The Synergistic Air-Breathing Rocket Engine, or SABRE, designed by UK-based Reaction Engines Ltd is a hybrid jet and rocket engine designed for a single-stage-to-orbit space plane. Incorporating innovative precooler technology (seen left of the right-side intake) able to chill superheated air in a fraction of a second, SABRE would use oxygen from the atmosphere until it reaches above Mach 5, after which it would shift to a closed-cycle rocket mode. The concept paves the way for true spaceplanes – lighter, reusable and able to fly from conventional runways. Reaction Engines plan for SABRE to power a 84 m-long pilotless vehicle called Skylon, which would do the same job as today’s rockets while operating like an aeroplane, potentially revolutionising access to space.