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2nd International Symposium

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2nd International Symposium Powered By Docstoc
					      NEXT GENERATIONS SPACE TRANSPORTATION SYSTEMS
                                                         Gennaro Russo

                                   CIRA, Centro Italiano Ricerche Aerospaziali
                                     Via Maiorise, 81043 Capua (CE), Italy
                       Phone +39 0823 623334, Fax +39 0823 623335, e-mail g.russo@cira.it

                               Abstract
Future generations Reusable Launch Vehicles (RLV) need to be                          The ISTP top level strategy is the following:
developed through an extensive use of flight demonstration. But, instead
of full scale, expensive, highly system-integrated flight vehicles, future        •   Reduce technical and business risks to achieve
research light vehicles need to be simpler and cheaper. Consequently,
the approach emphasizes sub-scale, unmanned, autonomous or remotely
                                                                                      significant increases in safety and reliability and
piloted vehicles to be flight tested at reduced cost and risk.                        drastic reduction in cost of 2nd generation manned
     The Italian Aerospace Research Program PRORA has allowed up                      reusable launch systems with operations capability
to now the realization of a number of ground based laboratories and                   by 2012.
world-class facilities, like the 70MW Plasma Wind Tunnel SCIROCCO.
In 2000, the Unmanned Space Vehicles (USV) program was approved                   •   Enable a competition at acceptable level of risk for a
dealing with technology maturation toward RLVs.                                       2nd generation RLV development decision by 2006
     USV is a technology development program including theoretical,                   which could include Shuttle-derived and new design
numerical, on-ground experimental and flight test activities. It aims also
to realise experimental flying platforms that can complement and
                                                                                      concepts (including CTV).
integrate the available ground facilities at CIRA.                                •   Develop revolutionary technologies for 3rd
     USV was defined based on the belief that in the long run space                   generation RLV concepts to achieve safety and
access and re-entry will be guaranteed by aviation-like vehicles (SSTO-               reliability comparable to commercial airlines.
HTHL, sometime called aerospaceplanes). Among others not less
important, such vehicles will require innovation and maturation in three          •   Ensure continued safe access to space through the
main areas: atmospheric re-entry, reusability, sustained hypersonic                   Space Shuttle Safety Upgrades until a replacement
flight. The USV Program includes thus technology developments along                   alternative has been demonstrated.
these three directions, up to their validation either on ground and on
board Flying Test Beds.                                                           •   Support military and commercial applications to the
                                                                                      maximum extent possible.
Key-words: RLV, Re-entry, Experimental Vehicle, Space
Transportation System                                                                 The major program of the ISTP is the SLI. This 4.8
                                                                                  B$ programme covers the period 2001-2006. The first
                                                                                  series of contracts has recently been awarded for a total
1.    International Scenario Regarding RLVs                                       of 767 M$. The driving requirements for these contracts
The USA is the country which has the largest experience                           are:
(also an operational one with the use of the Space
Shuttle) on RLVs. In 1996, the U.S. National Space                                •    Focus on critical design trade studies and evaluation
Policy gave NASA the responsibility to initiate                                        criteria emphasising safety and affordability as well
partnership with industry to jointly develop reusable                                  as performance (with the goal of 100 times safer and
launcher technologies, based on the assumption that the                                10 times cheaper than the Space Shuttle).
satellite market development would support the                                    • Inclusion of safety and economic analyses as equal
commercial development of a new reusable launch                                        partners in the design team.
vehicle around the turn of the century. The program                               • Use architecture studies to identify, drive, and
pursued aggressive SSTO (single stage to orbit)                                        quantify critical technology needs.
technologies with compressed schedule and limited
budget. In 1999, NASA initiated a new series of system
                                                                                  • Pursue technologies critical to a wide range of
                                                                                       architectures, but with well-defined and controlled
activities, the Space Transportation Architecture Studies
                                                                                       risk mitigation plans.
taking into account the evolved market conditions, which
                                                                                      In Japan the concentration of the efforts toward the
led to the definition of an Integrated Space Transportation
                                                                                  development of the H-IIA expendable rocket has lead to
Plan (ISTP).
                                                                                  placing on hold the development of an operational
    The ISTP includes the following separate programs:
                                                                                  HOPE-X re-entry vehicle, limiting the work to transonic
•    Space Shuttle Safety Upgrades to continue improve                            flight demonstration and basic technology activities for
     the Space Shuttle reliability and operability.                               propulsion, cryogenic tanks and thermal protection
•    Space Launch Initiative (SLI or 2nd generation RLV)                          systems for future RLVs.
     to prepare the ground for a Shuttle replacement                                  In preparation for the HOPE-X, Japan already
     decision in 2006 by the U.S. government, for the new                         launched several experimental vehicles, namely:
     vehicle operational around 2012.                                             HYFLEX (launched in 1995 to study the hypersonic
                                                                                  flight regime), OREX (with a capsule shape, launched in
•    3rd Generation RLV focused on more long term
                                                                                  1994 to collect information on the structural design and
     technologies (e.g. air-breathing).
                                                                                  construction of the vehicle re-entering the atmosphere)

