GUY NORRIS / SALT LAKE CITY
Unlike previous versions, P&W and USAF-developed engine will use liquid hydrocarbon fuel to help logistic support
Assembly of the first of two flightworthy supersonic combustion ramjets (scramjet) to be developed under the US Air Force's Hypersonic Technology (HyTech) programme is under way with tests expected to begin early next year.
Unlike previous experimental scramjets, which have been hydrogen powered, the Pratt & Whitney/ USAF-developed engine is designed to use liquid hydrocarbon fuel to ease logistic support. The programme aims to demonstrate the operability, performance and durability of a scramjet that operates from Mach 4 to 8, and which could power low-cost space access vehicles and hypersonic missiles.
The first scramjet ground demonstrator engine (GDE-1) is being assembled for P&W by Connecticut-based Dynamic Gunver Technologies. Unlike the uncooled performance test engine (PTE) which was the forerunner to the GDE and the first hydrocarbon fuelled scramjet to run successfully under operational conditions, the GDE-1 will be representative of an airworthy engine. It will have integrated cooling passages through which fuel will be pumped.
This system is critical for scramjet operation as it cools the engine structure and converts, or "cracks", the large JP-7 fuel molecules into shorter, lighter hydrocarbon molecules that burn more easily. "A United Technologies-developed approach allows us to 'crack' the fuel. Moreover, by using this type of fuel, we take advantage of the endothermic reaction to cool the engine as well," P&W Liquid Space Propulsion hypersonic programmes manager Joaquin Castro told delegates at the Joint Propulsion conference in Salt Lake City in early July.
Tests are to begin in early 2002 at a supersonic/hypersonic blowdown test complex operated by GASL in Ronkonkoma, New York. Separate rig and bench tests of crucial elements such as flightworthy fuel pumps and hot gas valves will be conducted in parallel with GDE-1 tests. "Depending on how successful the tests on GDE-1 are, these may be put into the engine," says HySET (hypersonic scramjet engine technology) and X-43C programme manager Curtis Berger. "The main aim of GDE-1 is the mechanical thermodynamic structural validation of the design. When the valves and pumps are through bench testing, they could be used for GDE-2 risk reduction."
The "full-up" GDE-2 engine is timed for tests in 2003. A derivative of GDE-2 may be used as the powerplant for the NASA/USAF X-43C Hyper-X's hypersonic demonstrator in 2005.
Source: Flight International
