NASA's second X-43A hypersonic research aircraft flew successfully Saturday, the first time an air-breathing scramjet-powered aircraft has flown freely. The 12-foot-long unpiloted vehicle's scramjet -- a supersonic-combustion ramjet -- ignited and burned through its hydrogen fuel supply, which lasted about 10 seconds. The X-43A reached its test speed of Mach 7, and was ditched in the Pacific Ocean, as planned. "Today was a grand-slam in the bottom of the 12th," said Joel Sitz, NASA Dryden Flight Research Center's X-43A project manager. During NASA's first scramjet flight test, in June 2001, a rocket booster failed and the aircraft had to be destroyed. "It's been a great, record-breaking day," said Larry Huebner, of NASA's Langley Research Center. "We achieved positive acceleration of the vehicle while we were climbing, and maintained outstanding vehicle control. This was a world-record speed for air-breathing flight." The flight, originating from NASA's Dryden Flight Research Center, in Edwards, Calif., began at 12:40 p.m. PST, as NASA's B-52B launch aircraft carrying the X-43A lifted off the runway. The X-43A, mounted on a modified Pegasus booster rocket, was launched from the B-52B just before 2 p.m. The rocket boosted the X-43A up to its test altitude of about 95,000 feet over the Pacific Ocean, where the X-43A separated from the booster and flew freely for several minutes following scramjet engine operation, in order to gather aerodynamic data.
NASA's seven-year, $230 million Hyper-X program is aimed at providing unique "first-time" data on hypersonic air-breathing engine technologies. A scramjet is a ramjet engine in which the airflow through the whole engine remains supersonic. A ramjet operates by subsonic combustion of fuel in a stream of air compressed by the forward speed of the aircraft itself, as opposed to a normal jet engine, in which the compressor section (the fan blades) compresses the air. Ramjets operate from about Mach 3 to Mach 6. Scramjet technology is challenging, NASA says, because only limited testing can be performed in ground facilities. NASA plans to launch a third hypersonic plane in the fall with the goal of flying the aircraft at Mach 10, or about 6,750 mph. Meanwhile, Pratt & Whitney is continuing work on its own version of a scramjet engine together with the Air Force.