Transcript Space Elevators Craig Borchard Scott Shjefte 13 April 2004 Reference: http://www.isr.us/Spaceelevatorconference/2003presentations.html Towers • In early 1962 the Convair Division of General Dynamics carried out a feasibility.

Space Elevators
Craig Borchard
Scott Shjefte
13 April 2004
Reference: http://www.isr.us/Spaceelevatorconference/2003presentations.html
Towers
• In early 1962 the Convair Division of General
Dynamics carried out a feasibility study, to see if
very high towers would be of value for
astronomy, high altitude research,
communications and rocket launching platforms
– steel towers could be built up to 6 km high
– aluminium ones up to almost 10 km high
• Calculations show that a tower built of graphite
composite struts could reach the very
respectable height of 40 km, tapering from a 6
km-wide base.
What is a Space Elevator?
• A space elevator is a physical connection from
the surface of the Earth, or another planetary
body such as Mars, to a geostationary orbit - for
the Earth at roughly 35,786 km in altitude.
• Video clip at http://www.isr.us/SEanimation.asp
Carbon Nanotube (CNT) Bundles
Fullerene Nanotubes
• 1997: Yakobson, B. I., Smalley, R. E., “Fullerene Nanotubes:
C1,000,000 and Beyond,” American Scientist, 85, pp. 324-337, JulyAugust 1997
• Carbon Nanotubes (CNT)
• Single-Wall Nanotubes (SWNT)
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Strength ( ~ 100 x steel, 10 x kevlar)
Electrical conductivity (~ copper)
Thermal conductivity (~ diamond)
Manufacturing is difficult (now)
• Its future in manufactured products…
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High tensile strength
Ultimate laminate
Low mass
Forms strong fibers
Good electrical conductor
Excellent thermal conductor
Ribbon
Deployment
Deployment
•
Small ribbon (10 to 20 cm wide and microns thick) deployed from geosynchronous
orbit using four rockets and a magnetoplasmadynamic upper stage
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230 Climbers (one every 3 to 4 days) add small ribbons alongside the first for 2.3
years
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Free-electron laser (840 nm) and 13 m diameter segmented dish with adaptive optics
Received by GaAs photocells (80% overall efficiency at this wavelength) on the climber's
underside
conventional, niobium-magnet DC electric motors and a set of rollers to pull the climbers up
the ribbon at speeds up to 200 km/hr.
Spacecraft and construction climbers would become counterweights
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Supports 20,000 kg cargo climbers
These add to counterweight
Power (100kW to 2.4 MW) is beamed up
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Supports 990 kg payloads
Space end of the 100,000 km long ribbon
An ocean-going platform would be used for the Earth anchor and located in the
equatorial Pacific
Deployment of Ribbon 2
• Job 1 for Ribbon 1
• Capacity doubles with new ribbon
• Cost for future ribbons declines
exponentially
– First one costs ~$6B
– Second one costs ~$2B
Overview of Hazards
• Lightning
– Placement of base
• Meteors
– Large – Maneuvering of base
– Small – Ribbon design
• Wind Loading
– Placement of base
• Atomic Oxygen
– Ribbon design
• Radiation
– Ribbon design
• Induced Oscillations
– Tension adjustment in Active Vibration Control (AVC) system
Magnetospheric Hazards
• Extreme electromagnetic disturbances can move
the cable, perhaps by 10’s of kms.
• The cable itself is not very vulnerable despite
passing through most intense radiation belts.
• Radiation effects on electronics (cargo and
crawler) can be solved at a cost.
• Extremely severe radiation effects on humans
have never been faced before (200x Apollo
dosage, due to low speed).
• If not solved, humans cannot travel on the
Space Elevator.
Base Location
• Initially targeted off the western coast of
South America, near the equator, as
shown in clips
– Lightning strikes minimal
– Wind minimal
– Floating base can be moved to avoid storms
and large debris
Planet Accessibility
•Flung off the end of the cable
•Initial payload (to Mars) could be self-deploying elevator
Space Elevators
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CNT or SWNT shows promising capability
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Some manufacturing challenges remain
Health hazards completely unknown
Robustness to micrometeorites important
Orbit “Cleanup Day”
Atomic oxygen needs coating development
Robotic manufacture of ribbons in situ
– Including bonding, coating, QA, repair
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Active control of oscillations and avoidance maneuvers
Easier hazards
– Lightning
– Wind
– Radiation (except to humans)
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"The Space Elevator: 3rd Annual International Conference"
– June 28-30, 2004 in Washington, D.C.
– http://www.isr.us/SpaceElevatorConference/aboutSE.html