The European Space Agency (ESA), together with the UK Space Agency (UKSA), has reviewed the preliminary design of the demonstrator engine core of the Synergetic Air-Breathing Rocket Engine (SABRE).

The core will be used by Reaction Engines — the British company that developed the SABRE concept — to carry out ground-based testing at a dedicated test facility which is currently under construction. Further test milestones are scheduled over the next 18 months.

SABRE is designed to “breathe in” atmospheric air during the initial part of its ascent to space at up to five times the speed of sound. At an altitude of around 25km, it would then switch to pure rocket mode for its final climb to orbit.

The concept is seen as the basis of a reusable launch vehicle that operates like an aircraft. Because it would carry much less bulky onboard oxygen supplies, such a vehicle could deliver the same payload to orbit at half the vehicle mass of current launchers, as well as potentially offering a large reduction in cost and higher launch rate.

ESA, has invested €10m in SABRE development via UKSA, together with £50m from the British agency. ESA also performs a technical oversight role on behalf of UKSA.

Reaction Engines launched the programme to design, build and demonstrate the SABRE engine core in October 2016. The test item consists of an engine core, but without the pre-cooler and rocket nozzle in place. Earlier testing had validated the performance of the pre-cooler, which cools the hot airstream entering the engine at hypersonic speed.

The complete air-breathing core demonstrator will be fully representative of the SABRE thermodynamic core cycle, fuelled by liquid hydrogen, and will contain heat exchangers plus combustion and turbomachinery modules.