Pratt & Whitney Rocketdyne’s X-1 supersonic-combustion ramjet engine for the X-51A hypersonic demonstrator has made its first simulated flight at Mach 5, in a windtunnel at NASA Langley Research Center in Virginia.

The X-1 hydrocarbon-fuelled scamjet is under development to power the Boeing-designed X-51A, which is planned to fly at speeds ranging from M4.5 to M6.5 over four test flights beginning in 2009.

Engine performance exceeded predictions, says Mike McKeon, PWR’s manager of hypersonics and advanced programmes, describing the test as “a major step toward bringing hypersonic flight into practical use”.

A US Air Force Laboratory programme involving the US Defense Advanced Research Projects Agency and NASA, the X-51A is intended to demonstrate scramjet technology for future hypersonic missiles.


The engine tested in NASA Langley’s high-temperature tunnel from December to April, designated SJX61-1, is the first of two ground-test engines featuring flight hardware, including full-authority digital engine control.

The X-1 has closed-loop thermal management system in which the JP-7 fuel is routed around the engine to cool the hardware before being injected into the combustor, where it mixes with supersonic airflow and burns.

This contrasts with the hydrogen-fuelled scramjet that powered NASA’s X-43A at M9.6 in 2004. That engine, also P&W-designed, was uncooled and melted from the heat generated by its brief supersonic combustion and hypersonic flight.