The first flight, which took place in May of last year was aborted to overheating after 146 seconds of acceleration. The Air Force said that the X-51A achieved 80-90% of its program goals during its first flight, but did not reach the expected speed of Mach 6. Data collected during the first flight enabled engine creator Pratt & Whitney Rocketdyne as well as X-51A designer Boeing Phantom Works to modify the remaining three X-51As.
The next flight is scheduled for March 22, when the second Waverider will be dropped from a B-52 bomber airplane. The X-51A is built using materials such as aluminum, steel, inconel, carbon composites and titanium. Other than traditional (space) rockets, the engine is powered by regular JP-7 jetfuel. Scramjets are able to burn atmospheric oxygen and don't need to carry large fuel tanks containing oxidizer like conventional rockets, the Air Force said.