http://news.bbc.co.uk/1/hi/sci/tech/4018117.stm
Nasa flew an unmanned experimental jet on Tuesday to a speed that was in excess of nine times the speed of sound - a world record.
The X-43A - a supersonic combustion ramjet (scramjet) - was released on its test run from beneath a bomber's wing.
The 3.7m-long aircraft had already set a world best for an "air breathing" jet of Mach 6.83 - nearly seven times the speed of sound - on a flight in March. Preliminary data confirming the success came through in real-time. Scramjets are being developed in a number of countries as an alternative propulsion system to rockets. Future applications could include hypersonic missiles and airplanes, and reusable single- or two-stage-to-orbit space launchers.
"The US space agency's goal has been to get to space more routinely and in a safer fashion," Joel Sitz, project manager for the X-43A, told the BBC News website. Some commentators have even speculated that scramjets could one day be used on passenger airliners, dramatically cutting long-haul journey times.
The latest flight of the X-43A was supposed to have taken place on Monday. But pre-flight avionics checks overran and the vehicle, which holds the world speed record for an "air-breathing" jet, was stood down for 24 hours. On Tuesday, the flight went ahead as planned over the Naval Air Warfare Center Weapons Division Sea Range, which is just to the northwest of Los Angeles. The X-43A was positioned on the nose of a Pegasus booster rocket and attached to the underside of a B52B aircraft's wing.
The paired X-43A and booster were then lifted to an altitude of 12km (40,000ft) and released; the booster taking the scramjet higher still. Separation and onward flight of the scramjet was designed to take place at an altitude of about 33.5km (110,000ft). Engineers expected the X-43A to travel about 1,370km (850 miles) before plunging into the Pacific.
Scramjets achieve their fantastic speeds by burning a hydrogen propellant but without the need to carry heavy oxygen tanks as rockets must. They take their oxygen from the air, which is naturally compressed by the forward speed of the vehicle and the shape of the vehicle's inlet. Unlike a conventional jet engine, there are no rotating blades to compress the air. Getting fuel to ignite in a supersonic air stream has been likened to "striking a match in a hurricane"; so, successful combustion relies on controlling temperature and pressure within the engine. The concept should allow for greater payload capacity at reduced cost.
Also, rockets tend to produce full thrust or nearly full thrust all the time; whereas scramjets can be throttled back and flown more like an aeroplane, making them potentially safer. Tuesday's flight was the third and final mission for the Nasa vehicle - and it is not clear where the technology the agency has spent years developing will now fit into its future plans. A proposal to develop a larger hypersonic vehicle - the X-43C - was scrapped following President Bush's announcement in January that America would revive manned missions to the Moon by 2015 and attempt an expedition to Mars. As a result, funding has been channelled into the development of a conventional rocket-powered vehicle, at the expense of longer-term programmes such as Hyper-X.
In addition to Nasa's $230m programme, a group at the University of Queensland in Australia plans to conduct two Mach 8 flights and a Mach 10 flight in September 2005.The Queensland team will test three separate scramjet configurations designed by the UK's QinetiQ company, the US Defense Advanced Research Projects Agency (Darpa) and the Japanese Aerospace Exploration Agency (Jaxa).
The US Air Force has a programme called HyTech, which is aimed at developing a hypersonic cruise missile. Researchers have been working on the scramjet concept for several decades. "The last X-43A flight did show evidence of thrust - something that people have sought since the 1960s," commented Professor Douglas Fletcher, of the department of aeronautics and aerospace at the Von Karman Institute in Belgium.
"It's nice for those people who have now retired to finally see the results of what they worked for."
Topic: Superfast Nasa jet pushes Mach 10 (Read 809 times)