Editing Space elevator (section)

{{short description|Proposed type of space transportation system}}
{{Use dmy dates|date=August 2024}}
{{Use American English|date=April 2021}}
[[File:Space elevator structural diagram--corrected for scale+CM+etc.svg|thumb|upright=1.2|alt=Diagram of a space elevator. At the bottom of the tall diagram is the Earth as viewed from high above the North Pole. About six earth-radii above the Earth an arc is drawn with the same center as the Earth. The arc depicts the level of geosynchronous orbit. About twice as high as the arc and directly above the Earth's center, a counterweight is depicted by a small square. A line depicting the space elevator's cable connects the counterweight to the equator directly below it. The system's center of mass is described as above the level of geosynchronous orbit. The center of mass is shown roughly to be about a quarter of the way up from the geosynchronous arc to the counterweight. The bottom of the cable is indicated to be anchored at the equator. A climber is depicted by a small rounded square. The climber is shown climbing the cable about one third of the way from the ground to the arc. Another note indicates that the cable rotates along with the Earth's daily rotation, and remains vertical. |A space elevator is conceived as a cable fixed to the equator and reaching into space. A counterweight at the upper end keeps the [[center of mass]] well above geostationary orbit level. This produces enough upward [[centrifugal force]] from Earth's rotation to fully counter the downward gravity, keeping the cable upright and taut. Climbers carry cargo up and down the cable.]]
[[File:Space elevator in motion viewed from above north pole.ogv|thumbtime=28|thumb|upright=1.2|Space elevator in motion rotating with Earth, viewed from above North Pole. A free-flying satellite (green dot) is shown in geostationary orbit slightly behind the cable.]]

A '''space elevator''', also referred to as a '''space bridge''', '''star ladder''', and '''orbital lift''', is a proposed type of planet-to-space transportation system,<ref>{{cite web|url=https://www.isec.org/faq/#What%20is%20it |title=What is a Space Elevator? |publisher=The International Space Elevator Consortium |year=2014 |access-date=22 August 2020}}</ref> often depicted in science fiction. The main component would be a cable (also called a [[space tether|tether]]) anchored to the surface and extending into space. An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end attached to a counterweight in space beyond [[geostationary orbit]] (35,786&nbsp;km altitude). The competing forces of gravity, which is stronger at the lower end, and the upward centrifugal pseudo-force (it is actually the inertia of the counterweight that creates the tension on the space side), which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position on Earth. With the tether deployed, climbers (crawlers) could repeatedly climb up and down the tether by mechanical means, releasing their cargo to and from orbit.<ref name="Edwards">{{cite report|last=Edwards|first=Bradley Carl|title=The NIAC Space Elevator Program|url=http://www.niac.usra.edu/studies/521Edwards.html|publisher=NASA Institute for Advanced Concepts|archive-url=https://web.archive.org/web/20080512225341/http://www.niac.usra.edu/studies/521Edwards.html|archive-date=12 May 2008|access-date=24 November 2007|url-status=bot: unknown}}</ref> The design would permit vehicles to travel directly between a planetary surface, such as the Earth's, and orbit, [[non-rocket spacelaunch|without the use of large rockets]].