U.S. Department of Defense Aircraft Breaks Hypersonic Flight Record

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WASHINGTON — The U.S. Defense Department’s newest hypersonic aircraft completed its first flight test May 26, flying at five times the speed of sound for a longer period than any previous vehicle of its type, the Air Force announced May 26.

The missile-shaped X-51A Waverider aircraft flew under the power of its supersonic combustion ramjet (scramjet) engine for more than 200 seconds while flying at Mach 5, or roughly 6,100 kilometers per hour, according to the Air Force press release.

Boeing Defense, Space & Security Systems of St. Louis began developing the aircraft in 2003 on behalf of the Air Force Research Laboratory and Defense Advanced Research Projects Agency. Boeing built a total of four X-51 aircraft.

“We are ecstatic to have accomplished most of our test points on the X-51A’s very first hypersonic mission,” Charlie Brink, the Air Force’s X-51 program manager, said in a May 26 press release. “We equate this leap in engine technology to the post-World War II jump from propeller-driven aircraft to jet engines.”

Though previous scramjet-powered aircraft have flown faster, those flights have been far shorter in duration: NASA’s X-43A demonstrator in 2004 conducted an 11-second flight that reached Mach 7 and a 10-second flight that approached Mach 10 and set the world record for fastest jet-powered flight. Boeing also built the X-43A craft.

Scramjet engines like those on the X-43A and X-51 must be accelerated to very high speeds to deliver compressed air to their combustion chambers. Both craft rely on rocket propulsion to create this initial speed.

For the first flight test, the X-51A was carried under the wing of a B-52 Stratofortress jet aircraft that took off from Edwards Air Force Base, Calif., the release said. Flying at 15,000 meters above the Pacific Ocean, the X-51A was released from its carrier aircraft and dropped for four seconds before its solid-rocket booster ignited and powered the craft to more than 5,800 kilometers per hour. The rocket booster was then jettisoned, and the craft’s air-breathing scramjet engine took over.

The SJY61 scramjet engine, built by Pratt & Whitney Rocketdyne of Canoga Park, Calif., was ignited first with a mix of ethylene and JP-7 jet fuel and then powered by JP-7 alone, the same fuel that has powered supersonic aircraft such as the SR-71 Blackbird. The X-51A reached an altitude of 21,000 meters and flew for more than 200 seconds, the release said.

The scramjet-powered flight was intended to last about 300 seconds, but a vehicle anomaly occurred and the test was terminated, the press release said.

Onboard sensors transmitted terabytes of data from the X-51A to a trailing U.S. Navy P-3 aircraft as well as ground stations at Point Mugu Naval Air Station, Vandenberg Air Force Base and Edwards Air Force Base, all in California, according to a May 26 Boeing press release. The next three flight tests will be scheduled after all recorded data are reviewed, it said.

“This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation,” Joe Vogel, Boeing’s director of hypersonics, said in the release.

Since 2003 the government has spent about $250 million on the X-51 program, Boeing said recently.