The world’s first hydrogen-fueled hypersonic jet may be able to reach a simply astounding speed of 12 times the speed of sound. That’s about half the speed of satellites in low Earth orbit. The aircraft comes from the imagination of Hypersonix Launch Systems, a Brisbane-based company.

This article discovers the host of factors that could make aviation at Mach 12 possible. This includes the SPARTAN scramjet engine, impressive financial backing, and a testing program in partnership with the US military. The choice of hydrogen fuel could also be game-changing for hypersonic aviation. For all the engineering challenges that Hypersonix needs to overcome to achieve its lofty goal, the greatest challenge could be maintaining the backing needed to get the aircraft into the skies.

A Unique Engine Design

A conventional jet engine with a turbine would not be able to spin fast enough to push an aircraft up to Mach 12. Such fast flying is more suited to scramjets, which have no moving parts. Scramjet means ‘supersonic combustion ramjet’. When an aircraft is traveling at extremely high speeds, usually in excess of Mach 5, the air entering an engine is forcefully compressed. Fuel can be injected into this compressed air to expel the hot gas at a ridiculously fast speed.

Hypersonix’s scramjet is called the SPARTAN. The engine is fully 3D printed and will burn hydrogen, rather than kerosene. The engineering firm hopes that this choice of fuel will combine zero-carbon flying with unprecedentedly high speed and comparatively low maintenance.

The former Nasa research scientist and University of Queensland professor, Dr Michael Smart, who founded Hypersonix and now serves as its chief technology officer, said: “SPARTAN is more than a propulsion system. It’s a breakthrough in reusable hypersonic flight. What we’re building is a sovereign platform that’s clean, cost-effective, and engineered for the real world.”

Test Flights Will Put SPARTAN Through Its Paces

Hypersonix cannot simply strap a SPARTAN engine to its planned Delta Velos fuselage, the airframe that it thinks could reach MACH 12. Instead, it will use the DART AE demonstrator vehicle to add further refinement to the engine as needed to get it to such a high speed. The testing on this 11.5 feet (3.5 meters) long aircraft will be conducted in partnership with NASA and the Pentagon. Tests will take place through the HyCAT program overseen for the US Department of Defense’s Defense Innovation Unit. This is the body responsible for bringing commercial technology into the US military.

A scramjet only works once an aircraft is already at an absurdly fast speed. The testbed will reach this speed attached to Rocket Lab’s HASTE (Hypersonic Accelerator Suborbital Test Electron). This rocket can take a payload of up to 1540 lbs (700 kg) on a hypersonic and suborbital trajectory. The DART AE demonstrator will then decouple, where it will then hopefully complete the world’s first hydrogen-powered and sustained hypersonic flight.

The table below features key specifications for the HASTE rocket according to Rocket Lab’s data:

This testing partnership is a sign of the interest that Hypersonix’s work is getting from the world’s most powerful military. Major Ryan Weed, the Defense Innovation Unit’s program manager, said that the work represents a “paradigm shift, viewing the hypersonic realm as a place for aircraft, not just missiles and weapons.”

What Airframes Does Hypersonix Plan To Strap Its SPARTAN Engine To?

Hypersonix envisions three airframes that the SPARTAN engine will be attachable to. All three of the airframes will be able to reach hypersonic speeds and fly using hydrogen fuel. The specifications detailed in the paragraphs below have been released by Aerospace Testing International, Hypersonix, and the Government of Australia

First is the aforementioned DART AE testbed, flown in partnership with the US Defense Innovation Unit (DIU) ‘HyCAT’ program. Next is VISR. This is a larger and fully reusable aircraft. It will be 26.2 ft (8 m) long and powered by four SPARTAN engines. The airframe will be constructed from high-temperature ceramic-matrix composites. It is thought that this aircraft will find use for military intelligence and reconnaissance work. It should be able to reach Mach five to ten.