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and ALFLEX (with a test campaign conducted in mid-             focused on elements of the re-entry test vehicle X-38 V-
1996 to examine the automatic landing equipment and            201 foreseen in 2003. This vehicle will perform an end-
GNC algorithms). The High Speed Flight Demonstrator            to-end demonstration of the CRV mission, including the
(HSFD) to study transonic regime, is scheduled for             ascent in the Space Shuttle cargo bay, the on-orbit and re-
launch in 2002. After the recent H-II flight, discussions      entry phases, the automatic landing phase under parafoil.
have restarted, especially in the Space Activities                 Under a single cooperative agreement among NASA,
Commission, on RLVs, with a special emphasis on                ESA (through the Applied Re-entry Technologies
manned systems.                                                Program) and DLR (through the national TETRA
    Russia developed a reusable vehicle, Buran which           program), Europe provides the X-38 program with
flew only once in 1988. In the Buran development               several contributions (e.g. aerodynamic shape definition
programme, six full scale functional mock-ups were built       and aerothermal database, definition of flight control
and three experimental vehicles were flown:                    laws, hot structures, TPS, mechanisms etc.).
                                                                   Although not all the program elements will be
•   Buran Analogue for horizontal flight tests                 applicable to RLVs, the X-38 V-201 flight test is
•   BOR-4 for hot structure tests                              expected to provide in-flight verification of thermal
•   BOR-5 for aerodynamic tests                                protection blankets and hot structure design concepts,
                                                               associated technologies and operational techniques; such
    Despite the lack of an operational RLV and despite
                                                               a flight test will provide useful data for the development
today’s economical difficulties, technological know-how
                                                               of future reusable space transportation systems.
as well as hardware and facilities are still available in
                                                                   The ISS CRV vehicle is conceived as a reusable
Russia.
                                                               transportation system, in the form of a lifting body,
    Recently, Khrunicev has performed studies and
                                                               whose mission is under demonstration through several
developed an engineering model of Baikal, proposed as a
                                                               atmospheric drop tests and the X-38 V201 orbital re-entry
reusable first stage for the Angara family.
                                                               flight.
    In Europe several system studies were conducted
                                                                   The present European participation to the CRV
during the 80’s to investigate possible concepts for a
                                                               consists mainly in contributions in the field of re-entry
European RLV, both at ESA level (FLS, WLC, RRL,
                                                               aerothermodynamics, hot structures, thermal protections,
FESTIP as well as with the Hermes program which dealt
                                                               mechanisms and manned technologies (man-machine
with some studies, technologies and facilities related to
                                                               interface, crew seats).
RLVs), and at national level (HOTOL, SAENGER,
                                                                   In 1999, DLR set up the ASTRA national program
TARANIS, STAR-H). In 1998, ESA flew the ARD
                                                               dedicated to technologies for future launch vehicle
capsule which gave valuable information on the
                                                               applications. A major development in this program is the
atmospheric re-entry.
                                                               Phoenix flying test bed for the demonstration of the
    The FLTP (Future Launchers Technologies
                                                               automatic landing techniques. The program also includes
Programme) was approved in 1999 with the objectives of
                                                               system work on selected vehicle concepts and on-ground
confirming the interest of launcher reusability under
                                                               technology developments in the propulsion, structures,
realistic assumptions, and of identifying, developing and
                                                               and avionics and GNC this being mainly targeted to the
validating the required technologies. The unbalanced
                                                               Phoenix test-bed.
participation to the programme and the problems in
                                                                   ASI funds at national level the FAST-2 program
implementing procedures brought to the decision to put
                                                               including some RLV technology developments in areas
FLTP on hold.
                                                               considered of strategic industrial interest, mainly in the
    Several programs are on-going in Europe, both at
                                                               field of turbomachinery, liquid oxygen/ hydrocarbon
national level (e.g. ASTRA, PRORA-USV) and ESA
                                                               combustion, advanced metallic cryogenic tanks, metallic
level (X-38/CRV), to foster the development of some of
                                                               thermal protections and aerothermodynamics.
the technologies required for future reusable space
transportation systems. Moreover, some specific
technologies are being developed within the ESA TRP            2.   The USV Program
and GSTP programs, which also have an interest for
                                                               The lack of physical knowledge and the large sensitivity
RLVs.
                                                               of the design solution on main parameters impose that
    Even if the objectives and the requirements of these
                                                               future generation Reusable Launch Vehicles (RLV) be
programs are different, technological activities of interest
                                                               developed through an extensive use of flight test and
for future RLV developments are being carried out.
                                                               demonstration. The lack of available funds, from another
However, these activities are relatively fragmented and
                                                               side, imposes the search for solutions that can combine
dispersed.
                                                               low development costs with sufficiently effective results.
    The X-38 program, led by NASA, is directed towards
                                                                   So, instead of expensive, highly system-integrated
the design, development, fabrication and flight testing of
                                                               flight vehicles, future research light vehicles need to be
a re-entry vehicle, the X-38, that would serve as the
                                                               looked at.
prototype for the International Space Station Crew Return
                                                                   As a direct consequence, the approach to be used
Vehicle (CRV). Beside the participation to the definition
                                                               emphasises small-scale, unmanned, physically significant
of the vehicle shape and the establishment of the
                                                               rather than geometrically similar, vehicles to be flight
associated aerodynamic and aerothermal databases, the
                                                               tested at reduced cost and risk.
ESA contribution to this programme is specifically

