Hypersonic jet ready for launch

BBC News 03/23/2006 Author: Jonathan Fildes

A new jet engine design able to fly seven times the speed of sound is scheduled to launch over Australia on Friday.

The scramjet engine, known as Hyshot III, has been designed by British defence firm Qinetiq.

If successful, it could pave the way for ultrafast, intercontinental air travel, and substantially cut the cost of putting small payloads into space.

The engine will launch on a rocket owned by the University of Queensland.

It is the first of three test flights planned for this year by the international Hyshot consortium.

The first Hyshot engine was launched in 2001 but the test flight failed when the rocket carrying the engine flew off course.

Simple engines

A supersonic combustion ramjet, or scramjet, is mechanically very simple. It has no moving parts and takes all of the oxygen it needs to burn hydrogen fuel from the air.

This makes it more efficient than conventional rocket engines as they do not need to carry their own oxygen supply, meaning that any vehicle could potentially carry a larger payload.

However scramjets do not begin to work until they reach five times the speed of sound.

At this speed the air passing through the engine is compressed and hot enough for ignition to occur. Rapid expansion of the exhaust gases creates the forward thrust.

To reach the critical speed, Hyshot III will be strapped to the front of a conventional rocket and blasted to an altitude of 330km before being allowed to plummet back to Earth.

On its descent the engine is expected to reach a top speed of Mach 7.6 or over 9,000km/ hour.

Making sure the flight happens correctly is incredibly difficult, according to Dr Allan Paull, project leader of the Hyshot programme at the University of Queensland.

"You are dealing with extremes of conditions. You're working out on the edge and with a lot of the stuff no one has ever tried [it] before," he told the BBC News website. "You've got to expect things to go wrong".

If everything goes to plan, the experiment will begin at a height of 35km. As the engine continues its downward path the fuel in the scramjet is expected to automatically ignite.

The scientists will then have just six seconds to monitor its performance before the £1m engine eventually crashes into the ground.

New design

The scramjet will not provide forward thrust during the flight, necessary if the engine is ever to power a vehicle. But the test will be enough to show that burning starts automatically and to verify trials already done in a wind tunnel.

"The wind tunnels operate for milliseconds," Dr Paull explained. "The difficulty is whether or not you can even see the supersonic combustion in this period of time."

Although the Qinetiq engine has never left the ground it is more realistic than previous Hyshot experiments.

It has a more efficient air intake on the front and can operate over a greater range of speeds. It also scoops air into the combustion chamber at a lower temperature, closer to that needed in a commercially useful engine.

If the test flight is successful, it will be followed four days later by the test flight of another Hyshot engine designed by the Japanese Aerospace Exploration Agency (Jaxa). This will be followed in June by the launch of an engine that will fly at Mach 10, designed by the Australian Defence Science and Technology Organisation (DSTO).

Commercial reality

The Hyshot tests will bring the idea of a commercial scramjet one step closer to reality.

In the first instance these would probably be used to launch satellites into low earth orbit but many have speculated that they could also allow passenger airlines to fly between London and Sydney in just 2 hours.

Although this vision maybe many years off, it was given a huge boost when Nasa successfully flew its X-43A plane over the Pacific Ocean in 2004. The unmanned aircraft flew at 10 times the speed of sound, a new world speed record.

The team at the University of Queensland is also currently designing a vehicle that can fly under its own power.

If the plane works, it could be flying over the Australian desert within the next two years.