The Lunar Space Elevator                                                                                                                      

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The idea of a Space Elevator was first mooted by Russian Yuri Artsutanov in 1960 and his successors in scientific circles have come up with various proposals as to how this concept might be turned into a reality.

Basically, the concept involves launching a satellite into a geostationary (or geosynchronous) orbit above the earth after which in this location it would rotate around the earth at the same angular velocity as the earth's daily rotation, therefore appearing to be stationary above a fixed point on the planet. Once established in orbit, a cable could then be lowered from the satellite and fixed to an anchor point on the earth's surface, enabling a specially designed vehicle to climb up and down the cable, transporting supplies and materials to and from the satellite. This would eliminate the need for rockets to service the satellite and transport astronauts between earth and satellite. 

A system such as this, however, would face insurmountable problems including the following:

·  The geostationary orbit is located approximately 35,800 km above the earth’s surface, and a cable of this length would be required to tether the satellite to the planet. The cable connected to the satellite would have to support the total weight of cable below which would result in a strain on the cable that no known materials could withstand.

·  The cable climbing vehicle would need to be powered on its ascent to the satellite. Storage of the required fuel aboard the vehicle would add mass, increasing the strain well past breaking point of the cable. Using solar power might be an option but the weight of solar panels required would again add to the mass pulling on the cable.

·  The cable would be exposed to adverse weather events, high velocity stratospheric jet streams, lightning strikes, cyclones and meteorite impact.

The Lunar Space Station; A new use for an old concept

For any 2 bodies in an orbital system there exist 5 locations (known as Lagrange points) at which the pull of gravity of each body and their orbital motion results in zero gravity at that point. For the earth/moon system the Lagrange point no. 1 shown on the diagram below is located just 58,000 Km above the lunar surface.

Although the distance of 58,000 Km for an L1 Lagrange satellite above the moon is greater than the 35,800 Km cable required for a satellite/earth elevator, it can be considered feasible as a site for a satellite connected to the lunar surface for the following reasons:

• Lunar gravity is 1/6th of earth's and this would result in a dramatic reduction in the load, and therefore the strain, on the cable
• The strain would be further reduced by the fact that the lunar pull on the cable would be counteracted by earth's gravity for a substantial part of the distance.
• A large solar panel array on the moon could supply electricity via the cable to power the travelling elevator cab.
• The elevator would not be subject to the atmospheric disturbances posed by an earth/satellite elevator.

The main benefit in establishing such an elevator at Lagrange 1 would allow personnel, equipment and construction materials to be delivered to a moon base without delivery rockets required to carry sufficient fuel to escape lunar gravity on their return leg.