Defence giant BAE Systems has announced that it is to invest £20.6m in Reaction Engines Limited, an Oxfordshire firm that hopes to revolutionise access to space through the development of a new class of aerospace engine.
Under the terms of the deal, BAE will acquire a 20 per cent share in the company and will collaborate on the development of Reaction’s SABRE engine, a new aerospace engine that combines both jet and rocket technologies.

The partnership is expected to draw on BAE’s aerospace technology development and project management expertise and will provide Reaction Engines with access to critical industrial, technical and capital resources to progress towards the demonstration of a ground based engine – a key milestone in the development of the technology.
BAE will also enter into a preferred supplier relationship with Reaction Engines in certain agreed areas and will have representation on the board of Reaction Engines.
SABRE (Synergetic Air-Breathing Rocket Engine) is an advanced combined cycle air-breathing rocket engine designed to enable aircraft to operate from standstill on the runway to speeds of over five times the speed of sound in the atmosphere.
At this point it is designed to transition to a rocket mode of operation, allowing spaceflight at speeds up to orbital velocity, equivalent to twenty five times the speed of sound.
Through its ability to ‘breathe’ air from the atmosphere, the engine offers a significant reduction in propellant consumption and weight compared to conventional rocket engines which have to carry their own oxygen.

One of the key elements of the design is an ultra-lightweight heat exchanger that allows the cooling of very hot airstreams from over 1,000 °C to -150 °C in less than 1/100th of a second whilst preventing the formation of ice at sub-zero temperatures.
The technology has already undergone extensive independent technical assessments which have confirmed its viability and potential vehicle applications, one of which is Reaction’s Skylon concept: an unpiloted, reusable space plane intended to provide reliable and cost-effective access to space. Currently in the development phase, the vehicle is expected to be capable of transporting 15 tonnes of cargo into space.

Mark Thomas, managing director, Reaction Engines Limited said: “Today’s announcement represents an important landmark in the transition of Reaction Engines from a company that has been focused on the research and testing of enabling technologies for the SABRE engine to one that is now focused on the development and testing of the world’s first SABRE engine.
”BAE Systems brings industry leading capabilities in programme delivery and wider engineering systems integration that will accelerate the development of SABRE as a new engine class and its vehicle applications technology from experts at the European Space Agency.”
Nigel Whitehead, group managing director, Programmes & Support, BAE Systems said: “Reaction Engines is a highly innovative UK company and our collaboration gives BAE Systems a strategic interest in a breakthrough air and space technology with significant future potential.”
The UK government is expected to confirm grant funding of a further £60m for Reaction Engines to further SABRE’s development towards a ground based test engine and to investigate its applications for space access vehicles.
Excellent news. This should be a UK Key Strategic Technology. I wish them the very best.
Fantastic! This is what we should be doing as a country. Gerry Anderson would be very proud.
Couldn’t agree more. Excellent news and lets keep this one in house as it where.
Whilst being a big supporter of such research being done in the UK, I note the statement “One of the key elements of the design is an ultra-lightweight heat exchanger that allows the cooling of very hot air-stream from over 1,000 °C to -150 °C in less than 1/100th of a second…”
My, admittedly limited, knowledge of the science behind this is largely using what I recall of Boyle’s Law (P1V1/T1 = P2V2/T2) which seems to indicate that the removal of heat from air compressed in the quantities needed to produce sufficient thrust will require a massive, no matter how efficient, heat exchanger especially to cool the compressed air by such a large amount in the times quoted. To use external temperature air across a heat exchanger will probably also produce significant drag and at the velocities envisioned, significant amounts of heat. I am concerned this engine may prove less practicable than is being promoted.
JohnK, whilst scepticism is a good attribute in an engineer, this is far more than just a PowerPoint concept and facts are readily available:
http://reactionengines.co.uk/sabre_enabletech.html
REL have produced production-ready full-scale HX modules tested in-front of a Viper engine (pictured above). An independent ESA report commissioned by the UK Space Agency in 2011 found “no impediments” to further development of Reaction Engines’ SKYLON Spaceplane.
http://reactionengines.co.uk/press_release/Confidence_in_SKYLON_24.05.2011.pdf
More recently, the US AFRL have confirmed feasibility of the SABRE engine concept:
http://reactionengines.co.uk/press_release/AFRL-REL_CRADA_Press_Release_15April2015.pdf
IanC – Thanks for the pointers and I had a good look at the 1st one which seems to encompass the others as well in its scope. I have no argument with the heat exchanger technology itself, but with the sheer amount of heat that must be removed and disposed of. This practical need was not addressed, either by you or by Reaction Engines website, so your response does not provide any answers to my questions.
So why is it slightly bent in the drawings?
JohnK:
The practical need for the HX is to pre-cool the hot inlet air-stream (1,000 °C heat due to deceleration from Mach 5 to sub-sonic within the nacelle) before it enters the compressor, to prevent blades and other components from melting. This is the reason why the SR71 Blackbird and other supersonic aircraft are limited to ~Mach 3.
A closed helium loop takes this large amount of heat (400 MW from memory) and disposes of it by dumping it into the liquid hydrogen fuel carried by Skylon, which has a very high heat capacity (higher than water). Part of this (now gaseous) hydrogen is burnt with the compressed air in the rocket combustion chamber generating the air-breathing thrust. The rest is mixed with by-pass air (uncompressed) and combusted in by-pass ramjets surrounding the main rocket nozzles (see diagram above). These ramjets provide little thrust, but do help overcome drag.
Rob Pipien:
The banana shape of the SABRE engine has two reasons. The inlet curves down so that it directly hits the Mach 5 airstream while Skylon flies with a small angle-of-attack. The nozzles point down in-order that thrust passes directly through Skylon’s centre of mass while accelerating to Mach 25 in pure rocket mode.
JohnK: I should add, the hot incoming air and the cryogenic liquid hydrogen form the hot and cold sides of a heat engine, with the helium loop (working fluid) passing through its own compression and expansion stages.
This generates the mechanical power used to drive the main compressor – I find that to be a very clever and efficient design concept!
To Editor: I’m curious where the ‘Skylon’ design image has come from? As it is different to those presented on reaction engines website or anything else I’ve seen related to the design concept.
IanC – Thank you. Your clear and precise explanation is most welcome.