
                                                                                                                                   Mars Surface Mission Time Allocation

                                      (Total Time = 8 crew X 24 hr/day X 600 days = 115,200 hr)

                                                                                                                                                                                                                8 crew X 24 hr day = 200)


                                                                                    Personal                                                                                                                                                                                                                                       Hr/Over
                                                                                       14 hr                                                                                                                                                                                                                                        head                                                                                                                                                                     Production
                                                                                (total 67,200 hr)                                                                                                                                                                                                                                                                                                                                                                                                                7 hr
                                                                                                                                                                                                                                                                                                                                     3 hr                                                                                                                                                                  (33,600 hr total)
                                                                                                                                                                                                                                                                                                                                  (14,400 hr)

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Site Prep,
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Construction        90 days




                                                                                                                                                                                                                                                                                                                                      Group Socialization, Meetings, Life Sciences Subject, Health Monitoring, Health Care: 1 hr
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Verification
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days




                                                                                                                                                                                                                                                                                                                                                                                                                                   System Monitoring, Inspection, Calibration, Maintenance, Repair: 1 hr
                                                                                                                                                                                                                                                          General Planning, Reporting, Documentation, Earth Communication: 1 hr
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Local Excursions

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           100 days
                                                                                 Hygiene, Cleaning, Personal Communication: 1 hr




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion   10 days
                                                                                                                                   Recreation, Exercise, Relaxation: 1 hr
                                      Sleep, Sleep Prep, Dress, Undress: 8 hr




                                                                                                                                                                                                                   One Day Off Per Week: 3 hr (per day)
600 day (or 20 months, or 86 weeks)




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis            40 days
                                                                                                                                                                            Eating, Meal Prep, Clean-up: 1 hr




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Charge Fuel Cells
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Check Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Load Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Plan Excursion
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Drive Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Navigate
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Don Suits (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off                         Pre-breathe (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Egress (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               100 days     Unload Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Set up Drill (X 10)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Operate Drill
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Collect Samples
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         In Situ Analysis
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Take Photos
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Flare Retreat       15 days      Communicate
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off            7 days       Disassemble Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Load Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion                Ingress (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Clean Suit (X 20)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Stow Suit, Equip
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Distant Excursion   100 days     Inspect Vehicle
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Analysis                         Secure for night
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            (Sleep, eat, cleanup
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Week Off
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               7 days       hygiene, etc.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Sys Shutdown                     covered)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Departure Prep      60 days

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          3 Crew X 7 hr X 10 Day =
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                210 hrs total


                                                                                                                                        Figure 3-10 Possible surface mission time line.




                                                                                                                                                                                                                                                                                                                                                                                                                                                    3-53
in accordance with the protocols in effect at             Figure 3-11 illustrates the surface outpost
the time. The crew’s re-adaptation to a 1-g         configuration at the end of the second crew's
environment will be monitored in detail to          stay.
learn more about how the human body
                                                         As before, the second crew will continue
adapts to the varying gravity conditions and
                                                    with the general type of activities conducted
to better prepare for the return of subsequent
                                                    by the first crew: diverse observations by
crews.
                                                    robotic vehicles and human explorers,
                                                    collection of samples and their examination in
3.5.4.3 Third Mission: Second Flight Crew,
                                                    the outpost laboratory, and experiments
2011 Opportunity
                                                    designed to gauge the ability of humans to
     In the third opportunity opening in            inhabit Mars. Specific crew activities will
December 2011, two additional cargo                 build on the lessons learned and questions
missions and the second crew mission will be        generated by the first crew. Table 3-7 lists a
launched. As in the second opportunity, all         representative set of science and exploration
assets previously delivered to Mars are             equipment that will be delivered as part of
checked out and the MAV is verified to be           the cargo on Flight 8. Note in particular that
fully fueled. Any non-mission-critical              this manifest contains a drill designed to
maintenance items identified by the first crew      reach depths of 1 kilometer. (The deep drilling
or items noted prior to the departure of            operation must be consistent with planetary
Flights 7 through 9 are added to the spares         protection protocols.) This tool will be used to
manifest and delivered with other surface           gather subsurface core samples that will help
equipment. Table 3-6 lists the manifested           reconstruct the geologic history of Mars, and
payloads for launch in the 2011 opportunity.        to try to locate subsurface deposits of water in
     Prior to the arrival of the second crew, the   either liquid or solid form. Such a discovery
ISRU plants are producing not only the              will substantially enhance the habitability
propellants needed for the ascent vehicle, but      prospects for future crews by possibly
also water, oxygen, and buffer gases to serve       upgrading propulsion systems to the use of
as an emergency cache for the life support          hydrogen and oxygen and expanding
system. Teleoperated rovers are deployed on         agricultural activities.
extended traverses, perhaps to distances of              The second crew will repeat the activities
more than 100 kilometers, to take measure-          of the first crew in preparing themselves, the
ments, gather samples, and reconnoiter sites        ascent vehicle, and the surface habitat for a
for the human crew to investigate in more           departure from Mars during December 2013.
detail.                                             The third crew will already be in transit to




                                                 3-54
                   Table 3-6 General Launch Manifest: 2011 Launch Opportunity

 Flight 7: Cargo                       Flight 8: Cargo               Flight 9: Second Crew
                                          Surface Payload
 • None                                • Ascent Capsule              • Crew
                                       • Empty Ascent Stage          • Surface Habitat
                                       • LOX/CH4 Production          • Consumables
                                         Plant                       • Spares
                                       • LH2 Propellant Seed         • EVA Equipment
                                       • Pressurized Rover           • Science Equipment
                                       • Science Equipment
                                       • Additional Payload/
                                         Spares

                                         Mars Orbit Payload
 • Earth-Return Vehicle                • None                        • None
   • Fueled (LOX/CH4)
     TEI Stage
   • Transit Habitat
   • Earth-Return Capsule

                                    Space Transportation Vehicles
 • NTR Transfer Stage                  • NTR Transfer Stage          • NTR Transfer Stage
 • LOX/CH4 TEI Stage                   • LOX/CH4 Descent             • LOX/CH4 Descent
   w/Mars Aerobrake                      Stage w/Mars Aerobrake        Stage w/Mars Aerobrake

TEI:   Trans Earth Injection           LOX:     liquid oxygen         LH2:    liquid hydrogen
NTR:   Nuclear Thermal Rocket          CH4:     methane



Mars, again necessitating a debriefing of the       the third crew mission will be launched. As in
second crew, with participation by the third        the second and third opportunities, all assets
crew, during the return to Earth. Once on           previously delivered to Mars are checked out
Earth, the second crew will likely benefit from     and the MAV is verified to be fully fueled.
observations of the first crew, particularly in     Any non-mission-critical maintenance items
the areas of modifications to the re-adaptation     identified by the first two crews or items
regime and quarantine protocols.                    noted prior to the departure of Flights 10
                                                    through 12 are added to the spares manifest
3.5.4.4 Fourth Mission: Third Flight Crew,          and delivered with other surface equipment.
2014 Opportunity                                    Table 3-8 lists the manifested payloads for
   In the fourth opportunity opening in             launch in the 2014 opportunity. As listed, the
March 2014, the final two cargo missions and        manifests do not use the full cargo-carrying




                                                3-55
                                                                     MAV:    Mars Ascent Vehicle
                                                                     TROV:   teleoperated rover
                                                                             (unpressurized)
                                                                     ROV:    pressurized rover
                                                                     LSS:    life support system
                                                                     ISRU:   in-situ resource utilization
                                                                     PVA:    photo-voltaic array




3-56
       Figure 3-11 Mars surface outpost at the end of second flight crew's stay.
                   Table 3-7 Surface Science Payload for Second Flight Crew
                               Payload Description                     Payload Mass (kg)
             Field Geology Package: geologic hand tools, cameras,            335
               sample containers, documentation tools
             Geoscience lab instruments: microscopes,                         125
               geochemical analysis equipment, camera
             Exobiology laboratory: enclosures, microscopes,                   50
               culture media
             Biomedical laboratory                                            500
             Plant and animal lab                                             500
             Traverse geophysics instruments                                  400
             Geophysics/meteorology instruments (8 sets)                      200
             1 kilometer drill                                             20,000
             10-meter drill                                                   260
             Meteorology balloons                                             200
             Discretionary PI science                                         600
             Total                                                         23,000


capacity of the landers. The experience gained        capabilities available at this stage, the surface
by the first two crews will dictate any               outpost will be able to support larger crews
additional equipment that can be used to              for longer periods of time. The potential level
either upgrade existing equipment or add              of self-sufficiency on Mars should also be
new equipment to enhance the capabilities of          evident by this time, and a decision can be
this outpost.                                         made regarding any further use or expansion
                                                      of the outpost.
     Prior to the arrival of the third crew, the
ISRU plants are again producing not only the               As before, the third crew will continue
propellants needed for the ascent vehicle, but        with the general type of activities conducted
also water, oxygen, and buffer gases to serve         by the first and second crews: diverse
as an emergency cache for the life support            observations by robotic vehicles and human
system. Teleoperated rovers are again                 explorers, collection of samples and their
deployed on extended traverses to take                examination in the outpost laboratory, and
measurements, gather samples, and                     experiments designed to gauge the ability of
reconnoiter sites for the third crew to               humans to inhabit Mars. Specific crew
investigate in greater detail.                        activities will build on the lessons learned
                                                      and questions generated by the first two
     Figure 3-12 illustrates the surface outpost
                                                      crews and should be focused on providing
configuration at the end of the third crew's
                                                      information needed to determine the future
stay. This represents the complete outpost
                                                      status of the outpost. Table 3-9 lists a
configuration as envisioned by the Mars
                                                      representative set of science and exploration
Study Team. With the facilities and




                                                   3-57
                  Nuclear Power Plant   Nuclear Power Plant
                                                                     MAV:    Mars Ascent Vehicle
                                                                     TROV:   teleoperated rover
                                                                             (unpressurized)
                                                                     ROV:    pressurized rover
                                                                     LSS:    life support system
                                                                     ISRU:   in-situ resource utilization
                                                                     PVA:    photo-voltaic array




3-58
       Figure 3-12 Mars surface outpost at the end of third flight crew's stay.
                Table 3-8 General Launch Manifest: 2014 Launch Opportunity

 Flight 10: Cargo                      Flight 11: Cargo                 Flight 12: Third Crew

                                          Surface Payload
 • None                                • Ascent Capsule                 • Crew
                                       • Empty Ascent Stage             • Surface Habitat
                                       • LOX/CH4 Production             • Consumables
                                         Plant                          • Spares
                                       • LH2 Propellant Seed            • EVA Equipment
                                       • Science Equipment              • Science Equipment
                                       • Additional Payload/
                                         Spares

                                        Mars Orbit Payload
 • Earth-Return Vehicle                • None                           • None
   • Fueled (LOX/CH4)
     TEI Stage
   • Transit Habitat
   • Earth-Return Capsule

                                   Space Transportation Vehicles
 • NTR Transfer Stage                  • NTR Transfer Stage             • NTR Transfer Stage
 • LOX/CH4 TEI Stage                   • LOX/CH4 Descent                • LOX/CH4 Descent
   w/Mars Aerobrake                      Stage w/Mars Aerobrake           Stage w/Mars Aerobrake

TEI:   Trans Earth Injection           LOX:      liquid oxygen          LH2:     liquid hydrogen
NTR:   Nuclear Thermal Rocket          CH4:      methane




equipment that will be delivered as part of          missions use assumed hardware systems and
the cargo on Flight 11.                              mission design principles to place the flight
                                                     crews in the martian environment for the
     As with the first two crews, the third
                                                     longest period of time at a satisfactory level of
crew will repeat those activities necessary to
                                                     risk. The major distinguishing characteristics
prepare themselves, the ascent vehicle, and
                                                     of the Reference Mission, compared to
the surface habitat for a departure from Mars
                                                     previous concepts, include:
during January 2016.
                                                          •No extended LEO operations, assembly,
3.5.4.5 Mission Summary                                    or fueling
    This section has illustrated a feasible               •No rendezvous in Mars orbit prior to
sequence of missions that can satisfy the                  landing
Reference Mission goals and objectives. These




                                                 3-59
               Table 3-9 Surface Science Payload for Third Flight Crew

                        Payload Description                     Payload Mass (kg)
        Field Geology Package: geologic hand tools, cameras,         335
          sample containers, documentation tools
        Geoscience lab instruments: microscopes,                     125
          geochemical analysis equipment, camera
        Exobiology laboratory: enclosures, microscopes,               50
          culture media
        Plant and animal lab                                         500
        Traverse geophysics instruments                              400
        Geophysics/meteorology instruments (8 sets)                  200
        Advanced Meteorology Laboratory                             1000
        10-meter drill                                               260
        Meteorology balloons                                         200
        Discretionary PI science                                    1000
        Total                                                       4070

•Short transit times to and from Mars (180            The characteristics of the hardware
 days or less) and long surface stay-times       systems used in these missions are more
 (500 to 600 days) for the first and all         completely discussed in the following
 subsequent crews exploring Mars                 sections.

•A heavy-lift launch vehicle (HLLV),
                                                 3.6    Systems
 capable of transporting either crew or
 cargo direct to Mars, and capable of                 The following sections discuss the
 delivering all needed payload with a            characteristics and performance capabilities
 total of four launches for the first human      of the various hardware elements needed for
 mission and three launches of cargo and         the Reference Mission. The hardware
 crew for each subsequent opportunity            elements include a launch vehicle large
                                                 enough to place cargo bound for Mars into a
•Exploitation of indigenous resources
                                                 suitable Earth parking orbit, the
 from the beginning of the program, with
                                                 interplanetary transportation elements
 important performance benefits and
                                                 necessary to move crew and equipment from
 reduction of mission risk
                                                 Earth to Mars and back, and the systems
•Availability of abort-to-Mars-surface           needed to sustain the crew and perform the
 strategies, based on the robustness of the      proposed exploration activities on the martian
 Mars surface capabilities and the cost of       surface. Each section describes the principal
 trajectory aborts                               characteristics of the hardware system as
                                                 developed by the Mars Study Team.




                                              3-60
3.6.1 Operational Design                             common hardware and software where
Considerations                                       applicable. System commonality in power
     Several operational factors related to          sources, interfaces, payload locker sizes, etc.,
utilization, training, and repair influence the      among all vehicles will ease nominal
design of hardware and software systems for          operational activities such as replacements,
all vehicles. Early incorporation of these           reconfigurations, and hardware transfers.
factors into the vehicle design process will         Commonality will also help maintain
enhance utility and functionality of the             corporate knowledge bases and simplify crew
systems, prevent costly workarounds late in          operations and repair procedures as
the development cycle, and maximize overall          experience with one system can be applied to
mission success.                                     many. The cost savings associated with the
                                                     use of common hardware and software
     This section discusses some of the design
                                                     elements are obvious, and may be increased
considerations identified as important in the
                                                     by using as much off-the-shelf hardware as
eventual detailed design and construction of
                                                     possible. This, too, helps with familiarity as
systems used for the Reference Mission.
                                                     crews and technicians may have previous
While the system descriptions in the sections
                                                     experience with similar systems. Repair
that follow may not reach a level of detail that
                                                     operations will also be simplified by requiring
reflects the specific topics mentioned here, the
                                                     a smaller set of standard tools for use by the
design considerations should be considered
                                                     crew during mission execution.
as guiding principles that should be used as
more detailed studies are performed.                      The need for training facilities will have a
                                                     significant impact on vehicle design. Due to
     A primary operational consideration in
                                                     the extended duration of the mission, training
system development is the subsequent ease
                                                     facilities will be required on board crew
with which users, specifically crew members,
                                                     vehicles during various phases of the mission.
can become familiar with the system prior to
                                                     Trainers on Earth will need to match trainers
the mission. The more familiar crew members
                                                     on vehicles which in turn will need to match
are with vehicle hardware and software, the
                                                     actual system performance. The requirement
less time will be spent on systems operations
                                                     for crew training facilities during various
and the more time will be available for
                                                     mission phases will place additional
science and exploration activities. By the same
                                                     hardware and software design constraints on
token, the more familiar technicians are with
                                                     the vehicles. Incorporation of training
the systems, the easier and less costly
                                                     facilities into appropriate vehicles is an
production, maintenance, and repair will be
                                                     important operational factor influencing the
during the development process. To facilitate
                                                     design process.
this, all vehicles and systems need to use




                                                  3-61
     For both crew safety and operational          discretionary system failures can require
simplicity, system designs will require some       some crew response to enhance mission
level of automatic fault detection for all life-   objectives. A balance between the cost of
critical, mission-critical, and mission-           automation and crew time and training for
discretionary elements. For those elements         such activities will be needed. In general,
pertaining to crew safety and mission-critical     maximizing crew science time and
objectives, auto-fault detection and correction    minimizing crew system maintenance and
should be incorporated into the design. Crew       operations throughout the mission will
action should not be required for life-critical    improve overall mission success.
systems failures; backup system activation
should be automatic. Mission-critical system       3.6.2   Launch Vehicles
failures should be as automated as possible,            The scale of the ETO launch capability is
leaving only the most complex tasks (such as       fundamentally determined by the mass of the
complete hardware replacement or repair) to        payload that will be landed on the martian
the crew. In addition, many of the routine, yet    surface. The nominal design mass for
important, system operations should be             individual packages to be landed on Mars in
automated to the greatest extent possible. For     the Reference Mission is 50 tonnes for a crew
example, an often overlooked aspect of             habitat (sized for six people) which must be
operations is consumables tracking and             transferred on a high-energy, fast-transit orbit.
forecasting for all life-critical and mission-     This in turn scaled the required mass in LEO
critical systems. Crew time is better spent on     to about 240 tonnes.
science activities than on tracking and
forecasting consumables such as propellant,             A number of different technologies could
water, and breathable air. Many of these           be used to construct a single launch vehicle
functions are currently done for Space Shuttle     capable of placing 240 tonnes into a 220-
crews by flight controllers on the ground. Due     nautical mile circular orbit. These launch
to the long delay time in communications           vehicle concepts used various combinations
during the Reference Mission, maintenance of       of past, present, and future U.S. expendable
this function by ground personnel is               launch vehicle technology and existing launch
impractical. Periodic verification of              vehicle technology from Russia and Ukraine.
consumables tracking activities by ground          Table 3-10 summarizes some of the key
personnel can validate the crew activities;        parameters for a representative set of the
however, means by which the crew can               vehicle options examined (Huber, 1993). Each
independently monitor and forecast                 option is covered in more detail in the
propulsive and nonpropulsive consumables           following paragraphs.
while not expending significant resources is a         Option 1 (Figure 3-13) illustrates the
necessity. Where cost effective, mission-          capabilities possible through the use of




                                               3-62
Energia and Zenit launch vehicle technology          combination of largely existing components
combined with STS technology. All of the             does not meet the desired payload launch
engines used for this option are existing types      mass.
that have flown numerous times. The core
                                                          Option 2 (Figure 3-14) illustrates what is
stage is assumed to be a modification of the
                                                     possible if a large launch vehicle makes
existing Energia stage. The modification
                                                     extensive use of existing STS and Russian
involves changing the vehicle from one that
                                                     technology. The first stage core and upper
uses a side-mounted payload container to an
                                                     stage use the SSME, and the propellant tank
in-line configuration with strap-on boosters
                                                     structure is based on the STS external tank.
surrounding the core. The upper stage is a
                                                     Strap-on boosters for this vehicle use the
new development using STS external tank
                                                     Russian RD-170 engine and a newly designed
technology combined with a single SSME.
                                                     propellant tank structure. Note that this
The shroud is entirely new and would be
                                                     combination also does not meet the desired
sized for the largest of the Reference Mission
                                                     payload launch mass.
payloads. Note, however, that this


                Table 3-10 Launch Vehicle Concepts for the Reference Mission

     Option         Payload Mass (tonnes) to 220          Key Technology Assumptions
                    n.mi. Circular Orbit

        1                     179                         Modified Energia core with eight Zenit-
                                                          type strap-on boosters. New upper stage
                                                          using a single Space Shuttle Main Engine
                                                          (SSME).
        2                     209                         New core stage based on Space
                                                          Transportation System (STS) external tank
                                                          and SSMEs. Seven new strap-on boosters
                                                          each use a single RD-170 engine. New
                                                          upper stage using a single SSME.
        3                     226                         New core stage based on STS external tank
                                                          and four of the new Space Transportation
                                                          Main Engines. Four strap-on boosters each
                                                          with a derivative of the F-1 engine used on
                                                          the first stage of the Saturn V. New upper
                                                          stage using a single SSME.
        4                     289                         New vehicle using technology derived
                                                          from the Saturn V launch vehicle. Boosters
                                                          and first stage use a derivative of the F-1
                                                          engine, and the second stage uses a
                                                          derivative of the J-2 engine.




