The orbital elevator is a short variant of skyhook. A sounding rocket carries cargo to the bottom end of an elevator orbiting the Earth at 6 km/s. The cargo gains only 1 km/s when it travels up the elevator. Elevator made of high-strength plastic would be vulnerable to space radiation and thermal fatigue. Perhaps the best material for the elevator is a rope made of strong (6.5GPa) carbon fibers coated with a thin layer of aluminum and fused together in a hot press. To avoid the extreme radiation of the Van Allen belts, the elevator is restricted to altitudes ranging from 5,000 km to 13,000 km. The minimum mass of a carbon elevator (for 1-ton cargo) is 100 tons.

The Coriolis force of moving cargo compromises the stability of the elevator. An electrodynamic tether alone cannot restore its orbital momentum, because it would operate at the bottom end of the elevator and would further destabilize it. The electrodynamic tether has to be aided by an ion engine or a solar sail placed at the top end of the elevator.


Robert Zubrin, "The Hypersonic Skyhook," Analog Science Fiction/Science Fact, Vol. 113, No. 11, September 1993, pp. 60-70.

Eagle Sarmont, "How an Earth Orbiting Tether Makes Possible an Affordable Earth-Moon Space Transportation System," SAE Technical Paper 942120, given at Aerotech '94, Los Angeles, CA, October 3-6 1994.

Robert Zubrin, "The Hypersonic Skyhook," Journal of the British Interplanetary Society, Vol. 48, No. 3, March 1995, pp. 123-128.

Orbital elevator