Air-Breathing Rocket Engine Technology

July 20, 2022
Air-Breathing Rocket Engine Technology
Integrated Hydrogen Preburner System to commence ground testing

Reaction Engines is proud to announce the completion of a critical subsystem, integral to air-breathing rocket engine technology development for space access.  At Reaction Engines’ UK headquarters, our skilled team has successfully integrated our high performing HX3 heat exchanger and advanced Hydrogen Preburner modules to form the ‘Integrated Preburner System’, part of our advanced engine cycle development.


The “Integrated Preburner System” provides a controllable heat source within an air-breathing SABRE engine cycle to enable flight at low speeds and low altitudes.  This system allows the overall engine to bridge the gap between low and high-speed operation, generating and harvesting heat to power various internal components at low-speed conditions.

The Preburner component is a lean hydrogen-air combustor that can be throttled to generate varying amounts of thermal energy.  The HX3 is a unique extreme-temperate heat exchanger. HX3 transfers thermal energy from the Preburner into a helium loop for powering adjacent subsystems within the system. The hot gas produced from hydrogen-air combustion in the Preburner generates temperatures up to 1450K. HX3 extracts energy from the hot combustion gas via heat transfer using Reaction Engines’ innovative heat exchanger design.

The design, manufacture and testing of this technology is a great example of how the team at Reaction Engines is progressing air-breathing technology, integration and testing represents an important milestone in overall development.  This step also serves to show the strength of the UK in researching, designing and manufacturing unique forward-looking aerospace propulsion technology. The learning received in the development of this technology will also be applied to spin-out opportunities adjacent to space access and will advance thermal management capability for use within other applications and industries.

Extreme Temperature Heat Exchanger

The fully Integrated Preburner System is possibly the most extreme heat exchanger that has ever been developed. Its combustion temperatures can reach over 1450K (1100° C), which is enough to melt gold and at 100% throttle, generates approximately 2.5MW of energy.  For a sense of scale, the volume of the matrix performing the thermal heat transfer could fit in an airplane suitcase.

Sam Fox, Senior Systems and Test Engineer, had this to say about the successful integration of the HX3 and Preburner subsystems: “Successful assembly of such an advanced system does not come without challenges. Our team of highly experienced engineers and technicians did a fantastic job to coordinate and manage this activity, demonstrating again the strong assembly, integration, and testing capabilities within the Company.

Ground Testing

The full Preburner System has been transported to Cotswold Airport where we will once again be working with our UK partners S&C Thermofluids to conduct this testing campaign. The system is now in the process of being integrated into the test site with ground support equipment, full control systems, and data acquisition systems. Integration will be followed by the official commissioning of the full test site arrangement configuration, with testing due to commence in July. The results of this test campaign will provide demonstration of the Preburner System design concept and valuable learning for system performance and operation that will be fed directly into future development.

Shaun Driscoll, Programme Director of Reaction Engines had this to say about the milestone: “The successful design, build and integration of the HX3 and Preburner subsystems represents a phenomenal effort from the Reaction Engines’ team. The Preburner System provides quite astonishing capability and is a vital element of an advanced engine cycle like SABRE. I am excited to see it perform in testing!”

If you would like to find out more about our air-breathing rocket technology and the ground testing of the Preburner System, come and meet us at Farnborough International Airshow, July 18-22 in the Space Zone.