                                                  3-63
Figure 3-13 Mars Energia-derived HLLV with eight Zenit-type boosters.




                                3-64
Figure 3-14 STS External Tank-derived HLLV with seven LOX/RP boosters.




                                 3-65
     Option 3 (Figure 3-15) uses new and old             Because a 240-ton-class launch vehicle
as well as existing technology to create a          would be such a development cost issue,
vehicle that can deliver a payload that is          consideration was given to the option of
reasonably close to the desired value. The first    launching several hardware elements to LEO
stage core propellant tank structure is based       using smaller vehicles, assembling (attaching)
on the STS external tank but uses newly             them in space, and then launching on the
designed and as yet untested STME engines.          outbound trajectory to Mars. This smaller
The strap-on boosters use an updated version        launch vehicle (with a 110- to 120-ton payload
of the F-1 engine that powered the first stage      capability) would have the advantage of more
of the Saturn V in conjunction with newly           modest development costs and is in the
designed propellant tanks. The upper stage is       envelope of capability demonstrated by the
comparable to those discussed for the first         unmodified U.S. Saturn V and Russian
two options, using STS external tank                Energia programs (Figure 3-18). However,
technology and a single SSME.                       this smaller launch vehicle introduces several
                                                    potential difficulties to the Reference Mission
     Option 4 (Figure 3-16) is indicative of a
                                                    scenario. The most desirable implementation
launch vehicle that uses technology derived
                                                    using this smaller launch vehicle is to simply
from the Saturn V launch vehicle. The first
                                                    dock the two elements in Earth orbit and
stage core is virtually identical to the first
                                                    immediately depart for Mars. To avoid boiloff
stage of the Saturn V launch vehicle in its
                                                    losses in the departure stages (assumed to use
basic size and its use of five F-1A engines.
                                                    liquid hydrogen as the propellant), all
Strapped to this stage are four boosters, each
                                                    elements must be launched from Earth in
with two F-1A engines and roughly one-third
                                                    quick succession, placing a strain on existing
of the propellant carried by the core stage.
                                                    launch facilities and ground operations crews.
The second stage uses six of the J-2 engines
                                                    Assembling the Mars vehicles in orbit and
that powered the second stage of the Saturn
                                                    loading them with propellants just prior to
V. However, this upper stage is considerably
                                                    departure may alleviate the strain on launch
larger than the Saturn second stage.
                                                    facilities, but the best Earth orbit for Mars
     This last option was the largest of a          missions is different for each launch
family of launch vehicles derived using             opportunity, so a permanent construction
Saturn V launch vehicle technology. Figure          and/or propellant storage facility in a single
3-17 illustrates some of the other vehicle          Earth orbit introduces additional constraints.
configurations examined and provides
                                                         Several launch vehicle designs that could
additional information on their capabilities.
                                                    provide this smaller payload capability using
All of these options can deliver a payload
                                                    existing or near-term technology were
almost as large as the stated need for 240
                                                    examined. Figure 3-19 illustrates one possible
tonnes in a 220-nautical mile circular orbit.




                                                 3-66
Figure 3-15 STS External Tank-derived HLLV with four strap-on boosters, each
                           having two F-1 engines.




                                    3-67
Figure 3-16 Saturn V-derived Mars HLLV with F-1A/J-2S propulsion.




                              3-68
                               VAB Height Limit - 410'

                         400




                         300
  Vehicle Height (ft.)




                         200




                         100




                          0




                               2x2 F-1A Boost            2x2 F-1A Boost     2x2 F-1A Boost     2x2 F-1A Boost     2x2 F-1A Boost
                               5 F-1A Core               5 F-1A Core        5 F-1A Core        5 F-1A Core        5 F-1A Core
                               6 J-2S 2nd Stage          6 J-2S 2nd Stage   6 J-2S 2nd Stage   6 J-2S 2nd Stage   6 J-2S 2nd Stage

Shroud Diameter (Usable)               10 m                    13 m                16 m              17 m                14 m

Payload to 220 nm Circular*            237 t                   228 t               219 t             285 t               289 t
(Kickstage performs circ.)




                                                  Figure 3-17 Saturn V-based Mars HLLV concepts.




                                                                            3-69
Figure 3-18 Energia launch vehicle adapted to Mars mission profile.




                               3-70
                                          320 ft




                              172 ft

                                                       27.6 ft D




                                                        89 ft
              Side View                               Base View




Figure 3-19 Mars mission launch vehicle with two external tank boosters and
                                kick stage.




                                       3-71
vehicle configuration and provides additional         landed in close proximity to one another. The
information on its capabilities. This particular      transportation strategy adopted in the
option uses the STS external tank for its             Reference Mission eliminates the need for
propellant storage and main structure.                assembly or rendezvous in LEO of vehicle
Engines for the core stage and the two strap-         elements and for rendezvous of a crew
on boosters were assumed to be the STME               transport vehicle with a Mars lander in Mars
engine that was under development at the              orbit, both features of many previous mission
time of this study.                                   designs for Mars (NASA, 1989). But the
                                                      Reference Mission scenario does require a
      A 240-ton payload-class launch vehicle is
                                                      rendezvous on the surface with previously
assumed for the Reference Mission. However,
                                                      landed hardware elements and a rendezvous
it is beyond the experience base of any
                                                      in Mars orbit with the ERV as the crew leaves
spacefaring nation. While such a vehicle is
                                                      Mars. The transportation strategy emphasized
possible, it would require a significant
                                                      the use of common elements wherever
development effort for the launch vehicle,
                                                      possible to avoid development costs and to
launch facilities, and ground processing
                                                      provide operational simplicity.
facilities; and its cost represents a
considerable fraction of the total mission cost.
                                                      3.6.3.1 Trans-Mars Injection Stage
The choice of a launch vehicle remains an
unresolved issue for any Mars mission.                      A single TMI stage was developed for
                                                      both piloted and human missions. The stage
3.6.3   Interplanetary Transportation                 is designed for the more energetically
                                                      demanding 2009 human mission and is then
     The interplanetary transportation system
                                                      used in the minimum energy cargo missions
assembled for the Reference Mission consists
                                                      to launch the maximum payload possible to
of seven major systems: a TMI stage, a
                                                      Mars. Because of the energetic trajectories
biconic aeroshell for Mars orbit capture and
                                                      used for human flights and the desire to
Mars atmospheric entry, habitation systems
                                                      deliver large payloads to the martian surface,
for the crew (both outbound and return), a
                                                      nuclear thermal propulsion was selected for
descent stage for landing on the surface, an
                                                      this stage not only for its performance
ascent stage for crew return to Mars orbit, an
                                                      advantages but also because of its advanced,
ERV for departure from the Mars system, and
                                                      previously demonstrated state of technology
an ECCV (comparable to Apollo) for Earth
                                                      development, its operational flexibility, and
entry and landing. As mentioned earlier, the
                                                      its inherent mission enhancements and crew
Reference Mission splits the transportation of
                                                      risk reduction (Borowski, et al., 1993).
people and equipment into cargo missions
and human missions, all of which are targeted             After completion of two TMI burns
to the same locale on the surface and must be         (required by the selected thrust-to-weight




                                                   3-72
ratio), the stage is disposed of by allowing it              ND engines. So for cost and performance
to drift on a relatively stable interplanetary               reasons, one ND engine and the shadow
trajectory. Calculations (Stancati and Collins,              shield are removed from this version of the
1992) using the Planetary Encounter                          TMI stage.
Probability Analysis code indicate that the
                                                                  The TMI stage adopted for the Reference
probability of a collision of a nuclear engine-
                                                             Mission could be designed around any of four
equipped vehicle and the Earth is quite low.
                                                             reactor options studied by the Team: (1)
The probabilities of a collision with Earth in
                                                             Rocketdyne and Westinghouse NERVA-
one million years are 3.8 percent for the
                                                             derivative reactor (ND), (2) Pratt and Whitney
piloted TMI stages and 12 percent for the
                                                             and Babcock and Wilcox (B&W) CERMET fast
cargo TMI stages.
                                                             reactor, (3) Aerojet and B&W particle bed
     The basic TMI stage is shown in Figure                  reactor and (4) Russian Energopool and B&W
3-20. For piloted missions, the TMI stage uses               engine concept using the “twisted ribbon”
four 15,000 lb. thrust NERVA* derivative                     ternary carbide fuel form. Work done in
(ND) engines to deliver the crew and their                   Russia is especially promising, with the
surface habitat/descent stage onto the trans-                possibility of higher Isp (approximately 950
Mars trajectory. Engines of this size are well               seconds versus a 900-second demonstrated
within the previous development history of                   capability by NERVA engines) at a thrust-to-
NERVA engines (Borowski, et al., 1993). This                 weight ratio of about 3.0 (for a 15,000 pound
version of the TMI stage incorporates a                      thrust engine) being a possible development
shadow shield between the ND engine                          target. The Reference Mission adopts the
assembly and the LH2 tank to protect the crew                more conservative ND engine concept, with a
from radiation generated by the engines that                 projected Isp performance of 900 seconds.
will have built up during the TMI burns. For                 Table 3-11 lists the mass estimates for the
cargo missions, this transportation system can               various components of the TMI stage for
deliver approximately 65 tonnes of useful                    piloted and cargo versions. In both versions,
cargo to the surface of Mars or nearly 100                   this stage is assumed to have a maximum
tonnes to Mars orbit (250 I 33,793 km) on a                  diameter of 10 meters and an overall length of
single launch from Earth. The TMI stage for                  25.3 meters.
cargo delivery requires only the use of three
                                                             3.6.3.2 Biconic Aeroshell

                                                                  On each cargo and piloted mission, Mars
      From 1955 to 1973, the Nuclear Engine for Rocket       orbit capture and the majority of the Mars
Vehicle Application (NERVA) program designed, built,         descent maneuver are performed using a
and tested a total of twenty rocket reactors. The
feasibility of using low molecular weight LH2 as both a      single biconic aeroshell. The decision to
reactor coolant and propellant was convincingly              perform the Mars orbit capture maneuver
demonstrated.




                                                          3-73
              2007 Cargo Mission 1                        2007 Cargo Mission 3               2007 Cargo Mission 2         2009 Piloted Mission 1
           "Dry" Ascent Stage & Lander                    LOX/CH4 TEIS & Hab                 Hab Module & Lander    Surface Hab with Crew and Lander




                                                                                        19.0 m        7.6 m

                                                                                                                        16.3 m
                                                 16.3 m

 15.0 m




 20.6 m*         86.0 t LH2                                   86.0 t LH2                              86.0 t LH2                      86.0 t LH2
                 (@ 100%)                                     (@ 100%)                               (@ 91.9%)                        (@ 100%)




                                                                10 m                                  10 m                               10 m
                    10 m




  4.7 m




IMLEO =           216.6 t                                     216.6 t                               204.7 t                           212.1 t
* Expendable TMI Stage LH2 Tank (@ 18.2 m length) sized by 2009 Mars Piloted Mission




IMLEO Initial Mass to Low Earth Orbit
TEIS  Trans Earth Injection Stage




                           Figure 3-20 Reference Mars cargo and piloted vehicles.




                                                                                 3-74
                       Table 3-11 Mass Estimates for TMI Stage Alternatives


                 TMI Stage Element                 Piloted Version     Cargo Version


      ND Engines (4 for piloted, 3 for cargo)            9.8                7.4
      Radiation Shield                                   0.9                0.0
      Tankage and Structure                             18.4                18.4
      LH2 Propellant (maximum)                          86.0                86.0
      Control System Tankage and Propellant              3.1                3.0

      Total (tonnes)                                    118.2              114.8


using an aeroshell (that is, aerocapture) was       biconic aeroshells that can be used for both
based on the fact that this option typically        Mars orbit capture and descent maneuvers.
requires less mass than an equivalent               Given the demands on a descent aeroshell of
propulsive capture stage (Cruz, 1979), and          the Mars entry and landing requirements, the
aerodynamic shielding of some sort will be          additional capability to permit aerocapture is
required to perform the Mars descent                considered modest.
maneuver no matter what method is used to
                                                         The aerodynamic maneuvering and
capture into Mars orbit. Previous Mars
                                                    thermal protection requirements for the
mission concepts employing aerocapture have
                                                    aeroshells used in the Reference Mission were
typically used more than one aeroshell to
                                                    studied in some detail (Huber, 1993). Based
deliver the crew to the surface. The use of two
                                                    on the studies, it was determined that a
aeroshells was driven by one or both of the
                                                    biconic aeroshell with similar forward and aft
following factors. First, Mars entry speeds
                                                    conic sections provided sufficient
may have been higher than those proposed
                                                    maneuverability for the aerocapture and
for the Reference Mission and therefore more
                                                    entry phases of flight. Figure 3-21 illustrates
maneuverability and thermal protection were
                                                    two of these aeroshells, one for the Mars
required for this phase of the mission. Second,
                                                    ascent vehicle and the other for the surface
the mission profile may have required a post-
                                                    habitat. For this family of aeroshells, the nose
aerocapture rendezvous in Mars orbit with
                                                    section is a 25° half-angle cone ending in a
another space transportation element,
                                                    spherical cap. The skirt section is a 4° half-
possibly delivered during the same launch
                                                    angle cone with a 10-meter diameter base.
opportunity or during a previous
                                                    The skirt section consists of two parts: a fixed
opportunity. Neither of these features is in the
                                                    length aft section and a variable length center
Reference Mission. Thus, the strategy
                                                    section (“center” indicating its location
employed was to develop a single family of
                                                    between the aft skirt and the nose section).




                                                3-75
     6.0 (m)                                  25 %                                                  18 (m)


14.9 (m)
            7.7 (m)
            to Cg
            & Cp




                                                     4%




     8.9 (m)




                            Dia = 10.0 (m)                                  Dia = 10.0 (m)



               Reference Biconic: 10 (m) Dia by 15 (m)            Extended Center Section Biconic
               length. I/D = 0.65 At 25° Angle of Attack          10 (m) Dia by 18 (m) length.


Cg         = center of gravity
Cp         = center of pressure




   Figure 3-21 Biconic aeroshell dimensions for Mars lander and surface habitat
                                    modules.




                                                           3-76
The length of the skirt center section is              laboratory deployed robotically on a previous
determined by the size of the payload carried          mission. Although a smaller habitat might
within. Table 3-12 lists the overall lengths of        suffice for a crew of six during the
the various aeroshells used in the Reference           approximately 6 months of transit time,
Mission.                                               designing the habitat so that it can be used
                                                       during transit and on the surface results in a
     Table 3-12 also lists an estimated mass for
                                                       number of advantages to the overall mission.
the various aeroshells. The Mars Study Team
                                                       Duplicating habitats on the surface provides
did not conduct a detailed study of the mass
                                                       redundancy during the longest phase of the
of the various aeroshells used. Based on
                                                       mission and reduces the risk to the crew. By
previous studies of aerocapture vehicles, a
                                                       landing in a fully functional habitat, the crew
simple scaling factor of 15 percent of the entry
                                                       does not have to transfer from a “space-only”
mass was used to determine the aeroshell
                                                       habitat to the surface habitat immediately
mass (Scott, et al., 1985). As more detail
                                                       after landing, allowing them to re-adapt to a
regarding the aeroshell is developed,
                                                       gravity environment at their own pace. This
variations in aeroshell mass will result caused
                                                       approach also allows the development of only
by differences in the amount of thermal
                                                       one habitat system instead of two or more
protection material used (some missions are
                                                       unique, specialized systems (although some
flown on faster trajectories and will encounter
                                                       subsystems will have to be tailored for zero-g
higher entry speeds with correspondingly
                                                       operation). The performance of the transit
higher heat loads) and in the size of the
                                                       habitat may be tested by attaching a
aeroshell structure. At the present level of this
                                                       development unit to the International Space
study, the simple scaling factor is considered
                                                       Station (Figure 3-22).
sufficient to estimate the aeroshell mass.
                                                            Each habitation element will consist of a
3.6.3.3 Transit/Surface Habitat                        structural cylinder 7.5 meters in diameter and
    The crew is transported to Mars in a               4.6 meters long with two elliptical end caps
habitat that is identical to the surface habitat/      (overall length of 7.5 meters). The internal

               Table 3-12 Mass and Size Estimates for Biconic Aeroshell Family

                                                           Mass Estimate   Overall Length
                        Aeroshell Payload
                                                            (tonnes)         (meters)


          Ascent Stage and Lander                             17.3              15.0
          Surface Habitat and Lander                          17.3              16.3
          TEI Stage and Habitat                               17.3              19.0
          Surface Habitat with Crew and Lander                17.3              16.3




                                                    3-77
3-78
       Figure 3-22 Transit habitat attached to International Space Station.
volume will be divided into two levels             doubling the usable pressurized volume (to
oriented so that each “floor” will be a cylinder   approximately 1,000 cubic meters) available
7.5 meters in diameter and approximately 3         to the crew for the 600-day surface mission.
meters in height. The primary and secondary        This configuration is illustrated in Figure 3-26
structure, windows, hatches, docking               with the first of the transit habitats joined to
mechanisms, power distribution systems, life       the previously landed surface habitat/
support, environmental control, safety             laboratory.
features, stowage, waste management,
communications, airlock function and crew          3.6.3.4 Mars Surface Lander
egress routes will be identical to the other            A single common descent stage was
habitation elements (the surface habitat/          developed for delivery of all hardware
laboratory and the Earth-return habitat). After    systems (the habitats, ascent vehicle,
establishing these basic design features, there    propellant production plant, and other
exists an endless array of feasible internal       surface cargo) to the surface of Mars. The role
architecture designs. Deciding among feasible      of this stage is to complete the descent-to-
internal designs involves a trade of resources     landing maneuver once the biconic aeroshell
derived from a specific set of habitation goals.   ceases to be effective and to maneuver the
At this level of detail, habitation goals are      surface systems into the appropriate relative
somewhat subjective and open for discussion.       position at the surface outpost.
Figures 3-23, 3-24, and 3-25 illustrate one
                                                        The descent stage consists of four
internal arrangement for the transit/surface
                                                   subsystems: a basic structure to which all
habitat that was investigated for feasibility
                                                   other elements (including payload) are
and cost purposes.
                                                   attached, a parachute system to assist in
     The Mars transit/surface habitat will         slowing the stage, a propulsion system to
contain the required consumables for the           slow the stage prior to landing, and a surface
Mars transit and surface duration of               mobility system.
approximately 800 days (approximately 180
                                                        The use of parachutes has been assumed
days for transit and approximately 600 days
                                                   to help reduce the descent vehicle’s speed
on the surface) as well as all the required
                                                   after the aeroshell has ceased to be effective
systems for the crew during the 180-day
                                                   and prior to the final propulsive maneuver
transfer trip. Table 3-13 provides a breakdown
                                                   (Figure 3-27). Sufficient atmosphere is present
of the estimated masses for this particular
                                                   for parachutes to be more effective than an
habitat.
                                                   equivalent mass of propellant.
    Once on the surface of Mars, this transit/
surface habitat will be physically connected
with the previously landed surface laboratory,




                                               3-79
  Figure 3-23 The crew exercise facility component of the countermeasures
system designed to inhibit crew degradation from exposure to reduced gravity
                                environments.




