Until now, launching a vehicle into space required a large rocket with a combination of liquid and solid fuels. The Skylon Spaceplan is, remarkably, a reusable vehicle that does not need a rocket to break the gravitational pull of the Earth. The Skylon uses a British engine called the SABRE (Synergistic Air-Breathing Rocket Engine) that is a single stage engine that can go from take-off to orbit in one phase.
It does so by taking in air, compressing and cooling it before mixing in liquid hydrogen. The high pressure/low temperature engine can be made out of lightweight materials reducing the overall weight of the vehicle and hefty fuel bill. When it’s at an altitude of 28km, the engine switches from using air, since there isn’t much air that high up, and starts burning its reserve tanks of liquid oxygen. The Skylon vehicle will be able to carry a payload of 15 metric tonnes at a cost of only R9.80 per kilogram. At the moment the Skylon is being developed as an unmanned vehicle, but it will eventually be certified to carry human passengers.