A cikin 1990s, Air Force Research Laboratory (AFRL) ya fara shirin HyTECH don propulsion hypersonic. Pratt & Whitney ya sami kwangila daga AFRL don haɓaka injin scramjet mai amfani da hydrocarbon wanda ya haifar da ci gaban injin SJX61. An tsara injin SJX61 ne don NASA X-43C, wanda aka soke shi a ƙarshe. An yi amfani da injin ɗin a cikin shirin Scramjet Engine Demonstrator na AFRL a ƙarshen 2003. An sanya motar gwajin jirgin scramjet X-51 a ranar 27 ga Satumba 2005. Tambaya: Menene makomar shirin jirgin sama na NASA X-43C?
an soke shi