Figure 3-24 EVA suit storage locations are critical in a robust crew safety system.




                                       3-80
Figure 3-25 Conceptual Mars habitation module - wardroom design.




                              3-81
                       Table 3-13 Mars Transit/Surface Habitat Element


                                                  Subsystem      Consumables        Dry Mass
                    Subsystem
                                                     Mass          Subtotal         Subtotal
                                                   (tonnes)        (tonnes)         (tonnes)

   Physical/chemical life support                       6.00          3.00              3.00
   Plant growth                                         0.00          0.00              0.00
   Crew accommodations                                 22.50         17.50              5.00
   Health care                                          2.50          0.50              2.00
   Structures                                          10.00          0.00             10.00
   EVA                                                  4.00          3.00              1.00
   Electrical power distribution                        0.50          0.00              0.50
   Communications and information                       1.50          0.00              1.50
     management
   Thermal control                                      2.00          0.00              2.00
   Power generation                                     0.00          0.00              0.00
   Attitude control                                     0.00          0.00              0.00
   Spares/growth/margin                                 3.50          0.00              3.50
   Radiation shielding                                  0.00          0.00              0.00
   Science                                              0.90          0.00              0.90
   Crew                                                 0.50          0.50              0.00

   Total estimate                                      53.90         24.50             29.40



     The propulsion system employs four            previously landed pressurized rover. Figure
RL10-class engines modified to burn LOX/           3-28 illustrates one possible configuration for
CH4 to perform the post-aerocapture                this lander with its mobility system.
circularization burn and to perform the final
                                                       The descent lander is capable of placing
approximately 500 meters per second of
                                                   approximately 65 tonnes of cargo on the
descent velocity change prior to landing on
                                                   surface. The dry mass of this lander is
the surface.
                                                   approximately 4.7 tonnes, and it can carry
     Once on the surface, the lander can move      approximately 30 tonnes of propellant to be
limited distances to compensate for landing        used for orbital maneuvers and for the final
dispersion errors and to move surface              descent maneuver.
elements into closer proximity. This allows,
for example, the surface laboratory to be          3.6.3.5 Mars Ascent Vehicle
connected to the transit/surface habitats.              When the surface mission has been
Mobility system power is provided by on-           completed, the crew must rendezvous with
board regenerative fuel cells and from the         the orbiting ERV. This phase of the mission is




                                                3-82
3-83
       Figure 3-26 Habitat and surface laboratory joined on Mars surface.
3-84
       Figure 3-27 Mars surface lander descending on parachutes.
Figure 3-28 Mars surface lander just prior to landing illustrating landing legs and
                            surface mobility system.




                                       3-85
accomplished by the MAV which consists of              rendezvous has been completed and all crew,
an ascent propulsion system and the crew               equipment, and samples have been
ascent capsule.                                        transferred to the ERV, the MAV is jettisoned
                                                       and remains in orbit around Mars.
     The MAV is delivered to the Mars surface
atop a cargo descent stage (Figure 3-29                     The MAV is depicted in Figure 3-31
illustrates the MAV inside the biconic                 showing basic dimensions for the vehicle. The
aeroshell and deployed on the surface). The            ascent propulsion system will require
ascent propulsion system is delivered with its         approximately 26 tonnes of propellant to
propellant tanks empty. However, the same              accomplish the nearly 5,600 meters per
descent stage also delivers a nuclear power            second of velocity change required for a
source, a propellant manufacturing plant               single-stage ascent to orbit and rendezvous
(both discussed in later sections), and several        with the previously deployed ERV. The
tanks of hydrogen to be used as feedstock for          structure and tankage needed for this
making the required ascent propellant. This            propellant and the other attached hardware
approach was chosen because the mass of the            elements have a mass of 2.6 tonnes, including
power source, manufacturing plant, and seed            the mass of the engines but not the crew
hydrogen is less than the mass of the                  capsule. The ascent propulsion system uses
propellant required by the ascent stage to             two RL10-class engines modified to burn
reach orbit (Stancati, et al., 1979; Jacobs, et al.,   LOX/CH4. These engines perform with an
1991; Zubrin, et al., 1991). Not carrying this         average specific impulse of 379 seconds
propellant from Earth gave the Reference               throughout the MAV flight regime.
Mission the flexibility to send more surface
                                                            The ascent crew capsule has a maximum
equipment to Mars or to use smaller launch
                                                       diameter of 4 meters, a maximum height of
vehicles or some combination of the two
                                                       2.5 meters, and a mass of 2.8 tonnes. This
options.
                                                       capsule contains the basic crew life support
      The crew rides into orbit in the crew            systems and all guidance and navigation
ascent capsule (Figure 3-30). This pressurized         equipment for the rendezvous with the ERV.
vehicle can accommodate the crew of six,
their EVA suits, and the samples gathered              3.6.3.6 Earth-Return Vehicle
during the expedition and from experiments                  Returning the crew from Mars orbit to
conducted in the surface habitat/laboratory.           Earth is accomplished by the ERV which is
Life support systems are designed for the              composed of the TEI stage, the Earth-return
relatively short flight to the waiting ERV. This       transit habitat, and the ECCV. The ERV is
ascent capsule does not have a heat shield, as         delivered to Mars orbit with the TEI stage
it is not intended for reentering the                  fully fueled, and it loiters there for nearly 4
atmosphere of Earth or Mars. Once the                  years before being used by the crew returning




                                                   3-86
      Figure 3-29 Mars surface lander and biconic aeroshell.




Figure 3-30 Crew ascent capsule just after launch from Mars surface.




                                3-87
9 (m)                4 (m)




                                        One center (core)
                                        3.6 (m) dia spherical
                                        LO2 tanks




                                        One center (core)
                                        3.3 (m) dia spherical
                                        LOH4 tanks




                                        6 (m)




 Figure 3-31 Methane/LOX ascent stage configuration.




                         3-88
to Earth. For the return to Earth, the crew will     stage, and liquid oxygen/liquid methane
jettison the MAV and wait for the appropriate        with the same engine used by the lander and
departure time to leave the parking orbit.           the MAV. With the 4-year loiter time in Mars
During the 180-day return trip, the crew will        orbit, propellant boiloff was the major design
recondition themselves as much as possible           consideration. Liquid hydrogen would
for the return to an Earth gravity                   require active refrigeration for this extended
environment, train for those procedures they         period in orbit to avoid excessive boiloff
will use during the entry phase, perform             losses. Liquid oxygen/liquid methane boiloff
science experiments and maintenance tasks,           losses could be held to acceptable levels using
and prepare reports. As they approach Earth,         passive insulation and appropriate
the crew will transfer to the ECCV, along with       orientation of the vehicle while in Mars orbit
the samples they are returning, and separate         (to minimize radiative heat input from Mars,
from the remainder of the ERV. The TEI stage         the largest source). The 30 kWe solar power
and the transit habitat will fly by Earth and        system (used primarily for powering the ERV
continue on into deep space. The crew in the         on the return to Earth) is also on board and
ECCV will deflect their trajectory slightly so       could be used for active cooling of these
that they reenter the Earth’s atmosphere and         propellants. Based primarily on this trade-off,
land on the surface.                                 liquid oxygen and liquid methane were
                                                     chosen as the TEI stage propellants.
     The propulsion system for the ERV is
sized for the velocity change needed to move              With this selection, the TEI propulsion
the Earth return habitat and the ECCV from           system uses two RL10-class engines modified
the highly elliptical parking orbit at Mars to       to burn LOX/CH4. Again, these are the same
the fast-transit return trajectory to Earth. As      engines developed for the ascent and descent
with the TMI stage, the energetically                stages, thereby reducing engine development
demanding 2011 return trajectory was used to         costs and improving maintainability. To
size this system for a 180-day return; less          achieve the velocity change for the 2011 fast-
energetically demanding returns could be             transit return requires approximately 52
accomplished faster or with larger return            tonnes of liquid oxygen and liquid methane.
payloads.                                            The remainder of the TEI propulsion system,
                                                     including tanks, structure, engines, and
    Several propellant and engine
                                                     reaction control systems, has a dry mass of
combinations were considered by the Mars
                                                     approximately 5.2 tonnes.
Study Team for the TEI propulsion system.
The two options given the most consideration             The return habitat is a duplicate of the
were liquid hydrogen with a NERVA                    outbound transit/surface habitat used to go
derivative engine comparable to the TMI              to Mars but without the stores of consumables




                                                  3-89
in the surface habitat. As with the surface          3.6.3.7 Interplanetary Transportation Power
habitats, the primary structure of this habitat      Systems
consists of a cylinder 7.5 meters in diameter             A source of power will be required for all
and 4.6 meters long with two elliptical end          of the interplanetary transportation systems
caps (overall length of 7.5 meters). The             during the flight times to and, in the case of
internal volume will be divided into two             the ERV, from Mars. While several alternatives
levels, oriented so that each “floor” will be a      are available as a primary source of power for
cylinder 7.5 meters in diameter and                  these vehicles, solar energy is readily
approximately 3 meters in height. The                available throughout these transit phases and
primary and secondary structure, windows,            photovoltaic energy is a known technology.
hatches, docking mechanisms, power                   Thus, a basic photovoltaic power capability is
distribution systems, life support,                  assumed for those vehicles that are operating
environmental control, safety features,              in interplanetary space. A source of stored
stowage, waste management,                           power will also be needed for the
communications, airlock function and crew            interplanetary vehicles during periods of
egress routes will be identical to the other         eclipse and of array retraction prior to capture
habitation elements. Table 3-14 details the          into Mars orbit, and for vehicles not typically
mass estimate for this habitat module.               operating in interplanetary space (such as the
     The ECCV is similar in concept to the           Mars surface lander, the MAV, and the ECCV).
Apollo Command Module and is eventually              During the eclipse periods and for the other
used by the crew to enter the Earth’s                vehicles, a regenerative fuel cell (RFC) system
atmosphere and deliver the crew to a safe            will be used to provide necessary power.
landing on land. The ECCV will have the                   The most significant power requirements
necessary heat shield for Earth reentry and          for the interplanetary transportation system
will be heavier than the ascent capsule              come from the transit/surface habitat and the
specialized only for that portion of the             ERV. Table 3-15 shows the estimated power
mission. This vehicle has all of the life            requirements to support the six-person crew
support, guidance and navigation, and                for both nominal and powerdown emergency
propulsion systems to keep the crew alive for        mode. The life support system is a major
several days and to maneuver the vehicle into        constituent of the almost 30 kWe needed for
the proper entry trajectory. Once the reentry        these two vehicles under nominal conditions.
phase has been completed, the ECCV will use          The life support system is based on a partially
a steerable parafoil to land at a designated         closed air and water system design that per-
location on the surface (Figure 3-32). The           forms CO2 reduction, O2 and N2 generation,
ECCV has an estimated mass of 5.5 tonnes.            urine processing, and water processing
                                                     (potable and hygiene). The emergency mode




                                                  3-90
Figure 3-32 ECCV returning to Earth on a steerable parafoil.




                            3-91
                   Table 3-14 Earth-Return Habitat Element Mass Breakdown


                                                   Subsystem      Consumables       Dry Mass
                    Subsystem
                                                      Mass          Subtotal        Subtotal
                                                    (tonnes)        (tonnes)        (tonnes)

  Physical/chemical life support                         6.00          3.00            3.00
  Plant growth                                           0.00          0.00            0.00
  Crew accommodations                                   22.50         17.50            5.00
  Health care                                            2.50          0.50            2.00
  Structures                                            10.00          0.00           10.00
  EVA                                                    4.00          3.00            1.00
  Electrical power distribution                          0.50          0.00            0.50
  Communications and information                         1.50          0.00            1.50
    management
  Thermal control                                        2.00          0.00             2.00
  Power generation                                       0.00          0.00             0.00
  Attitude control                                       0.00          0.00             0.00
  Spares/growth/margin                                   3.50          0.00             3.50
  Radiation shielding                                    0.00          0.00             0.00
  Science                                                0.90          0.00             0.90
  Crew                                                   0.50          0.50             0.00

  Total estimate                                        53.90         24.50           29.40




value is based on the life support system           outbound transit/surface habitat can be
operating in an open loop mode with                 safely powered down to 20 kWe during these
reductions in noncritical operations.               mission phases to save RFC mass and
                                                    volume, and that the RFC and solar array will
     The solar array as it would appear on the
                                                    remain with the transit/surface habitat to be
ERV (Figure 3-33) is designed to produce the
                                                    used on the surface as a backup system.
required 30 kWe in Mars orbit at the worst-
case distance from the Sun, 1.67 AU. The                 Based on the size of the energy storage
energy storage system is sized to provide           system, eclipse power requirement, and
power before and after Mars orbit capture as        available power from the array, it will take
well as during attitude control, array              seven orbits of Mars to fully charge the RFC.
retraction, orbit capture, array extension          The RFC delivers power when the solar array
maneuvers, and orbit eclipse. A nominal             is retracted during entry, descent, and landing
power profile for these activities is shown in      of the transit/surface habitat. The RFC can
Figure 3-34. It is currently assumed that the       also deliver 20 kWe for 24 hours after landing,




                                                 3-92
            Table 3-15 Estimated Power Profile for Outbound and Return Transits

 Element                                             Mode               Notes
                                        Nominal          Emergency
 Life Support System (LSS)               12.00              8.00        Open Loop in Emergency
 Thermal Contract System (TCS)            2.20              2.20        Mode
 Galley                                   1.00              0.50        Emergency values
 Logistic Module                          1.80              1.80        Derated from nominal where
 Airlock                                  0.60              0.10        appropriate
 Communications                           0.50              0.50
 Personal Quarters                        0.40              0.00
 Command Center                           0.50              0.50        Values adapted from NAS8-
 Health Maintenance Facility (HMF)        1.70              0.00        37126, “Manned Mars System
 Data Management System                   1.90              0.80        Study
 Audio/Video                              0.40              0.10
 Lab                                      0.70              0.00
 Hygiene                                  0.70              0.00
 SC/Utility Power                         5.00              5.00
 Total                                   29.40             19.50



and it will be the prime power source for the        Utility Power” in Table 3-15) is estimated at 5
transit/surface habitat and crew until the           kWe. This value is assumed as the power
habitat is moved to its final location and           requirement for the unmanned cargo-only
connected to the main power grid. The RFC            vehicles during the outbound transit.
could also provide power for moving the
                                                          Tables 3-16 and 3-17 show the mass
habitat from the landing site to its final
                                                     estimates for the two power systems
emplacement location, assuming no solar
                                                     discussed: the 30 kWe system used for the
array deployment.
                                                     habitats and the 5 kWe system used for the
     A duplicate of the solar array and RFC          cargo flights. Both tables show the resulting
system will be used on the ERV, saving               system characteristics if the RFCs must be
development costs for a unique system. All           recharged over the course of one orbit versus
other spacecraft discussed will use a subset of      recharging them over seven orbits. The
the RFC system (assumed to be modular or at          savings in mass, volume, and array area are
least manufactured in smaller units) used in         obvious and support the choice to stay in
the transit/surface habitat. The base power          orbit for a longer period of time.
load for vehicle avionics, communications,
and the propulsion system (noted as “S/C




                                                  3-93
3-94
       Figure 3-33 Solar array power source for interplanetary spacecraft.
                     30

                                                                                                       Max. orbit eclipse, 4.2 hr                       Descent (2hr)
 Power Level (kWe)



                                                                               1st Sol              2nd Sol               6th Sol             7th Sol
                                 Transit from Earth Orbit    10 hr
                     20
                                      to Mars Orbit


                                                                         AD                                                                                AR

                                                                              10.6 hr                                                            10.6 hr
                     10
                                         180 days




                          0     8 hr                        MO
                                                                                        Time

               NOTES:                                                                                                      Solar arrays
               Time axis was not drawn to scale
               MO = Mars Orbit, period is 1 sol (Martian day = 25 hrs)                                                     Batteries or RFC
               AD = Array Deployment (4 hr)
               AR = Array Retraction (4 hr)                                                                                Solar arrays and batteries



                                Figure 3-34 Nominal power profile for the transit/surface habitat.


