Weather permitting, the unmanned X-51A is to be taken aloft from Edwards Air Force Base, Calif., under the wing of a B-52 aircraft before being released off the California coast at approximately 50,000 feet. A solid rocket booster is to accelerate the X-51A to about Mach 4.5, the minimum speed at which the air-breathing scramjet engine operates.
The booster then will fall away and the scramjet is to kick in, accelerating the aircraft to at least Mach 6 — six times the speed of sound — for an approximately five-minute flight, reaching almost 70,000 feet, before crashing into the ocean. There are no plans to recover the X-51A, one of four test versions built for flight testing.
“In those 300 seconds, we hope to learn more about hypersonic flight with a practical scramjet engine than all previous test flights combined,” said Charlie Brink, X-51A program manager with the AFRL’s propulsion directorate at Wright-Patterson.