Too Much Thrust?

The second test flight of the Air Force’s X-51A hypersonic test vehicle was hampered by too much pressure inside the combustion chamber, said program manager Charlie Brink. Speaking at a House Aerospace Caucus lunch last week on Capitol Hill, Brink said the Air Force is conducting a “very structured systems engineering process” to rule out various potential causes why the X-51’s supersonic combustion ramjet engine failed to ignite in the June test. Contrary to reports, Brink said the X-51 “separated cleanly” from its Army Tactical Missile System booster vehicle, but what happened thereafter is still uncertain. Engineers received telemetry showing there was “too much thrust” inside the vehicle, which may have shifted the shockwave patterns necessary to achieve scramjet combustion, he said. Other potential causes may have been “an upset of the aerodynamics of our inlet,” which could have shifted the shockwaves, he told the Daily Report. It’s also possible there was a slightly incorrect attitude of the vehicle, which could have caused disruption of the shockwave. There also was possibly a fuels issue. “We could have flooded it because we turned a knob incorrectly or put too much fuel into it,” he explained.