GUY NORRIS / INDIANAPOLIS
New engine set to power X-43C flight demonstrator to speeds above Mach 5 by 2007
The US Air Force and Pratt & Whitney are starting tests this week on the first flight-weight, hydrocarbon-fuelled, supersonic-combustion ramjet (scramjet) engine at engineering services company GASL's test site in Ronkonkoma, New York.
Tests of the ground demonstrator engine (GDE) will pave the way for follow-on GDE 2 tests late next year and for flight-worthy engines that will power the NASA/US Air Force X-43C hypersonic propulsion technology demonstrator to speeds above Mach 5 by early 2007.
"We'll be starting from where we left off with the PTE [performance test engine]," says P&W GDE manager of flowpath and systems analysis Stephen Beckel. The 900kg (1,980lb) PTE, which first ran in 2000, was made from heavy heat-absorbent copper. The GDE weighs less than 90kg and is made of Inconel, a nickel-based alloy. "That's the advantage of using fuel as a coolant," adds Beckel.
He says a full-scale flow-path cooling system employs the engine's own JP7 fuel as a heat sink. The heating process also "cracks" the JP7's longer molecular structure into a shorter, more easily combusted fuel. The PTE, by contrast, used pre-treated fuel produced off-engine in a specially-developed fuel reactor.
Tests will start at M4.5 followed by runs up to M6.5 in the GASL chamber, with 12 tests planned, says Curtis Berger, programme manager for the X-43C, HySET (hydrocarbon scramjet engine technology) effort. The GDE test will evaluate the thermo-mechanical aspects of the engine, the various aerodynamic and thermal tests having been run through on the PTE and in subcomponent trials.
"This is the first time on one engine we've been able to put it all together," says Beckel, adding that the M4.5 condition will test the GDE's behaviour under high pressure, as it represents the greatest g-loading during the acceleration of the vehicle. The M6.5 condition will test operability under the highest temperatures.
Preliminary design review of the GDE 2 engine will be held next month, with tests expected to begin in the fourth quarter of next year. GDE 2 will add a complete engine fuel system, with valves and electronic controls, as well as a variable geometry flowpath.
The fixed geometry GDE 1 uses a simpler compression surface for the inlet. NASA plans M5-7 windtunnel evaluations of a 75%-scale model of the X-43C at Langley Research Center, Virginia. A full-scale, three-module flight clearance engine will be assembled in 2005.
Source: Flight International