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    The Italian Aerospace Research Program PRORA has                                             PRORA includes thus technology developments along
allowed up to now the realisation of a number of ground                                      these directions up to their validation either on ground
based laboratories and world-class facilities, like the                                      and on board Flying Test Beds.
70MW Plasma Wind Tunnel SCIROCCO. In 2000, the                                                   With the goal of an incremental test objective
Unmanned Space Vehicles (USV) program was approved                                           approach, starting from a proposal made in 1940’s and
dealing with technology maturation toward RLVs.                                              recently re-appreciated and tested under the label of
    USV was proposed as a scientific and technological                                       “rockoon” (from rocket + balloon), PRORA-USV has
knowledge development effort toward future generations                                       indicated in an experimental vehicle launched from a
RLVs maturation. Its second important objective was                                          stratospheric balloon the best compromise between
defined as the integration of available on ground testing                                    vehicle performance, test objectives and development
capabilities (laboratories and facilities) with Flying Test                                  costs.
Beds, i.e. with experimental flying laboratories.                                                The USV program has the final aim to flight test a
    The USV program was defined based on the belief                                          number of technologies during a full orbital re-entry, with
that in the long run space access and re-entry will be                                       energies of the order of 25 MJ/kg. To arrive at proper
guaranteed by aviation-like vehicles (SSTO-HTHL,                                             maturation of flight capability and efficient
sometime called aerospaceplanes). Such vehicles will be                                      experimentation, a step-by-step approach has been
characterised by so many important innovative solutions                                      selected that is characterised by an “increasing mission
that brought for example to the cancellation of the                                          complexity”. In fact, the program includes some
National Aero Space Plane (NASP) program in USA.                                             intermediate steps (Flying Test Beds, FTBs) that are
    Looking at nearer term, it is today commonly believed                                    characterised by the foreseen achievement of concrete
that 2nd generation RLV will be a Two Stage To Orbit                                         technological and system objectives aimed at execution
(TSTO), with the first stage able to accelerate up to Mach                                   of technological flight tests and contemporaneous
6-8 for staging, thus performing a more or less real                                         acquisition of good confidence level about the
sustained hypersonic flight before returning and landing.                                    development of the selected technologies.
The second stage will be able to further accelerate in                                           The USV road-map is shown in Fig. 1 where it is
order to reach orbital speed at the desired altitude, carry                                  evidenced that the program is subdivided into two parts.
on the mission and re-entry the earth atmosphere finally                                     Part 1 shall last three years (2002-2004) with the
landing on a runway.                                                                         ambitious goal to fly the first two missions (DTFT, SRT).
    Some of the fundamental technological areas                                              Part 2 shall last another 3.5 years (2005-2008). This
requiring innovation and maturation assumed as of                                            planning will guarantee, among others, a proper national
national specific interest were identified as:                                               technology readiness in 2007-2008 when everybody
                                                                                             agrees a final decision on the launch of the new RLV
          -     atmospheric re-entry,                                                        development will probably be taken.
          -     sustained hypersonic flight,
          -     reusability.


