A U.S. military test flight of the experimental hypersonic “Waverider” ended prematurely when the aircraft broke apart in the air over the Pacific Ocean due to a failure with its cruiser control fin, the U.S. Air Force said on Wednesday.
The problem with the fin was identified 16 seconds after a rocket booster on the unmanned X-51A aircraft was ignited to increase its speed, the Air Force said in a statement.
About 15 seconds later, when the X-51A separated from the rocket booster it lost control due to a “faulty control fin,” the statement said.
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.
A B-52 bomber had launched the remotely monitored, nearly wingless experimental aircraft, officially known as the X-51A, between 10 a.m. and 11 a.m. on Tuesday, John Haire, a spokesman for the 412th test wing at Edwards Air Force Base in California, said in a statement.
The Waverider is designed to reach speeds of Mach 6 or above, fast enough to zoom from New York to London in less than an hour. But rather than commercial air travel, the military has its eye on a more readily achievable application - using it to develop high-speed cruise missiles.
The X-51A was launched off the coast of California near Naval Air Station Point Mugu, which is northwest of Los Angeles, Mr. Haire said. It flew north over the Pacific through a range that is designed for test flights.
“The X-51 is not retrievable, in other words once you fly it, it’s going to end up in the ocean,” Mr. Haire said.
The aircraft is known as the Waverider because it stays airborne, in part, with lift generated by the shock waves of its own flight.
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.
After being dropped from the B-52, a solid-rocket booster is used in the initial phase of the plane’s flight to bring it up to speeds that can allow its scramjet engine to take over, by inhaling air through the craft’s forward momentum.
In 2004, NASA reached a speed of Mach 9.6, or nearly 11,265 kph, with a jet-powered aircraft. But that vehicle, known as X-43, only flew for a few seconds and its copper-based engine was not designed to survive the flight.
Engineers have hoped to see the hypersonic X-51A travel for five minutes of powered flight. For protection from extreme heat, it uses insulation tiles, similar to those on the NASA space shuttle orbiters, according to a 2011 military description of the project.
Hypersonic flight is normally defined as beginning at Mach 5, which is five times the speed of sound.