Editing Space elevator (section)

==Construction==
{{Main|Space elevator construction}}

The construction of a space elevator would need reduction of some technical risk. Some advances in engineering, manufacturing and physical technology are required.<ref name="Edwards" /> Once a first space elevator is built, the second one and all others would have the use of the previous ones to assist in construction, making their costs considerably lower. Such follow-on space elevators would also benefit from the great reduction in technical risk achieved by the construction of the first space elevator.<ref name="Edwards" />

Prior to the work of Edwards in 2000,<ref name="EDWARDS_PHASE_I_2000_472Edwards.html" /> most concepts for constructing a space elevator had the cable manufactured in space. That was thought to be necessary for such a large and long object and for such a large counterweight. Manufacturing the cable in space would be done in principle by using an [[asteroid]] or [[Near-Earth object]] for source material.<ref name="Smitherman"/><ref>Hein, A. M., [https://www.academia.edu/2111184/A.M._Hein_Producing_a_Space_Elevator_Tether_using_a_NEO_A_Preliminary_Assessment_ Producing a Space Elevator Tether Using a NEO: A Preliminary Assessment], International Astronautical Congress 2012, IAC-2012, Naples, Italy, 2012.</ref> These earlier concepts for construction require a large preexisting [[space infrastructure|space-faring infrastructure]] to maneuver an asteroid into its needed orbit around Earth. They also required the development of technologies for manufacture in space of large quantities of exacting materials.<ref name="ISEC_SE_way_forward_2013">{{cite book |editor-last1=Swan |editor-first1=Peter A. |editor-last2=Raitt |editor-first2=David I. |editor-last3=Swan |editor-first3=Cathy W. |editor-last4=Penny |editor-first4=Robert E. |editor-last5=Knapman |editor-first5=John M. |date=2013 |title=Space Elevators: An Assessment of the Technological Feasibility and the Way Forward |url=http://www.virginiaedition.com/media/spaceelevators.pdf |url-status=live |archive-url=https://web.archive.org/web/20140516231842/http://www.virginiaedition.com/media/spaceelevators.pdf |archive-date=16 May 2014 |publisher=[[International Academy of Astronautics]] |isbn=9782917761311}}</ref>{{rp|326}}

Since 2001, most work has focused on simpler methods of construction requiring much smaller space infrastructures. They conceive the launch of a long cable on a large spool, followed by deployment of it in space.<ref name="Edwards" /><ref name="EDWARDS_PHASE_I_2000_472Edwards.html" /><ref name="ISEC_SE_way_forward_2013" />{{rp|326}} The spool would be initially parked in a geostationary orbit above the planned anchor point. A long cable would be dropped "downward" (toward Earth) and would be balanced by a mass being dropped "upward" (away from Earth) for the whole system to remain on the geosynchronous orbit. Earlier designs imagined the balancing mass to be another cable (with counterweight) extending upward, with the main spool remaining at the original geosynchronous orbit level. Most current designs elevate the spool itself as the main cable is payed out, a simpler process. When the lower end of the cable is long enough to reach the surface of the Earth (at the equator), it would be anchored. Once anchored, the center of mass would be elevated more (by adding mass at the upper end or by paying out more cable). This would add more tension to the whole cable, which could then be used as an elevator cable.

One plan for construction uses conventional rockets to place a "minimum size" initial seed cable of only 19,800&nbsp;kg.<ref name="Edwards" /> This first very small ribbon would be adequate to support the first 619&nbsp;kg climber. The first 207 climbers would carry up and attach more cable to the original, increasing its cross section area and widening the initial ribbon to about 160&nbsp;mm wide at its widest point. The result would be a 750-ton cable with a lift capacity of 20 tons per climber.

===Safety issues and construction challenges===
{{Main|Space elevator safety}}
For early systems, transit times from the surface to the level of geosynchronous orbit would be about five days. On these early systems, the time spent moving through the [[Van Allen radiation belts]] would be enough that passengers would need to be protected from radiation by shielding, which would add mass to the climber and decrease payload.<ref>{{cite web|url=https://www.newscientist.com/article/dn10520 |title=Space elevators: 'First floor, deadly radiation!' |access-date=2 January 2010 |date=13 November 2006|work=New Scientist |publisher=Reed Business Information Ltd.}}</ref>

A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be diverted by [[air-traffic control]] restrictions. All objects in stable orbits that have [[perigee]] below the maximum altitude of the cable that are not synchronous with the cable would impact the cable eventually, unless avoiding action is taken. One potential solution proposed by Edwards is to use a movable anchor (a sea anchor) to allow the tether to "dodge" any space debris large enough to track.<ref name="Edwards" />

Impacts by space objects such as meteoroids, micrometeorites and orbiting man-made debris pose another design constraint on the cable. A cable would need to be designed to maneuver out of the way of debris, or absorb impacts of small debris without breaking.{{Citation needed|date=July 2022}}

===Economics===
{{Main|Space elevator economics}}
With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2022, conventional rocket designs cost about US$12,125 per [[kilogram]] (US$5,500 per [[Pound (mass)|pound]]) for transfer to geostationary orbit.<ref>{{cite web|url=https://www.spacex.com/rideshare/#:~:text=%24275k%20for%2050kg%20to,LEO%2C%20GTO%2C%20and%20TLI.|title=Smallsat Rideshare Program|date=1 March 2022|work=SpaceX|access-date=1 May 2023}}</ref> Current space elevator proposals envision payload prices starting as low as $220 per kilogram ($100 per [[Pound (mass)|pound]]),<ref>{{cite web |author=The Spaceward Foundation |title=The Space Elevator FAQ |url=http://www.spaceward.org/elevator-faq |url-status=dead |archive-url=https://web.archive.org/web/20090227115101/http://www.spaceward.org/elevator-faq |archive-date=27 February 2009 |access-date=3 June 2009 |location=Mountain View, California}}</ref> similar to the $5–$300/kg estimates of the [[Launch loop]], but higher than the $310/ton to 500&nbsp;km orbit quoted to Dr. [[Jerry Pournelle]] for an orbital airship system.<ref>{{cite web |first=Jerry |last=Pournelle |date=23 April 2003 |url=http://www.jerrypournelle.com/archives2/archives2view/view306.html#Friday |title=Friday's VIEW post from the 2004 Space Access Conference |access-date=1 January 2010}}</ref>

Philip Ragan, co-author of the book ''Leaving the Planet by Space Elevator'', states that "The first country to deploy a space elevator will have a 95 percent cost advantage and could potentially control all space activities."<ref>{{cite news |url=http://www.news.com.au/news/race-to-build-worlds-first-space-elevator/story-fna7dq6e-1111118059040 |title=Race on to build world's first space elevator |date=17 November 2008|work=news.com.au|first=Andrew |last=Ramadge|author2=Schneider, Kate|access-date=January 14, 2016|url-status=dead|archive-date=13 September 2015 |archive-url=https://web.archive.org/web/20150913204538/http://www.news.com.au/news/race-to-build-worlds-first-space-elevator/story-fna7dq6e-1111118059040}}</ref>