The aspiration that jets may some day fly at over six-times the speed of sound took a very real step toward reality recently as the US Air Force said it successfully married the test aircraft, known as the X-51A WaveRider to a B-52 in preparation for a Dec. 2 flight test.
The X-51A flight tests are intended to demonstrate the engines can achieve their desired speed without disintegrating. While the X-51 looks like a large rocket now, its applications could change the way aircraft or spaceships are designed, fly into space, support reconnaissance missions and handle long-distance flight operations.
At the heart of the test is the aircraft's air-breathing hypersonic scramjet system.
During the test, the B-52 will carry the X-51A to 50,000 feet over the Pacific Ocean and release it. A solid rocket booster on the X-51 will then ignite and accelerate the X-51 to about Mach 4.5. Then the fun starts. That's because after that, the supersonic combustion scramjet will blast the vehicle for five minutes to more than Mach 6. The longest-ever previous scramjet test, lasted only about 10 seconds, the Air Force stated.
Hypersonic combustion generates intense heat and routing of the engine's own JP-7 fuel will help keep the engine at the desired operating temperature, the Air Force stated. As the scramjet engine ignites it will initially burn a mix of ethylene and JP-7 jet fuel before switching exclusively to JP-7. Once the test is over the X-51 will splash into the Pacific.
The X-51 test vehicle is now back at the Boeing facility in Palmdale where additional systems integration and testing are taking place in preparation for its inaugural flight test, the Air Force stated. There are four planned test flights of the X-51.
The X-51A WaveRider program is a joint effort by the Air Force, Defense Advanced Research Projects Agency (DARPA), Pratt & Whitney Rocketdyne, and Boeing.
The X-51 ISN'T the only hypersonic research going on. Until it was cancelled earlier this year, DARPA was working on the Blackswift reusable hypersonic aircraft . The Blackswift was to take off on its own, climb and acceleratE to a Mach 6+ cruise speed, sustain this Mach 6+ cruise speed in level flight for at least 60 seconds, and demonstrate maneuverability by executing an aileron roll and land under its own power.
Last year NASA and the Air Force said it would be offering up to $35 million to help fund research that could ultimately develop aircraft that can fly at over five-times the speed of sound or faster. Such hypersonic aircraft face myriad trajectory control, propulsion and heat-related issues akin to what a spacecraft would endure, experts say.
The joint announcement said: "Hypersonic aerodynamics research is critical to the Air Force's interest in long-range and space operations. The size and weight of a hypersonic vehicle, and thus its flight trajectory and required propulsion system, are largely determined by aerothermodynamic considerations. Research areas of interest emphasize the characterization, prediction and control of high-speed fluid dynamic phenomena including boundary layer transition, shock/boundary layer, and shock/shock interactions, and other phenomena associated with airframe-propulsion integration. High-temperature gas kinetics, aerothermodynamics and interactions between the hypersonic flow and thermal protection system materials are of particular interest."
Specifically, NASA's Aeronautics Research Mission Directorate in Washington and the Air Force Research Laboratory's Office of Science Research at Wright-Patterson Air Force Base in Dayton, Ohio, said they would establish three national hypersonic science centers. NASA and the Air Force said they plan to set aside as much as $30 million to fund the centers over five years.
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