Scramjet

A form of jet engine that has no propellers but the air is compressed into the engine by the sheer speed at which the craft moves. Therefore it must be accelerated to Mach 3 by a "normal" jet engine which uses a propeller to compress air. Once started, howewer, the scramjet can accelerate to Mach 11 and thus escape the Earths gravity. It is a technology for better launches partly because the whole craft can be used many times before service and partly because the use of compressed surrounding air eliminates the need to carry oxidant for the launch. The latter also saves so much weight the amount of fuel can be greatly reduced. The craft can also start and land on normal airports.