Materials Issues for the Space Elevator

							                 The Space Elevator:
                 An Exciting Challenge

                        Tom Nugent
                      Research Director
                        LiftPort, Inc.
                   tom.nugent@liftport.com

Sept. 15, 2006             Exploratorium     1
Think Big!




Sept. 15, 2006   Exploratorium   2
A Space Elevator?




        Railroad to space                    Port of the
                                            Solar System

Sept. 15, 2006              Exploratorium                  3
How Does It Work?

• Just like twirling a ball-on-a-string over your head




• Balance forces above and below
  GEO
• Taper ribbon cross-sectional
  area for constant stress
• Net tension in ribbon allows
  vehicles (“Lifters”) to climb into
  orbit

Sept. 15, 2006                 Exploratorium             4
The Liftport




Sept. 15, 2006   Exploratorium   5
Ribbon+Lifter




Sept. 15, 2006   Exploratorium   6
Counterweight




Sept. 15, 2006   Exploratorium   7
Deployment

                                 • Seed ribbon
                                    – ~1 tonne capacity
                                 • Assemble in
                                   LEO, boost to
                                   GEO via power
                                   beaming
                                 • Lower one end of
                                   ribbon towards
                                   Earth, boost other
                                   end
                                 • Gravity-gradient
                                   stabilization

Sept. 15, 2006   Exploratorium                        8
Why Build It? (1)

• Safety & Reliability
      – Rockets have ~5% failure rate
      – SE gives a gentle ride
             • Reduced vibrations etc. for cargo




Sept. 15, 2006                  Exploratorium      9
Why Build It? (2)

• Economics
      – Rockets are Expensive
      – Ferries vs. Bridge, or Covered Wagon vs.
        Railroad
• Capacity
      – SPS?
      – Bigger satellites
      – Real estate (GEO port)
• Profit!


Sept. 15, 2006          Exploratorium              10
Why Now?

• Carbon nanotubes
  (discovered 1991)
  make the SE feasible
      – High strength
      – Low density




Sept. 15, 2006           Exploratorium   11
         Strength!


• Strength-to-weight
  is most important
  property
• Requires
  improvement of
  11x-25x!
      – Get mass reduction
        by factor of trillions


      – What is appropriate
        safety factor?
Sept. 15, 2006                   Exploratorium   12
Research Questions (1)

•   Lightning
•   Wind
•   Twist of ribbon
•   Weight of precipitation
•   Atomic oxygen
•   Orbital Debris
•   Deployment
•   Power Beaming


Sept. 15, 2006           Exploratorium   13
Research Questions (2)

• Elastic energy
      – Cascading failure?
• Ribbon safety factor
      – Learn from structural
        engineers, current systems




Sept. 15, 2006               Exploratorium   14
Research Questions (3)

• Thermal flux
      – Earth's shadow
      – CTE mismatch between CNTs and matrix
• Electromagnetic interaction




Sept. 15, 2006        Exploratorium            15
Research Questions (4)

                   • Lifter vehicle
                         – Endurance
                         – Multiple physical regimes
                         – Heat management
                   • Others:
                         – Radiation damage to ribbon
                         – Ribbon inspection and position
                           monitoring
                         – Adequate testing of pre-cursor
                           components
                         – Cumulative damage
                         – Vehicle acceleration limits
                         – Alternate designs (e.g., balloon
                           platform)
Sept. 15, 2006      Exploratorium                         16
Roadmap




Sept. 15, 2006   Exploratorium   17
How Do We Tackle Questions?

• Piggyback on research in other fields
      – Space tethers, laser launch, debris
        mitigation, weather forecasting,
        magnetosphere, material fatigue, etc.
• “Volunteers”
      – Most current SE researchers
• Partner with interested researchers
      – Collaborate on grant-writing
• Pay big $$ for detailed engineering
  work
Sept. 15, 2006          Exploratorium           18
Finding Solutions

• Partnering
      – Universities: professors,
        graduate students,
        undergrads, research staff
• Guidance
      – Thesis topics
      – Independent study projects
      – Volunteers
• Interns and LiftPort in-
  house work
• Let’s talk!
                                                 and more!
Sept. 15, 2006                   Exploratorium               19
Want More?

• To Learn More and Get Involved:
      – Sign up for our Newsletter
                 – Newsletter box at http://www.liftport.com
      – Join our Forums
                 – http://www.liftport.com/forums/
      – Buy our new book!
      – Tell your friends and colleagues




                    www.LiftPort.com
          Tom.Nugent@LiftPort.com
Sept. 15, 2006                     Exploratorium               20