The Audacious Space Elevator

NASA Building from a satellite towards Earth was propsed in 1960.

One "spinoff" use of Tsiolkovsky's tower would be the ability to launch objects into orbit without a rocket. Since the elevator would attain orbit velocity as it rode up the cable, an object released at the tower's top would also have the orbital velocity necessary to remain in geosynchronous orbit.

Building from the ground up, however, proved an impossible task. It took until 1960 for another Russian scientist, Y.N. Artsutanov, to propose another scheme for building a space tower. Artsutanov suggested using a geosynchronous satellite as the base from which to build the tower. By using a counterweight, the cable would be lowered from geosynchronous orbit to the surface of the earth while the counterweight was extended from the satellite away from the earth.

Making a cable 35,000 kilometers long is a difficult task. In 1966, four American engineers decided to determine what type of material would be required to build a space tower, assuming it would be a straight cable with no variations in its cross section. They found that the strength required would be twice that of any existing material including graphite, quartz and diamond.

NASA The weight of the material needed for this tower would require 24,000 space shuttle trips.

Nine years later another American scientist, Jerome Pearson, designed a tapered cross section that would be better suited to building the tower. He suggested using a counterweight that would be slowly extended out to 144,000 kilometers (half the distance to the moon) as the lower section of the tower was built. His analysis included disturbances such as the gravitation of the Moon, wind and moving payloads up and down the cable. The weight of the material needed to build the tower would have required 24,000 Space Shuttle trips, although part of the material could be transported up the tower when a minimum strength strand reached the ground.

Later, Pearson thought about building a tower on the Moon. He determined that the center of gravity needed to be at the L1 or L2 Lagrangian points, which are special stable points that exist about any two orbiting bodies where the gravitational forces are balanced. The cable would have to be 291,901 kilometers long for the L1 point and 525,724 kilometers long for the L2 point. Compared to the 351,000 kilometers from the Earth to the Moon, that's a long cable, and the material would have to be gathered and manufactured on the Moon.