Editing Space elevator (section)

===Climbers===
[[Image:SpaceElevatorInClouds.jpg|thumb|upright|A conceptual drawing of a space elevator climber ascending through the clouds.]]

A space elevator cannot be an elevator in the typical sense (with moving cables) due to the need for the cable to be significantly wider at the center than at the tips. While various designs employing moving cables have been proposed, most cable designs call for the "elevator" to climb up a stationary cable.

Climbers cover a wide range of designs. On elevator designs whose cables are planar ribbons, most propose to use pairs of rollers to hold the cable with friction.

Climbers would need to be paced at optimal timings so as to minimize cable stress and oscillations and to maximize throughput. Lighter climbers could be sent up more often, with several going up at the same time. This would increase throughput somewhat, but would lower the mass of each individual payload.<ref name="LangGTOSS">{{cite web |url=http://spaceelevatorwiki.com/wiki/images/2/2b/Paper_Lang_Climber_Transit.pdf |last=Lang |first=David D. |title=Space Elevator Dynamic Response to In-Transit Climbers |access-date=9 February 2016 |archive-date=28 May 2016 |archive-url=https://web.archive.org/web/20160528232403/http://spaceelevatorwiki.com/wiki/images/2/2b/Paper_Lang_Climber_Transit.pdf |url-status=dead }}</ref>

[[File:Space elevator balance of forces--circular Earth--more accurate force vectors.svg|thumb|upright=1.2|As the car climbs, the cable takes on a slight lean due to the Coriolis force. The top of the cable travels faster than the bottom. The climber is accelerated horizontally as it ascends by the Coriolis force which is imparted by angles of the cable. The lean-angle shown is exaggerated.]]
The horizontal speed, i.e. due to orbital rotation, of each part of the cable increases with altitude, proportional to distance from the center of the Earth, reaching low [[orbital speed]] at a point approximately 66 percent of the height between the surface and geostationary orbit, or a height of about 23,400&nbsp;km. A payload released at this point would go into a highly eccentric elliptical orbit, staying just barely clear from atmospheric reentry, with the [[periapsis]] at the same altitude as low earth orbit (LEO) and the [[apoapsis]] at the release height. With increasing release height the orbit would become less eccentric as both periapsis and apoapsis increase, becoming circular at geostationary level.<ref>{{cite web |first=Blaise |last=Gassend |title=Falling Climbers |url=http://gassend.net/spaceelevator/falling-climbers/index.html |access-date=16 December 2013}}</ref><ref>{{cite web |title=Space elevator to low orbit? |url=http://www.endlessskyway.com/2010/05/space-elevator-to-low-orbit.html |date=19 May 2010 |website=Endless Skyway |access-date=16 December 2013 |archive-url=https://web.archive.org/web/20131216184533/http://www.endlessskyway.com/2010/05/space-elevator-to-low-orbit.html |archive-date=16 December 2013 |url-status=dead}}</ref>

When the payload has reached GEO, the horizontal speed is exactly the speed of a circular orbit at that level, so that if released, it would remain adjacent to that point on the cable. The payload can also continue climbing further up the cable beyond GEO, allowing it to obtain higher speed at jettison. If released from 100,000&nbsp;km, the payload would have enough speed to reach the asteroid belt.<ref name="PhaseII" />

As a payload is lifted up a space elevator, it would gain not only altitude, but horizontal speed (angular momentum) as well. The angular momentum is taken from the Earth's rotation. As the climber ascends, it is initially moving slower than each successive part of cable it is moving on to. This is the [[Coriolis force]]: the climber "drags" (westward) on the cable, as it climbs, and slightly decreases the Earth's rotation speed. The opposite process would occur for descending payloads: the cable is tilted eastward, thus slightly increasing Earth's rotation speed.

The overall effect of the <!--n.b. the elevator is in a non inertial reference frame, so centrifugal is correct--->centrifugal force acting on the cable would cause it to constantly try to return to the energetically favorable vertical orientation, so after an object has been lifted on the cable, the counterweight would swing back toward the vertical, a bit like a pendulum.<ref name="LangGTOSS" /> Space elevators and their loads would be designed so that the center of mass is always well-enough above the level of geostationary orbit<ref>{{cite web |url=http://gassend.net/spaceelevator/center-of-mass/index.html |title=Why the Space Elevator's Center of Mass is not at GEO |first=Blaise |last=Gassend |access-date=30 September 2011}}</ref> to hold up the whole system. Lift and descent operations would need to be carefully planned so as to keep the pendulum-like motion of the counterweight around the tether point under control.<ref>{{cite journal|doi=10.1016/j.actaastro.2008.10.003|title=The effect of climber transit on the space elevator dynamics|year=2009|last1=Cohen|first1=Stephen S.|last2=Misra|first2=Arun K.|journal=Acta Astronautica|volume=64|issue=5–6|pages=538–553|bibcode=2009AcAau..64..538C}}</ref>

Climber speed would be limited by the Coriolis force, available power, and by the need to ensure the climber's accelerating force does not break the cable. Climbers would also need to maintain a minimum average speed in order to move material up and down economically and expeditiously.<ref>{{Cite web|last=Courtland|first=Rachel|title=Space elevator trips could be agonisingly slow|url=https://www.newscientist.com/article/dn16223-space-elevator-trips-could-be-agonisingly-slow/|access-date=2021-05-28|website=New Scientist|language=en-US}}</ref> At the speed of a very fast car or train of {{convert|300|km/h|mph|abbr=on}} it will take about 5 days to climb to geosynchronous orbit.<ref>{{cite book |last1=Fawcett |first1=Bill |title=LIFTPORT |last2=Laine |first2=Michael |last3=Nugent Jr. |first3=Tom |date=2006 |publisher=Meisha Merlin Publishing, Inc. |isbn=978-1-59222-109-7 |location=Canada |page=103 |language=en |name-list-style=amp}}</ref>