DRYDEN TO TEST X-43A JET; RESEARCHERS AIM AT TOPPING 7 TIMES SPEED OF SOUND.

Byline: Jim Skeen Staff Writer

NASA's Dryden Flight Research Center is gearing up for another X-plane program, this time to determine if it's possible to develop a jet-powered aircraft capable of flying seven to 10 times faster than the speed of sound.

At Dryden, the National Aeronautics and Space Administration is preparing for the first flight of the X-43A, also known as the Hyper-X, a 12-foot-long, unpiloted aircraft that will be attached to a modified Pegasus space booster rocket.

The ultimate goal is to create a scramjet-powered aircraft, one that would use air from the atmosphere, rather than carry oxygen like a rocket.

``We think there's a big payload advantage in this if you don't have to carry this weight in fuel,'' said Don Gatlin, deputy project manager for the X-43A.

A scramjet is a high-altitude, very-high-speed version of a ramjet, an engine that lacks traditional jets' whirling fan blades for compressing air to oxidize fuel.

In a ramjet, the fuel is continuously compressed by being rammed into the inlet by the aircraft's high velocity. In a scramjet, the airflow through the whole engine remains supersonic.

Three X-43A aircraft will be used for test flights ranging from Mach 7, which is about 5,320 mph, to Mach 10, about 7,600 mph.

In comparison, the famous X-15 research plane of the 1950s and 1960s reached a top speed of Mach 6.7, powered by a rocket engine, not a jet engine. The jet-powered SR-71 Blackbirds travel at Mach 3.

During each mission, an X-43A attached to a Pegasus booster rocket will be taken aloft from Edwards by a modified B-52. The X-43A will be dropped from the B-52 off the coast near Vandenberg Air Force Base.

The Pegasus booster will hit Mach 7 and carry the X-43A to more than 100,000 feet in about 90 seconds. From there, the X-43A will separate from the booster, and the aircraft's scramjet will fire for about five to seven seconds.

``We are going to get a lot of information in a real-world environment,'' Gatlin said.

After the engine burn, the X-43A will perform a series of preplanned aerodynamic maneuvers before it slams into the Pacific Ocean.

Two flights will be done at Mach 7 and a third will be performed at Mach 10. Each flight will range in distance from 500 to 800 miles.

The X-43A is essentially a scaled-down version of the national aerospace plane, the X-30. In the X-30 program, NASA officials hoped to design a spacecraft that could get into orbit in a single stage and take off and land from conventional runways, but the program was canceled in the early 1990s.

The forward part of the X-43A's body is designed to compress the air being fed into the engines. The rear portion of the body serves as the expansion ramp for the thrust.

Workers at Dryden are preparing a modified Pegasus booster for the first flight.

The first X-43A aircraft is expected to arrive in late September or early October.

The first of three flights in the $170 million program is scheduled for spring.

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