On Wednesday 10th March 2021, nearly 400 people joined our IET Central London webinar  where Sophie Harker, a Senior Aerospace Engineer at BAE Systems and a recognised young engineer, enlightened us on SABRE: A New Class of Propulsion.Important note: These are the author's personal recollections and interpretations, which are likely to suffer from errors and selectivity. There is no endorsement from the IET or the speaker.


For those like me who were new to the subject, it was a great introduction to the 'Synergetic Air Breathing Rocket Engine' from Reaction Engines.

We learnt how we currently get to high speeds with conventional gas turbine engines and Ram/Scramjets, and the main drawbacks of those technologies. Sophie clearly took us through the development history of SABRE and the two modes of operation: the air-breathing cycle for atmospheric travel up to about Mach 5.4 and 28km in altitude; the rocket cycle to go up to 100km and beyond.

The technology development required for just the pre-cooler has been outstanding, truly breaking new ground. Testing has been successful so far, and continues.

Skylon is the concept design for an uncrewed reusable spacecraft to use a pair of SABREs to take a payload up into space or to bring items back. 

To help us appreciate the enormous size of the SABREs and the Skylon, Sophie overlaid a fighter plane (that was the approxiate length of the Skylon tail) and an A380 airliner (which is about 3/4 of the Skylon length). Not surprisingly, it will need a very long runway for its horizontal takeoff and, as it is very loud indeed, the airports will need to be away from built-up areas, probably near the coast.

There are many other applications of SABRE that are being researched. Imagine being able to get from UK to Australia in 4.5 hours, or New York in half an hour!


This is a topic that could have been expanded upon almost infinitely; there were certainly too many good questions from our engaged audience for them all to be answered, but Sophie managed at least 30.


I wish that we could have shared a recording of the talk and the slide pack, but this was not possible for confidentality reasons. However, a number of YouTube videos are available to illustrate some aspects that Sophie discussed:



Robert Heaton