The turbojet is the oldest kind of general-purpose airbreathing jet engine. Two engineers, Hans von Ohain in Germany and Frank Whittle in the United Kingdom, developed the concept independently into practical engines during the late 1930s.
Turbojets consist of an air inlet, an air compressor, a combustion chamber, a gas turbine (that drives the air compressor) and a nozzle. The air is compressed into the chamber, heated and expanded by the fuel combustion and then allowed to expand out through the turbine into the nozzle where it is accelerated to high speed to provide propulsion.[1]
Turbojets are quite inefficient if flown below about Mach 2[citation needed] and very noisy. Most modern aircraft use turbofans instead for economic reasons. Turbojets are still very common in medium range cruise missiles, due to their high exhaust speed, low frontal area and relative simplicity.