                              2000                                        2005                                2010                        2015

                                                                                                                     <100 kg payload and/or Techn.
                  Payload
                                                                                                                           Passenger Experiments



                                                                                                                     Semi-Reusable Winged-Body.
                  3 FTBs
                                                                                                                          Configuration evolution




                                                                                                                       Balloon for DTFT, SRT, HFT.
               Launching Stage
                                                                                                                                     VEGA for ORT




                                               DTFT           SRT                HFT                ORT
                                               Dropped      Sub-orbital     Hypersonic             Orbital
                                              Transonic      Re-entry         Flight               Re-entry
                                                                                                                                     AEROSPACEPLANE
                                                                                                                                      TECHNOLOGIES




                                              Flight Test      Test            Test                 Test

              PRORA                            8/2003        7/2004              8/2005            9/2007
               USV           Part 1                                                       Part 2

                      Transonic/Supersonics
                      Re-entry
                      Hypersonics


                                                      Fig. 1 – USV Program Road Map




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                                                               −   Validation of the propelled FTB configuration
3.   The USV Experimental Missions
                                                                   equipped with expendable solid motor
The USV will perform a set of missions defined in such a       −   Verification of the Balloon + Propelled Vehicle
way as to acquire the capability to manage several aspects         (Rockoon) System
that are peculiar of a future generations RLV.                 −   CFD validation and PWT-Flight correlation
    In order to reduce costs, some operational                 −   Passenger experiments (for examples Health
assumptions have been taken:                                       Management, UHTC, TPS, Reentry GNC,
         − Launch shall be made via aerostatic                     Propulsion, …)
              stratospheric balloon
         − Baseline Launch Base shall be the ASI                   It is important to note that being a sub-orbital mission,
              station of Trapani-Milo in Sicily                SRT is characterised by available low energy levels
         − The vehicle shall be recovered on the sea           (around 2 MJ/kg). In order to try to satisfy the above-
              without implementing TEAM and automatic          mentioned objectives, it is necessary to fly non-standard
              landing, but via parafoil.                       trajectories. In fact, the nominal trajectory has been
    The USV system shall perform the missions described        selected by imposing the condition to maximise the heat
here below.                                                    flux, rather than minimise it as normally done when the
Dropped Transonic Flight Test (DTFT)                           target is just to re-enter in the safest way possible.
The balloon achieves a floating altitude of 24.2 km, then
the first USV Flying Test Bed named FTB-1 is dropped.
At about 16 km the vehicle will experience the maximum
Mach of 1.05 at 8.8 degrees AoA (see Fig. 2).
    The main objective of this 1st CIRA flight test is to             24.2 km
verify the stability, manoeuvrability and controllability of
the FTB-2 vehicle when flying in transonic conditions. A
secondary but also important objective of DTFT is to
have operational and technical confidence on:
    − Separation from Balloon and manoeuvres during
         the first few seconds of the mission
                                                                                        16 km
    − Capability to cope with the recovery phase                                Mach = 1.05 @
         (parafoil deployment, capability to foresee and                        AoA = 8.8 deg
         achieve the landing zone, ….)
    − Duplication of typical reentry final phase, with
         specific regard to SRT (second mission)                     Fig. 2 – Outline of Dropped Transonic Flight Test
    − Codes and design flight validation                                                   (DTFT)
    − Passenger experiments shall be arranged on
         board.
    Useful testing flight can extend down to subsonic
conditions of Mach 0.6. This happens at a dynamic
                                                               Hypersonic Flight Test (HFT)
pressure of 4.3 kPa and at an altitude of about 13 km
                                                               The balloon achieves a floating altitude of about 35 km.
where the drogue start to inflate.
                                                               After the release from the balloon the main motor is
                                                               ignited, pushing the vehicle to reach its maximum speed
Sub-orbital Re-entry Test (SRT)
                                                               along a horizontal flight path. It is foreseen that USV will
The balloon achieves a floating altitude of about 35 km;
                                                               fly above Mach 6 for at least 25 sec and will reach the
and after the release from balloon the main motor is
                                                               maximum speed at Mach 7.
ignited accelerating the vehicle along a sub-orbital
                                                                   These conditions are achieved at a constant attitude of
trajectory up to a maximum altitude of about 120 km.
                                                               3 deg and a constant altitude of about 30 km, the latter
Then the vehicle starts the re-entry phase along a
                                                               being determined by the fact that, while accelerating
trajectory designed to maximise heat fluxes, achieves the
                                                               horizontally, the vehicle drops down until sufficient
maximum heat flux at about 25 km and keep a heat flux
                                                               velocity and lift are reached, as indicated in the sketch
higher than 650 kW/m2 for about 15 sec (see Fig. 3). The
                                                               Fig. 4. Objectives of HFT are:
main objectives of SRT are:
−    Acquisition of operational and technical confidence                            120-km
     on re-entry aspects by duplicating a large part of
     typical reentry trajectory (sub-orbital flight) in real
     conditions (pressure-thermal flux)
−    Provide the research community with a Flying Test                                                               2
                                                                                                            650-kW/m ; 15 “
     Bed able to test advanced materials under very
     severe conditions                                                  35-km

