The US Air Force has confirmed that its X-51A Waverider cruise missile – a next-generation vehicle powered by scramjet technology – hit speeds of Mach 5 during a test run over the Pacific Ocean on Wednesday morning. According to the Air Force, the X-51A Waverider was carried by a B-52 aircraft to an altitude of 50,000 feet, and launched somewhere off the southern California coast.
The X-51A Waverider reportedly sustained a Mach 5 speed for approximately 200 seconds, before "a vehicle anomaly occurred and the flight was terminated." Still, the 200 seconds at Mach 5 was enough to beat the previous scramjet record of 12 seconds. In an interview with the Associated Press, Charlie Brink, an X-51A program manager at the Air Force Research Laboratory, called the flight historic.
"We are ecstatic to have accomplished many of the X-51A test points during its first hypersonic mission," Brink said. "We equate this leap in engine technology as equivalent to the post-World War II jump from propeller-driven aircraft to jet engines." A USAF source interviewed by Wired magazine agreed, noting "some hitches at the end of flight," but calling the Waverider test "a magnificent first flight."
Pratt and Whitney, which designed the scramjet engine on the Waverider described the launch from the B-52 thusly:
A solid rocket booster fired and propelled the cruiser to greater than Mach 4.5, creating the supersonic environment necessary to operate the engine. The booster was then jettisoned and the Pratt & Whitney Rocketdyne SJY61 scramjet engine ignited, initially on gaseous ethylene fuel. Next the engine transitioned to JP-7 jet fuel, the same fuel once carried by the SR-71 Blackbird before its retirement.
The X-51A program is the product of a partnership between the USAF, Pratt and Whitney, the Defense Advanced Research Projects Agency (DARPA), NASA, and the Boeing Company. According to Pratt and Whitney, the scramjet technology on the X-51A could be used in a range of scenarios, including defense and space flight.
[Editor's note: The original version of this story misstated the speed of the missile. X-51A hit Mach 5 for 200 seconds.]