Editing Space Shuttle external tank (section)

== Overview ==
{{multiple image|direction=vertical|image1=Space Shuttle Columbia launching.jpg|image2=STS-3 launch.jpg|caption1=The external tank was painted white for the first two Space Shuttle launches.|caption2=From [[STS-3]] on, it was left unpainted.}}
The ET was the largest element of the Space Shuttle, and when loaded, it was also the heaviest. It consisted of three major components:
* the forward liquid oxygen (LOX) tank
* an unpressurized intertank that contains most of the electrical components
* the aft liquid [[hydrogen]] (LH<sub>2</sub>) tank; this was the largest part, but it was relatively light, due to liquid hydrogen's very low density.

The ET was the "backbone" of the shuttle during launch, providing structural support for attachment with the [[Space Shuttle Solid Rocket Booster]]s (SRBs) and orbiter. The tank was connected to each SRB at one forward attachment point (using a crossbeam through the intertank) and one aft bracket, and it was connected to the orbiter at one forward attachment bipod and two aft bipods. In the aft attachment area, there were also [[Umbilical cable|umbilicals]] that carried [[fluid]]s, [[gas]]es, [[electric]]al signals and electrical power between the tank and the orbiter. Electrical signals and controls between the orbiter and the two solid rocket boosters were also routed through those umbilicals.

Although the external tanks were always discarded, it may have been possible to re-use them in orbit.<ref name="etuse">{{cite web |title=STS External Tank Station |url=http://www.astronautix.com/craft/stsation.htm |url-status=dead |archive-url=https://web.archive.org/web/20150407010201/http://www.astronautix.com/craft/stsation.htm |archive-date=April 7, 2015 |access-date=January 7, 2015}} astronautix.com (NASA Report, ''Utilization of the external tanks of the space transportation system'' [https://web.archive.org/web/20100513080246/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940004970_1994004970.pdf])</ref> Plans for re-use ranged from incorporation into a space station as extra living or research space, as rocket fuel tanks for interplanetary missions (e.g. Mars), to raw materials for orbiting factories.<ref name=etuse/>

Another concept was to use the ET as a cargo carrier for bulky payloads.<ref name=vlst/> One proposal was for the primary mirror of a 7-meter aperture telescope to be carried with the tank.<ref name=vlst>
{{cite web
|url= http://optics.nasa.gov/concept/vlst.html 
|title= The Very Large Space Telescope (VLST)
|archive-url= https://web.archive.org/web/20130512174258/http://optics.nasa.gov/concept/vlst.html
|archive-date= May 12, 2013
|work= SOMTC - Advanced Concepts Studies
|url-status= dead
|publisher= NASA
}}</ref> Another concept was the Aft Cargo Carrier (ACC).<ref>[https://www.wired.com/wiredscience/2012/05/shuttle-with-aft-cargo-carrier-1982/ D. Portree - Space Shuttle with Aft Cargo Carrier - Beyond Apollo (wired.com)]</ref>