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}} A Graphite-Epoxy Motor (GEM) is a solid-fuel rocket motor (SRM) produced by Orbital ATK (Formerly Alliant Techsystems) with an epoxy composite casing. GEM boosters have been used on the Delta II, Delta III, and Delta IV, and are planned for future use on the Atlas V and Vulcan. ==Variants== ; GEM-40 :The GEM-40 is a SRM used on Delta II beginning in 1990. The use of composite materials allowed for booster casings several times lighter than the steel casings of the Castor 4 SRMs they replaced.〔(【引用サイトリンク】url=http://mars.jpl.nasa.gov/mer/mission/launch_srm.html )〕 The first flight of a GEM-40 occurred in 1990 on a Delta II 7925.〔(【引用サイトリンク】url=http://www.astronautix.com/engines/gem40.htm )〕 Delta II vehicles can use three, four, or nine GEM-40s. When using three or four boosters, all GEM-40s ignite on the ground, while on Delta IIs using nine boosters six are ignited on the ground, and the remaining three are ignited in the air when the first six burn out.〔(【引用サイトリンク】url=http://www.ltas-vis.ulg.ac.be/cmsms/uploads/File/DataSheetSolidATK.pdf )〕 ; GEM-46 :The GEM-46 was a lengthened solid motor originally developed for Delta III. This solid motor variant also included thrust vector control (TVC) to help steer the vehicle. After the discontinuation of the Delta III, GEM-46 motors (without TVC)〔 were used on the Delta II to create the Delta II Heavy, which could only be launched from a modified pad at Cape Canaveral.〔(【引用サイトリンク】url=http://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/ )〕 Both Delta III and Delta II-Heavy used nine GEM-46s, with six ignited on the ground and three air-lit.〔(【引用サイトリンク】url=http://www.spaceflight101.com/delta-ii-7920h-10.html )〕〔(【引用サイトリンク】url=http://www.spacelaunchreport.com/delta3.html )〕 ; GEM-60 :The GEM-60 is a solid motor used on the Delta IV family of launch vehicles. These motors are available with and without TVC.〔 A Delta IV can use two or four GEM-60s, and is classified as a Delta IV Medium+ launch vehicle.〔(【引用サイトリンク】url=http://www.spaceflight101.com/delta-iv-medium-42.html )〕 ; GEM-63 :The GEM-63 is being developed as a drop-in replacement for the Aerojet Rocketdyne AJ-60A booster used on the Atlas V. An extended GEM-63, the GEM-63XL, is planned for use on the Vulcan launch vehicle.〔(【引用サイトリンク】url=http://spaceflightnow.com/2015/09/22/orbital-atk-beats-out-aerojet-in-ula-booster-selection/ )〕 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「Graphite-Epoxy Motor」の詳細全文を読む スポンサード リンク
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