UPDATE 2-US hypersonic aircraft crashes seconds into military test flight

* Program details classified; cost undisclosed
* Goal to be able to get missiles anywhere in an hour

By Alex Dobuzinskis

LOS ANGELES, Aug 15 (Reuters) - An unmanned experimental aircraft designed to fly six times the speed of sound broke apart over the Pacific Ocean seconds into a military test flight due to a faulty control fin, the U.S. Air Force said on Wednesday.

The problem with the fin on the craft known as the Waverider or X-51A was identified in a test flight on Tuesday, 16 seconds after a rocket booster on the remotely monitored craft was ignited to propel it forward, the Air Force said in a statement.

Fifteen seconds later, when the X-51A separated from the rocket booster, it lost control due to a "faulty control fin," the statement said. The 31 seconds of flight fell far short of the military's goal for the X-51A to fly for five minutes.

The aircraft broke apart immediately and fell into the Pacific Ocean near Point Mugu northwest of Los Angeles, said Daryl Mayer, a spokesman for the 88th Air Base Wing at Wright-Patterson Air Force Base in Ohio.

Even if the test had been a success, the aircraft would have crashed at the end of the flight in any case and was not considered retrievable.

The Waverider was designed to reach speeds of Mach 6 or above, six times the speed of sound and fast enough to zoom from New York to London in less than an hour. The military has its eye on using the Waverider program to develop missiles with non-nuclear explosives that could strike anywhere in the world within an hour, analysts said.

The cost of the experimental aircraft, which military officials said was dropped from a B-52 bomber before its rocket booster was ignited, has not been disclosed because many details of the program are classified.

The aircraft is known as the Waverider because it stays airborne, in part, with lift generated by the shock waves of its own flight. The Boeing Co's Phantom Works division performed design and assembly on the craft, the military said.

The fins on the rocket booster kept the aircraft on-course during the initial phase of the flight, despite the problem with the control fin on the X-51A itself, Mayer said.

A Boeing spokeswoman declined to comment on the test flight, citing an Air Force request to have all public communication come from the military.

FUTURE X-51A FLIGHT

This was the third of four X-51A aircraft built for the military, one of which flew for over three minutes at nearly five times the speed of sound during a 2010 test flight, the Air Force said in a statement.

The Air Force, which is analyzing data from Tuesday's test flight, said one X-51A aircraft remains and that a decision has not been made "when or if that vehicle will fly at this time."

The Waverider is part of efforts by the U.S. military to develop a prompt global strike capability to hit targets anywhere in the world within an hour, said Guy Ben-Ari, senior fellow with the Center for Strategic and International Studies.

Over the years, the global strike program will likely eat up billions of dollars in development costs, Ben-Ari said. If the program becomes operational, targets could include conventional military sites or militants, he added.

A missile would likely not be fired from a vehicle like the X-51A, but the craft itself would be the missile, he said.

"The differences between what's an aircraft and what's a missile and what you would call a drone or a remotely piloted vehicle are becoming very fuzzy," Ben-Ari said.

That the test flight crashed early due to a problem with a fin would likely be frustrating for the military because that part was relatively easy to build, unlike the largely untested Scramjet engine, said John Pike, director of GlobalSecurity.org, a website for military policy research.

"The only way that you can develop this stuff is to actually take it out and fire it, and so the problem is they've got computer models but not much data," Pike said.

Pratt & Whitney Rocketdyne designed the X-51A's "Scramjet" engine, which uses the forward motion of the craft to compress air for fuel combustion, according to a description of the project from the military.

"It is unfortunate that a problem with this subsystem caused a termination before we could light the Scramjet engine," Charlie Brink, X-51A Program Manager for the Air Force Research Laboratory, said in a statement.

"All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives," Brink said.

Could we fly from London to New York in an hour? NASA scientists test 4,500mph hypersonic jet

* Scramjet engine can accelerate craft to over Mach 6
* Could dramatically slash journey times by travelling at five times the speed of sound

By Daily Mail Reporter

It looks like something you’d expect to see launch from Tracy Island.

But this Thunderbirds-style aircraft could be the future of long-haul flights.

The hypersonic X-51A WaveRider belongs to the US military and uses a revolutionary ‘scramjet’ engine to reach 4,500mph within seconds.

Arduous journeys for holidaymakers could be a thing of the past if the technology takes off. A trip across the Atlantic from London to New York would take the plane just one hour, travelling at five times the speed of sound.

Today the cutting-edge craft will be dropped from a B52 bomber over the Pacific Ocean in its latest test.

It will be flown from Edwards Air Force Base in the Mojave Desert in California, attached to the bomber’s wing.

The jet will then be dropped from almost 50,000ft near the Point Mugu promontory. A rocket booster will ignite and speed it up to about Mach 4.5 and, if all goes well, the aircraft’s engine will take over from there, pushing the speed to more than Mach 6 and lifting the craft to 70,000ft.

The mission will last 300 seconds – the longest the craft has ever flown to date. After the historic test, the plane will crash into the sea, and there are no plans to recover it.

Hypersonic flight – which relates to speeds of more than five times the speed of sound – is seen as the next step for aircraft. ‘Attaining sustained hypersonic flight is like going from propeller-driven aircraft to jet aircraft,’ Robert Mercier, deputy for technology in the high speed systems division at the Air Force Research Laboratory in Ohio told the Los Angeles Times.

‘Since the Wright brothers, we have examined how to make aircraft better and faster. Hypersonic flight is one of those areas that is a potential frontier for aeronautics. I believe we’re standing in the door waiting to go into that arena.’

The project is being funded by Nasa and the Pentagon, which hope it can be used for military stealth aircraft and new weapons.

The WaveRider programme is estimated to cost £89million, according to Globalsecurity.org, a website for military policy research. It has had a mixed history, with previous tests being aborted after the engine stalled.

Currently the fastest passenger plane in the world is the Cessna Citation X, which has a top speed of 700mph or Mach 0.9, although it takes only seven passengers.

In its wake is the Falcon 7X at 685mph and the Gulfstream G550, which is capable of 675mph

The experimental craft will be tested strapped to the wing of a B-52 bomber. Once released, it's radical scramjet engines will be fired, hopefully accelerating the craft up to Mach 6, over 2,000 metres per second.

The X-51A Waverider on the wing of a B-52 Stratofortress. A previous test was the longest supersonic combustion ramjet-powered hypersonic flight to date.

Mach is a measure of the ratio of the velocity of an object, in this case a plane, to the velocity of sound, which equals Mach 1, or 761.2 miles per hour.

Any plane that flies past the speed of sound creates a sonic boom, which often results in a major noise disturbance over close-by areas. Before its 2003 retirement, Concorde was long the shuttle of choice for executives eager to spend as little time as possible in the air and unafraid to shell out thousands for a 3.5-hour transatlantic flight.

An attempt to launch a hypersonic flight in August last year failed when the soaring heat caused the craft’s surface to peel and the experiment ended prematurely.

The Pentagon’s research arm calls hypersonic flight ‘the new stealth’ for its promise of evading and outrunning enemy fire. The effort to develop hypersonic engines is necessary because they can propel vehicles at a velocity that cannot be achieved from traditional turbine-powered jet engines.

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

The scramjet engine is designed to ride on its own shockwave, and should see the test craft accelerate to about Mach 6.