Mounted under a wing of NASA's B-52 launch aircraft, the X-43A and its Pegasus XL booster departed Edwards Air Force Base, California at 3:30 p.m. EDT (19:30 GMT) and flew to the altitude for the deployment of the combination of vehicles.
The drop took place at 4:44 p.m. EDT (20:44 GMT), and was successfully executed. But shortly after the Pegasus booster -- with the X-43A attached to its nose -- ignited, the combined craft went out of control.
"Some parts came off, but we can't tell what those pieces were," said Alan Brown, a spokesman for the NASA Dryden field center. "There is instrumentation onboard, so that data should tell us what took place," he told SPACE.com.
"We're a little frustrated right now," Brown said. "From all we could tell at this point, it was the Pegasus that failed. The rocket was still firing, but the Pegasus seemed to go out of control and went into wild gyrations at that point," he said.
"We had to destruct," Brown said. "We don't know where those parts came from," he said.
It is yet to be determined from what vehicle -- the modified Pegasus or the X-43A -- the parts fell off, Brown said.
"What impact this will have on the program, I don't think anybody knows at this point," Brown said.
After separation from the Pegasus, the X-43A was to have sped on its own to a blistering mach 7 (seven times the speed of sound), powered by a supersonic-combustion ramjet (known as a "scramjet") engine. Mach 7 is almost 5,000 miles (8,045 kilometers) per hour.
The experimental aircraft was then to splash down in Pacific Ocean waters. The entire free flight was to take place over a 10-minute period.
At a "postflight incident" press conference held following the failure, NASA officials said they would not speculate as to the cause of the unsuccessful flight. A board of experts is being pulled together to understand why the mishap occurred. More time will be needed to analyze both video and data sent back to the ground from the flight vehicles, the officials said.
After its midair destruction, debris from the X-43A and its booster impacted within a pre-cleared area within the Pacific Ocean off the California coast.
"This is a high risk, but a high payoff mission," said Jeremiah Creedon, director of NASA's Langley Research Center. He said that two more X-43A flights are scheduled and would provide NASA the research results it seeks in hypersonic flight.
"There is a significant amount of telemetry available," said Vincent Rausch, Hyper-X program manager at the Langley Research Center. "We're disappointed. But we'll fix it and fly again successfully," he said.
The NASA test was the first of three planned hypersonic free flights in the six-year, $185 million Hyper-X series of research aircraft. A second flight of an X-43A to mach 7 was slated for this winter and a final X-43A flight to mach 10 is set for late next year.
Technology thrust
Gulping up the atmosphere as it goes, the X-43A pushes that air into a scramjet -- a supersonic-combustion ramjet) engine.
A traditional ramjet operates by subsonic combustion of fuel in a stream of air compressed by the forward speed of the craft.
Carried onboard the X-43A is a small quantity of hydrogen that mixes with the incoming oxygen. That mix is then combusted, pushing the plane forward to high-mach speeds.
Ground facilities offer only limited glimpses at such speeds, whereas the actually flying the X-43A serves as a wind tunnel test, allowing engineers to gain knowledge, confidence and the technology to master high-mach flight.
The world's fastest air-breathing aircraft in operation is the SR-71. It cruises slightly above mach 3. NASA's X-15 rocket plane that flew from the late 1950s into the 1960s, reached a top speed of mach 6.7.
Hyper-X aircraft are built to fly faster than any previous air-breathing aircraft.
The X-43A weighs in at approximately 2,200 pounds (1,000 kilograms). The craft is 12 feet (3.7 meters) long, with a width of 5 feet (1.5 meters) and measures 2 feet (0.6 meters) in height.
MicroCraft, Inc. of Tullahoma, Tennessee built the three X-43A vehicles. The Pegasus rocket booster is made by Orbital Sciences of Dulles, Virginia.
The Hyper-X Phase 1 is a NASA Aerospace Technology Enterprise program being conducted jointly by the Langley Research Center, Hampton, Virginia and the Dryden Flight Research Center, Edwards, California.
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