X-51’s Achilles Seal

A breached seal forced Air Force testers to terminate the flight of the first X-51A Waverider hypersonic demonstrator vehicle last May off the coast of California before the vehicle flew its full mission profile, according to the Air Force Research Lab official overseeing this work. “We only ran for 143 seconds before we had a vehicle anomaly” causing exhaust gasses to accumulate inside the fuselage, severing the craft’s telemetry datalink and damaging avionics, said Charles Brink, USAF’s X-51 program manager. He said engineers subsequently determined that the culprit was a discrepancy between the design intent and the actual fabrication of the interface between Boeing’s air vehicle and Pratt and Whitney’s engine. The Waverider design team went back and made the interface “much more robust” on the three remaining X-51 test vehicles, said Brink. Despite the anomaly, the flight was an overwhelming success, he said. The flight of the second X-51 is scheduled to occur by month’s end.