Lunar space elevator
A lunar space elevator or lunar spacelift is a proposed transportation system for moving a mechanical climbing vehicle up and down a ribbon-shaped tethered cable that is set between the surface of the Moon "at the bottom" and a docking port suspended tens of thousands of kilometers above in space at the top.
Without the Earth's gravity to attract it, an L2 cable's lowest kilogram would require 1,000 kg of counterweight at a distance of 120,000 km from the Moon.
A tramway could be used to bring the cable the rest of the way to the pole, with the Moon's low gravity allowing much taller support towers and wider spans between them than would be possible on Earth.
An Earth-based elevator would require high strength-to-weight materials that are theoretically possible, but not yet fabricated in practice (e.g., carbon nanotubes).
Compared to an Earth space elevator, there would be fewer geographic and political restrictions on the location of the surface connection.
The connection point of a lunar elevator would not necessarily have to be directly under its center of gravity, and could even be near the poles, where evidence suggests there might be frozen water in deep craters that never see sunlight; if so, this might be collected and converted into rocket fuel.
The study done for NASA's Institute of Advanced Concepts states "Current composites have characteristic heights of a few hundred kilometers, which would require taper ratios of about 6 for Mars, 4 for the Moon, and about 6000 for the Earth.
However a pulley configuration would require a strut at the counterweight hundreds of kilometers long to separate the up-tether from the down-tether and keep them from tangling.
The idea of space elevators has been around since 1960 when Yuri Artsutanov wrote a Sunday supplement to Pravda on how to build such a structure and the utility of geosynchronous orbit.
[citation needed] Then in 1966, John Isaacs, a leader of a group of American Oceanographers at Scripps Institute, published an article in Science about the concept of using thin wires hanging from a geostationary satellite.
[citation needed] In 1972, James Cline submitted a paper to NASA describing a "mooncable" concept similar to a lunar elevator.
His article inspired Sir Arthur Clarke to write the novel The Fountains of Paradise (published in 1979, almost simultaneously with Charles Sheffield's novel on the same topic, The Web Between the Worlds).
[8][9][10] In April 2019, LiftPort CEO Michael Laine reported no progress beyond the lunar elevator company's conceptualized design.
[1] This would make it possible to build the elevator much sooner, since available carbon nanotube materials in sufficient quantities are still years away.
If a 540 kg climber traveled at a velocity of fifteen meters per second, by the time it was seven percent of the way to the L1 point, the required power would drop to less than a hundred watts, versus 10 kilowatts at the surface.
As President Bush noted,[14] "(Lunar) soil contains raw materials that might be harvested and processed into rocket fuel or breathable air."
For example, the proposed Ares V heavy-lift rocket system could cost-effectively[15] deliver raw materials from Earth to a docking station, (connected to the lunar elevator as a counterweight,)[16] where future spacecraft could be built and launched, while extracted lunar resources could be shipped up from a base on the Moon's surface, near the elevator's anchoring point.
[1] One disadvantage of the lunar elevator is that the speed of the climbing vehicles may be too slow to efficiently serve as a human transportation system.