−    Flight test the second USV hardware (FTB-2). It will
     be characterised by a design refinement with respect
     to FTB-1, after DTFT

                                                                                   Aerotecnica Missili e Spazio Vol. 81 – 2/2002
                                                                      Fig. 3 - Outline of Sub-orbital Re-entry Test (SRT)
                                                         68
G. Russo


     −     Acquisition of operational and technical
           confidence about horizontal sustained hypersonic
           flight in terms of aerodynamics and flight                                            25”
                                                                                        M > 6 forM = 7; Mmax = 7
           mechanics behaviour prediction
                                                                35-km
     −     First European Mach 7 Sustained Flight and
           second civil test in the world after the X-15
           experience
     −     Utilisation of the same FTB-2 hardware used for
           SRT, after adequate refurbishment.
     −     CFD validation and WT-Flight correlation               Fig. 4 - Outline of Hypersonic Flight Test (HFT)
     −     Passenger Experiments (for example, Health
           Management, UHTC, Hypersonic GNC, Air-                −      General shape as slender as possible
           breathing Propulsion, ...)                            −      Maximum length 7.5 m
                                                                 −      Maximum wing span 3.5 m.
    A further mission is being considered that is dubbed
HFT-LP, standing for Hypersonic Flight Test with Liquid          The vehicle will be used as a flying test facility, so a
Propulsion engine. It will be essentially a repetition of     good level of modularity has to be implemented:
HFT but using a new 10 t class LOx-Methane engine
under development at FiatAvio. So, the objectives shall          −    The nose and the leading edge shall be removable
be summarised as:                                                     in order to be able to test different materials at
                                                                      different heat load conditions
     −     Second European Mach 7 sustained Flight               − It shall be possible to install at least 2 classes of
     −     Modified FTB-2                                             motors
     −     New LOx-HC motor flight test                          − The TPS shall be completely removable.
     −     Same hardware as SRT                                  The design approach for the winged vehicle definition
     −     Passenger Experiments (for example, Health         was defined on the basis of the general constraints that
           Management, UHTC, Hypersonic GNC, ...)             frame the program:
                                                                 −      Reduced development time (1st flight in mid-
Orbital Re-entry Test (ORT)
                                                                        2003) and budget w.r.t. very ambitious objectives
The final USV mission is dubbed ORT and will
                                                                        of the 4 missions
implement a full orbital re-entry experiment. A third
hardware FTB-3 will be realised having less slender              −      Very different flight conditions with similar
configuration than previous vehicles. It will be brought at             vehicles
an low earth orbit of 200 km by the VEGA small                   −      Long term plan (final experimental mission at
launcher. Major objectives are:                                         end 2007).

     −     Execution of a multi-objective mission oriented       On the basis of that, the most important concepts that
           toward flight demonstration of future RLV          have applied at system level are:
           generation technological advances
     −     Reaching LEO (First CIRA Experience)                  −      Trade-off areas reduced to the possible minimum
     −     Management of a complex mission of a complete         −      Robust design approach not only in terms of
           multi-stage system [VEGA (1st stage) + FTB-3                 design margins but also in terms of mid-long
           (2nd stage)]                                                 term H/W availability, programmatic risks,
                                                                        decision margins on several areas (e.g. choice of
     −     Small payload to LEO demonstration.
                                                                        the main motor, minimum radius at nose, and
                                                                        other topics).
4.       The USV Configuration
                                                                   The hypersonic mission HFT is “driving” for the
The general shape definition criteria of the FTB vehicles
                                                              definition of several requirements and characteristics of
comes on one side from the objective to simulate to a
                                                              the vehicle (aerodynamic performances and shape, motor
certain extent the environment typical of future
                                                              performances, ….). The SRT re-entry mission is the
generations launch and reentry vehicles.
                                                              sizing case for what concerns the thermal and mechanical
    On the other side, it has to be considered as a
                                                              loads. Several hypotheses have been considered in the
requirement directly derived from the willingness to
                                                              definition of the mission in terms of vehicle mass, release
address topics concerning 3rd generation RLV and
                                                              altitude, maximum altitude during coasting, type of
beyond. As a matter of facts, that sort of RLVs will spend
                                                              motor.
most of energy during the atmospheric flight so their
                                                                   The system configuration has been defined to have a
aerodynamic characteristics must be much better than the
                                                              vehicle intrinsically stable and controllable in all flight
1st and 2nd generations ones.
                                                              conditions. The centre of gravity (CoG) is determinant,
    The main shape requirements are the following:
                                                              and has shown to range between 65% and 67.5% from the
     −     Radius at nose 10 mm                               vehicle nose.
     −     Maximum wing profile thickness < 8%

