HAMPTON, Va. -- They call it a "scramjet," an engine so blindingly fast that it could carry an airplane from San Francisco to Washington, D.C., in about 20 minutes -- or even quicker. So fast it could put satellites in space. So fast it could drop a cruise missile on an enemy target, almost like shooting a rifle.
Next week, NASA plans to break the aircraft speed record for the second time in 7 1/2 months by flying its rocket-assisted X-43A scramjet craft 110,000 feet above the Pacific Ocean at speeds close to Mach 10 -- about 7,200 mph, or 10 times the speed of sound.
NASA hopes to break the aircraft speed record again with its 12-foot-long X-43A.
How the Scramjet Works: Supersonic air compression in the Scramjet engine boosts thrust exponentially over conventional jet engines.
The flight will last perhaps 10 seconds and end with the pilotless aircraft plunging to a watery grave 850 miles off the California coast. But even if the X-43A doesn't set the record, it has already proved that the 40-year-old dream of "hypersonic" flight -- using air-breathing engines to reach speeds above Mach 5 (3,800 mph) -- has become reality.
Unlike rockets, which must carry oxygen with them as a "combustor" to ignite the fuel supply, scramjets take oxygen from the atmosphere, offering a huge savings in aircraft weight, and researchers around the world would like to take advantage.
In northeast Australia, a scramjet team funded by the U.S. and Australian armed forces will try for Mach 10 next year as a first step in using a scramjet to put satellites in space. The U.S. Air Force hopes to demonstrate within five years a scramjet-driven cruise missile fast enough to drive explosives deep into hardened targets. Other projects are moving forward in France and Japan.
Under NASA's $250 million Hyper-X program, engineers at Langley Research Center here and the Dryden Flight Research Center in Edwards, Calif., designed and built three aluminum scramjet aircraft, each one 12 feet long and weighing about 2,800 pounds . Controllers aborted the first test flight in 2001 after the rocket booster malfunctioned.
But the second, on March 24, reached Mach 6.83 (5,200 mph), shattering the world speed record for air-breathing, non-rocket aircraft, previously held by a jet-powered missile. The highest speeds by manned aircraft were achieved by SR-71, the U.S. spy plane known as the "Blackbird," capable of flying in excess of Mach 3 (2,300 mph).
"The idea was to demonstrate these technologies," said Luat T. Nguyen, deputy manager for the program that designed X-43A. "We've done that. This is the first scramjet to work, and it is the only one at this point."
Next week's third flight will test the limits of the X-43A. Temperatures will be significantly higher: The leading edge of the aircraft's nose will reach about 3,700 degrees Fahrenheit, 1,600 degrees hotter than during the March flight.
Also, Nguyen added, "it's more of a challenge to get it to operate at Mach 10 rather than Mach 7. You want it to be robust enough to give us the level of performance we're looking for, and at Mach 10, the constraints are a little narrower."
Regardless of the outcome, however, the third flight will be the last. The Hyper-X program ends, and there are no plans to replace it. The next steps are largely up to researchers elsewhere.
"What they have done is lay the foundation on how to go further," Allan Paull, of Australia's University of Queensland, the leader of the U.S.-Australia "HyShot" scramjet project, said of NASA. "We live in a society of high tech that's built over time. We went from the horse and cart to scramjets in 200 years."
Barring mechanical glitches or bad weather, the X-43A and its Pegasus rocket booster will leave Dryden between 9:30 a.m. and 2 p.m. Pacific time, slung below the belly of a B-52B launch aircraft.
About 50 miles off the California coast, the B-52 will drop the craft at an altitude of 40,000 feet. The booster rocket will ignite and bring the X-43A's speed close to Mach 10 at an altitude of 110,000 feet. At that point, controllers will fire two small pistons to jettison the rocket. Then they will open the cowl covering the X-43A's air intake and light the engine.