Rockets are a spectacular way to get into space. But they are also inefficient. Unlike jet engines, which combine atmospheric oxygen with stored fuel to obtain thrust, rockets must work in a vacuum, and so must carry their oxygen with them. That increases their weight, with the result that a large fraction of a rocket's fuel is expended just lifting the rest of the fuel off the launch-pad. Now Reaction Engines, a small British firm, reckons it has a way around the problem. On November 28th it said it had completed a series of tests of its sabre engine, a high-tech hybrid of a rocket and a jet.
展开▼
