EDWARDS AIR FORCE BASE, Calif. - NASA's supersonic surfboard, the unmanned X-43A aircraft, streaked into history yesterday, setting an unofficial world speed record for jet aircraft of Mach 9.6, about 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 about 5:30 p.m.
A Pegasus rocket booster accelerated the X-43A - rectangular, 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, at a news conference that quickly 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 the country in minutes and send passengers into space far more cheaply than today.
"What NASA does is open doors," said Griff Corpening, the senior adviser 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 such 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, five times the speed of sound. Mach 1 is about 750 mph at sea level and less at higher altitudes, 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.
Compared with rocket-powered vehicles such as the space shuttle, scramjet vehicles promise more airplane-like operations to improve safety and keep costs down on future hypersonic flights either in or below orbit.
To cope with the extreme heat at hypersonic velocities, the X-43A has a tungsten nose with carbon-carbon leading edges. At Mach 10, temperatures reach 3,700 degrees Fahrenheit.
The top of the vehicle is as flat as a bowling alley. The scramjet engine, essentially a copper box, is suspended from the underside of the plane.
During its 10-second engine burn yesterday, the X-43A traveled nearly two miles a second. At that speed, a trip to New York from Los Angeles would take about 20 minutes.
There remain a number of hurdles, however, before scramjets could be introduced to commercial flight. The primary one is that the engine won't work at speeds less than Mach 4.
One answer might be to include more conventional engines on board to lift the plane off the ground. Another solution would be to attach it to a rocket, though that would require future passengers to become comfortable with the chin-stretching forces of rocket takeoffs. In the near term, scramjets are more likely to be used on bunker-busting type missiles.
Asked whether scramjets could be used for commercial transportation, X-43A project manager Joel Sitz, said: "Absolutely." But he added, "Who knows when it will be?"
Until this year, the speed record for a jet aircraft was 2,100 mph, about Mach 3, established by the SR-71 spy plane.
The first X-43A test in 2001 was a failure when the craft went out of control.
The Los Angeles Times is a Tribune Publishing newspaper.
