“I see that flight happening sometime late spring. early summer,” said Charlie Brink, program manager for the X-51A Waverider, during a conference call Wednesday. The majority of time spent on the call, however, was to review his team’s preliminary findings regarding the August test flight. Details about that failed flight, were not provided at the time, and it was unclear whether the fourth craft would be flown.
In the tests, both a rocket booster and a supersonic combustion ramjet — or scramjet — are attached to the X-51 cruiser. The 25-foot-long assembly, which weighs 4,000 pounds, is carried to 50,000 feet by a B-52 bomber, and released. The booster takes the cruiser from just under Mach 1 to just under Mach 5. The supersonic flight produces shockwaves, which compress the air. After the booster detaches, the compressed air, combined with jet fuel, is then ignited inside the scramjet, ideally propelling the cruiser to hypersonic speeds (any speed over Mach 5, or five times the speed of sound).
The goal of the roughly $300 million research program, is to get in-flight data of an operating scramjet to further understand the technology and its potential applications in areas such as intelligence gathering, weapons development and even space travel.
The third test flight, according to Brink, was “uneventful” during take-off and the B-52 flight. But, after its release, the craft’s upper-right fin “inexplicably” unlocked, eventually sending the craft into a very slow “corkscrew” spiral, ending with the crash. The early fin releasedid not prevent the X-51A from reaching its intended speed — just under Mach 5, according to Brink.
“For this flight, we didn’t have a propulsion experiment,” said Brink. That was because the team was unable to light the engine prior to the crash. Brink says it is likely that vibrations are what caused the fin’s locking mechanism to release. The findings, however, are still preliminary. Brink anticipates the review to be completed in December. In light of the early findings, a potential solution to the problem, he said, may be to release the fins earlier.
The next flight is scheduled to be the last for the X-51A, but according to Brink this will not be the end of hypersonic flight research.
“I believe that the Air Force is committed to continue this research,” said Brink.
Hypersonic flight is “one of those things that ... takes a paradigm shift,” he continued. It forces war planners to think in terms of being able to strike targets that are further away much faster than they otherwise would. That is assuming, of course, the technology gets to the production stage. Brink estimates the technology is still 10 to 15 years away from being used in combat, although it is being incorporated into war-fighter games. “We need to be realistic about when this technology will be ready.”
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