3.6.4                         Surface Systems                                                  autonomy and require support from the flight
    The surface systems assembled to                                                           crew or Earth-based supervisors only in
support the long-duration science and                                                          extreme situations where built-in capabilities
exploration activities of the Reference Mission                                                cannot cope.
consist of six major systems: a surface
                                                                                               3.6.4.1 Surface Habitat/Laboratory
laboratory and habitat module, a
bioregenerative life support system, ISRU                                                          The primary function of the Mars surface
equipment, surface mobility systems (rovers),                                                  habitat/laboratory is to support the scientific
extravehicular mobility systems (EVA suits or                                                  and research activities of the surface crews.
space suits), and power systems. All of these                                                  The same structural cylinder (7.5 meters in
systems, with the possible exception of the                                                    diameter, bi-level, and vertically oriented)
EVA suits, are sent to Mars, landed on the                                                     used for the other habitat elements was used
surface, deployed, and determined to be                                                        here, but it is more specialized for the
functioning before departure of the flight                                                     research activities. It will operate only in 3/8
crew. This requires that each system be                                                        gravity.
developed with a high degree of built-in




                                                                                        3-95
            Table 3-16 30 kWe Power System With Fuel Cells and Solar Arrays

   Power                     1-Orbit                            7-Orbit
System Type                 Recharge                           Recharge

                 Mass     Volume       Array Area   Mass                  Array Area
                                                           Volume (m3)
                 (kg)      (m3)           (m2)      (kg)                     (m2)

Fuel Cell       1481      0.194         N/A         1102       3.83          N/A
Radiator         259      3.260           47         190       1.5            35
Array           2971       N/A           918        1682      N/A            520

Total           4711      3.454          965        2974       5.38          555




            Table 3-17 5 kWe Power System With Fuel Cells and Solar Arrays

   Power                     1-Orbit                            7-Orbit
System Type                 Recharge                           Recharge

                 Mass     Volume       Array Area   Mass                  Array Area
                                                           Volume (m3)
                 (kg)      (m3)           (m2)      (kg)                     (m2)

Fuel Cell         398      9.498          N/A       347       0.456         N/A
Radiator           76      0.971          14         49       0.653           9
Array             795      N/A           246        431       N/A           138

Total            1269       1.469        260        827       1.109         147




                                          3-96
      This surface habitat/laboratory will be      extended periods of time in the habitat/
one of the first elements landed on the surface    laboratory. The primary airlock for EVA
of Mars. Once moved to a suitable location         activities will be located in this module (with
(should the actual landing site prove              backup capability in one of the other habitat
unsuitable or to accommodate other                 modules) with an EVA suit maintenance and
operational needs), this facility will be          charging station located near the airlock.
connected to the surface power systems and         Table 3-18 details the estimated mass for this
all internal subsystems will be activated. Only    module.
after these internal subsystems and other
landed surface systems have been verified to       3.6.4.2 Life Support System
be operating satisfactorily will the first crew          An important reason for sending humans
be launched from Earth.                            to live on and explore Mars is to determine
     The surface habitat/laboratory contains a     whether human life is capable of surviving
large stowage area on the first level and the      and working productively there. The life
second level is devoted entirely to the            support system (LSS) for a Mars surface
primary science and research laboratory. The       mission will be an integral part of the mission
stowage area will initially contain                architecture, and must be viewed in terms of
nonperishable consumables that can be sent         its requirements to maintain the health and
to the surface prior to the arrival of the first   safety of the crew and its capability to
crew. As these consumables are used, this          minimize the dependence of a Mars outpost
space will become available for other uses—        on materials supplied from Earth. Proving
likely to be plant growth and greenhouse-          that human, and by extension animal and
type experiments. The other subsystems of          plant, life can inhabit another world and
this module, such as the primary and               become self-sufficient and productive will be
secondary structure, windows, hatches,             a major objective of this LSS.
docking mechanisms, power distribution                  Four options were examined for use as
systems, life support, environmental control,      the LSS for the Mars surface facilities: open
safety features, stowage, waste management,        loop, physical/chemical, bioregenerative, and
communications, airlock function, and crew         cached stocks of consumable materials.
egress routes, will be identical to the other
                                                         •The open loop option is the simplest to
habitats with a few exceptions. No crew
                                                   implement but typically the most expensive
quarters or accommodations will be included
                                                   in terms of the mass required. For this option,
in this module except for a minimal galley
                                                   life support materials are constantly
and minimal waste management facility.
                                                   replenished from stored supplies as they are
However, the life support subsystem will be
                                                   used (for example, as air is breathed by the
capable of supporting the entire crew should
                                                   crew, it is dumped overboard and replaced
it become necessary for the crew to spend




                                               3-97
                Table 3-18 Mars Surface Habitat/Laboratory Mass Breakdown

                                                    Subsystem        Consumables       Dry Mass
                   Subsystem                           Mass            Subtotal        Subtotal
                                                     (tonnes)          (tonnes)        (tonnes)

  Physical/chemical life support                          4.00            2.00             2.00
  Plant growth                                            3.00            1.00             2.00
  Crew accommodations                                     7.50            7.50             0.00
  Health care                                             0.00            0.00             0.00
  Structures                                             10.00            0.00            10.00
  EVA                                                     1.50            1.00             0.50
  Electrical power distribution                           0.50            0.00             0.50
  Communications and information                          1.50            0.00             1.50
    management
  Thermal control                                         2.00            0.00             2.00
  Power generation                                        0.00            0.00             0.00
  Attitude control                                        0.00            0.00             0.00
  Spares/growth/margin                                    5.50            0.00             5.00
  Radiation shielding                                     0.00            0.00             0.00
  Science                                                 3.00         Uncertain           3.00
  Crew                                                    0.00            0.00             0.00

  Total estimate                                         38.50           11.50            27.00



with “new” air). While not seriously
considered, this option was carried for                     Life Support System, although it is often
comparison purposes.                                        described colloquially as a “greenhouse
                                                            system.”
   •The physical/chemical option is typical
    of the systems used in current spacecraft              •The cached stocks option makes use of
    and relies on a combination of physical                 the ISRU equipment already in place for
    processes and chemical reactions to                     manufacturing propellants to also make
    scrub impurities from the air and water.                usable air and water for the crew. Trace
                                                            amounts of the constituents of usable air
   •The bioregenerative option uses higher
                                                            and water will be by-products (in fact
    plant life species to provide food,
                                                            impurities that must be removed) of the
    revitalize air, and purify water. This type
                                                            propellant manufacturing process.
    of approach is technically embodied in
                                                            Capturing and storing these impurities
    the concept of a Controlled Ecological
                                                            as well as oversizing some of the




                                                  3-98
     production processes can allow the crew          stay. A physical/chemical system was chosen
     to at least augment other elements of the        due to the mature nature of the technology.
     LSS.                                             Thus, the first habitat and the surface
                                                      laboratory constitute the primary and first
     Combinations and hybrids of these
                                                      backup (although not strictly a functional but
options are also possible and were also
                                                      rather a redundant backup) for the crew life
examined for this report. Using a combination
                                                      support.
of systems or a hybrid system would provide
more levels of functional redundancy and                   It is highly desirable for the second
thus provide an attractive option for                 backup to use indigenous resources so that
enhancing the viability of the Mars surface           the backup life support objective and the live
facilities as a safe haven. Figure 3-35               off the land objective are both met. Table 3-19
illustrates a hybrid system using physical/           compares the various options for the
chemical and bioregenerative elements.                combined LSSs with an open system. Each of
                                                      these options was sized for a crew of six
      In this example, certain life support
                                                      spending 600 days on the martian surface.
functions, such as CO2 reduction and water
purification, can be shared by both elements,              Because of the life-critical nature of the
while other functions, such as fresh food             propellant manufacturing facility and the
production, can only come from the                    high level of reliability that must be designed
greenhouse. As an integrated system, neither          into this system, the cached stocks option was
element needs to provide 100 percent of the           chosen as the second backup. However,
full life support demand on a continuous              demonstrating the capability to produce
basis. Both elements however, should be               foodstuffs and revitalize air and water using
capable of being periodically throttled to            bioregenerative processes is considered a
satisfy from 0 percent to 100 percent of the          mission-critical objective for the Reference
LSS load.                                             Mission. For that reason, an experimental
                                                      bioregenerative life support system capable of
      The Reference Mission adopted the
                                                      producing a small amount of food is included
philosophy that life-critical systems (those
                                                      as a science payload to be delivered for use by
systems absolutely essential to ensure the
                                                      the second crew.
crew’s survival) should have two backup
levels of functional redundancy. That is, if the           Several options exist for the location of
first two levels fail, the crew will not be in        the experimental bioregenerative LSS. One is
jeopardy, but will not be able to complete all        to use the storage space in the surface
mission objectives. As previously discussed,          habitat/laboratory that will become available
each habitat is equipped with a physical/             as consumables are used. This is the simplest
chemical LSS capable of providing for the             to implement but would require artificial
entire crew for the duration of their surface         lighting and would be restricted to the




                                                   3-99
                                                                           SUPPLY
                                     RECYCLE
                                     PATH
                                                                           HIGHWAY



                              LSS   O2        H 2O         FOOD H2O O2      EFFL.
                                                                            BUS


                                                      H2O
              DISPOSAL
              PATH
                                                      O2

                               PHYS. / CHEM.          CO2
                                                               BIO-REGEN.

                                                                           INFL.
                                                                           BUS
                              MASS CO 2       H2O             H 2O   CO2




                                    WASTE                        ELECT.
                                    PRODUCT                      POWER
                                    HIGHWAY                      HIGHWAY

                  Figure 3-35 Hybrid LSS process distribution.



                 Table 3-19 LSS Mass, Volume, Power Comparison.

                                    Functional         Mass     Volume              Maximum ∆
          Architecture              Redundant          (mt)      (m^3)               Power Over
                                      Levels                                       Open Loop (kW)


Open Loop                                 1            180           290                 0

Physical/Chemical with Cached
                                          2             60           470                 7
Stocks

Bioregenerative with Cached
                                          2             60           410                 60
Stocks

Hybrid Physical/Chemical and
Bioregenerative with Cached               3             80           600                 60
Stocks




                                              3-100
volume available in the storage area. Two             first follow-up mission. Each ISRU plant will
other options involve attaching an external           produce propellants for at least two MAV
pressurized structure to one of the habitat           missions. However, only the first plant is
modules. One external option would use a              required to produce life support caches.
hard opaque structure for the external shell
                                                           For each MAV mission, a plant is
and would also require artificial lighting. The
                                                      required to produce 20 tonnes of oxygen and
other external option would use an inflatable
                                                      methane propellants at a 3.5 to 1 ratio: Each
transparent structure for the external shell.
                                                      plant must produce 5.8 tonnes of methane
Natural sunlight would be used to illuminate
                                                      and 20.2 tonnes of oxygen. Further, the first
the plants which would reduce the power
                                                      ISRU system is required to produce 23.2
needed by the system; however, the potential
                                                      tonnes of water, 4.5 tonnes of breathing
risk of a puncture due to natural or human-
                                                      oxygen, and 3.9 tonnes of nitrogen/argon
derived events would be increased.
                                                      inert buffer gasses for use by any of the three
     In either external scheme, the greenhouse        Mars crews. The system liquefies and stores
atmospheric volumes would normally                    all of these materials as redundant life
communicate directly with the atmospheric             support reserves or for later use by the MAV.
volume of the habitat without further
                                                          The approach to ISRU production uses
processing, but could be sealed off in
                                                      the martian atmosphere for feedstock and
contingencies. The greenhouse(s) could be
                                                      imports hydrogen from Earth. The main
erected or inflated at the convenience of the
                                                      processes used are common to both ISRU
crew. The loss of a greenhouse module for
                                                      plants. The significant difference between the
any reason, such as puncture, mechanical or
                                                      two is that the second plant is smaller and
electrical failure, or loss of shielding integrity,
                                                      excludes equipment for buffer gas extraction.
would not seriously impact overall mission
                                                      Should sources of indigenous and readily
success.
                                                      available water be found, this system could be
                                                      simplified.
3.6.4.3 In Situ Resource Utilization

     ISRU for the Reference Mission provides          3.6.4.3.1      Processes
two basic resources: propellants for the MAV
                                                           The Mars atmosphere, which is used as a
and cached reserves for the LSSs. Using
                                                      feedstock resource, is composed primarily of
indigenous resources to satisfy these needs
                                                      carbon dioxide with just over 3 percent
instead of transporting resources from Earth
                                                      nitrogen and argon. The ISRU plants must be
reduces launch mass and thus mission cost.
                                                      capable of converting the carbon dioxide to
ISRU production for the Reference Mission
                                                      methane, oxygen, and water. Since hydrogen
includes two virtually redundant ISRU plants,
                                                      is not substantially present in the atmosphere
the first delivered before the initial piloted
                                                      in gaseous form and indigenous sources of
mission and the second delivered prior to the




                                                  3-101
water are uncertain, hydrogen must be                Water electrolysis is well known and has
imported from Earth. The first plant must also   been used for numerous terrestrial
be capable of extracting the nitrogen and        applications for many years. The combined
argon for buffer gas reserves. The reference     Sabatier and electrolysis processes generate
ISRU system uses Sabatier, water electrolysis,   oxygen and methane for use as propellants at
carbon dioxide electrolysis, and buffer gas      a mass ratio of 2:1. In this combined process
absorption processes to achieve these ends.      case, the hydrogen is recycled into the
                                                 Sabatier process so that 0.25 tonnes of
   •Methane production - The Sabatier
                                                 hydrogen are needed for each tonne of
    reaction was discovered by French
                                                 methane. The engines selected for the
    chemist P. Sabatier in the nineteenth
                                                 Reference Mission use oxygen and methane at
    century and is one of the most often
                                                 a mass ratio of 3.5 to 1. Therefore, an
    cited for ISRU on Mars (Sullivan, et al.,
                                                 additional source of oxygen is needed to
    1995). The reaction converts carbon to
                                                 avoid overproduction of methane.
    methane and water by reacting it with
    imported hydrogen at elevated                     The carbon dioxide electrolysis process is
    temperatures. This process is also           used in the Reference Mission to provide the
    commonly used in closed physical/            needed additional oxygen. The process
    chemical LSSs for reduction of metabolic     converts the atmospheric carbon dioxide
    carbon dioxide. It results in a water to     directly into oxygen and carbon monoxide
    methane mass ratio of 2.25:1 and             using zirconia cells at high temperature. The
    requires 0.5 tonnes of hydrogen for each     zirconia cell system is not as well developed
    tonne of methane produced. The               as the Sabatier process but is under
    resultant methane is stored cryogenically    development (Sridhar, et al., 1991; Ramohalli,
    as fuel. The water can either be used        et al., 1989; and Colvin, et al., 1991). This
    directly as cached life support reserves     process eliminates the overproduction of
    or can be broken down into oxygen and        methane during propellant production except
    hydrogen to be recycled.                     during the first mission when the Sabatier-
                                                 produced water is also needed.
   •Oxygen production - Oxygen production
    is accomplished with two different               The two strong alternatives to carbon
    processes. The Reference Mission uses        dioxide electrolysis—methane pyrolysis and
    both water electrolysis to produce           reverse water gas shift—were not studied in-
    oxygen from water produced in the            depth for the Reference Mission report, but
    plant and carbon dioxide electrolysis to     they should be considered seriously in further
    directly convert the Mars atmosphere to      studies of manned Mars missions.
    oxygen.




                                             3-102
•Buffer gas extraction - The buffer gas       3.6.4.3.2      Initial ISRU Plant
 extraction process has not been
                                                   The first ISRU plant is delivered to Mars
 examined in detail during this study. It
                                              over a year prior to the first departure of
 will most likely be a nitrogen and argon
                                              humans from Earth, and during that year the
 absorption process in which compressed
                                              plant produces all the propellants and life
 atmosphere is passed over a bed of
                                              support caches that will be needed. Thus,
 material which absorbs the nitrogen and
                                              humans do not even leave Earth until
 argon. The gases are then released by
                                              reserves and return propellants are available.
 heating the bed and the products are
                                              This plant also produces propellants for the
 passed on to the cooling and storage
                                              MAV mission of the third crew in the overall
 system. Parallel chambers are used so
                                              Reference Mission scenario.
 that one bed is absorbing in the presence
 of atmosphere while the other is                  A schematic of this initial plant is shown
 releasing its captured gases.                in Figure 3-36. The plant integrates all the
                                              processes needed for both propellant and life
•Ancillary Systems - Systems for
                                              support products. The water electrolyzer is
 atmosphere intake, product liquefaction,
                                              not used in the plant during the first period of
 and product storage and transfer will be
                                              operation. Because of the total mass of the
 needed. These systems have not been
                                              water cache, all of the water produced by the
 detailed for the Reference Mission at this
                                              Sabatier reactor is stored and the carbon
 stage of study but their necessary
                                              dioxide electrolysis reactor is responsible for
 functions can be described. The filter
                                              producing all the oxygen needed. In addition,
 and compressor equipment cleans the
                                              over 10 tonnes of excess methane are
 martian atmosphere of dust and
                                              produced as a by-product of the water
 compresses it to a pressure usable by the
                                              production process for the LSS cache.
 rest of the ISRU plant. Product
 liquefaction must include cryogenic               When the plant is operated for the third
 liquefaction of oxygen, methane and          MAV launch propellants, the water
 nitrogen as well as condensation of the      electrolyzer is brought on-line. Instead of
 water stored as cached reserves. Storage     being condensed, the water from the Sabatier
 systems will include cryogenic tanks for     reactor is split by the electrolyzer into
 cached oxygen and buffer gasses. An          hydrogen (which is recycled to the Sabatier
 expandable bladder-type tank is              reactor) and oxygen (which is liquefied and
 anticipated for cached water. Propellant     sent to the MAV tanks). For this operation of
 storage will be accomplished in the MAV      the plant, no methane overproduction is
 tanks and so is not considered part of the   needed.
 ISRU system.




                                          3-103
                                                                                    Buffer Gas Extraction


                                               Filter/          Mars                      O2(trace)
                                             Compressor      Atmosphere                  H2O (trace)




                                                                                              H2
                                                 N2/Ar
                                                                     CO2

                       CO2 Electrolysis                                                  H2                  Water Electrolysis
                                      CO                                       NC
                                      Vent                                                                                                 NC

                                                                                                                               Water
                                                                                                                             Condenser
        Buffer Gas
                                                                           Sabatier                         NC
        Cryo Cooler

                                                          CH4        CH4                        H20
                                   MAV                    Vent                            MAV
                                   First                                                 Second
                                   Stage                                                  Stage
                                                                                                                                                O2

                                           CH4                                   CH4

         Buffer gas
       storage cache                                        Cryo Cooler                                  Breathing         Water Storage
                                                                                                        O2 Storage            Cache
                                                                                                           Cache
                                             O2                                   O2




                                   Figure 3-36 Schematic of the first ISRU plant.


     The size of the ISRU plant has only been                              3.6.4.3.3                   Second ISRU Plant
estimated parametrically. These estimates are
                                                                                 The second ISRU plant is delivered at
based on some previous work on the options
                                                                           essentially the same time as the arrival of the
for ISRU and on the rates needed to produce
                                                                           first crew on Mars. This allows time for
requisite materials over a 15-month period.
                                                                           propellant production prior to the Earth
The mass and power requirements for this
                                                                           departure of the second crew. The second
plant are given in Table 3-20. The power
                                                                           plant is only charged with production of
requirements represent those of the plant’s
                                                                           propellants since, the life support reserves are
initial period of operation.
                                                                           presumably still present.




