Frazer-Nash has announced that it is leading a new spaceplane programme called INVICTUS, with the help of the European Space Agency (ESA).
Funded by €7 million from ESA, the plan is to use air-breathing rocket technology to build a test aircraft capable of Mach 5 by 2031. The reusable vehicle will take-off horizontally from a runway like an aeroplane – but using an air-breathing rocket engine called SABRE (Synergetic Air Breathing Rocket Engine). The trick of the air-breathing mode is it will pre-cool the air to compress and inject it into a rocket chamber. As altitude increases to a level where it becomes too thin, the spaceplane’s hydrogen burning engines would then switch to use on-board oxygen to continue the burn. It is here that the programme uses SABRE engine technology originally developed by Reaction Engines Limited (REL).
INVICTUS air-breathing hypersonic rocket plane concept. Courtesy: Frazer-Nash Consultancy
REL was itself working on an orbit-capable spaceplane design dubbed Skylon. While having revenue streams for its pre-cooler technology from the likes of Formula One motor-racing, REL never made an operating profit. In effect, REL was still in ‘start-up’ mode despite operating for 35 years. With a large staff to fund, it eventually fell into administration last year after a cash flow crisis.
Frazer-Nash to the rescue
In effect, the INVICTUS programme saves this technology. Frazer-Nash, an aerospace consultancy that started as a car manufacturer, has welcomed a team of experts from REL, along with its technology, into their company.
INVICTUS has been tasked to deliver a preliminary design of the full system in 12 months that will culminate in its first flight. Partners in the programme include Spirit AeroSystems, Cranfield University, and several small to medium sized enterprises.
The technology behind the programme
Aircraft that fly at hypersonic speeds – more than five times the speed of sound – face extremely high temperatures due to shock heating and friction from the air. The planned Mach 5 velocity of INVICTUS is more than twice as fast as the cruising speed of Concorde.
A video animation of the INVICTUS rocket plane is here.
Typical aircraft engines cannot operate in these conditions as the air is too hot to handle. Some specialised engines capable of operating in this flight envelope do exist, such as scramjets. However, they present their own drawbacks such as limited windows of performance and the inability to start on the ground.
The pre-cooler, originally developed and tested by REL, chills the air before it reaches the engine, allowing conventional aircraft engines to travel at hypersonic speeds. Previous tests by REL validated the technology at hypersonic flight conditions, successfully demonstrating its integration with existing jet engine architecture.
It showed its ability to cool airflow at significantly faster speeds than other heat exchangers. It cooled inlet airflow temperatures by 1,000 °C in less than 1/20th of a second.
The opportunities
While the INVICTUS programme will only be a test machine, it could lead to hypersonic cruise missiles, aircraft and even single-stage launch vehicles – something envisaged by its original designers, Alan Bond and Richard Varvill, at REL.
Dr Tommaso Ghidini, Head of the Mechanical Department at ESA, said: “With INVICTUS, Europe is seizing the opportunity to lead in technologies that will redefine how we move across the planet and reach beyond it.”
ESA has previously explored air-breathing rocket technology. However, REL’s bid to build a new reusable launch vehicle as a successor to the Ariane 5 was ultimately unsuccessful. Instead, the Ariane 6 expendable rocket, considered the technically less risky option, won the agency’s backing. The rise of the partly reusable SpaceX Falcon 9, and the subsequent development of the fully reusable Starship/Super Heavy design, has led some to question this decision. Even so, ESA was impressed enough to partially fund the REL air-breathing rocket technology.
