LOS ANGELES Since test pilot Chuck Yeager broke the sound barrier in 1947, engineers and scientists have dreamed of ever-faster aircraft. Now they face one of their toughest challenges yet: sustaining hypersonic flight going five times the speed of sound or more for more than a few minutes.
In a nondescript hangar at Edwards Air Force Base in Californias Mojave Desert, a team of aerospace engineers has been putting the finishing touches on an experimental aircraft designed to fly above the Pacific Ocean at 3,600 mph. A passenger aircraft traveling at that speed could fly from Los Angeles to New York in 46 minutes but thats just a pipe dream at this point.
A key test is set Tuesday for the unmanned aircraft X-51A WaveRider. It will take the aircraft attached to a B-52 bombers wing from Edwards to about 50,000 feet over the Pacific Ocean near Point Mugu, which is not far from Malibu. From there, its high-speed journey at Mach 6 is expected to last only five minutes, which would be twice as long as its ever gone at that speed.
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.
Attaining sustained hypersonic flight is like going from propeller-driven aircraft to jet aircraft, said Robert A. Mercier, deputy for technology in the high speed systems division at the Air Force Research Laboratory in Ohio. 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 were standing in the door waiting to go into that arena.
NASA and the Pentagon are financing three national centers across the country to study hypersonic flight. The Pentagons research arm, known as the Defense Advanced Research Projects Agency, or DARPA, 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.
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 currently 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 is funding six major hypersonic technology programs. Over the past 10 years, it said it spent as much as $2 billion on hypersonic technologies and supporting engineering.
The WaveRider program is estimated to cost $140 million, according to Global-security.org, a website for military policy research.
Yet the funding has turned up few positive results.
One of the more recent attempts was in August 2011, when DARPA carried out a test flight of an arrowhead-shaped unmanned aircraft, dubbed Falcon Hypersonic Technology Vehicle 2. Its designed to travel at 20 times the speed of sound. The launch had received worldwide attention and much fanfare, but minutes into the flight, searing high speeds caused portions of the Falcons skin to peel from the aerostructure and the flight ended prematurely.
Charlie Brink, the Air Force Research Laboratorys program manager, and his team will try again on a test flight Tuesday. The WaveRider will fall like a bomb for about four seconds before its booster rocket engine ignites and propels the nearly wingless aircraft for 30 seconds to about Mach 4.5, before being jettisoned.
Then the cruisers scramjet engine, notable because it has virtually no moving parts, ignites. The ignition sequence begins burning ethylene, transitioning over about 10 seconds to JP-7 jet fuel. The WaveRider is expected to accelerate to about Mach 6 as it climbs to nearly 70,000 feet.
After five minutes of flight, the WaveRider is set to break up after splashing into the Pacific.
There are no plans to recover it.
Dora Musielak, an adjunct professor of physics at the University of Texas at Arlington whose research focuses on high-speed propulsion, said aircraft like the WaveRider are crucial to commercial planes one day flying nonstop at high speeds from one side of the planet to the other.
Other than the turbojet-powered Concorde retired in 2003 commercial transportation has not advanced beyond the speed of sound.