ESA go-ahead heralds core testing on SABRE air-breathing hybrid rocket engine

Reaction Engines given green light to start testing programme for the core section of SABRE, its proposed single-stage-to-orbit spaceplane engine.

A three-year programme to design, build and demonstrate the core of an engine that could take a spaceplane from the ground into low-Earth orbit in a single stage looks set to pass a series of important milestones now that the European Space Agency (ESA) has approved a testing programme. The UK Space Agency (UKSA) and ESA have been reviewing the preliminary design of the demonstrator core.

“The positive conclusion of our preliminary design review marks a major milestone in SABRE development,” said Mark Ford, heading ESA’s Propulsion Engineering section. “It confirms the test version of this revolutionary new class of engine is ready for implementation.”

Detail of the SABRE engine core demonstrator. Image: ESA

Reaction Engines is building a test facility for the core at Wescott Venture Park in Buckinghamshire, on a site where the engines for the last generation of British-developed rockets, Blue Streak and Black Arrow, were tested in the 1950s and 60s.

The SABRE is a hydrogen-fuelled engine which, from launch to the top of the atmosphere, uses atmospheric oxygen in its combustion cycle, and once out of the atmosphere switches to an on-board liquid oxygen supply. Its essential components include a pre-cooler that ensures that the engine core runs with cold inputs and keeps the core components cool despite the heating effect of its high velocity; the engine core, containing heat exchangers plus combustion and turbomachinery modules; and the rocket nozzle. The pre-cooler was tested and validated under ambient air conditions in a program started in 2012.

ESA’s involvement began in 2010 with an independent review of SABRE’s viability, which opens the way to UK government investment via the UK space agency. ESA has invested €10m in SABRE development via UKSA, along with £50m from UKSA, and continues to provide technical oversight for the project on behalf of UKSA. As ESA is not a European Union organisation, this relationship will continue unbroken and unaffected by the Brexit process.

The core demonstrator has been developed and built at a scale as representative of a SABRE flight engine, according to Reaction Engines, and testing is set to begin this year culminating in full system testing in 2020, by which point the entire cycle accelerating from a standing start to Mach 5 – the velocity limit in air breathing mode – will have been demonstrated. In rocket mode, the engine is capable of propelling its vehicle at Mach 25.

“One of the great advantages of the SABRE propulsion concept is that it is totally modular from both design and operational perspectives” said Richard Varvill, CTO of Reaction Engines. “Therefore it is possible to subject each of the key components of the engine to rigorous ground testing, which fully mimic the operational conditions the engine will face up to Mach 5 flight at 25km altitude.”

Chris Castelli, director of programmes at the UKSA, said: “As the home of the jet engine, the UK has a rich aerospace heritage and world-renowned skills and expertise. This is an exciting landmark for Reaction Engines in the development of its SABRE engine, which could revolutionise both access to space and international travel by powering aircraft to five times the speed of sound.

“The government’s modern industrial strategy is putting the UK at the forefront of pioneering aerospace technologies and ensuring we thrive in the new commercial space age. Our £60m investment in SABRE is a great example of how we are backing the businesses of tomorrow.”