                                                                      3-104
                 Table 3-20 Mass and Power Estimates for the First ISRU Plant

        Plant Component       Production Rate      Component Mass         Component Power
                                 (per day)              (kg)                  (kWe)

      Compressor                 269.7 kg                 716                     4.09

      CO2 Electrolysis            53.2 kg                2128                    63.31

      Sabatier                    22.9 kg                 504                     1.15

      H2O Electrolysis            27.8 kg                 778                     0.00

      Buffer Gas Extraction        8.7 kg                  23                     0.13

      Cryogenic Coolers           84.8 kg                 653                     3.59




     The plant schematic is essentially the         provided for basic maintenance and
same as that shown in Figure 3-36. The              operations activities as well as for exploration
second plant does not include the buffer gas        of the surface. Prior to the first crew’s arrival
extraction, liquefaction, and storage               and during all subsequent periods whether a
equipment or the water condensation and             crew is present or not, exploration at short
storage equipment. Further, the size of the         and long ranges will be performed by
reactors is reduced because of the lower            automated rovers. Surface facility setup
production rates needed. Table 3-21 shows the       activities will require rovers acting under the
estimated mass and power requirements for           supervision of Earth-based operators.
this plant. Plant operations are the same as        Maintenance and operations by the surface
those of the first plant during its second          crews can be more productive with the
period: All Sabatier-produced water is              availability of mobile utility systems. And
electrolyzed, and the extra oxygen needed is        finally, long-range, long-duration exploration
produced by the carbon dioxide electrolyzer.        by the surface crews will be possible only
                                                    with the use of pressurized, autonomous
3.6.4.4 Surface Mobility                            rovers.
     Mobility on a local scale and regional              The Reference Mission identifies three
scale will be required during all phases of the     classes of mobility systems, based on the time
surface exploration of the Reference Mission.       and distance to be spent away from the
The basic objectives for the Reference Mission      surface habitats.
require that a variety of mobility systems be




                                                3-105
                  Table 3-21 Mass and Power Estimates for the Second ISRU Plant

         Plant Component       Production Rate      Component Mass         Component Power
                                  (per day)              (kg)                  (kWe)
       Compressor                  87.8 kg atm             233                     1.33

       CO2 Electrolysis            18.5 kg O2              740                    22.00

       Sabatier                    12.4 kg CH4             272                     0.62

       H2O Electrolysis            27.8 kg H2O             778                     5.79
       Cryogenic Coolers           30.8 kg                 238                     2.3



   •Immediate vicinity of the surface base           distance will be determined by their
    facilities: hundreds of meters and the 6-        capability to walk back to the outpost within
    to 8-hour limit of the EVA portable LSS          the time set by the recharge limits of the
                                                     portable LSS. During these activities, the EVA
   •Local vicinity of the surface base facility:
                                                     crew will have a variety of tools, including
    several kilometers and the 6- to 8-hour
                                                     rovers, carts, and wagons, available for use.
    limit of the EVA portable LSS
                                                          For distances perhaps beyond a kilometer
   •Regional distances: a radius of up to 500
                                                     from the habitats but less than 10 kilometers
    km in exploration sorties that allow 10
                                                     distant, exploration will be assisted by
    workdays to be spent at a particular
                                                     unpressurized self-propelled rovers. This
    remote site, and with a transit speed
                                                     rover is functionally the same as the Lunar
    such that less than half of the excursion
                                                     Rover Vehicle used in the Apollo Program
    time is used for travel (for example, for
                                                     and is meant to assist the EVA crews by
    10 workdays, no more than 5 days to
                                                     transporting them and their equipment over
    reach the site and 5 days to return).
                                                     relatively short distances. Figure 3-37
    These divisions resulted in three basic          illustrates one concept for this rover (partially
rover types and a number of other mobility           hidden behind one of the teleoperated long-
systems to support the kinds of activities at        range rovers) with a gabled radiator above
these ranges and for these amounts of time.          the aft end. This rover is driven by six cone-
     On the local scale, any time the crew is        shaped wheels and has an estimated mass of
outside of the habitat(s) they will be in EVA        4.4 tonnes. Three of these vehicles will be part
suits and will be able to operate at some            of the cargo carried to the surface for use in
distance from the habitat. The maximum               and around the surface facilities.




                                                 3-106
     On the regional scale, beyond the safe          this rover is the power system. The choice of
range for exploration on foot or in                  the specific power system is discussed in a
unpressurized rovers, crews will explore in          later section. However, this system will be
pressurized rovers, allowing them to operate         mounted on a separate trailer to be towed by
for the most part in a shirtsleeve                   the rover whenever it is in operation. At times
environment. Figure 3-38 illustrates one             when the rover is dormant, the power trailer
possible concept for this rover. The rover is        can be used for other purposes, including its
assumed to have a nominal crew of two                use as a backup power source for any of the
people, but can carry four in an emergency.          surface facilities. Two pressurized rovers will
Normally, the rover would be maneuvered              be carried to the surface. This allows for
and EVAs would be conducted only during              redundancy in this function, including the
daylight hours, but sufficient power will be         possibility of rescuing the crew from a
available to conduct selected investigations at      disabled rover located at a distance from the
night. Crew accommodations inside the rover          habitats. Each rover is driven by four cone-
will be relatively simple: a drive station, a        shaped wheels and is estimated to have a
work station, hygiene facilities, a galley, and      mass of 16.5 tonnes.
sleep facilities. An airlock on this rover will be
                                                          Exploration at a regional scale will also
capable of allowing not only surface access
                                                     be undertaken by small teleoperated rovers.
for an EVA crew, but also direct connection to
                                                     The foreground of Figure 3-38 illustrates one
the habitat, thus precluding the need for an
                                                     possible concept for this rover. The main
EVA to transfer either to or from the rover.
                                                     purpose for these rovers is to explore the
Each day on an excursion away from the
                                                     martian surface at long distances, hundreds to
main surface facilities, the rover has the
                                                     thousands of kilometers, from the habitats.
capability of supporting up to 16 person-
                                                     The activities carried out by this type of rover
hours of EVAs. Facilities for recharging the
                                                     will be to conduct scientific investigations,
portable LSSs and for making minor repairs
                                                     collect and return samples to the habitats, and
to the EVA suits are also included. The work
                                                     scout possible locations for human crews to
station will be used, in part, to operate two
                                                     investigate in more detail. Three of these
mechanical arms that can be used to
                                                     rovers will be delivered as part of the first
manipulate objects outside the rover without
                                                     cargo mission and will be supervised from
leaving the pressurized environment. These
                                                     Earth during the time between landing and
arms, along with other mobility subsystems,
                                                     the arrival of the first crew. Determining sites
can also be operated remotely by Earth-based
                                                     for the crews to investigate and safe routes to
personnel. This feature is required to allow
                                                     the sites will be the primary activity before
many of the deployment, setup, and
                                                     the first crew arrives and during those
monitoring activities to be carried out prior to
                                                     periods when no crew is at the surface base.
the arrival of the first crew. A final feature of
                                                     When a crew is on the martian surface, these




                                                 3-107
Figure 3-37 Concepts for the unpressurized and automated surface rovers.




                                 3-108
Figure 3-38 Concept for the large pressurized surface rover.




                           3-109
rovers will be available for teleoperation by     allow the crew to safely exit and enter the
the crews. Focused exploration, sample            pressurized habitats.
collection, and scientific measurements will
                                                       The EVA system will have the critical
be the main tasks for these rovers while under
                                                  functional elements of a pressure shell,
the control of the surface crew, who will be
                                                  atmospheric and thermal control,
able to operate these rovers from the
                                                  communications, monitoring and display, and
shirtsleeve environment of the surface
                                                  nourishment and hygiene. Balancing the
habitat/laboratory. Each rover is estimated to
                                                  desire for high mobility and dexterity against
have a mass of 440 kilograms.
                                                  accumulated risk to the explorer will be a
     This range of mobility systems will allow    major design requirement on a Mars EVA
exploration activities to be carried out          system. Lightweight and ease of maintenance
continuously once the first cargo mission has     will also contribute to the design. Specific
delivered its payload to the martian surface.     concepts for an EVA suit that will satisfy these
The variety of range requirements and surface     requirements were not investigated in this
activities leads to a suite of mobility systems   study. Further effort will be required to
that have overlapping capabilities.               translate these general needs into specific
                                                  requirements and an actual implementation.
3.6.4.5 EVA Systems
                                                       The airlock system, although integral
     The ability for individual crew members      with the habitation system, was developed as
to move around and conduct useful tasks           an independent element capable of being
outside the pressurized habitats will be a        “plugged” or relocated as the mission
necessary capability for the Reference            requires. Because EVA will be a substantial
Mission. EVA tasks will consist of                element of any planetary surface mission, the
constructing and maintaining the surface          design and location of the associated airlock
facilities, and conducting a scientific           facilities will have a major impact on the
exploration program encompassing geologic         internal architecture of each pressurized
field work, sample collection, and                element.
deployment, operation, and maintenance of
                                                       A conceptual airlock configuration was
instruments. EVA systems provide a primary
                                                  prepared (Figure 3-39). In the foreground of
operational element and a critical component
                                                  this conceptual design is an airlock sized for
of the crew safety system and must be
                                                  two suited crew members. In the rear of the
integrated into the design of a habitation
                                                  illustration is a facility for EVA suit
system during the very early stages. Two
                                                  maintenance and consumables servicing.
systems will make EVA possible for the crews:
                                                  Each habitat will have an airlock located
an EVA suit designed for use in the martian
                                                  within it. The maintenance and consumables
environment and an airlock system that will




                                              3-110
                                                    synergies that would suggest common
                                                    hardware (duplicates of the same or similar
                                                    design) or multiuse (reuse system in a
                                                    different application or location) wherever
                                                    prudent, the specific requirements for the
                                                    fixed and mobile power sources were
                                                    examined individually.

                                                    3.6.4.6.1     Fixed Surface Power Systems

                                                         To best determine the type and design of
                                                    the fixed power system, an estimated power
                                                    profile was developed and is shown in Figure
 Figure 3-39 Conceptual airlock and                 3-40.
    EVA suit maintenance facility.
                                                          The power system must be one of the
servicing facility will be located in the surface   first elements deployed because it provides
habitat/laboratory.                                 power to produce the life support cache and
                                                    ascent vehicle propellants prior to the launch
3.6.4.6 Surface Power Systems                       of the first crew. Approximately 370 days will
     A source of power will be required for a       be available to produce the required life
number of diverse systems operating on the          support cache and ascent propellant.
surface of Mars. A large fixed power source is      However, this will be reduced by the time to
required to support the propellant                  deploy the power system. With an estimated
manufacturing facility and the surface              power system deployment time of 30 to 60
habitats. A mobile source of power is required      days, about 320 days remain for producing
to support the three categories of rovers that      these products. An initial 60 kWe power level
will move crew and scientific instruments           was determined by this required deployment
across the martian surface. Various power           time and the energy required to produce the
system options were reviewed for their              life support cache and ascent vehicle
appropriateness to meet mission                     propellants during the time remaining. As the
requirements and guidelines for these surface       outpost reaches full maturity, power levels
systems. Contending power system                    approach 160 kWe due to increased habitation
technologies include solar, nuclear, isotopic,      volumes and life support capability.
electrochemical, and chemical for both the              Significant design requirements are also
fixed and mobile power source.                      placed on all the surface equipment delivered
    While all surface element power system          on the initial cargo flights. Each system must
requirements were assessed for application          be deployed to its respective locations and




                                                3-111
      175


      150


      125
  P
  o
  w   100
  e
  r
        75
  kWe

        50


        25




                     1           2          3           4          5         6         7
                                         Years After First Cargo Landing

                         Figure 3-40 Mars surface power profile.

function autonomously for almost 2 years.                The power management, transmission,
Crew safety and well-being demands                  and distribution system masses (at 95 percent
reliability and robustness in all surface           efficiency) have been included in each of the
elements. (Part of this risk is mitigated by        system sizing estimates. Transmission cable
backup and redundant systems or systems             masses were calculated using 500 volts due to
that can perform multiple functions.) These         the Paschen breakdown limit associated with
requirements all impact the design and              Mars’ atmospheric pressure. (For a wide
selection of the power system for the central       range of conditions, exposed conductors at an
base.                                               electrical potential greater than 500 volts
                                                    could experience large power drains due to
    To meet the evolutionary power                  atmospheric discharges.)
requirements of the base, two types of power
systems were evaluated: nuclear and solar.              Due to the potential radiation hazard of a
Table 3-22 shows estimated mass, volume,            nuclear power source, the nuclear power
and area for each of these options.                 system is configured with a completely




                                                3-112
              Table 3-22 Characteristics for Fixed Surface Power System Options

    Main Power                    Type                     Mass     Volume
                                                                                     Area (m2)
   System (kWe)                                            (MT)      (m3)

                    NUCLEAR-                                14        42
                    SP-100 type, low-temp, stainless
        160                                                                   321 radiator area
                    steel, dynamic conversion, 4-Pi
                    shielding
                    SOLAR - tracking,
        120                                                19.6       341     6,400 array area
                    O.D. = 0.4
                                                                              45,000 field area

                    SOLAR - nontracking,                   33.5       686     13,000 array area
                    O.D. = 0.4                                                39,000 field area

                    SOLAR - tracking,                                         7,600 array area
    Backup 40                                               14        390
                    O.D. = 6.0                                                53,000 field area

                    SOLAR - nontracking,                    26        816     16,000 array area
                    O.D. = 6.0                                                48,000 field area

    Emergency       Use Pressurized Rover Power System (See Table 3-21)

O.D. - optical depth


enveloping shield for remote deployment and            mission requirement, but it will not be turned
is integrated with a mobile platform. The              on unless required.
entire system is deployed from the landing
                                                           The second option, a solar power system,
site (trailing distribution cables) to a site at
                                                       requires array panels to supply the main base
least 1 kilometer from the base. It is planned
                                                       load and recharge the energy storage for
to use one of the rovers for this task. Power
                                                       nighttime operations. The primary 120 kWe
from the rover will be used to start up the
                                                       system was sized to produce required power
power system, deploy radiators, and obtain
                                                       during winter diurnal cycles at the equator.
operating conditions. All of these activities
                                                       The backup habitat power system was
will be supervised remotely by personnel on
                                                       designed to operate at worst-case global dust
Earth and will be performed in a manner that
                                                       storm conditions, characterized by an optical
will minimize the risk to this critical piece of
                                                       depth (O.D.) equal to 6.0, since these
equipment. The first nuclear power system
                                                       conditions could be present at the base when
will be capable of delivering the full base
                                                       an emergency power situation arose. Under
needs of 160 kWe. A second system is
                                                       nominal conditions, these two systems were
delivered during the first opportunity and is
                                                       assumed to be operating in unison to provide
deployed to satisfy the fail-operational
                                                       the maximum 160 kWe required for the




                                               3-113
mature base. The ISRU plant was not                 3.6.4.6.2      Mobile Surface Power Systems
considered a life-critical function so the
                                                         The other major category of surface
power system was designed to produce full
                                                    systems needing a power source will be the
power at an O.D. of 0.4 or a clear Mars sky.
                                                    rovers. The three types of rovers identified,
Both sun tracking and nontracking arrays
                                                    long-range pressurized, local unpressurized,
were evaluated. The solar tracking array total
                                                    and long-range robotics, each have power
land area is greater that the nontracking
                                                    requirements driven by their range and the
because of the required panel spacing needed
                                                    systems they must support. Several power
to eliminate shadows from one panel upon
                                                    source options were evaluated for the rovers,
the other.
                                                    including solar arrays/RFCs, combustion
     O.D., or the intensity of the solar            engines, and isotopes. Solar array systems
radiation reaching the surface of Mars, has a       were not considered due to the large size of
significant impact on system size and mass.         the array needed to support each vehicle.
For example, if the entire 160 kWe were solar
                                                         The long-range pressurized rover must
generated, the array field would encompass
                                                    be able to support a crew of 2 to 4, with a 500-
about 11 (O.D. = 0.4) to 40 (O.D. = 6.0) football
                                                    km range sortie (5 days out, 10 days at site, 5
fields. In addition, the need for prompt
                                                    days back). The power estimate for this rover
telerobotic emplacement of the array panels
                                                    is 10 kWe continuous. It is anticipated that the
and interconnecting cables would present a
                                                    pressurized, regional rover or its power
significant challenge. Dust erosion, dust
                                                    system would be used to assist in the
accumulation, and wind stresses on the array
                                                    deployment of the main power system,
panels raise power system lifetime issues. For
                                                    situate future habitat modules, and serve as
these reasons, nuclear power was deemed the
                                                    backup emergency power when required. A
most appropriate primary power source for
                                                    desirable feature for the rover power system
the fixed surface power system. However, use
                                                    is that it be mounted on its own cart. This
of the “in-space” solar array and fuel cell
                                                    would add considerable versatility to its use
power system is assumed as the habitat
                                                    when the rover is not on a sortie.
emergency/backup power systems, which
could be stowed until needed. The MAVs will              The local unpressurized rover is
also be provided with this same solar array         conceptually the same as the Apollo lunar
backup system to ensure that the                    rover. It would function to transport the crew
manufactured propellants are maintained in          10's of kilometers, 3 hours out and back, and 4
their cryogenic state should power from the         hours at the site.
nuclear system be lost (Withraw, et al., 1993).         Table 3-23 shows the estimated mass,
                                                    volume, and array or radiator area for the
                                                    four power system options listed.




                                                3-114
     The Dynamic Isotope Power System                 scenario, anticipating suspended operations
(DIPS) was considered primarily for its low           during potential global dust storm season.
mass and significantly lower radiator size
                                                           Methane is a possible fuel for the rover
compared to the photovoltaic array (PVA)
                                                      since the propellant plant could produce
area. The 238Pu isotope has a half life of 88
                                                      additional fuel, given that extra hydrogen is
years and can be the same design as the flight
                                                      brought from Earth. Methane could be used
proven radioisotope thermoelectric generator
                                                      in an appropriately designed fuel cell. The
(RTG). The isotope fuel would be reloadable
                                                      reactant water would be returned and fed
into other power units in the event of a
                                                      through an electrolyzer to capture the
failure, thus preserving its utility. Another
                                                      hydrogen. However, once the water has been
feature of isotope fuel is that it does not need
                                                      electrolyzed into H2 and O2, which the fuel
to be recharged and is always ready as a
                                                      cell actually uses to operate, it is not prudent
backup, emergency power source
                                                      from an energy utilization standpoint to make
independent of solar availability or
                                                      methane again. Storing and maintaining
atmospheric conditions. However, the 238Pu
                                                      reactants on the rover also needs further
isotope availability, quantity, and cost are
                                                      study.
issues to be addressed.
                                                           A methane-burning internal combustion
     The PV/RFC power option seems
                                                      engine could be used to operate either rover.
impractical for the regional rover due to the
                                                      However, combustion materials would need
large array area. The arrays would have to be
                                                      to be collected to reclaim the H2.
sized to provide required power output
during a local dust storm, the worst-case


                          Table 3-23 Rover Power System Characteristics

                                 Mass                      Area    Mass                     Area
         Power System                    Volume (m3)                        Volume (m3)
                                 (MT)                      (m2)    (MT)                     (m2)

                                         Regional Rover                      Local Rover

  Dynamic isotope                  1.1         10           33       0.5          4           16

                                               66          1,275
                                   2.8
  Photovoltaic (PV) RFC                     (RFC-4)                recharge by fueling
                                             PV-62)

  Primary Fuel Cell                6.5         29           13      0.160         1           6

  Methane/Oxygen Internal
                                   12          36          n/a      0.160        0.4         n/a
  Combustion Engine