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    The external shape has to be considered as a                 equipment. In-depth probes are to be installed in the
requirement, aimed at translating the meaning and the            Thermal Protection System, aimed to detect temperature
main objectives of PRORA. These requirements have                and incoming heat fluxes, both for monitoring critical
been translated in an 8% maximum wing profile                    zones and for validating/tuning the aerothermodynamic
thickness, and a fuselage diameter as small as possible          prediction tools used in the design. Similarly, the
compatibly with the mechanical problems.                         distribution of pressure ports on the airframe shall be
    The total vehicle mass is constrained by the need to         designed in such a way to allow the completion of the
be launched by existing balloons. The vehicle dry mass           aerodynamic characterisation of the vehicles.
has been estimated around 1200 kg.                                   The ADS shall exploit both nose ports and mid

    The general configuration of the vehicle is shown in
Fig. 5. The structure is sized on the basis of the loads
induced by the SRT mission. The wing box sizing
criteria, in any case, could be the stiffness needed to cope
with wing flap induced flutter.

    Fig. 6 shows a sketch of the flight instrumentation
system with the identification of suitable zones for the
measurements of pressure and temperature/heat.
    The measurement instrumentation of the USV
vehicles is aimed to reconstruct the flight history in all its
major features, to support the navigation and flight
control functions, to monitor the state of the vehicle itself                    Fig. 5 – USV Configuration
and to provide people with all data necessary for the
verification of the accomplishment of the scientific and
                                                                 fuselage ports, for static pressure estimate. Wings, tails
technological goals. Ground tracking, a GPS, an inertial
                                                                 and base pressure distributions are also to be detected, so
measurements unit and accelerometers will allow the
                                                                 as wing flaps and rudders efficiency. Stagnation points
reconstruction of the trajectory, included free stream
                                                                 temperatures and fluxes are envisaged to be monitored;
Mach number, and of inertial attitude. The Mach number,
                                                                 moreover, base temperatures will give a check for the
as well as the thermal free stream parameters, will also be
                                                                 exhaust plume radiation extent. A dense distribution of
estimated on the basis of on board pressure and
                                                                 temperature probes in the windward mid section shall
temperature measurements.
                                                                 allow the detection of laminar-turbulent transition points.
    The aero Flight Control System (FCS) is based on the
                                                                     The experimental Flying Test Beds to be developed in
accurate knowledge of the angles of attack, whose
                                                                 the course of the USV program are supposed to be
detection is obtained by a pressure measurements based
                                                                 recovered. Although automatic landing technology and
system (Air Data System). Like for Mach number, a
                                                                 features are excluded by the program, each mission is
redundant estimate based on inertial attitude and ground
                                                                 designed and planned to minimise the probability of
velocity will be performed on board.
                                                                 loosing the vehicle.
    As USV will experience a variety of conditions




                                    Fig. 6 – Flight Instrumentation System
during its flights, the ADS has to work in wide ranges of            One of the major concerns in this direction is the
Mach and attitude, this implying the exploitation of             utilisation of stratospheric balloons, being their reliability
different assemblies of pressure ports, the use of more          relatively poor (0.85-0.90). However, this is not the only
than one type of transducers and the implementation of           weak or risky point or element. The already investigated
suitable switches in the onboard flight control software.        or considered “counter-measures” include:
Monitoring of the vehicle will include inside pressure and       • Shock-absorbing protection system attached to the
surface temperatures and strains on structures and                    lower side of USV in order to prevent vehicle

