X-43A Aircraft Sets Speed Record at 6,500 MPH

The aircraft -- powered by an experimental engine known as a scramjet -- was carried to an altitude of 40,000 feet under the wing of a B-52 bomber and released at about 2:30 p.m.

A Pegasus rocket booster accelerated the X-43A -- a rectangular disc of metal with fins at the back -- before the scramjet on the underside of the aircraft took over, shooting the craft to its record-breaking run at 111,000 feet.

The scramjet burned for about 10 seconds, before flaming out and plunging into the Pacific Ocean about 800 miles off the California coast, officially ending the X-43A program after three flights.

"We had a phenomenal flight today. Everything went really well," said Laurie Marshall, the chief engineer for the flight, speaking at a news conference that turned into a celebration of the program's achievements.

The flight was part of a $230-million project aimed at showing the capabilities of a new breed of jet aircraft that could conceivably speed passengers across country in minutes and send passengers into space far more cheaply than today.

"What NASA does is open doors," said Griff Corpening, the senior advisor to the X-43A program at the Dryden Flight Research Center. "We've just opened the door to Mach 10 flight for jet aircraft."

The heart of the X-43A is its revolutionary scramjet -- a contraction of Supersonic Combustion Ramjet. The engine compresses air at hypersonic velocities and ignites it in a hydrogen mixture.

Most commercial aircraft today use turbines to compress air, which ignites with kerosene to create combustion and thrust. Air flows are too low to produce high speeds with those engines.

Engineers developed the ramjet decades ago to solve those problems. A ramjet is basically a hollow tube with no moving parts; air flows into the front of the ramjet, is compressed and mixed with fuel. But the ramjet cannot go faster than Mach 5, or five times the speed of sound. Mach 1 is about 680 mph, depending on atmospheric conditions.

The ramjet's limitations led to development of the scramjet, in which gases flow into the ignition chamber at supersonic speeds. The igniting substance is called Silane, which explodes in the presence of oxygen.