                                               3-115
     Given these system characteristics, the          weather and provide global maps of martian
DIPS system was selected for the long-range           surface topography and mineral distribution.
pressurized rover, and the primary fuel cell          The Mars Pathfinder will validate entry,
was selected for the local rover. The DIPS            descent, and landing technologies and will
system can be another level of functional             also deploy a microrover on the surface to
redundancy for the base systems, and the              analyze the elemental composition of martian
small amounts of radiation emitted can be             rocks and soil.
mitigated by a small shield and distance to
                                                           NASA’s Mars Surveyor Program will
the rover crew. The primary fuel cell would
                                                      continue the robotic exploration of Mars with
meet the local rover requirements at less mass
                                                      two spacecraft launches planned during each
than other options. However, this power
                                                      of the 1998, 2001, and 2003 opportunities. A
system design assumes refueling after every
                                                      Mars sample return mission is scheduled for
sortie. The power system for the long-range
                                                      2005. The goals of the Mars Surveyor Program
robotic rover was not specifically addressed
                                                      are to expand our knowledge of the geology
in this analysis. However, the long range over
                                                      and resources on Mars, to understand the
rugged terrain and long duration of this
                                                      meteorology and climate history, and to
rover’s missions will likely drive the selection
                                                      continue the search for evidence of past life.
to an RTG- or DIPS-type system.
                                                      3.7.2   Mars Sample Return With ISRU
3.7     Robotic Precursors
                                                           Detailed laboratory analyses of martian
     Robotic precursor missions will play a           rock, soil, and atmosphere samples at Earth
significant role in two important facets of the       will provide essential information needed
Reference Mission. The first will be to gather        before sending humans to Mars. In addition
information about Mars that will be used to           to an understanding of the martian
determine specific activities the crew will           environment, a sample return mission will
perform and where they will perform them.             afford the opportunity to validate the
The second will be to land, deploy, operate,          technology of ISRU for propellant production.
and maintain a significant portion of the             As discussed in Section 3.6.4.3, ISRU is a
surface systems prior to the arrival of the           critical technology for the Reference Mission.
crew.                                                 To ensure that this technology is available for
                                                      the human missions, it should be
3.7.1   Current Robotic Program Plans
                                                      demonstrated on the Mars sample return in
    In November and December 1996, NASA               2005.
launched two missions to Mars: the Mars
Global Surveyor (MGS) and the Mars
Pathfinder lander. MGS will monitor global




                                                  3-116
3.7.3 Human Exploration Precursor                     various candidate sites. Detailed maps of
Needs                                                 candidate landing sites built from data
     Robotic precursor missions offer the             gathered by these precursor missions will
capability to demonstrate and validate the            define the safety and operational hazards of
performance of key technologies that are              the sites, as well as confirm access to
essential to the Reference Mission (such as           scientifically interesting locations and
ISRU, aerobraking and aerocapture at Mars)            resources.
and to provide information needed for site                In summary, then, the Reference Mission
selection.                                            assumes a set of robotic precursor missions
     Critical to selection of the landing site for    which includes:
the humans will be the availability of                    •The Mars Surveyor Program
indigenous resources, and of paramount
                                                          •A Mars sample return mission in 2005
importance is water. Precursor missions
                                                           which also demonstrates in situ
which can identify the location and
                                                           propellant production
accessibility of water will be invaluable in the
Mars exploration program. To satisfy the                  •Other sample return missions to various
human habitation objectives in particular, it              interesting regions
would be highly desirable to locate an
                                                          •A demonstration of aerobraking/
outpost site where water can be readily
                                                           aerocapture
extracted from minerals or from subsurface
deposits. Such a determination may only be                •Mission(s) to search for resources,
possible from data collected by a surface                  particularly water
mission.                                                  •Site reconnaissance landers to aid in the
     With the three human missions all                     selection of the human landing site
landing at the same site, selection of that                The last two mission types may have
landing site is very important. The location          their objectives incorporated into the Mars
chosen must permit the objectives of the              Surveyor Program or the Mars sample return
Reference Mission to be achieved.                     mission; or a separate set of missions may be
Consequently, the site will be chosen on the          required.
basis of proximity to a region of high science
yield, availability of water or other                 3.7.4 Autonomous Deployment of
indigenous resources, and operations                  Surface and Orbital Elements
considerations such as a hazard-free terrain
                                                           As described in Section 3.5.3.2, a key
for safe landing and surface mobility. Final
                                                      strategy of the Reference Mission is to use a
site selection may require several robotic site
                                                      split mission concept that will allow
reconnaissance landers to be sent to survey




                                                  3-117
unmanned cargo to be sent to Mars on low               •Provision of the facilities and an
energy, longer-transit-time trajectories. These         environment which allow users (such as
unmanned elements must arrive at Mars and               scientists, payload specialists, and to an
be verified to be operating properly before the         extent crew members) to conduct
human crew is launched from Earth. The                  activities that will enhance the mission
arrival, precision landing, deployment, and             objectives.
operation of these surface or orbital elements
                                                       •Successful management and operation of
will be performed using robotic systems. The
                                                        the overall program and supporting
detailed nature of these robotic systems was
                                                        organizations. This requires defining
not examined as part of this study; however,
                                                        roles and responsibilities and
the discussion of the surface facilities and the
                                                        establishing a path of authority. Program
nature of the operations involved to set up,
                                                        and mission goals and objectives must
maintain, and, if necessary, repair these
                                                        be outlined so that management
facilities can well be imagined. This area of
                                                        responsibilities are clear and direct.
technology development will be a very active
                                                        Confusing or conflicting objectives can
one to meet the needs of the Reference
                                                        result in loss of resources, the most
Mission.
                                                        important of which are time and money.
                                                        In addition, minimizing layers of
3.8  Ground Support and Facilities
                                                        authority will help avoid prolonged
Operations
                                                        operational decision-making activities.
     The overall goal of mission operations is          This is key when considering large,
to provide a framework for planning,                    complex programs such as the Reference
managing, and conducting activities which               Mission.
achieve mission objectives. (In general,
                                                        As with the discussion of crew operations
mission objectives can be considered all
                                                   (Section 3.4), specific hardware, software, and
activities which maintain and support human
                                                   system recommendations will not be made in
presence and support scientific research
                                                   this section. Guidelines for the organization
during the mission.) Achieving this
                                                   and management of operations are put
operational goal requires successful
                                                   forward as foundation on which an actual
accomplishment of the following functions.
                                                   operations philosophy and detailed plan
   •Safe and efficient operation of all            should be built.
    resources (includes, but is not limited to,
                                                       The organization of supporting facilities
    vehicles, support facilities, training
                                                   must follow the lower costing and innovative
    facilities, scientific and systems data, and
                                                   approaches being taken by other areas of the
    personnel knowledge and experience
                                                   Reference Mission. One way of achieving this
    bases).




                                               3-118
is to use the related expertise and                     benefit of involving system and payloads
functionality of existing facilities to keep to a       experts in the overall planning, yet giving
minimum the layers of authority and                     crews the flexibility to execute the tasks. This
overhead in the program and take advantage              approach differs from current Space Shuttle
of the existing knowledge bases at each                 operations where detailed plans are prepared
facility. Proper and efficient organization of          by ground personnel, crew members execute
mission operations and support facilities is            the plans, and ground personnel monitor in
required for any program to be successful.              near real-time. The crew members are fully
                                                        involved in execution but do little in terms of
     The Reference Mission has the added
                                                        planning. The proposed method for the
complication of being a program with phases
                                                        Reference Mission would take advantage of
that cannot be supported with near real-time
                                                        the unique perspective of crew members in a
operations. Planetary surface operations pose
                                                        new environment but would not restrict their
unique operational considerations on the
                                                        activities because of the mission’s remote
organization of ground support and facilities.
                                                        nature. Additionally, it places the
Near real-time ground support, as provided
                                                        responsibility of mission success with the
for current manned space programs, is not
                                                        crew, while the overall responsibility for
possible. A move toward autonomy in vehicle
                                                        prioritizing activities in support of mission
operations, failure recognition and resolution,
                                                        objectives resides with Earth-based support.
and mission planning is needed; and ground
support must be structured to support these                   After dividing functional responsibilities
needs. Some of the specific criteria required           between Earth-based support and crew, the
for allocating functions between ground                 support may be structured to manage the
support and the Mars surface base will be the           appropriate functions. To accomplish mission
available resources at the remote site versus           objectives while maintaining the first
on Earth, criticality of functions for crew             operational objective of safe and efficient
safety and mission success, and desired time            operation of all resources, Earth-based
and resources available for achieving                   support can be organizationally separated
scientific mission objectives.                          into systems operations and science
                                                        operations, provided a well-defined interface
     In general, due to the uniqueness of
                                                        exists between the two. The systems
planetary surface operations, Earth-based
                                                        operations team would be responsible for
support should manage and monitor
                                                        conducting the safe and efficient operation of
operations planning and execution, and crew
                                                        all resources, while the science operations
members should be responsible for operations
                                                        team would be responsible for conducting
planning and execution. Crew members will
                                                        activities which support scientific research.
be told what tasks to do or what objectives to
                                                        Such an organizational structure would
accomplish, but not how to do it. This has the




                                                    3-119
dictate two separate operations teams with             of program resources. Thus, the systems
distinct priorities and responsibilities yet the       operations team has the responsibility for
same operational goal.                                 conducting the safe and efficient operation of
                                                       all such resources and consists of
     Crew and vehicle safety are always of
                                                       representatives from each of the primary
primary concern. When those are ensured,
                                                       systems (power, propulsion, environmental,
science activities become the highest priority.
                                                       electrical, etc.) used throughout the various
To accommodate this hierarchy of priorities
                                                       mission phases. This organizational structure
within the operations management structure,
                                                       is similar to current flight vehicle operations
the overall operations manager should reside
                                                       where representatives for each system are
within systems operations. A science
                                                       responsible for verifying the system’s
operations manager, who heads the science
                                                       operational functionality. Each system
operations team, should organizationally be
                                                       representative will have an appropriate
in support of the operations manager. Various
                                                       support team of personnel familiar with the
levels of interfaces between systems engineers
                                                       hardware and software of that system.
and science team members must exist to
maximize the amount of science and mission                  Real-time operational support will be
objectives that can be accomplished. For               applicable only during launch, Earth orbit (for
example, a proposed science activity may               vehicle and crew checkout), and Earth entry
need systems information for its planning and          phases. As a result, the systems operations
feasibility studies, and such information,             team will function in a response, tracking,
including providing access to the systems’             and planning mode throughout most of the
experts, must be made available. There may             other mission phases. Thus, Earth-based
be a few overlapping areas of responsibility           operations will be a checks and balances
between the systems and science teams. (In             function analogous to the mission
the area of crew health and safety, for                engineering functions executed during Space
example, scientific investigators doing                Shuttle missions. Hardware and software
biomedical research on the crews will have to          documentation will be available to the crew
interface with the systems medical team                on board for real-time systems operations and
responsible for maintaining crew health.)              failure response. However, Earth-based
Avenues for such interaction and exchange              support must be provided for instances where
must be provided to ensure mission success.            documentation is limited or does not cover a
                                                       particular situation.
3.8.1   Systems Operations
                                                            Except for the above mentioned near
    Systems operations are those tasks which           real-time mission phases, data monitoring by
keep elements of the program in operational            Earth-based personnel must be limited to
condition and support productive utilization           periodic evaluations. Data and




                                                   3-120
communication constraints will make real-          the primary interface between the science
time system monitoring by Earth-based              team and the operations manager.
personnel impractical and unfeasible. Failures
                                                        As science activities (such as initial
and other systems issues will be worked by
                                                   investigations, clarification of previous
Earth-based personnel on an as needed basis
                                                   research, and follow-up investigations) are
and in support of long-term trend analysis.
                                                   proposed by various principle investigators,
Vehicle and system maintenance and
                                                   the science team will evaluate the proposed
checkout will be evaluated by the Earth-based
                                                   research, determine feasibility and
systems experts to assist in crew monitoring
                                                   appropriateness of the study, and select
and verification. Consumables management
                                                   appropriate crew activities based on available
such as usage planning and tracking will be
                                                   time and personnel. This process is similar to
done by the crew (with some degree of
                                                   the process used by the National Science
automation) with Earth-based personnel
                                                   Foundation for the U.S. Antarctic Program
doing verification only.
                                                   which has successfully operated remote
                                                   scientific bases in Antarctica since 1970
3.8.2   Science Operations
                                                   (Buoni, 1990). Selected science proposals will
     The science operations team’s sole            be presented to the systems operations team
function is to recommend, organize, and aid        for evaluation of feasibility and resources. For
in conducting all activities which support         example, appropriate members of the systems
scientific research within the guidelines of the   operations team will determine if there are
mission objectives. The team will consist of       enough consumables to support the required
representatives from the various science           activities and if all of the desired activity is
disciplines (biology, medicine, astronomy,         operationally feasible from a systems
geology, atmospherics, etc.) which support         standpoint. Upon verification, the proposed
the science and mission objectives. Each           research activity will be submitted to the crew
scientific discipline will have an appropriate     for execution.
support team of personnel from government,
                                                        An initial set of science activities will be
industry, and academia who have expertise in
                                                   planned before each crew departs Earth. This
that field. The science operations team will act
                                                   is especially true of the scientific
as the decision-making body for all science
                                                   investigations which support not only crew
activities from determining which activities
                                                   health and safety but also the primary
have highest priority to handling and
                                                   mission objectives. As new discoveries are
disseminating scientific data. The science
                                                   made and new avenues for research are
operations team will be coordinated and
                                                   opened, an iterative science planning process
managed by the science operations manager,
                                                   will become essential for the success and
who will be the ultimate decision maker and
                                                   effectiveness of all scientific activities.




                                               3-121
Successful scientific operations will also              resources in this program or some
require, when needed, crew access to the                alternative program. As many of the
principal investigators for a given research            benefits of an exploration program are
avenue. Such access must be made feasible               intangible and long term, reducing the
within the structure of mission operations.             program costs to an understandable and
                                                        supportable level is of prime
3.9      Programmatic Issues                            importance.
     Three significant programmatic issues             •Whatever the total cost, the program will
must be considered in an undertaking of this            not be undertaken if resources are not
magnitude, if the undertaking is to be                  available. Thus, cost estimates can be the
successfully achieved: cost, management,                basis for apportionment of resource
and technology development. Each of these               requirements between participants,
factors was examined to determine how they              phasing of resource provisions, or
should be incorporated into this and further            phasing of mission elements to avoid
studies of the Reference Mission or                     peak-year funding issues that could
comparable endeavors.                                   stymie the program. Little has been done
                                                        in the Reference Mission costing to
3.9.1    Cost Analysis                                  address this question; however, the
    Cost analysis is an important element in            database is available to analyze cost-
assessing the value of a program such as this           phasing strategies.
and should be used from the very beginning.            •The cost of mission elements and
But at the beginning of a program and, in               capabilities needs to be understood in
many cases, up to the time that specifications          order to prioritize early investments in
are written and contracts are let, it is not            technology and initiate other cost-
possible to analytically determine the cost of a        reduction strategies. The estimated cost
program. If new systems need to be                      of each element (for example, ETO
developed for programs, it is not possible to           launch) is related to the program risk,
know at the outset what the total cost will be          with higher relative costs associated
because hardware is not on the shelf. For               with larger perceived risks of
these reasons, cost models are used that are            development or operation. Thus,
typically based on historical data for similar          understanding the cost can be a first step
programs.                                               in designing program risk-reduction
      •The total program cost will be important         strategies. As part of this process,
       to the beneficiaries and resource                estimates were also made of the cost
       providers, who will be interested in             uncertainty for each of the technical
       whether to invest current and future             elements of the mission, which are also




                                               3-122
     useful in understanding the appropriate      program. It is also a major reason to seek
     capability development strategies. In the    examples or benchmarks in other programs to
     past, technology development efforts         determine the best possible management
     have focused primarily on improving          approaches to design and development, or to
     performance. Now, it is important to         conduct specific programs under new
     address reduction of cost as a goal of the   management rules as prototypes for the
     technology development program.              approach that will be used in the actual
                                                  program.
    The cost of a program such as the
Reference Mission is a function of two major           The cost of doing space missions lies at
variables: the manner in which it is organized    the extreme edge of costliness in comparison
and managed and the technical content of the      to other high technology systems. The
program.                                          technical reasons for this appear to be that
                                                  space missions:
3.9.1.1 Organizational Culture and Cost
                                                      •Are usually one of a kind or are projects
     Management systems and the                        with small numbers of production units
organization under which programs are
                                                      •Are typically aimed at expanding
conducted are a major factor in the cost of a
                                                       capability and technology, so are
program. Basing costs simply on historical
                                                       designed with small margins of mass,
data implies that the management system
                                                       power, volume, etc.
under which the historical programs were
carried out will be assumed for the new               •Have high transportation costs, so high
program. This is a particularly serious                reliability in the spacecraft is important
problem in estimating the Reference Mission
                                                      •Are expected to operate for extended
costs, as the environment in which future
                                                       periods of time in difficult environments
space exploration will be carried out will be
                                                       and, in the case of crewed vehicles, they
much more cost-conscious than in the past.
                                                       must meet high standards of safety
Changes in management, for which no
comparative costs are available, will have to          The engineering and management
occur. Because management style and culture       culture that has been built up around these
are introduced at each level of design and        characteristics has stressed excellence of
production, the leverage of management            performance, safety, and high reliability. Cost
changes in making cost reductions can be          has typically been a secondary criterion. It is
quite high. However, such changes are             not clear that high quality performance and
difficult to estimate. This is a major reason     high reliability always require the
why cost analysis should be considered a          corresponding costly culture.
design tool to be used at all stages of a




                                              3-123
     To illustrate the effect of culture on cost,   (Cyr, 1988). This model considers the scale
consider Figure 3-41 which shows the relative       (particularly mass), the scope (number of
cost of programs developed using different          production and test articles) of the
management approaches. Point 0 is the               development of each of the systems required
relative cost for human spacecraft, point 1 is      to undertake the program, the complexity or
for robotic spacecraft, point 2 for missiles, and   technical readiness for each of the systems
point 3 for military aircraft. Differences in       and their subsystems, the schedule under
management styles develop as a result of the        which the program will be carried out, and
different environments in which programs are        the production generation in which the item
carried out.                                        is produced. To the extent that experience
                                                    exists or off-the-shelf hardware can be
     Table 3-24 depicts the differences
                                                    procured, more precise numbers can be
between a “Skunk Works” management
                                                    estimated. The newer or more untried a
environment, such as might be used on a
                                                    technology is, the greater will be its cost in the
military aircraft development program (point
                                                    model.
2 in Figure 3-41) and the environment for
NASA’s human programs. Some of these                     Input for the AMCM model was derived
differences will have to be addressed if the        from previous experience and information
cost of human space exploration is to be            provided by members of the Study Team.
reduced. To further illustrate differences,         Included in the estimate were the
Table 3-25 compares the parameters of the           development and production costs for all of
development culture for commercial aircraft         the systems needed to support three human
and NASA human programs. These are                  crews as they explore Mars. In addition,
starting points that indicate the changes that      ground rules and assumptions were adopted
will be necessary.                                  that incorporated some new management
                                                    paradigms, as discussed later in the Program
    The cost model used for the Reference
                                                    Management and Organization section. The
Mission (see next section) takes these
                                                    management costs captured program level
variables into account in a “culture” variable,
                                                    management, integration, and a Level II
which can be characterized in more detail by
                                                    function. Typical pre-production costs, such
such attributes as organizational structure,
                                                    as Phase A and B studies, were also included.
procurement approach, and the degree of
program office involvement in production.                Not included in the cost estimate were
                                                    selected hardware elements, operations, and
3.9.1.2 The Cost Model                              management reserve. Hardware costs not
    The cost model used for the technical           estimated include science equipment and EVA
content of the Reference Mission is the             systems, for which data were not available at
Advanced Missions Cost Model (AMCM)                 the time estimates were prepared; however,




                                                3-124
      Figure 3-41 The relative cost of programs using different management
                                   approaches.

