Hypersonic test failure

The US Air Force said the unmanned aircraft, otherwise known as the X-51A, broke apart over waters northwest of Los Angeles, because a cruiser control fin had malfunctioned, 16 seconds after the ignition of the aircraft's rocket booster.

The Waverider had just been dropped from a B-52 Stratofortress bomber. Within five minutes the booster was supposed to accelerate to 7,000 kilometers (4,349 miles) per hour, before its own Scramjet engine activated, accelerating it further to 10,000 kilometers per hour.

"Once the X-51 separated from the rocket booster, approximately 15 seconds later, the cruiser was not able to maintain control due to the faulty control fin and was lost," the Air Force said in a statement.

The component which went awry had worked properly on previous test flights. Engineers were now analyzing flight data, the Air Force said.

Only one of four X-51A built by Boeing remains in the test series. On its first test in May 2010, the X-51A reached Mach 5, but that flight lasted only three minutes.

In the Scramjet, hydrogen is injected into the air stream rushing through the engine, with the resulting hot gases providing additional thrust. Theoretically, the Waverider is supposed to ride on the shock waves generated by its high speed.

Six times the speed of sound would shorten a flight from New York to London to less than an hour. The US military, however, has its eye on the Waverider to develop high-speed cruise missiles.

ipj/jlw (AFP, dpa, Reuters)