Kerosene-fuelled engine now due for static tests under simulated hypersonic conditions

A "flight-weight" supersonic combustion ramjet (scramjet) has passed inspection by Pratt & Whitney, and will be transported to a supersonic/hypersonic blowdown test complex operated by GASL in Ronkonkoma, New York, for thermal and structural validation tests early this month.

The P&W/US Air Force-developed ground demonstration engine (GDE-1) is expected to form the basis for a follow-on GDE-2 engine which is likely to be tested early next year. NASA says a derivative of the GDE-2 is being considered as an option to power the USAF/NASA X-43C hypersonic demonstrator in 2005. Baseline technology for the GDE has been developed under a three-phase, six- year USAF-sponsored hydrocarbon scramjet engine technology (HySET) effort which aims to develop and demonstrate a Mach 4-8 hydrocarbon-fuelled scramjet. The original aim included an engine for a hypersonic missile, but the concept is now being steered towards vehicle propulsion.

GDE uses liquid hydrocarbon fuel instead of the hydrogen fuel used in previous scramjet studies. The liquid fuel is logistically more supportable and the design of the engine is adapted to use the fuel as a coolant as well as a propellant. Fuel runs through a honeycomb of passageways and, as it cools the engine, the larger JP-7 fuel molecules are "cracked" into shorter, lighter hydrocarbon molecules that burn more easily.

P&W has also completed critical design reviews of major engine elements, including hot-gas valves and fuel pumps designed to operate at extremely high temperatures and pressures. These will form essential units of the fuel system which, in the case of the GDE-1, will not be fully integrated with the engine itself.

GDE-1 will be a complete flow-path, fuel-cooled, flight-weight engine weighing less than 90kg (200lb). The design of the fuel system elements is "geared towards a flight-worthy design", says HySET programme manager Curtis Berger.

GDE-1 is being assembled for P&W by Connecticut-basedDynamic Gunver Technologies, which also built its predecessor, the uncooled performance test engine, the first hydrocarbon-fuelled scramjet to run under operational conditions.

Source: Flight International