these are not expected to add significantly to        When compared to earlier estimates of a
the total. No robotic precursor missions are     similar scale (NASA, 1989), the cost for the
included in the cost estimate although their     Reference Mission is approximately an order
need is acknowledged as part of the overall      of magnitude lower. A distribution of these
approach to the Reference Mission.               costs is shown in Figure 3-42. It can be seen
Operations costs have historically been as       from this figure that the major cost drivers are
high as 20 percent of the development cost.      those associated with the transportation
However, due to the extended operational         elements: the ETO launch vehicles, the TMI
period of the Reference Mission and the          stages, and the Earth-return systems. In
recognized need for new approaches to            addition, the organization mechanisms
managing and running this type of program,       chosen have significantly reduced the cost for
estimating the cost for this phase of the        these elements of cost, when compared to
progam was deferred until an approach is         traditional programs of this type, creating a
better defined. Similarly, the issue of          significant challenge for those who would
management reserve was not addressed until       manage this program.
a better understanding of the management             The Mars Study Team recognizes that,
approach and controls has been developed.        even with a significant reduction in the
                                                 program cost achieved by this team, the




                                             3-125
             Table 3-24 Program Environment Effects on Program Management Style

                                                                        NASA Human Program
   Environment Factor            "Skunk Works" Management
                                                                           Management
Political Environment      - Major threat perceived by all        - Non-urgent
                             involved                             - Threat not perceived as critical


Cost of Failure            - Hidden                               - Public
                                                                  - Potentially catastrophic to
                                                                    Agency

Products                   - High technology                      - High technology
                           - Prototypes                           - High quality "mature" designs
                           - Experimental

Risk to Life               - Acceptable, but                    - Unacceptable
                           - Worthy of spending major resources - Worthy of spending major
                             to avoid                             resources to avoid
Public Perception          -   Secret                             -   Public
                           -   Defense                            -   Science, exploration
                           -   Urgent                             -   Discretionary
                           -   Unaware of existence until after   -   Every detail open to public
                               deployment                             scrutiny and criticism


Schedule                   - Typically 2 years                    - Typically 8 to 10 years
Quantities                 - Small to moderate                    - Small to moderate
Management Teams           - Very small (under 10)                - Moderate to large (dozens)
• Contractor               - Very small (3 to 10 typically)       - Large (hundreds)
• Government

Political Support          - High                                 - High
Cost                       - Small portion of parent agency       - High percentage of parent
                             budget                                 agency budget
                           - Low specific cost (e.g., $/1b)       - High specific cost




                                                 3-126
Table 3-25 A Comparison of Development Culture Parameters for Commercial Aircraft and
                              NASA Manned Programs


           Parameter            Commercial Aircraft Program               NASA Human Program
                                                                             Management
Customer Role                 Requirements definition, arms        Highly interactive
                              length
                                                                   Detailed build specifications, some to
Type of Requirements          Performance of the product
                                                                   piece part level
                              Small (tens or less)
Program Office Size and                                            Large (hundreds)
                              Interaction for clarification of
Type of Interactions                                               Interaction to lowest WBS levels
                              details
Proximity of Program Office   Geographic separation, frequent      Geographic separation, with frequent
Relative to Customer          travel by very small groups          travel for face-to-face meetings by
                                                                   large numbers of project people

                              Commitment to fixed price by         Three phases: end of preliminary
Competition Through
                              supplier                             design, program definition, start of
                                                                   detailed design and development
                              Totally demonstrated flight          Proof of concept
Technology Status at Full
                              systems
Scale Development Start

                              Supplier's systems only:
Management Systems                                                 Customer imposed, often duplicative
                              occasional tailored reports to the
                                                                   with contractor systems
                              customer

Length of Full Scale          2 to 3 years                         6 to 15 years
Development
Budget Strategy               Full commitment with guarantees Annual, incremental, high risk
                              by both parties

Changes                       None to very few                     Thousands per year
                                                                   Fixed, and/or award, based on
Fee Type                      Included in fixed price
                                                                   supplier performance
Contract Type                 Fixed price with incentives          Cost plus fixed, award fee
SR&QA                                                              Customer specified
                              Industry and supplier standards




                                                 3-127
magnitude is probably still too high in today’s         carried out using two HLLV launches
fiscal environment. More work to further                per opportunity (requires some
reduce these costs is needed.                           reduction of capability) (Zubrin, et al.,
                                                        1991). Reducing the number of launches
      The largest cost element of the Reference
                                                        from 12 to 8 would reduce the
Mission is the ETO transportation system
                                                        production costs by one-third and would
which makes up approximately 32 percent of
                                                        reduce total costs of this element by 26
the total program cost. This element was
                                                        percent. Developments in new materials,
assumed to be a new HLLV capable of lifting
                                                        which are rapidly occurring, could
220 tonnes of payload to LEO. Although this
                                                        improve systems performance and
is a launch vehicle larger than any previously
                                                        reduce the mass of the protective shells
developed, its design was assumed to be
                                                        and vehicle systems.
based on the Saturn V technology, and
engines were selected from existing designs.           •Reduce the size of the HLLV (also
The costs of development were approximately             proposed by Zubrin). This might or
20 percent of the total ETO Line Item, and              might not reduce total costs, because
production costs (assuming that 12 HLLVs                additional costs for on-orbit operations
would be produced to support the program,               might be required. Reducing the cost of
using 3 HLLVs for the first opportunity and 3           launch to LEO using reusable vehicles
HLLV launches at each of the remaining 3                currently under consideration in the
launch opportunities) were 80 percent of the            reusable launch vehicle program would
ETO Line Item.                                          require very large investments in LEO
                                                        assembly. The trade-off might be
    To reduce the cost of the HLLV
                                                        favorable, but may or may not make a
component, several possible strategies could
                                                        significant reduction in total cost. The
be used.
                                                        availability and use of an in-orbit
   •Reduce the mass of systems,                         assembly capability like the International
    infrastructure, and payloads that need to           Space Station could make this an
    be launched into Earth orbit for                    effective strategy.
    transport to Mars to support the surface
                                                       •Improve the production efficiency for
    mission (assume that mission capability
                                                        HLLVs. The AMCM model includes a
    is not going to be reduced, which is also
                                                        learning curve assumption that each
    possible but not desirable). This could
                                                        time the number of items produced
    reduce the total number of HLLV
                                                        doubles, the cost per item is 78 percent
    launches and the assumed production
                                                        of the previous production cost. More
    cost. For example, Robert Zubrin
                                                        production learning could be very
    believes that the program could be




                                               3-128
                                 TMI Stage                    Habitation
                                    16%                          14%
                                                                                R&D
           Resources
                                                                                 2%
              2%




Space Transport
     22%

                                                                               ETO
                                                                               32%
                        Surface Systems               CoF
                              11%                     1%


Figure 3-42 A comparison of the relative costs for Reference Mission elements.

   significant. For example, if 12 HLLVs of           conventional manner; however, some
   equal capability had been produced for             procurement aspects were assumed to be
   another program, the cost of HLLVs for             new, and credit was taken in the
   the Mars program could be cut by 22                estimates for these new ways of doing
   percent. To achieve these cost reductions          business. The HLLV might be developed
   would require that no special                      by industry at lower cost, to meet
   modifications be necessary for the ETO             performance specifications rather than
   vehicles used by the Mars program.                 government technical specifications. The
                                                      assured sale of 12 vehicles may be large
  •A significant reduction in HLLV cost
                                                      enough to achieve some amount of cost
   might be designed in at the start if new
                                                      reduction to LEO, but is not likely to
   techniques for manufacturing and
                                                      lead to major cost reductions. However,
   testing were introduced. However, the
                                                      industry might be able to consider the
   learning curve benefits of mass
                                                      government an “anchor tenant” for
   production might be less.
                                                      HLLV production, develop additional
  •The HLLV development was assumed to                markets for their technology, and
   be purchased by the government in a                amortize the investment over a larger




                                              3-129
    number of vehicles. This would imply an       included). The TMI stage was costed
    assumption that the space frontier is         separately because it was assumed to require
    expanding significantly.                      separate development of a nuclear thermal
                                                  propulsion system. The TMI stage was
   •The HLLV could be supplied by the
                                                  assumed to be jettisoned before reaching
    Russians or as a joint effort by multiple
                                                  Mars. Conventional space storable chemical
    international partners. This might be a
                                                  propellants were assumed to be used in the
    contribution to an international program
                                                  ERV stage to return to Earth. The nuclear
    where it would be an example of cost-
                                                  thermal stage assumed considerable
    sharing between partners. At the present
                                                  inheritance from the U. S. nuclear propulsion
    time, this does not appear to be a feasible
                                                  program that produced the NERVA engines in
    solution; however, it may be reasonable
                                                  the 1960s; development costs for the TMI
    in 15 years. If the U. S. or other partners
                                                  stage were projected to be 16 percent of the
    were expected to pay the Russians for
                                                  total cost. The space transportation vehicles
    their participation, it would require the
                                                  are all new and include several vehicles
    appropriate political rationale. If the
                                                  (ascent vehicle, crew capsule, and the TEI
    Russians were to contribute the HLLV
                                                  stage). The cost of the space transportation
    without payment, it would be the
                                                  vehicles comprises 22 percent of the total.
    equivalent of one-fourth of the total
    program cost, though it might not cost            The ratio of development cost to
    the Russians as much as it would cost         production cost for these vehicles is rather
    the U. S. in absolute dollars.                high, partly because of the smaller number of
                                                  vehicles produced for the return home.
   •Finally, innovative advances in
                                                  Various ways of reducing the costs of these
    propulsion could result in the
                                                  elements might be considered.
    development of new propulsion
    techniques; for example, electromagnetic          •Development of nuclear electric or solar
    propulsion for ETO could substantially             electric propulsion vehicles that are more
    decrease the transportation cost for some          efficient could lower transportation costs
    materials (propellant).                            for cargo but might not reduce costs of
                                                       human flights and might increase costs if
     The Earth-Mars vehicle (the TMI stage)
                                                       parallel development of two
and the Mars-Earth vehicle (the ERV)
                                                       transportation systems was necessary. If
elements provide for the delivery of humans
                                                       a single technology with higher
and payloads to Mars and the return of
                                                       efficiency than chemical rockets could be
humans to Earth. The costs are for the
                                                       used to go to Mars and return, much of
transportation elements alone (the
                                                       the cost associated with developing the
interplanetary habitat elements are not
                                                       space transportation stages might be




                                              3-130
     saved because the number of separate         habitats is development, production is the
     developments would be minimized.             remaining two-thirds. Thus, cost reductions
                                                  involving the improvement of design and
   •Systematic application of new
                                                  procurement processes are potentially the
    techniques of automated design to the
                                                  most important objectives. Note, however,
    development process and use of
                                                  that the habitats are also a significant mass
    concurrent engineering could reduce life
                                                  element; therefore, technology that reduces
    cycle costs of the systems.
                                                  their mass will also have a significant effect
   •General improvements in methods of            on the transportation system.
    procurement and program management
                                                       Surface systems, including mobility
    could have significant returns in these
                                                  systems and resource utilization systems,
    areas. Reduction of integration costs can
                                                  surface power, and other nonhabitat systems,
    be accomplished by centrally locating
                                                  constitute about 11 percent of the total
    design and development teams and
                                                  mission cost. Because these surface systems
    keeping simple interfaces between
                                                  are rather complex, critically determine
    systems manufactured by different
                                                  mission productivity, and are a small fraction
    providers.
                                                  of the total, this area does not appear to be a
   •Several vehicle elements could be             high-priority source of major additional cost
    provided by international partners. Each      reductions. However, mass reductions in the
    of the vehicles provided without cost to      hardware will have high leverage in the space
    the program could reduce total program        transportation cost elements, if the size of the
    costs by several percent.                     transportation vehicles or the number of
     Habitats are an essential part of the        launches can be reduced. Surface systems
Reference Mission scenario. They represent 14     costs are probably underestimated in the
percent of total mission cost and are assumed     current model, because no data for a closed
to have inheritance from the International        LSS, EVA hardware, and science hardware
Space Station program. The Reference              were included in this estimate. Development
Mission has made the assumption that all          of a suitable EVA suit will be a significant
habitats required by the program are              technology challenge and potentially
essentially identical, which is probably an       expensive. The closed environment LSS
oversimplification. To the extent the design of   hardware probably is not extraordinarily
space habitats and surface habitats diverges,     expensive. However, testing and
the cost could rise. Eight production habitats    demonstrating it will only partially occur in
are required. Modest learning curve cost          the International Space Station program, so
reductions are assumed for the production         additional cost and risk are involved in its
line. About one-third of the estimated cost of    development. Science equipment is not a




                                              3-131
major cost item, in comparison with the large       the expectation that optimizing the surface
costs ascribed to the transportation system.        mission for its benefit is also the way to
                                                    improve the benefit/cost ratio for the human
     Operations was not included as part of
                                                    exploration of Mars.
the cost analysis, but has been previously
estimated as a proportion (historically as high          The question of management style must
as 20 percent) of the total development costs.      now be addressed. Particular attention needs
The operations costs are incurred primarily in      to be paid to the process by which the
the 11 years of the operational missions. The       production elements are procured. The
allocation of budget that would be associated       current estimates probably are still influenced
with this estimate is equivalent to                 by current ways of doing business. If total
approximately 20,000 people per year for that       Reference Mission costs are to be reduced, it is
period of time. This is definitely an old way of    at this level of effort that the most effective
doing business which must change for the            changes can be made. Focusing on the wrap
Mars missions. A reasonable target would be         factors may not accomplish significant
an operational team of approximately l,000          additional reductions, although reducing the
persons. This is likely to be attainable in part    production costs will also reduce the amount
because automation and autonomy will be a           that must be spent in these areas.
necessary characteristic of the Mars missions.
A principal mechanism for reducing these            3.9.2 Management and Organizational
costs may be a directed program to reduce the       Structure
operational costs of the International Space             Organization and management is one of
Station as an analog to Mars missions.              the principal determinants of program cost.
     The number and type of systems                 This is a rather wide-ranging topic, which is
represented in the Reference Mission is near        not entirely divisible from the technical
minimal considering the desired surface             content of the program, because it includes
mission capability. It is always possible to        program level decision making that is
reduce costs by reducing the required               intimately tied to the system engineering
performance. For example, using the same            decision-making process.
assumptions used for this model if only a                The magnitude of the Reference Mission,
single landing were carried out, the total          once it has been initiated, is enormous. Many
program costs would be reduced by about 30          good examples exist of smaller programs that
percent in comparison to the full three piloted     have failed or have not performed well due to
mission program. Reducing the scope of the          management deficiencies. Thus, as the
surface activity will not have a big effect on      Reference Mission is examined and improved,
cost, as it is already a relatively small           continued consideration should be given to
proportion of total mission costs, confirming       streamlining its management; assigning




                                                3-132
authority, responsibility, and accountability at      •The human exploration of Mars will be
the right levels; and developing processes that        highly visible to the world, will be a tool
are simple, with clear-cut interfaces and              of international policy in many
measurable performance standards.                      countries, will be complex and
                                                       expensive, and will take several years to
     The relationship between cost and
                                                       develop. Under these conditions, it is
management style and organizational culture
                                                       essential that a philosophical and
is rather well-known in a general manner,
                                                       budgetary agreement be reached prior to
through a large number of lessons learned
                                                       initiating development. A formal
analyses made postprogram. The list of key
                                                       agreement should be reached between
elements of lower-cost programs is shown in
                                                       all parties as to the objectives and
Table 3-26. These have been pointed out in a
                                                       requirements that are imposed on the
series of analyses, but have not commonly
                                                       mission before development is initiated,
been applied at the critical stage of
                                                       and an agreement to fund the project to
developing program organization and
                                                       its completion should be reached prior to
management approaches. Rather, the
                                                       development. In the U. S., this would
organizational and management style has
                                                       include multiyear budgetary authority.
been determined rather late in the program,
                                                       This should be accompanied by a
generally because the program content and
                                                       management process that would protect
final design were typically delayed through
                                                       against program overruns through
redesign, changing requirements, and
                                                       appropriate incentives.
funding irregularities.
                                                      •The human exploration of Mars will
    To manage a Mars program to a lowest
                                                       have quite different risks than any space
possible cost, a number of considerations
                                                       mission which will have been
have been identified.
                                                       undertaken at its time. These include
   •The design of the organization and                 risks to the safety of the crew and
    management system should be an area                accomplishment of the mission
    of investigation in subsequent studies of          (primarily technical risks) and risks of
    the Reference Mission. The relationship            meeting cost and schedule objectives.
    between program cost and program                   Maintaining launch schedule is
    culture is illustrated in Figure 3-46.             exceedingly important, due to the
    Although several factors are involved,             dependency on several successful
    this figure indicates that significant cost        launches for mission success and the
    impacts are tied to the organizational             high cost of missed launch windows
    culture and the management system.                 (missed launch windows imply 2-year
                                                       program delays at potentially high




                                              3-133
                  Table 3-26 Key Elements of Lower-Cost Programs

• Use government to define only requirements
• Keep requirements fixed; once requirements are stated, only relax them; never add new
  ones
• Place product responsibility in a competitive private sector
• Specify end results (performance) of products, not how to achieve the results
• Minimize government involvement (small program office)
• Ensure that all technologies are proven prior to the end of competition
• Use the private sector reporting reporting system: reduce or eliminate specific
  government reports
• Don't start a program until cost estimate and budget availability match
• Reduce development time: any program development can be accomplished in 3 to 4
  years once uncertainties are resolved
• Force people off development programs when development is complete
• Incentivize the contractor to keep costs low (as opposed to CPAF, CPFF, or NASA)
• Use goegraphic proximity of contractor organizations when possible
• Use the major prime contractor as the integrating contractor




 program cost). Thus a risk management            control for the program. To accomplish
 plan can help identify the risks and             this:
 formulate a mitigation strategy.
                                                 -There should be a clear demarcation
•The Reference Mission requires a                 between the design phase and the
 number of elements, many of which are            development/production phase of the
 technically alike but serve somewhat             project, and development should not
 different functions over the duration of         begin before the design phase is ended.
 the program. For example, the surface
                                                 -All technologies should be proved prior
 habitat may be the basis for the transit
                                                  to initiation of production of program
 habitat, and each habitat delivered to the
                                                  elements.
 surface will have a different complement
 of equipment and supplies, according to         -Once the requirements have been
 its position in the delivery sequence. The       established, they should not be changed
 elements will be developed over a                unless they can be relaxed.
 period of several years, and there will be      -A system should be developed that
 a temptation to improve the equipment            documents the relationship and
 and supply manifest. It will be important        interaction of all requirements and
 for requirements to be fixed at the time         should be available for use prior to the
 of initial development to maintain cost          beginning of production.




