ESA, together with the UK Space Agency (UKSA) has given a positive evalution after reviewing the preliminary design of the demonstrator engine core of the Synergetic Air-Breathing Rocket Engine (SABRE). Reaction Engines will use to undertake ground-based testing at test facility at Westcott, Buckinghamshire, which is currently under construction. This will lead to major testing milestones being undertaken within the next 18 months. SABRE is uniquely designed to scoop up atmospheric air during the initial part of its ascent to space at up to five times the speed of sound. At about 25 km it would then switch to pure rocket mode for its final climb to orbit. In future SABRE could serve as the basis of a reusable launch vehicle that operates like an aircraft.