The most advanced airframe will be Delta Velos. This aircraft will also be reusable, but it will feature a launch system more suitable for high-cadence flying. It is the Delta Velos airframe that is slated to be capable of Mach 12.

Hypersonix Has Secured Funding To Back Their Ambition

The Australian engineering firm has secured $46 million in funding, provided by a conglomerate of international defense investors and bolstered by the Queensland Investment Corporation (QIC) and the National Reconstruction Fund Corporation (NRFC). It is backed up by the reusable nature of the aircraft, enhancing profitability once in service. This initial funding round was led by High Tor Capital, a leading investor in frontier defense technology from the United Kingdom. Co-investors include Saab and RKKVC, a Police investment group. Financial advice came from North Ridge Partners. Raising such a vast amount of money is essential as the firm works to make its ambition a reality.

Hypersonix is unsurprisingly delighted to have secured such a substantial initial investment. The firm’s CEO Matt Hill told Interesting Engineering: “This raise marks a major milestone as we prepare to launch the world’s first hydrogen-powered hypersonic aircraft. Having Australia’s sovereign investor in manufacturing capability behind such a critical strategic capability sends a powerful message. It shows confidence in our mission to build clean, reusable aerospace systems that meet today’s national security needs while shaping tomorrow’s industry.”

NRFC’s CEO, David Gall, shared similar sentiments: “Defense is one of our priority areas. We see huge potential in backing Australian companies and innovations that build sovereign capability while also tapping into the global market for hypersonic and counter-hypersonic technologies among our allies.” To become a profitable program, the aircraft will have to pick up commercial and military clients. The reusable nature of the planned aircraft should secure this.

Hydrogen And Hypersonic Flight

Hydrogen is a popular choice for speculative scramjets. The element is chemically easier to combust, a huge perk in the unforgiving environment inside a scramjet, where air is extremely compressed and rapid combustion is a necessity.

Hydrogen also packs in a lot more energy per kilogram than conventional aviation fuel. That means that less weight needs to be used to get the fuel up to hypersonic speeds. Hydrogen is also a pathway to bring the needs of low-carbon futures in line with hypersonic flight, as burning it does not reduce carbon dioxide.

However, hydrogen propulsion also comes with substantial challenges. It is a significantly lower density fuel than kerosene. As a result, it would need to be frozen in heavily insulated cryogenic flights. This would seem to contradict the enormous heat produced by air resistance during hypersonic flight. Extremely cold hydrogen could also help to keep the aircraft cool. Liquid hydrogen is already extensively used as a coolant in engineering, making this a tried and tested principle.

The Greatest Challenge For Hypersonix

Engineering programs of yesteryear have also pitched ambitious plans for hypersonic flight. Yet, they haven’t been able to maintain interest and funding for long enough to achieve their ambitions, with even the most promising projects not gettting further than a few test flights. The most notable example is NASA’s X-43A. This jet reached Mach 9.6 during testing in 2004. However, plans were made for a larger iteration of the vehicle that would have had the ridiculous target of Mach 15.

Known as the X-43D, this jet would be able to run its engine for long periods, compared with a few seconds for the X-42A. That capability would give it a host of military uses and allow extreme-speed flying to be done by air-breathing jets rather than rockets. Such a vehicle never took to the skies. The last work done on it was a feasibility study conducted by Donald B. Johnson of Boeing and Jeffrey S. Robinson of NASA’s Langley Research Center. It found that information on jet engine operation above Mach 10 could only be found through real-world testing.

The X-43 program has since collapsed, replaced by the Boeing X-51 Waverider. This unmanned aircraft has focused on maintaining hypersonic speeds for extended time periods, with much more modest top-speed goals. Following two unsuccessful test flights, the X-51 reached Mach 5 and maintained this speed for 210 seconds. This was the longest duration ever for powered hypersonic flight. But, the program always had short-term ambitions. This successful test flight was considered the successful completion of the project, and it has not been picked back up since then.