                                         3-134
•The design phase of the program is                    there may be a high enough production
 critical to successful cost control. The              rate that costs will drop as experience is
 design should be based on a set of                    gained. A new approach will be needed
 functional requirements established by a              to ensure that the development time for
 Program Office, which may well be a                   each individual element is strictly
 multinational activity. The Program                   limited.
 Office should be in place to manage
                                                      •The program will require two levels of
 technical requirements, provide
                                                       integration, similar to that of the
 decisions that require consultation and
                                                       International Space Station program: a
 trade-offs (technical and political), and
                                                       program level which ensures that overall
 manage development contracts. The
                                                       mission requirements will be met at each
 Program Office should also establish
                                                       stage of the mission, and a launch
 functional requirements for the design
                                                       package level integration in which all
 phase and conduct a competitive
                                                       required elements of each launch to
 procurement for the design phase with
                                                       Mars are packaged and their
 the selection of a prime contractor. To
                                                       performance ensured. To accomplish
 accomplish this:
                                                       this, both aspects of integration should
-Requirements should be provided for the               be the responsibility of a single
 design phase, describing the                          organization, a prime contractor to the
 performance expected, and a clear set of              Program Office.
 criteria for completeness of design as a
                                                      •The operational phase of the Mars
 function of resources expended in
                                                       program must be represented in the
 design.
                                                       design and development phase. This will
-A significant design cost margin should               require a concurrent engineering
 be used to manage the design resources.               approach which considers the
                                                       operational costs as well as the
-The successful prime contractor should
                                                       development costs in a life cycle cost
 be selected as integration contractor for
                                                       approach to the program. To accomplish
 the development phase.
                                                       this, operational considerations must be
•Once committed to development, the                    included in the design and development
 development time should be strictly                   phases of the program, and life cycle
 limited if costs are to be contained. This            costs should be used as the determinant
 will be difficult in the Mars program,                for program design and development
 where it probably will be effective to                decisions.
 produce common elements sequentially
 rather than all at one time, although




                                              3-135
    •Finally, at all stages of design,               the effort to bring the original technology to
     development, production, and                    its desired state.
     operations, all program office officials
                                                          At this particular stage in developing
     and contractor organizations must be
                                                     human exploration missions to Mars, it is
     incentivized to maintain program costs
                                                     difficult to do more than speculate about spin
     within approved levels, and positive
                                                     off and spill over technologies that could
     incentives must be put into place to
                                                     result from, or be useful to, this endeavor.
     reduce costs of each phase of the
                                                     However, identifying dual uses for some of
     program.
                                                     the assumed technologies can be started now
                                                     and, to a certain degree, will be required for
3.9.3   Technology Development
                                                     such a program to progress. In the current
     The Reference Mission was developed             political environment, investment in
with advances assumed in certain technology          technology is seen as a means of improving
areas known to be necessary to send people to        the general quality of life, and multiple use of
Mars for a reasonable investment in time and         technologies is emphasized to obtain the best
resources. The same objective could be               return on the resources invested in their
satisfied using other technologies in some           development. Space programs are not spared
cases, making it necessary to identify               this requirement. A program strategy that
selection criteria for the set of technologies the   emphasizes dual-use technologies, besides
Reference Mission should favor. A reasonable         being consistent with this current trend could:
investment also implies that there must be
                                                        •More easily generate funds through
some reliance on technologies developed for
                                                         increased cooperation and joint ventures
other uses or simply discovered during some
                                                         with other U.S. federal agencies,
other development activity.
                                                         international partners, and commercial
     Dual-use technologies are those which               concerns
are deliberately developed with more than
                                                        •Provide smaller projects which could be
one application in mind and which carry
                                                         more easily funded
requirements for these various uses through
the development period. Spin off or spin in             •Provide a step-by-step approach to the
technologies are those which are developed               Reference Mission
with a specific application in mind but which           •Provide a stimulus to local and national
find other uses with little or no additional             economies
development work. Spill over technologies
are those which grow to include entirely new,           •Foster an increase in advocacy for space
unplanned technologies as a by-product of                programs




                                                3-136
     To this end, the Reference Mission study       NASA and the Department of Energy to
identified and worked with 10 Mars mission-         develop small nuclear power sources for
related technology categories: propulsion,          robotic spacecraft could be expanded to
communications and information systems,             include the development of larger power
ISRU, surface mobility - suits, surface             sources (perhaps as part of a cooperative
mobility - vehicles, human support, power,          endeavor with the Russian government) or
structures and materials, science and science       for the propulsion system technologies
equipment, and operations and maintenance.          assumed for the Reference Mission. The
These categories were then associated with a        Department of Defense is currently studying
total of 54 technology areas along with their       an integrated propulsion and electrical power
applications. Tables 3-27 through 3-36              system driven by the heat of the Sun
document these various technology                   (Reference: Anon., 1995). This could be a
applications. In addition, the tables indicate      technology useful to the Reference Mission as
where these technologies may spin off into          an alternative to the nuclear system assumed
other applications and where developments           and form the basis for a cooperative
in other areas may, in fact, benefit or spin into   development program.
the Mars program.
                                                         Several specific examples may help
     Not all of the advantageous technology         illustrate how technology development for
for the Reference Mission must be developed         the Reference Mission will benefit from spill
by the program organization. International          over, spin off, and dual-usage.
cooperation can benefit from the technology
                                                         One of the precursor activities to the
advancements needed for this class of space
                                                    Reference Mission that has a high priority will
mission. Two obvious examples include
                                                    be the characterization of the martian surface
heavy lift launch technology and space-based
                                                    in great detail by orbiting robotic spacecraft.
nuclear power. The relatively heavy lift
                                                    Data collected by this vehicle or vehicles will
launch capabilities either developed or
                                                    be needed in many areas to prepare for this
nearing completion for the Russian Energia
                                                    Reference Mission. One of the most
and the European Ariane V could form the
                                                    significant areas will be the choice of a
basis for at least part of a cooperative
                                                    landing site at which the outpost will be
technology development program. The
                                                    established. This selection will be based in
former Soviet Union had also developed a
                                                    part on information ranging from hazards in
relatively sophisticated operational space-
                                                    the proposed landing zone to the proximity of
based nuclear power capability.
                                                    the site to a variety of surface features, the
    U.S. federal agencies can also cooperate        investigation of which will contribute to
to develop mutually beneficial technologies.        meeting the overall Reference Mission
The long-standing cooperation between               objectives. Technology to obtain this remote




                                                3-137
sensing data could be available from the U.S.,            •The Russian Energia heavy lift launch
Russia, Japan, and the Europeans, based on                 system can be maintained and upgraded
their previous Earth-orbiting, remote-sensing              until human missions to Mars can begin.
missions and other planetary explorations.                 A variation of this would be to evolve a
But due to the high cost of transporting these             higher capacity launch vehicle using
sensors to the vicinity of Mars, further                   technologies developed for Energia,
development or enhancement of these                        Ariane V, and the Space Shuttle. Either of
technologies could reduce their size, mass,                these options would offer an
and need for supporting resources (power,                  opportunity for international
communications band width, etc.).                          cooperation that would not only benefit
Advancements in other areas, such as the Ka                the Reference Mission but also allow for
band utilization, data compression, and                    heavier, more sophisticated payloads to
information processing technologies                        be launched into Earth orbit or used for
mentioned in the Communication and                         lunar missions.
Information Systems category or from
                                                          •The mass of hardware required to
technology developed as part of the explosive
                                                           support humans in Mars journeys can be
growth in the PC marketplace, can also serve
                                                           reduced. Few concepts now exist for
to improve performance and reduce costs for
                                                           this, but advancements in the technology
these systems and the data they return. Any
                                                           options mentioned in most, if not all, of
technology enhancement developed to
                                                           the 10 categories identified by the Mars
support the Reference Mission will then be
                                                           Study Team will lead to a reduction in
available for use in Earth-orbiting
                                                           the hardware mass that must be sent to
applications.
                                                           Mars. Each of the 10 categories also
     The single largest cost of a human Mars               identified Earth-bound applications that
exploration program may be the cost of ETO                 may also benefit from these
transportation. The development of a new                   advancements.
HLLV solely for the Mars program could
                                                           A third example involves the significant
require up to 30 percent of the total resources
                                                      level of automation assumed for the
for the program. However, approaches that
                                                      Reference Mission. The program assumes
can launch the appropriate payloads to Mars
                                                      infrastructure elements (including a system to
using smaller launch vehicles have not
                                                      produce propellant and life support
appeared to be viable in the past. This is a
                                                      consumables, the first of two habitats, power
conundrum which has and may still stymie
                                                      systems, and surface transportation elements)
human exploration of Mars. Other avenues
                                                      will robotically land on the surface at a
exist:
                                                      designated location. All of these systems will
                                                      be delivered, set up, and checked out using




                                                  3-138
                           Table 3-27 Dual-Use Technologies: Propulsion

              Terrestrial Application                      Technology              Space Application

 • Nuclear Reactors
 • Weapons and Nuclear Waste Disposal                                            • NTR
                                                  • High-Temp Materials
 • High-Efficiency Heat Engines                                                  • Aerobraking
   (Turbines, Thermostructural Integrity)

                                                  • High Efficiency              • Propellant
 • Clean-Burning Engines (H2/O2)
                                                    Cryo-Refrigeration             Maintenance

                                                  • Methane/O2 Rocket            • ISRU-Based Space
 • Higher Performance Commercial Launches
                                                    Engines                       Transportation




            Table 3-28 Dual-Use Technologies: Communications/Information Systems

           Terrestrial Application                  Technology                 Space Application

 • Communications High-Definition           • Ka Band or Higher          • Telepresence: Vision and
   TV Broadcast                                                            Video Data
                                                                         • Interferometers: Raw Data
                                                                           Transmission

 • Entertainment Industry                   • Machine-Human Interface     • Control Stations
 • Commercial Aviation                                                    • System Management

 • Communications                           • Data Compression            • Interferometers: Raw Data
 • Archiving                                  Information Processing        Transmission Information
                                            • Large Scale Data              Processing
                                              Management Systems          • System Management,
                                                                            Expert Data
                                                                          • Archiving/Neural Nets


spin-in
spin-off
Both




                                                  3-139
                 Table 3-29 Dual-Use Technologies: In Situ Resource Utilization

            Terrestrial Application                  Technology                Space Application

 • Mineral Analysis, Yield Estimation-      • Advanced Sensors           • Mineral Analysis, Yield
   Deep Mine Vein Location and Tracking                                    Estimation Surface Mineral
 • Wall and Ceiling Integrity                                              Analysis, and Resource
                                                                           Location
 • Deep Mine Robotic Operations             • Advanced Robotic           • Surface Mining Operations
   • Mining                                   Mining                       • Mining
   • Beneficiating                                                         • Beneficiating
   • Removal                                                               • Removal

 • Improved Automated Processing;
                                            • Automated Processing:      • Remote, Low-
   Increased efficiency
                                              Advanced FDIR                Maintenance, Processing

 • Reliable, Low-Pollution Personal         • Alternative, Regenerable   • ISRU-Based Engines
   Transmission                               Energy Economies           • Regenerable Energies
 • Regenerable Energy Economies               • Methane/O2               • High-Density Energy Storage
 • Small, Decentralized Power Systems for     • H2 /O2
   Remote or Third World Applications

 • Environmentally Safe Energy Production   • Space-Based Energy         • Surface Power Generation
                                              Generation and               and Beaming
                                              Transmission



spin-in
spin-off
Both




                                               3-140
                     Table 3-30 Dual-Use Technologies: Surface Mobility - Suits
       Terrestrial Application                        Technology                       Space Application

 • Hazardous Materials Cleanup            • Lightweight, Superinsulation       • Surface Suits: Thermal
 • Fire Fighting Protection and             Materials                            Protection
   Underwater Equipment

 • Robotic Assisted Systems               • Robotics                           •Robotic Assisted Suit Systems
 • Orthopedic Devices for Mobility        • Mobility Enhancement Devices
   Impaired Persons                         and Manipulators


 • Hazardous Materials Cleanup            • Dust Protection, Seals, Abrasive   • Surface Suits: Outer Garment
 • Fire Fighting Protection and             Resistant Materials
   Underwater Equipment

 • Hazardous Materials Cleanup,           • Lightweight Hi-Rel, Life Support   • Portable Life Support for Surface
   Underwater Breathing Gear                                                     Suits

 • Remote Health Monitoring               • Portable Biomedical Sensors and    • Surface EVA Crew Member
                                            Health Evaluation Systems            Health Monitoring

 • Hypo-Hyper Thermal Treatments          • Small, Efficient, Portable,        • Surface Suits: Thermal Control
 • Fire Fighting Protection and             Cooling/Heating Systems              Systems
   Underwater Equipment
 • Artic/Antartic Undergarments


                   Table 3-31 Dual-Use Technologies: Surface Mobility - Vehicles
           Terrestrial Application                        Technology                    Space Application

 • All-Terrain Vehicles                     • Mobility                           • Surface Transportation
   • Research (Volcanoes)                                                         • Humans
   • Oil Exploration                                                              • Science Equipment
                                                                                  • Maintenance and
                                                                                    Inspection

 • Reactor Servicing/Hazardous              • Robotics and Vision Systems        • Teleoperated Robotic Systems
   Applications
 • Earth Observation, Weather, Research     • Super-Pressure Balloons            • Mars Global Explorations
                                              (110,000 ft - Earth Equiv)

 • Efficient, Long-Term Operations          • Tribology                          • Surface Vehicles
   Low-Maintenance                                                                • Drive Mechanisms
 • Machines in Artic/Antaric                                                      • Robotic Arms
   Environments                                                                   • Mechanisms

 • Helicopers, Autos                        • Variable Speed Transmissions       • Surface Vehicles

 • Automated, Efficient Construction        • Multipurpose Construction          • Robotic Construction and
   Equipment                                  Vehicle Systems and Mechanisms       Set-up Equipment

spin-in
spin-off
Both



                                                         3-141
                          Table 3-32 Dual-Use Technologies: Human Support

        Terrestrial Application                      Technology                            Space Application

• Stored Food                            • Long-Life Food Systems               • Efficient Logistics
 • US Army                                • With High Nutrition                  • Planetary Bases
 • NSF Polar Programs                     • Efficient Packaging                  • Long Spaceflights
                                                                                 • Space Stations

• Improved Health Care                   • Physiological Understanding of the   • Countermeasures for Long-Duration
• Sports Medicine - Cardiovascular         Human/Chronobiology                    and/or Micro-g Space Missions
• Osteoporesis - Immune Systems          • Understanding of Psychosocial        • Health Management and Care
• Isolated Confined Environments/Polar     Issues
  Operations                             • Instrumentation Miniaturization
• Noninvasive Health Assessments

• Health Care                            • Long-Term Blood Storage              • Health Care for Long-Duration Space
• Disaster Response                                                               Missions
• US Army

• Office Buildings                       • Environmental Monitoring and         • Environmental Control for
         ("Sick Building" Syndrome)        Management                            • Spacecraft Cabins
• Manufacturing Plants                                                           • Planetary Habitats
                                                                                 • Pressurized Rovers

• Contamination Cleanup                  • Waste Processing/SCWO                • Closed Water Cycles for
• Waste Processing                       • Water Purification                    • Spacecraft Cabins
                                                                                 • Planetary Habitats
                                                                                 • Pressurized Rovers

• Long-Life Clothes                      • Advanced Materials/Fabrics           • Reduced Logistics Through Long-Life,
 • Work Clothes in Hazardous                                                      Easy-Care Clothes, Wipes, Etc.
   Environments                                                                 • Fire Proof/Low-Out-gassing Clothes
 • US Army

• Efficient Food Production              • Advanced Understanding of            • Reduced Logistics Through Local Food
                                           Food Production/Hydroponics            Production for
                                                                                 • Spacecraft Cabins
                                                                                 • Planetary Habitats


                                  Table 3-33 Dual-Use Technologies: Power
           Terrestrial Application                      Technology                           Space Application

• Batteries/RFCs for                        • High-Density Energy Storage           • Reduced Logistics for Planetary
 • Autos                                    • Alternate Energy Storage                Bases
 • Remote Operations                          (Flywheels)                           • High-Rel, Low-Maintenance
   • DOD                                                                              Power Systems
  • NSF Polar Programs

• Clean Energy From Space                   • Beamed Power Transmission            • Orbital Power to Surface Base
                                                                                   • Surface Power Transmission to
                                                                                     Remote Assets

• Remote Operations                         • Small Nuclear Power Systems           • Surface Base Power
 • DOD                                                                              •Pressurized Surface Rover
 • NSF Polar Programs                                                               • Interplanetary Transfer Vehicle

• Remote Operations                         • High-Efficiency, High-Rel,            • Energy Conversion for Planetary
 • DOD                                        Low-Maintenance Heat-to-                Bases
 • NSF Poloar Programs                        Electric Conversion Engines            • Low Servicing Hours
• High-Efficiency Auto Engines                                                       • Little or no Logistics

spin-in
spin-off
                                                       3-142
Both
                   Table 3-34 Dual-Use Technologies: Structures and Materials

             Terrestrial Application                  Technology                  Space Application

    • Vehicles                                 • Composite Materials       • Cryo Tanks
    • Fuel-Efficient Aircraft                   • Hard                     • Habitat Enclosures
    • Modular Construction (Homes, etc.)        • Soft                     • Pressurized Rover Enclosures
                                               • Advanced Alloys, High-    • Space Transit Vehicle Structures
                                                 Temperature

    TBD                                        • Superinsulation           • Cryo Tanks
                                               • Coatings                  • Habitable Volumes


    • Large Structures, High-Rises, Bridges    • Smart Structures          • Space Transit Vehicle Structures
    • Commercial Aircraft                      • Imbedded Sensors          • Planetary Habitat Enclosures
     • Improved Safety                                                     • Surface Power Systems
     • Lower Maintenance                                                   • Rover Suspensions




               Table 3-35 Dual-Use Technologies: Science and Science Equipment

           Terrestrial Application                       Technology                     Space Application

 • Energy Resource Exploration                • Spectroscopy                      • Geo-chem Mapping
 • Environmental Monitoring, Policing          • Gamma Ray                        • Resource Yield Estimating
                                               • Laser                            • Planetary Mining Operation
                                               • Other                              Planning

 • Undersea Exploration                       • Telescience                       • Remote Planetary
 • Hazardous Environment Assessments,                                               Exploration
   Remediation

 • Environmental Monitoring                   • Image Processing                  • Communication of Science
 • Medicine                                    • Compression Technique              Data
                                               • Storage                          • Correlation of
                                               • Transmission                       Interferometer Data
                                               • Image Enhancements

 • Improved Health Care                       • Physiological Understanding of    • Countermeasures for Long-
 • Sports Medicine - Cardiovascular             the Human                           Duration and/or Micro-g
 • Osteoporesis - Immune Systems              • Instrumentation Miniaturization     Space Missions
 • Isolated Confined Environments/Polar                                           • Health Management and
   Operations                                                                       Care
 • Noninvasive Health Assessments




spin-in
spin-off
Both




                                                      3-143
                Table 3-36 Dual-Use Technologies: Operations and Maintenance

           Terrestrial Application                       Technology                       Space Application

                                         • Task Partitioning
                                         • R & QA in Long-Term, Hazardous
                                           Environments
                                         • System Health Management and
                                           Failure Prevention Through A1
                                           and Expert Systems, Neural Nets

     We mentioned this area as important, but did not complete. Recommend that we work with Jon Ericson and bob
     Savely to get ir right.




spin-in
spin-off
Both


robotic systems perhaps operated from or,                   3.10     References
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                                            3-147
National Aeronautics and
Space Administration
Lyndon B. Johnson Space Center




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