A space elevator is a proposed structure designed to transport material from a celestial body’s surface into space. Many variants have been proposed, all of which involve traveling along a fixed structure instead of using rocket powered space launch. The concept most often refers to a structure that reaches from the surface of the Earth on or near the Equator to geostationary orbit (GSO) and a counter-mass beyond.
The concept of a space elevator dates back to 1895 when Konstantin Tsiolkovsky proposed a free-standing “Tsiolkovsky” tower reaching from the surface of Earth to geostationary orbit. Most recent discussions focus on tensile structures (specifically, tethers) reaching from geostationary orbit to the ground. This structure would be held in tension between Earth and the counterweight in space like a guitar string held taut. Space elevators have also sometimes been referred to as beanstalks, space bridges, space lifts, space ladders, skyhooks, orbital towers, or orbital elevators.
Current technology is not capable of manufacturing practical engineering materials that are sufficiently strong and light to build an Earth-based space elevator. The primary issue is that the total mass of conventional materials needed to construct such a structure would be so great that the cable would break under its own weight. Recent conceptualizations for a space elevator are notable in their plans to use carbon nanotube-based materials as the tensile element in the tether design, since the measured strength of microscopic carbon nanotubes appears great enough to make this theoretically possible. Current technology could produce elevators for locations in the solar system with weaker gravitational fields, such as the Moon or Mars.