NASA TO TEST HYPERSONIC X-43A SPACE AGENCY RESUMING TRIALS ON UNMANNED CRAFT.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - NASA is gearing up to resume tests of tiny unmanned aircraft designed to fly faster than 4,900 mph - seven times the speed of sound.

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 heading back into the sky after the first one was destroyed two years ago during its first test flight.

``We're getting down to the last closeout items before flight,'' said Keith Henry, spokesman for NASA Langley Research Center in Virginia, which is co-managing the project with Dryden Flight Research Center at Edwards Air Force Base.

The flight could occur as early as Dec. 6 over the Pacific Ocean off the California coast.

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.

Released over the ocean, 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. The engine will then 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 fights.

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 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 June 2001 failure, including launching of the mission at 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.

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.

``Instead of launching at 23,000 feet as they did before, they will launch at 40,000 feet,'' Henry said. ``It's not that they can't release from 23,000 feet, it's just something we're doing to reduce the risk. The atmosphere will be less dense and the aerodynamic loads will be less.''

Flights of two 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.

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 does.

A scramjet is a high-altitude, very-high-speed version of a ramjet, an engine without 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.

By not having to carry oxygen, a spacecraft could save fuel weight and carry more equipment.

NASA and the Air Force are working on a larger X-43 that would use the scramjet engine for up to five minutes. That vehicle, dubbed the X-43B, is in early development.

A third version of the X-43, the X-43C, was conceived after the X-43B idea, but will actually fly first. The C model, envisioned as a steppingstone between the A and B models, will fly a different type of scramjet engine. The C model will be boosted to Mach 5, about 3,500 mph, and will accelerate by itself to Mach 7.

The Air Force is interested in hypersonic aircraft that would allow them to reach any hot spot in the world within a couple of hours.

``When fully developed, these advanced propulsion systems will offer increased safety, payload capacity and economy of operation for future, reusable space access vehicles,'' said Paul Moses, manager of the X-43C project. ``The X-43C project will validate advanced technologies, design tools and test techniques that will enable design of such vehicles in the future,'' he said.

NASA awarded Allied Aerospace Industries of Tullahoma, Tenn., a $150 million contract to provide three X-43C aircraft.

Allied Aerospace, Flight Systems Division, will team with Pratt & Whitney, West Palm Beach, Fla.; Boeing Phantom Works, Huntington Beach; and RJK Technologies, Blacksburg, Va. on the project.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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Photo:

An X-43A is mounted atop a Pegasus rocket at Edwards Air Force Base, where NASA is resuming tests on the tiny unmanned craft, capable of reaching speeds up to 4,500 mph - seven times the speed of sound.

Jeff Goldwater/Staff Photographer