X-43A SET TO FLY SATURDAY CRAFT AIMS FOR 7 TIMES SPEED OF SOUND.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - More than two years after its first attempt ended in failure, NASA plans Saturday to fly a tiny unmanned aircraft designed to top 4,900 mph.

In a $230 million effort aimed at giving researchers information for future space launch vehicles and for ultra-high-speed military and civilian aircraft, the wingless, wedge-shape X-43A is headed for the sky after the first was destroyed in 2001 after a booster rocket malfunction.

``What we are talking about is an aviation first,'' said Vincent Rausch, Hyper-X program manager at the National Aeronautics and Space Agency's Langley Research Center in Virginia. ``This is the first time we will have flown an aircraft with an air-breathing engine at seven times the speed of sound.''

Powered by an experimental, extremely high-speed engine called a scramjet, the 12-foot-long X-43A will be attached to a Pegasus booster rocket and taken aloft by a modified B-52 bomber, then let go over the Pacific Ocean.

The goal of scramjet power is to create an ultra-high-speed craft whose engine would get its oxygen for combustion from the atmosphere, rather than carrying the extra weight of its own oxygen as a rocket must.

By not having to carry oxygen, a spacecraft could save fuel weight and carry more equipment. Released over the ocean off the California coast, the Pegasus booster rocket will take the X-43A to an altitude of 95,000 feet and a speed of Mach 7, roughly 4,900 mph.

Once let loose from its booster, the X-43A will fire its scramjet engine for about 10 seconds.

Although the engine runs just seconds, the data from it will help NASA researchers validate wind-tunnel tests and other analyses on hypersonic flight.

Research on the ground has provided great progress on hypersonic travel over the past six years, but Saturday's mission will let researchers ``get the truth from flight,'' said Joel Sitz, NASA Dryden Flight Research Center's X-43 program manager.

``The 10 seconds of data will tell you whether or not the last six years of trying are successful,'' Sitz said.

After its 10 seconds of firing, the X-43A's engine will shut down, and the craft will perform a set of preprogrammed maneuvers before it crashes into the ocean.

The craft won't be recovered. Other versions will be used for further test flights.

NASA is spending $230 million to build and flight-test three aircraft, including the one that was destroyed.

The first X-43 aircraft had to be blown up in June 2001 over the ocean by a self-destruction mechanism when the Pegasus booster rocket carrying it went out of control after its fins came off.

A number of factors apparently contributed to the failure, including the B-52 dropping the rocket at a 23,000-foot altitude, where the atmosphere is much denser than the 40,000 feet at which Pegasus rockets are launched when they go into space.

During the first mission, the focus had been on the X-43A vehicle itself, not on the proven booster rocket to which it was attached, officials said. This time there has been greater attention to what NASA refers to as ``the stack'' - the X-43A craft, the Pegasus booster, and the adapter that connects them.

The stack itself has been thought of as a new vehicle rather than just the X-43A, Sitz said.

For the resumed tests, the booster's fin actuator system was beefed up, and the rocket will be let go by the B-52 at a higher altitude.

Flights of two more X-43A aircraft are planned, with top speeds to reach Mach 10, about 7,000 mph.

The X-43 is NASA's first test program dedicated to hypersonic research since the last X-15 rocket plane flight at Edwards Air Force Base in 1969. The X-15's fastest flight was Mach 6.7, or about 4,520 mph, with W.J. ``Pete'' Knight - now the Antelope Valley's state senator - at the controls.

Plans for follow-on versions of the X-43A have been canceled by NASA as the result of President George W. Bush's new space initiative to return men to the moon. However, both the Air Force and NASA are planning to continue their hypersonic research.

NASA is in the process of developing a long-term hypersonic research program, Rausch said. The Air Force is interested in ultra-fast aircraft that could reach any spot in the world within a couple of hours.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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The unmanned X-43A, shown at Edwards Air Force Base in this file photo in April 2001, is set for a test flight Saturday.

Jeff Goldwater/Staff Photographer