A space elevator is a cable anchored on the equator, stretching past geostationary orbit at 35,786 km to a counterweight, held taut by Earth's rotation. Tsiolk…
Inspired by the Eiffel Tower, Konstantin Tsiolkovsky imagined a tower reaching geostationary height. As a tower it could never stand, but the idea of a fixed road to spa…
Yuri Artsutanov proposed lowering a cable from a satellite in geostationary orbit to the equator while extending a counterweight outward. It pulls instead of pushes.
Jerome Pearson showed the cable must be thickest at geostationary orbit, where tension peaks, and extended it to about 144,000 km as its own counterweight.
Arthur C. Clarke's novel put a space elevator on a mountain in a fictional Sri Lanka. Charles Sheffield used the same idea the same year.
Carbon nanotubes are extraordinarily strong for their weight at microscopic scale, the first material that looks good enough on paper.
NASA Marshall's workshop and David Smitherman's 2000 report treated the elevator as real infrastructure, but said it could not be built for at least 50 years.
Bradley Edwards proposed lowering a thin nanotube ribbon from orbit, then sending 207 climbers up to thicken it. He assumed a material strength of about 100 GPa.
LaserMotive's climber rode a 900 m cable hung from a helicopter on laser power. The tether prize was never won.
Obayashi's concept: a 96,000 km cable, a station at 36,000 km, climbers at 200 km/h taking about 7.5 days. The company says current technology is not yet sufficient.
Two small satellites joined by a 10 m tether were released from the ISS, with a tiny car designed to move along it.
A cable hanging from the Moon toward Earth could use Zylon, a fibre made today, because the Moon's gravity and spin are so much weaker.
None has been built or started. An Earth elevator needs a breaking length of about 3,100-8,200 km; the best bulk fibres manage about 400 km.
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