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     damage in case of problems at very early stage of the          •   USV program needs
     ascending phase (some m/s)                                     •   CIRA        background      (increase     existing
•    once the balloon has reached a certain altitude (from              competencies, promote new ideas)
     some 300 m altitude) any failure of the ascending             • Balance the II and III generation level research
     system can easily be overridden by using the safety                activities
     parachute included in the balloon chain                      The research lines selected up to now are illustrated in
•    even not analysed yet, air bag devices can be             Tab. I and Tab. II. They are classically grouped in
     mounted as further impact absorbing element               Material      &       Structures,    Aerodynamics        &
•    finally, a Flight Termination System (FTS) is             Aerothermodynamics, Propulsion, Heat Management,
     foreseen, in order to maximise the safety in case of      Health Management, Flight Systems.
     serious contingencies and consequent mission                 The final iteration to refine this Plan is running at
     abortion. FTS shall be defined in a way to guarantee      time of writing, so adjustments are expected.
     that the system and propellant fragmentation fulfil
     general safety requirements.                              6.   Conclusions
                                                                  The results of the phase A activities of the USV
5.    The Enabling Technologies Program Plan                   Program have been fully successful, collocating the
As USV is a technology development program, its overall        program itself well within the international scenario.
main objective is to provide a focus for identification,       These results can be summarised as follows:
development and validation of a number of key                  − The main objectives of PRORA have been well
technologies known to be representative of needs for               understood and translated into mission and system
future generations reusable space transportation vehicle.          requirements
More specifically, the Enabling Technologies Program           − The feasibility of the program has been demonstrated
Plan included in USV is intended to deal with either 2nd       − Large project margins exist, both in technical and
as well as further generations RLV, according to the               programmatic terms
NASA terminology.                                              − Meaningfulness of each single element of the
    Under this assumption future space transportation              program has been assessed with respect to the next
systems will have to satisfy many contemporary                     generation RLV technology needs identified by ESA
requirements of air transportation such as economy,            − The Enabling Technologies Program Plan has been
reliability, prolonged service life and short turn around          essentially identified, even if still waiting for final
time. For this purpose, the methods and processes                  freezing.
customary to space transportation must be combined with
                                                               7.   References
those of aeronautics. A merge of aeronautic and space
technologies seems probable and will be expressed in the       [1] “Future Launchers Preparatory Programme (FLPP) -
vehicle configuration.                                             Initial   Programme       Proposal”,    ESA/PB-
    The development of such an aerospace vehicle                   ARIANE(2001)112, 22 Oct. 2001
presupposes in particular the maturation of some specific
macro-technologies:                                            [2] G. Russo, S. Borrelli, G. Borriello, A. Denaro, F.
                                                                   Betti, A. Accettura, “Access to Space: Flying Test
1.   Atmospheric Re-entry - the aerospace vehicle has to           Beds as a Need for Long Term R&D“, 2nd Int.
     “handle” the typical large thermal loads encountered          Symp. on Atmospheric Re-entry Vehicles and
     during re-enter to earth from LEO, due to the                 Systems, Arcachon 26/29 March 2001
     necessity of reducing the vehicle speed from Mach
     25 or so down to few hundreds of km/h at landing;         [3] G. Russo, G. Borriello, S. Borrelli, F. Mura,
                                                                   “Preliminary Design And Performance OF The
2.   Hypersonic Flight – we suppose that the future space          PRORA-USV Experimental Vehicle“, 2nd Int.
     vehicles will have to fly for large part of its mission       Symp. on Atmospheric Re-entry Vehicles and
     to speed much greater that the speed of the sound,            Systems, Arcachon 26/29 March 2001
     and will have to manoeuvre in such conditions in
     security, having also to “handle” the heavy thermal       [4] G. Russo, “Next Generations Space Transportation
     loads generated from the friction with the air;               Systems: R&D and Need for Flying Test Beds”,
3.   Reusability - the most important characteristic from          AIAA/NAL/NASDA/ISAS 10th Int. Space Planes
     the operating point of view is the tendency to be as          and Hypersonic Systems and Technologies
     much like current airplane. This translates in the            Conference, Kyoto (Japan) 24/27 April 2001
     reusability concept.                                      [5] G. Russo, A. Capuano, “The PRORA-USV
                                                                   Program”,       4th    European Symp.     on
   Given these elements, the USV Enabling                          Aerothermodynamics for Space Vehicles, CIRA,
Technologies Program Plan has been drafted taking into             Capua (Italy) 8/11 October 2001
account the following criteria:
                                                               [6] M.    Serpico,  A.     Schettino,  “Preliminary
    • Italian industrial needs and competencies
                                                                   Aerodynamic Performances of the PRORA-USV
    • European         scenario     (avoid duplications,
                                                                   Experimental Vehicle”, 4th European Symp. on
         strengthen the Italian position)

