Pulse jet as used on the German flying bombs in their Second World War.
A jet propulsion engine containing neither a compressor nor a turbine. Air enters the engine through a grid of inlet valves that close as the air is heated. Expansion through the exhaust nozzle produces thrust, and the inlet reopens as the internal pressure drops. This cycle is repeated rapidly. A pulse jet is similar to a ramjet but with the added advantage of being able to produce thrust even at zero forward speed. See also aeropulse