CANBERRA, Australia - Scientists this week hope to achieve the first successful full-scale test of a scramjet, a futuristic propulsion system that could lead the way to a new generation of smaller, cheaper rockets.
An international consortium known as Hyshot will conduct the first atmospheric test of the jet engine Thursday at a military rocket range in the desert of central Australia.
Conventional rockets must carry both fuel, such as liquid hydrogen, and liquid oxygen to burn it. Scramjets, or "supersonic combustion ramjets," need only carry fuel, potentially halving a rocket's weight.
``Another term for this sort of engine is air-breathing,'' said Susan Anderson, a Queensland University engineer with the project. She explained that the jet sucks air from the atmosphere and compresses it in the combustion chamber, which is then injected with fuel.
With no moving parts, the jet is mechanically simple. The challenge lies in getting it up to speeds at which combustion can occur. The Hyshot scramjet is designed to combust at Mach 7.6, nearly eight times the speed of sound, which is 750 miles per hour at sea level.
If all goes as planned, the Hyshot scramjet will be fired as the payload on a rocket to an altitude of about 25 miles. The rocket's nose cone will then be thrown off and the 5.3-foot scramjet will begin falling, gaining speed as it goes.
Anderson said it will reach Mach 7.6 at about 23 miles above the earth, at which point the chamber will be injected with fuel and ``we'll hope we get combustion.''
Scientists believe the engine one day could be used to build aircraft capable of flying from London to Sydney in a few hours, a flight that takes at least 18 hours by passenger jet.
Its more immediate use would be as second-stage boosters in commercial satellite launch vehicles. As no liquid oxygen needs to be carried, the weight of the rocket can be substantially reduced, making room for extra payload and smaller rockets.
Australia's University of Queensland is leading the project. The 35-foot Terrier-Orion rocket that will carry the scramjet has been provided by Astrotech, an American member of the consortium.
The Australian Defense Department is providing the launch facility and about 30 members of its Aircraft Research Development Unit to help carry out the experiment.
NASA attempted to test its own scramjet, the X-43A, on June 2, but the jet was destroyed when the rocket used to launch it malfunctioned.
During another test in the United States in August, a four-inch scramjet prototype was fired from a 130-foot cannon at a speed of Mach 7.1. The scramjet engine aboard the titanium projectile then ignited, propelling it 260 feet in a fraction of a second, before crashing into steel plates set up to stop it.
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