Aerotecnica Missili e Spazio Vol. 81 – 2/2002
                                                         71
G. Russo



     Aerothermodynamics for Space Vehicles, CIRA,           TECHNOLOGIES                                                         Priority
                                                            MATERIAL & STRUCTURES
     Capua (Italy) 8/11 October 2001
                                                            • Advanced Thermal Protection System (TPS)

[7] S. Borrelli, M. Marini, “The Technology Program in          • Advanced CMC (UHTC)                                               1
                                                                • Hot Structures                                                    2
    Aerothermodynamics for PRORA-USV”, 4th                  • Tanks
    European Symp. on Aerothermodynamics for Space              • Filament Wound CFRP Cryo-Tank (oxidyser & eventually fuel)        1
    Vehicles, CIRA, Capua (Italy) 8/11 October 2001             • Elastomeric liner for Cryo Tank (oxidyser & eventually fuel)      1
                                                                • Advanced Tanks based on Nanotechnology                            2
                                                            AERODYN. & AEROTHERMODYN.
                                                            • New Configurations                                                    2
                                                            • Extrapolation to Flight                                               1
 TECHNO       Atmospher Sustained Reusability               • Laminar-Turbulent Transition                                          1
   LOGY           ic    Hypersonic                          • Base Flow                                                             2
                                                            • Real Gas, catalyticity                                                2
  FOCUS        Re-Entry   Flight                            • Control Surfaces                                                      1
                                                            PROPULSION - LOx/HC Engine
   FLIGHT      SRT, ORT         HFT          DTFT,          • System Level

    TEST                                    SRT, HFT,          • Optimal cycle (GG, SC, Expander, Bleed,…)                          1
                                                               • Sub-systems identification                                         2
                                              ORT           • Propellants
                                                               • Materials compatibility                                            2
 ENABLIN      - Transition   - Transition   - UHTC          • Sub-System Design

    G         - Extrapolat   - Extrapolat   - Hot              • Supercritical injector plate
                                                                    High temperature materials                                      1
 TECHNO         ion to         ion to         Structures            Combustion instabilities damping/detuning devices               1
  LOGIES        flight         flight       - Heat             • Ablative cooled combustion chambers                                2
              - Base         - New            Mgnt             • Ablative cooled nozzles                                            2

                Flow           configurat   - Health        • Engine Modelling
                                                               • Mass/energy budget analisys tools                                  1
              - Real Gas       ions           Mgnt Syst        • Turbulent combustion models for combustion chambers                1
                Effects      - Control      - LOx-HC           • Combustion modelling by LES                                        1
              - Micro-         Surfaces       rocket        PROPULSION - OTHER TOPICS
                Aerother     - UHTC                         • Hydrocarbon Liquid Ramjet/Scramjet Engines                            1
                                                            • Hybrid Propellant Ramjet/Scramjet                                     2
                modyn.       - Cryotank                     • Flight Experiments                                                    2
              - Control      - Smart                        HEAT MANAGEMENT
                Surfaces       Structure                    • Design Methodologies                                                  2
                                                            • Heat pipes based cooling panels                                       2
              - UHTC         - Heat
                                                            • Wing leading edge con raffreddamento basato su heat pipes             2
              - Heat           Mgnt                         • Active cooled panels (LH2, HC cracking)                               2
                Mgnt         - LOx-HC                       INTELLIGENT & INTEGR. HEALTH MANAGEMENT
              - Re-entry       rocket                       • HW e SW Innovative Architectures                                      1
                                                                 • Data Fusion                                                      1
                GNC          - Air-                              • Algorithms                                                       1
                               breathing                         • Modular Avionics                                                 1
                               Prop                              • Innovative EGSE, maintenance & re-design capability              1
                             - Hypersoni                    • Sensori Ottici a Reticolo di Bragg per Alte Temp.                     2
                                                            FLIGHT SYSTEMS
                               c GNC                        • Re-entry GNC                                                          1
                                                            • Hypersonic Flight GNC (M<7)                                           1
Tab. I - Relation between selected technologies and USV     • High Performance Bus                                                  2

                     Flight Test Beds
                                                            Tab. II Selected Enabling Technologies




                                                                                  Aerotecnica Missili e Spazio Vol. 81 – 2/2002
                                                       72

				
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