U.S. Air Force Set To Begin X-51 Hypersonic Flight Tests
The maiden flight of the X-51 Waverider aircraft â€” the first U.S. hypersonic vehicle to fly in six years â€” is scheduled to take place later in March. Boeing Defense, Space & Security Systems of St. Louis has been developing the aircraft since 2003 on behalf of the Air Force Research Laboratory and Defense Advanced Research Projects Agency.
The missile-shaped X-51 will be carried aloft under the wing of a B-52 bomber, Joe Vogel, Boeingâ€™s director of hypersonics, said in a Feb. 22 interview. It will be released from the jet over the Pacific Ocean and drop for four seconds until its rocket motor ignites and accelerates it to about 5,800 kilometers per hour, just shy of the widely accepted start of hypersonic flight at Mach 5, or about 6,100 kilometers per hour. At that point, its air-breathing scramjet â€” or supersonic combustion ramjet â€” engine, built by Pratt & Whitney Rocketdyne of Canoga Park, Calif., will kick in, shooting the craft to Mach 6, or more than 7,400 kilometers per hour.
Grand plans for hypersonic vehicles have been around for decades, but their goals were often unrealistic and not matched by budgets, resulting in failure. The approach on X-51 has been to demonstrate the technologies that could one day enable things like single-stage-to-orbit vehicles.
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