Mar 2009 Posts 1,772 Re: The SR-91 is real Also forgot about this one as well. X-43 Nasa has be working on is " unmanned experimental hypersonic aircraft " as well. http://en.wikipedia.org/wiki/X-43 http://en.wikipedia.org/wiki/Scramjet A scramjet ( s upersonic c ombustion ramjet ) is a variant of a ramjet airbreathing combustion jet