The Sabre (Synergetic Air Breathing Rocket Engine) is a new class of engine for propelling both high-speed aircraft and spacecraft

The UK Space Agency is awarding a £3.9m grant for the development of Reaction Engines’ Sabre technology.

Sabre – Synergetic Air Breathing Rocket Engine – is a new class of engine for propelling both high-speed aircraft and spacecraft, delivering the fuel efficiency of a jet engine with the power of a rocket. 

The engine is designed to operate in two modes. Within atmosphere it acts like a conventional jet engine to propel an aircraft from take-off to Mach 5. Outside atmosphere it switches to conventional rocket operation using stored liquid oxygen to reach 25 times the speed of sound.

“The innovative and disruptive nature of Sabre technology unlocks new ways of accessing space, furthering growth and sustainment of the future space economy,” said Mark Thomas, chief executive at Reaction Engines. The technology that Reaction Engines is developing for Sabre could also be used in the transport industry, for example, to help drive towards the government’s net-zero target.

Science minister Amanda Solloway said: “Backed by government, UK firms are leading the way in developing space technology that can reduce costs, improve sustainability and make space more accessible as we pursue our ambitious plans to grow the sector.” 

This latest investment of £3.9m builds on £50m of previous government funding since 2015. Reaction Engines’ Sabre technology is expected to bring new developments not just in space, but also potentially in other spin-out areas including sustainable aviation fuels, unlocking atmospheric high-speed flight and extending electric vehicle battery life through pioneering thermal management technology.

Technology validation

Transport minister Rachel Maclean said: “We will continue to invest in, and support, companies like Reaction Engines, as we look to a greener, cleaner future – including as we embark on sustainable space exploration.”

This new funding comes after successful validation of Sabre technology in February 2021, where Reaction Engines completed tests of two important sub-systems, the HX3 heat exchanger and the advanced hydrogen pre-burner. 

Together, these sub-systems deliver heat to the engine’s core. As the aircraft accelerates, heat energy is converted in the engine intake and extracted through the pre-cooler, progressively taking over the energy provided by the pre-burner extracted through the HX3 heat exchanger. 

The objectives of both test campaigns were to produce full-size test rigs to validate performance modelling and de-risk high-temperature operation in advance of further integration. The pre-burner test campaign also intended to show that the fuel-injection system would function at full scale, that it was able to control the heat output precisely and provide even temperature to the HX3.

The HX3 test was conducted at Airborne Engineering’s Buckinghamshire test facility where the company built a custom hot-gas source, which was capable of providing partially combusted air with variable mass flow and temperatures controlled from 428°C to well in excess of 928°C. The rig also required closed-loop feedback control of the mass flow of hydrogen and air for combustion, the mass flow of helium coolant and the pressure of the hot coolant exhausted from the heat exchanger.

The latest round of government funding will secure further near-term technology demonstrations in hydrogen combustion, thermal management, and engine control technologies, which are all critical to the air-breathing core of future Sabre systems.

This campaign has been conducted in partnership with S&C Thermofluids based at their facility at Cotswold Airport in Gloucestershire. Utilising their innovative gas turbine air delivery system, we were able to simulate temperature and mass flows that the preburner will experience in flight on SABRE.
Tony Smith, S&C Thermofluids Company Director had this to say about the campaign:

“During this campaign, the S & C control systems were combined with the REL Engine Control System for the first time and to great effect. The new N-site facility at Cotswold Airport proved to be a very suitable location for operating this and other future aerospace engine technologies using hydrogen.”

The completion of this test campaign marks an important step on the road to a full engine demonstrator. The next phase of development will take place imminently and will involve testing the preburner and HX3 together to establish a full early flight heat control system for the engine core.

Reaction Engines CEO Mark Thomas had this to say:

“The completion of this test campaign marks an important milestone in the realisation of SABRE. The hydrogen preburner is a vital element of the engine cycle and I am thrilled at the progress the team is making.”

source:institution of mechanical engineers , Reaction Engines