An aircraft resembling a shark-nosed missile detached from a flying B-52 bomber and then shot above the Pacific Ocean at more than 3,000 mph (4828 kmh), in a historic test flight for the US Air Force - and for the future of aviation.



The unmanned X-51A WaveRider sped westward for four minutes, reaching Mach 5.1, or more than five times the speed of sound, before plunging into the ocean as planned.



It flew for longer than any other aircraft of its kind and travelled more than 264 miles (370 kilometres), reigniting decades-long efforts to develop a vehicle that could travel faster than a speeding bullet.



A passenger aircraft travelling at that speed could fly from Los Angeles to New York City in less than an hour.



The Air Force has been flirting with hypersonic technology for more than half a century with little success. Aerospace engineers say that harnessing technology capable of sustaining hypersonic speeds is crucial to the next generation of missiles, military aircraft, spacecraft and even passenger planes.



The X-51A, built and tested in Southern California, was powered by an air-breathing engine that has no moving parts. But the technology has been exceedingly difficult to perfect, until Wednesday's flight.



"It was a full mission success," said Charlie Brink, X-51A program manager for the Air Force Research Laboratory Aerospace Systems Directorate. "I believe all we have learned from the X-51A WaveRider will serve as the bedrock for future hypersonics research and ultimately the practical application of hypersonic flight."



The X-51A took off from Edwards Air Force Base, slung under the wing of a B-52 bomber. At about 50,000 feet, near Point Mugu, it was released like a bomb and engaged a solid rocket booster that accelerated it to Mach 4.8 in about 26 seconds.

After separating from the booster, the X-51A scramjet engine then lit and sped to Mach 5.1 at 60,000 feet.



A scramjet engine involves hydrocarbon fuel injected into the combustion chamber, where it mixes with air rushing through the chamber and is ignited. The X-51A then is designed to ride its own shock wave; hence, the WaveRider nickname.



After the flight, the 14-foot cruiser hit the Pacific Ocean and broke up. There are no plans to recover it.



Although the aircraft was designed to reach Mach 6, engineers said they were happy because the program objective was to prove the viability of air-breathing, high-speed scramjet propulsion.



This was the last of four test X-51A vehicles originally conceived when the $300 million technology demonstration program began in 2004. None of the other flights went the distance.



Work on the X-51A was done by Boeing Co.'s research centre in Huntington Beach, Calif., and Pratt & Whitney Rocketdyne in Canoga Park, Calif. All told, 370 seconds' worth of data were collected from the experiment.



"This demonstration of a practical hypersonic scramjet engine is a historic achievement that has been years in the making," said Darryl Davis, president of Boeing's secretive Phantom Works division.



"This test proves the technology has matured to the point that it opens the door to practical applications, such as advanced defense systems and more cost-effective access to space."



The Pentagon believes that hypersonic missiles are the best way to hit a target in an hour or less. The only vehicle that the military has in its inventory with that kind of capability is the massive, nuclear-tipped intercontinental ballistic missile.



Other means of hitting a distant target, such as cruise missiles and long-range bomber planes, can take hours to reach their destination.



The Pentagon has funded major hypersonic technology programs over the last several decades, most notably with the X-15 rocket plane that was built by North American Aviation and flew in the 1960s.



The Pentagon said it spent as much as $2 billion on hypersonic technologies and supporting engineering in the last 20 years.



For now, there is no immediate successor to the X-51A program.



The Air Force said that it would continue hypersonic research on other programs and that the success of the X-51A probably would find its way to the high-speed strike weapon program, which is currently in its early formation phase.

-Los Angeles Times