First flight of the X-51A scramjet demonstrator is now on track for early December while captive carriage tests on the NASA-operated B-52H mothership at Edwards Air Force Base, Calif., are set to begin in October.(via Aviation Week)
A joint effort by the U.S. Air Force, Defense Advanced Research Projects Agency (DARPA), Pratt & Whitney Rocketdyne, and Boeing, the hypersonic vehicle is designed to be the first air-breathing craft to demonstrate sustained speeds in excess of Mach 4 using a “logistically friendly” hydrocarbon fuel.
Needs a boost from a rocket stage to get going, way too slow to achieve low Earth orbit, and probably going to be used for long-range cruise missiles or something equally gung-ho but it's a start . . .