This advanced combined cycle air-breathing SABRE rocket engine enables aircraft to operate easily at speeds of up to five times the speed of sound or fly directly into Earth orbit.

With the Pre-cooler heat exchanger and other SABRE engine advanced technology development programmes nearing completion, the next stage of the SABRE programme is the construction of a full engine demonstrator..

"ESA are confident that a ground test of a sub-scale engine can be successfully performed to demonstrate the flight regime and cycle and will be a critical milestone in the development of this program and a major breakthrough in propulsion worldwide."

European Space Agency Report to the UK Space Agency, 2011