Key tests for Skylon spaceplane project

The proposed Skylon vehicle would operate like an airliner, taking off and landing at a conventional runway. Its major innovation is the Sabre engine, which can breathe air like a jet at lower speeds but switch to a rocket mode in the high atmosphere. Reaction Engines Limited (REL) believes the test campaign will prove the readiness of Sabre’s key elements. This being so, the firm would then approach investors to raise the £250m needed to take the project into the final design phase. The test stand will not validate the full Sabre propulsion system, but simply its enabling technology - a special type of pre-cooler heat exchanger.Sabre is part jet engine, part rocket engine. It burns hydrogen and oxygen to provide thrust - but in the lower atmosphere this oxygen is taken from the atmosphere. The approach should save weight and allow Skylon to go straight to orbit without the need for the multiple propellant stages seen in today’s throw-away rockets.