US engine maker Pratt & Whitney says that Mach 4.5 ground testing on the world's first flight-weight, hydrocarbon-fueled, scramjet engine is complete and that ground testing at Mach 6.5 is expected to be finished by the end of this month.

This engine, known as the Ground Demonstration Engine (GDE-1), uses standard JP-7 fuel in an 'endothermic/regeneratively cooled cycle' during which the fuel cools the interior walls of the engine before being introduced to the combustion chamber to produce thrust.


The engine injects, mixes and burns the fuel to create thrust in a time span of less than 0.001 seconds.

Successful ground testing of GDE-1 represents a significant milestone for P&W Space Propulsion, which is teamed with USAF researchers under the Hypersonic Technology (HyTech) programme. GDE-1 testing followed the team's outstanding results on the Performance Test Engine (PTE) that completed testing in 2001.

"GDE-1 testing is a huge step toward flight-testing, which is an essential next step to the evolution of this technology," explains Larry Knauer, president of P&W Space Propulsion & Russian Operations.

"We are on track for this programme to change the aerospace industry forever, as this technology will create a paradigm shift in the way we employ propulsion for access-to-space and global-reach applications."

The GDE-1 engine, which weighs less than 150lb (68kg), produced net positive thrust during 45 runs at Mach 4.5 and 12 runs at Mach 6.5 between September 2002 and June 2003.

"The initial phase of this programme is intended to evaluate engine operation and structural/thermal margins at Mach 4.5 and 6.5," Knauer says.

"Engine testing is proceeding as planned, and the simulation and resultant engine performance is comparable to - or better - than our previous PTE. Our fuel-cooling flow rates are matched to combustor flow requirements and metal temperatures and fuel temperatures match predictions."

The next unit in this successful series of ground demonstration engines will be denoted GDE-2. It will also be fuel-cooled, with a flight weight similar to the GDE-1.


However, GDE-2 will feature a fully integrated fuel-system that will introduce control hardware and software, allowing the engine to run as a complete closed-loop system. GDE-2 will also incorporate a full authority digital engine controller (FADEC) to orchestrate the complex fuel controls and transitions.

"We expect the first full-up GDE-2 to be testing in 2004," says Knauer, "and we have a derivative of GDE-2 scheduled for flight test in 2006/07."

To develop the GDE design, the HySET team used a building-block approach that began with computational fluid dynamic codes.

The world-class hypersonic codes define combustion products while optimising the fueling locations and concentrations required. Computational results are used to refine engine lines, allowing optimisation of the engine design prior to test.


Near-term applications for the HyTech technology include a fast-reaction, long-range air-to-surface missile with a Mach 6.5-plus cruise capability to fly hundreds of nautical miles in minutes.

Such missiles could be carried on fighter and bomber aircraft in USAF inventory and on US navy aircraft, ships and submarines.

The long-term vision for the scramjet engines include power for launch vehicles that can substantially reduce the cost of access to space, along with military and commercial aircraft that can span the globe in less than a few hours.

The USAF established the HyTech Program in 1995 to maintain aggressive technology development in hypersonics after the National Aero-Space Plane's development was terminated. In 1996, P&W won a $48-million contract for HySET.

As a result of the programme's success, the X43-C (a joint USAF/NASA programme) has emerged, the goal being to flight test a derivative of the HySET engine in 2007.

Source: Flight Daily News