LONDON — A hypersonic propulsion company backed by Rolls-Royce, Boeing and BAE Systems has taken a step closer to developing an engine capable of powering combat jets and other aircraft at speeds of up to Mach 5 following tests of two subsystems vital to the success of the design.

British-based Reaction Engines said the recently completed tests of full-scale heat exchanger and hydrogen pre-burner subsystems validated the design of what are key components required to supply heat energy and air to the core of the air-breathing engine.

Reaction Engines, which also has a U.S. test operation in Denver, Colorado, has worked for decades on its Sabre synergetic, air-breathing rocket engine for aerospace applications, including for combat jets and to assist vehicles into space.

In recent years the work has attracted BAE Systems, Rolls-Royce, Boeing Horizon X and others to invest in the company. The British government has also ploughed millions of pounds into the company’s design effort. Ministry of Defence funding has gone toward Reaction Engines’ work with Rolls-Royce and BAE for the possible application of high-Mach know-how on the sixth-generation Tempest fighter project.

The latest test success comes as the field of hypersonic technology becomes increasing attractive in the West, triggered in part by rapid technological advances by potential adversaries.

Other Western engine companies are also investing in hypersonic propulsion. Pratt & Whitney recently confirmed it is developing a hypersonic engine it calls the Metacomet. The company designed the J58 engine that powered the SR-71 Blackbird spy plane to a record speed of about Mach 3.4 in the 1960s.

Adam Dissel, the president of Reaction Engines’ U.S. operation, said the effort to advance in the hypersonics sector is generating plenty of cross-Atlantic dialogue between Washington and London.

“There is great collaboration between the U.S. and U.K., and there are lots of discussions happening as to how we collaborate on these technologies,” he said.

The success of the trials on the heat exchanger, known as the HX3, and the pre-burner is another step in the right direction to maturing Reaction Engines’ technology. The latest tests follow trials undertaken in 2019 in Denver, where the company undertook high-temperature airflow testing for the Defense Advanced Research Projects Agency’s HTX program.

The company reported at the time that its proprietary ultra-lightweight heat exchanger used in the test was exposed to hypersonic conditions approaching 1,000 degrees Celsius, or roughly 1,800 degrees Fahrenheit. The heat exchanger performed its pre-cooler function by quenching about 1,800-degree Fahrenheit temperatures in less than one-twentieth of a second, according to the company.

Dissel said that together the three tests successfully demonstrate key subsystems not previously used in an aerospace environment.

“The company is very focused on maturing the subsystems that are fundamentally new to aerospace. Pre-cooler was the big one, and now with the innovative HX3 heat exchanger and pre-burner tests, these are three key components very specific to Sabre,” he told Defense News on March 5. “We are well past the hump in terms of validating the fundamental pieces. Putting it together as an integrated device able to go five times the speed of sound is still a big challenge, so from an overall integration standpoint we are at the beginning.

“There are some additional components that are in the works, but the next real, major milestone for us is to put several of those subsystems together in what would be cooperative operation of a Sabre on the ground. In the first instance it wouldn’t be a full engine generating thrust, but it would demonstrate the full behavior of the [engine] cycle to prove the validity of the concept.”

When might we see Reaction Engines move to the next stage and conduct a Sabre engine core test? The company said last year that could happen in the next 12-18 months. Now, however, there appears less willingness to discuss dates.

Answering a question about timing, Dissel said Reaction Engines continually evaluates what can be done in terms of funding and customers, including the British government. “Certainly it is in the technology plan, but timing is somewhat funding-dependent.”

In the meantime, Reaction Engines is generating revenue through its own by marketing efforts and making the individual elements of the technology it has developed available to commercial markets. The company has created an applied technologies division in the U.K. that offers thermal management and other products for the aerospace, energy, environmental and automotive sectors, among others. Dissel expects to see the company secure its first commercial contracts this year.

“As a company we are looking at the near-, mid- and far-term revenue-generating opportunities. Our investors would like to see a return on investment, and their interests span that gamut. So as a company we are very much diversifying and looking at what can be addressed in all three of those areas,” he said.

However, it’s not just about generating returns for shareholders, he noted.

“The revenue along the way is important, but we also see the opportunity to be maturing and gaining experience and credibility with these enabling technologies,” he said. “Midterm you will see coming online systems where we believe Sabre-derived technology will enable faster flight.”

That ambition potentially got a boost in 2019 when the British MoD signed a deal with Rolls-Royce, Reaction Engines and BAE to undertake high-Mach propulsion studies in parallel with early work being conducted on the Tempest sixth-generation fighter, under development by Britain and its partners Italy and Sweden.

Updating the EJ200 engine, which powers the Typhoon fighter, with Reaction Engines’ know-how might be another option, a senior Royal Air Force officer suggested at the time of the announcement.

“The full Sabre engine design is at the end of the road map, offering a complete revolution in the way we access space. That doesn’t come online until the mid-2030s as a fully operational system,” Dissel said.

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