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A Space Shuttle External Tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to the three Space Shuttle Main Engines (SSME) in the orbiter. The ET was jettisoned just over 10 seconds after MECO (Main Engine Cut Off), where the SSMEs were shut down, and re-entered the Earth's atmosphere. Unlike the Solid Rocket Boosters, external tanks were not re-used. They broke up before impact in the Indian Ocean (or Pacific Ocean in the case of direct-insertion launch trajectories), away from shipping lanes and were not recovered.〔 〕 == Overview == The ET is the largest element of the space shuttle, and when loaded, it is also the heaviest. It consists of three major components: *the forward liquid oxygen (LOX) tank *an unpressurized intertank that contains most of the electrical components *the aft liquid hydrogen (LH2) tank; this is the largest part, but it is relatively light, due to liquid hydrogen's very low density. The ET is the "backbone" of the shuttle during launch, providing structural support for attachment with the Space Shuttle Solid Rocket Boosters (SRBs) and orbiter. The tank is connected to each SRB at one forward attachment point (using a crossbeam through the intertank) and one aft bracket, and it is connected to the orbiter at one forward attachment bipod and two aft bipods. In the aft attachment area, there are also umbilicals that carry fluids, gases, electrical signals and electrical power between the tank and the orbiter. Electrical signals and controls between the orbiter and the two solid rocket boosters also are routed through those umbilicals. Although the external tanks were always discarded, it could have been possible to re-use them in orbit.〔http://www.astronautix.com/craft/stsation.htm astronautix.com (NASA Report, ''Utilization of the external tanks of the space transportation system'' http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940004970_1994004970.pdf)〕 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.〔 Another concept was to use the ET as a cargo carrier for bulky payloads.〔 One proposal was for the primary mirror of a 7-meter aperture telescope to be carried with the tank.〔 〕 Another concept was the Aft Cargo Carrier (ACC).〔(D. Portree - Space Shuttle with Aft Cargo Carrier - Beyond Apollo (wired.com) )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Space Shuttle external tank」の詳細全文を読む スポンサード リンク
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