| 'WaveRider' poised for hypersonic flight|
|The US military is preparing to test an experimental aircraft that can fly more than six times faster than the speed of sound on ordinary jet fuel.|
Officially, it's known as the X-51, but some like to call it the WaveRider because it stays airborne, in part, with lift generated by the shock waves of its own flight.
The design stems from the goal of the program - to demonstrate an air-breathing, hypersonic, combustion ramjet engine, known as a scramjet.
"We built a vehicle around an engine," says Joseph Vogel, the X-51 project manager with Boeing, which is building a series of four test planes under a US$246.5 million (A$338.5 million) program managed by the US Air Force Research Laboratory.
Scramjets use the forward motion of an engine to compress air for fuel combustion; similar to a ramjet engine, but at supersonic speeds.
NASA tested the concept in 2004, breaking the record for a jet-powered aircraft with a speed of Mach 9.6, or approximately 11,000 kilometres per hour.
But the vehicle, known as X-43, only flew for a few seconds and its copper-based engine was not designed to survive the flight.
"The heat from the combustion process was just absorbed by (X-43's) engine. It would hold its shape for a limited point of time and then start melting," says X-51 program manager Charlie Brink.
The X-51 engine is made from a standard nickel alloy and is cooled during flight by its own fuel. The program's goal is to fly for about five minutes.
"I truly believe this is one of those history leaps that will only happen every so many hundred years," says Vogel.
The military has its eye on high-speed cruise missiles as well as space vehicles that wouldn't need carry-on oxidisers. The space shuttle, for example, carries both liquid oxygen and liquid hydrogen, to power its main engines.
"The holy grail of scramjet is if you can capture air while you're flying very fast and not have to carry along an oxidiser," says Brink. "If you could do that you've made a lot more space for payload or cargo."
The WaveRider's first flight is scheduled for October over the Pacific Ocean.
It will be carried into the air by a B-52 bomber and released at an altitude of about 15,000 metres. A solid-rocket booster will ignite and speed it up to about Mach 4.8 and if all goes well, the aircraft's engine will take over from there, boosting the speed to more than Mach 6.
"If we can achieve five minutes of powered flight, it will surpass everything we've done by a magnitude," says Vogel.