Today, X-51A Waverider successfully did a 200+ second burn which was the longest-ever supersonic combustion ramjet-powered flight at Mach 5 (five times the speed of sound – rougly – 4,000 mph or 6,400 km/h at altitude). The 200+ second burn by the X-51’s Pratt & Whitney Rocketdyne-built air breathing scramjet engine accelerated the vehicle to Mach 5. The previous longest scramjet burn in a flight test was 12 seconds in a NASA X-43.

The X-51A was carried to about 49,500ft under the wing of a Boeing B-52H before release. Four seconds later an Army Tactical Missile solid rocket booster accelerated the X-51 to about M4.8 before it and a connecting interstage were jettisoned.


Air Force Research Laboratory X-51A programme manager Charlie Brink says preliminary data shows that the separation from the B-52H was “phenomenal” and the solid booster light was “perfect”. At 65,000ft the booster separated from the vehicle as planned, followed by the start of the scramjet engine with an ethylene mix and switchover to JP-7 fuel.

While the programme had a goal for a 300s flight to M6, Brink says that at roughly 140s of powered flight, engineers “started noticing some anomalies with some sensors”. The engine continued to run, but the telemetry stream to the ground was interrupted, requiring controllers to activate the self-destruct function.

Despite the shorter flight, the team was exhilarated over the results. “Up until 140s, everything was working textbook, per calculations”, says Joe Vogel, Boeing’s X-51A programme manager.



One specific application is in missiles and the other might be in space travel where we need faster space ships to reach further areas of the universe.

Kudos to the team!