Slow and steady wins the race – especially when it comes to hypersonic flight. Now Australia’s persistence in pursuing high-velocity engineering is paying off.
Brisbane-based Hypersonix Launch Systems has been awarded a $2.95 million grant from the Australian government to develop the world’s first entirely reusable aircraft that could travel at speeds of up to 12 times the speed of sound.
The ultimate goal is for a multi-mission autonomous vehicle capable of delivering satellites to orbit while emitting only water vapour as its exhaust.
It’s taken decades of effort to get to this point.
Australia’s Defence, Science and Technology Group (DST) and university sector have been plugging away at the technology since 1989, when they conducted their first scramjet ground tests. The HyShot flight test program took to the skies in 2022. And the HIFiRE 7 hydrogen-fuelled scramjet flew in 2015.
The new DART CMP drone will be a complete technology demonstrator package to be developed in conjunction with the University of Southern Queensland. At its core will be a 3D printed Spartan hydrogen-fuelled scramjet engine. But this must be fitted to an Australian-made airframe with associated control surfaces and flight avionics.
Hypersonic propulsion is a competitive field. More than 100 companies are tackling the technology internationally, but Hypersonix hopes its hydrogen-fuelled 3D scramjet combination will be a winner.
Now it has caught the attention of the United States after a slew of its own high-speed controlled flight projects failed. Australia’s hypersonic edge is its key contribution to the AUKUS technology sharing defence cooperation framework.
Lean, green machine
Unlike rockets, scramjets draw combustible oxygen from the atmosphere. This reduces the weight they must carry by some 60%. And the Spartan engine burns hydrogen fuel in a process that emits water vapour, not carbon dioxide, as its exhaust. If that hydrogen is sourced from renewable energy sources, the reusable 3D printed scramjet motor will be especially “green”.
But hypersonic flight is difficult to achieve. And even more difficult to sustain.
The scramjet engine itself achieves internal combustion temperatures greater than 1000°C. And the airframe is another challenge as it needs to absorb considerable stress as well as heat.
Hypersonix co-founder Dr Michael Smart says the advantage of the Spartan engine design is that it has no moving parts, which are potential points of failure. “Instead of having all the turning blades and compressors, we just use the shockwaves and the air itself to create combustion,” he says.
This makes the engine more resilient, reliable and reusable.
Hypersonix Managing Director David Waterhouse adds the engine can be turned off and on, enabling the craft to “skip off the atmosphere” like a pebble over water. This allows the craft to travel significant distances using minimal fuel.
Hypersonix has simulated how its scramjet engine and DART airframe will perform at speeds over Mach 5. It’s also been proven through a series of hypersonic shock-tunnel tests. Now it needs the appropriate manufacturing technology necessary to turn the engine and its airframe into reality.
And that’s where the new federal government grant kicks in. It’s designed to give Australia the sovereign capability of producing the advanced materials needed. This includes modern, high-temperature oxide-oxide ceramic matrix composites, which promise to become more cost-effective than titanium and other high-temperature alloys.
Hypersonix is currently in the process of assembling its DART AE 3D-printing demonstrator craft. The follow-up DART CMP will focus on integrating composite materials.
“AE stands for Additive Engineering (or 3D printing) and is the fully 3D printed version out of high-temperature alloys that are already available in Australia,” says Waterhouse.
Using 3D printing means the Spartan engine is both cheaper to build and more resilient with its seamless assembly. It’s capable of sustaining some 1500°C. And Hypersonix says it takes just three weeks to print a new one.
The autonomous technology demonstrator is intended to fly between Mach 5 and 12 for more than 500 kilometres. It must also be able to control its speed and flight profile and return to a landing location.
The DART AE is due to launch in 2023. The new DART CMP project will begin in July.
University of Southern Queensland’s Institute for Advanced Engineering and Space Sciences Executive Director Professor Peter Schubel says his team will develop and test the ultra-high temperature composite materials and coatings the new craft needs.
“Our expertise in liquid moulding technologies, automated fibre placement, pultrusion and filament winding capabilities with exotic materials allows us to develop revolutionary structures,” he says.
But not everything about the DART is likely to be custom made. Smart says its hydrogen fuel tank may be an off-the-shelf tank used for hydrogen-powered trucks and heavy vehicles as they’re already highly resilient.
A lot is riding on the back of the demonstrators’ success.
On 6 April, Australian Prime Minister Scott Morrison, US President Joe Biden, and UK Prime Minister Boris Johnson fleshed out their AUKUS defence technology cooperation plans. Developing hypersonic flight technology was high on that list.
Russia and China are generally believed to hold a technological edge in this arena after years of failed US projects. Moscow claims to have used such weapons against targets within Ukraine.
“There is an arms race, not necessarily for increased numbers, but for increased quality,” US Air Force Secretary Frank Kendall said late last year. “It’s an arms race that has been going on for quite some time. The Chinese have been at it very aggressively.”