Air-breathing rocket engine passes key initial tests


A key element of Reaction Engine’s SABRE air-breathing rocket engine has successfully passed the first phase of high-temperature testing.

The engine’s precooler technology has achieved all of the objectives in a set of high-temperature tests designed to replicate supersonic flight conditions.

The ground-based tests, which were conducted in a laboratory in Colorado, USA, saw the precooler quench an intake airflow of 420°C (788°F) in less than 1/20th of a second.

This intake temperature replicates the thermal conditions of Mach 3.3 flight, the speed record of the SR-71 Blackbird aircraft, the world’s fastest jet-engine powered aircraft produced to date.

The precooler is a crucial and complex part of the SABRE engine and could also be used in other advanced propulsion systems and commercial applications. It is designed to chill  incoming high-speed airflow to a temperature at which the engine can use it as part of its air-fuel mix to create thrust.

The compact precooler has also recently achieved 1.5 MW of heat transfer, successfully cooling incoming air from a temperature of around 460°C (900°F), during testing.

The tests are the first phase of a program which will eventually see the precooler test article (HTX) exposed to high-temperature airflow conditions in excess of 1,000°C (1800°F), the conditions the engine will experience during its maximum speed of Mach 5 hypersonic flight.

Reaction Engine’s TF2 test facility in Colorado has been built specifically to undertake the ground-based ‘hot’ testing of the precooler technology. The precooler has already passed an extensive range of tests in the UK where its performance was fully validated at ambient air temperatures.

Mark Thomas, CEO of Reaction Engines said, “The HTX test article met all test objectives and the successful initial tests highlight how our precooler delivers world-leading heat transfer capabilities at low weight and compact size.

“This provides an important validation of our heat exchanger and thermal management technology portfolio which has application across emerging areas such as very high-speed flight, hybrid electric aviation and integrated vehicle thermal management.”

To replicate the conditions the precooler will experience at hypersonic speeds, the TF2 test facility uses a General Electric J79 turbojet engine formerly used in a McDonnell Douglas F-4 Phantom aircraft to provide high-temperature airflow. Engineers at Reaction Engines’ Culham headquarters constructed the HTX precooler test article and after initial testing it was shipped to Colorado at the end of 2018.  ‘Hot’ tests commenced in early March 2019.

In addition to the hot precooler tests being conducted in the USA, Reaction Engines is in the final stage of constructing its TF1 test facility at Westcott, Buckinghamshire, UK, where it will undertake ground-based testing of a SABRE engine core.

Over the last four years Reaction Engines has raised over £100 million (US$130 million) from public and private sources and has secured investment from BAE Systems, Rolls-Royce and Boeing HorizonX.


Find out more about the SABRE test program in our in-depth feature here.

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About Author


Ben has worked as a journalist and editor, covering technology, engineering and industry for the last 20 years. Initially writing about subjects from nuclear submarines to autonomous cars to future design and manufacturing technologies, he was editor of a leading UK-based engineering magazine before becoming editor of Aerospace Testing in 2017.

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