A revolutionary jet engine capable of operating at eight times the speed of sound has arrived in Norway. Designed and built in Brisbane, Australia by the University of Queensland (UQ), the Scramspace is a hypersonic scramjet that will be fired by rocket in the Arctic Circle, where it will very briefly fly fast enough to travel from London to Australia in two hours. It’s part of a project to develop hypersonic technology that may one day be used to put payloads into orbit at a much lower cost than is possible today.

Scramspace is three-year research project by an international research team of 13 partners and sponsors from five countries led by Scramspace Director and Chair for Hypersonics at UQ, Professor Russell Boyce. Its AUD$14 million (US$13.7 million ) “shoestring budget” is small compared to similar American hypersonic project budgets that run into the hundreds of millions, but it draws on two decades of Australian hypersonic research into new engine designs and materials.

The heart of the 1.8-m (5.9-ft) Scramspace is a hypersonic scramjet. A standard jet engine, such as is found on an airliner, is a massively complex bit of machinery filled with turbine blades to compress the incoming air to make it suitable for burning the jet fuel. However, if the engine is traveling fast enough, the air compresses itself to support combustion. This is what happens in a ramjet, which is nicknamed the “flying stovepipe” for a reason – it’s an empty tube so lacking in moving parts that it seems like a joke at first glance. The fuel is sprayed straight into the combustion chamber and ignites in a surprisingly simple fashion that disguises some sophisticated engineering theory.

In a ramjet, the air is compressed, but it’s still only moving at subsonic speed as it passes through. But in a scramjet, the air is moving at supersonic speeds throughout the engine. This means that, just as a ramjet can operate at supersonic speeds, the scramjet engine can operate at hypersonic speeds.

The Scramspace uses a scramjet that differs from a ramjet in that the fuel is pumped into the air inlet instead of the combustion chamber, to give the fuel time to mix properly with the air at supersonic speed. Igniting the hydrogen fuel exploits the fact that in the engine, the compression isn't even. There are spots of very high pressure, much like the “diamonds” that you can see in a jet exhaust, that raise the temperature of the fuel/air mixture to the ignition point.

One thing Scramspace isn’t designed for is durability. That’s because its entire career will be over faster than you can say “hypersonic swan-dive.” Between September 15 and 21, weather pending, Scramspace will go on a Mach 8 (5,290 knots, 8,600 km/h, 6,090 mph) high-speed test flight when it is launched at Andøya Rocket Range, 300 km (186 mi) north of the Arctic Circle.

Scramspace will be shot into space to an altitude of 320 km (200 mi) by a two-stage rocket. When it leaves the atmosphere, the spacecraft will separate and small gas thrusters will turn it and aim it straight down at a very precise angle. Gravity will then take over and accelerate Scramspace to Mach 8. When the vehicle is at a height between 27 and 32 km (17 and 20 mi), the engine will fire while instruments record combustion and thrust data. This has to be done very quickly because three seconds after ignition, Scramspace will disintegrate over the North Sea.

The team hopes that the test will provide a better understanding of hypersonic physics, hypersonic combustion, how materials and components behave at hypersonic speeds, and how to improve hypersonic craft design. Though the technology is in its early days, they also hope that it will one day make it cheaper to send payloads into orbit by allowing launch vehicles to fly while carrying much less liquid oxygen than present rockets.

“As part of the Australian Space Research Program, this project supports Australia's access to space, as helps build the talent pool of engineers, scientists and specialists we need to do it,” Professor Boyce says.

Source: University of Queensland