Editing Alliant Techsystems (section)

====Graphite Epoxy Motors====
The [[Graphite-Epoxy Motor]] (GEM) is a [[solid rocket]] motor produced by ATK using [[Carbon-fiber-reinforced polymer|epoxy composite casing]]. GEMs are used as boosters for the [[Delta II]], [[Delta III]], and [[Delta IV]] [[launch vehicle]]s. The use of composite materials allows for booster casings several times lighter than the steel casings of the [[Castor (rocket stage)|Castor 4]] solid rocket motors they replaced.<ref>{{cite web|title=Launch Vehicle: Solid Rocket Motors|url=http://mars.jpl.nasa.gov/mer/mission/launch_srm.html|website=Jet Propulsion Laboratory|publisher=NASA|access-date=November 1, 2018|archive-date=May 9, 2022|archive-url=https://web.archive.org/web/20220509131137/https://mars.nasa.gov/mer/mission/launch_srm.html|url-status=dead}}</ref> The first flight of a GEM occurred in 1990 on a Delta II 7925.<ref>{{cite web|title=GEM 40|url=http://www.astronautix.com/engines/gem40.htm|website=Astronautix|url-status=dead|archive-url=https://web.archive.org/web/20170110090738/http://www.astronautix.com/engines/gem40.htm|archive-date=January 10, 2017|df=mdy-all}}</ref>