The X-51A WaveRider is one step closer to its inaugural test flight later this year, now that airmen at Edwards Air Force Base have successfully "mated" the scramjet-propelled vehicle to a B-52 Stratofortress.
In December, an Air Force Flight Test Center B-52 is scheduled to papoose the X-51A to 50,000 feet over the Pacific Ocean before cutting it loose. At that point, a solid rocket booster from an ATACMS missile will fire up, accelerating the X-51 to about Mach 4.5. That's when the supersonic combustion ramjet kicks in, pushing the WaveRider to more than Mach 6 for up to five minutes, longer than all of its predecessors combined. NASA tests have reached Mach 9.6, or nearly 7,000 mph, according to some reports, but not for very long. The previous record was less than 10 seconds. Flight data will be telemetered back to Edwards Force Base before the X-51A test vehicle crashes into the Pacific.
A scramjet is an air-breathing engine that burns regular jet fuel, and may be the key to allowing airplanes to travel at speeds normally reserved for rockets. The engine requires no onboard oxidizers, but rather uses its own forward motion to compress air for fuel combustion. The X-51's chiseled nose allows it to "ride" shock waves that would pulverize a lesser craft. The X-51 was developed by Boeing and Pratt & Whitney Rocketdyne for the U.S. Air Force Research Laboratory and DARPA in order to "demonstrate a reliable system capable of operating continuously on jet fuel and accelerating through multiple Mach numbers."
"The heart of this aircraft is its engine," said Charlie Brink, X-51 program manager at Wright-Patterson Air Force Base.
"We're really breaking new ground in our understanding of hypersonic propulsion, but our four planned test flights will also enhance our knowledge of airframe-engine integration, high-temperature materials and other technologies. Together they will help us bridge air and space."
Future applications for the scramjet include access-to-space, reconnaissance and speedy, global strike capability.