British scientists completed a test flight Saturday of a jet engine that could eventually turn long-haul flights to Australia or Japan into two-hour hops.

The Hyshot craft reached speeds of 6,000 mph — Mach 8, or eight times the speed of sound — over the outback in South Australia.

The craft, which was just 4 feet 6 inches long, was testing a revolutionary scramjet engine designed by Qinetiq, formerly the British government's defense research agency.

Scientists believe that the scramjet could one day be used to power super-fast intercontinental passenger planes.

"Ultimately, we hope to be able to use it to launch satellites into low-Earth orbit," said Professor Allan Paull, of the University of Queensland's center for hypersonics, which is working with Qinetiq.

The scramjet — the name comes from Supersonic Combustion RAMjet — is among the simplest of all engines because it has no moving parts.

It works by taking in air, mixing it with hydrogen and simultaneously compressing it, generating extremely high temperatures which ignite the mixture to create a surge of jet propulsion. The only by-product is water.

The big advantage of such craft is that they would not need to carry tanks loaded with a source of oxygen as well as fuel, meaning they would have much more space for payload.

However, there are many obstacles to making scramjets.

Perhaps the biggest is that they start working only at five times the speed of sound. Below this speed, the mixture of hydrogen and air would not be sufficiently compressed to ignite.

This means that scramjet-powered craft must first be accelerated by another means, such as a rocket-powered first stage.

This was the system used in Saturday's launch, in which the Hyshot was first propelled 200 miles into space by a two-stage rocket. It was thought to be the first British-powered craft to enter space since 1971.

Once it had reached the top of its trajectory, the nose cone detached, exposing four air intakes in its nose. Then, with the rockets switched off, the craft plummeted straight down towards earth.

At an altitude of about 22 miles, the scramjet activated, pushing the craft to speeds of about 6,000 mph before it ran out of fuel at a height of several thousand feet and plunged into the Australian desert.

How long it will take for Britain or any other country to develop commercial scramjets is uncertain.

NASA successfully flew its X-43A scramjet-powered plane over the Pacific in 2004.

Paull's team at the University of Queensland is also designing a scramjet-powered plane. If they are successful, it could be in the air over the Australian desert within two years.

Scramjet-powered jetliners would take decades to develop, but airlines are already taking an interest in the technology, attracted by the idea of offering flights that would go from London to Sydney and back on the same day.