Pulsejet

A pulsejet engine (or pulse jet) is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few^[1] or no moving parts,^[2][3][4] and is capable of running statically (that is, it does not need to have air forced into its inlet, typically by forward motion). The best known example is the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.

Pulsejet engines are a lightweight form of jet propulsion, but usually have a poor compression ratio, and hence give a low specific impulse.

The two main types of pulsejet engines both use resonant combustion and harness the expanding combustion products to form a pulsating exhaust jet that intermittently produces thrust. The first is a valved or traditional pulsejet. It has a set of one-way valves through which the incoming air passes. When the fuel mix is ignited, these valves slam shut, which means that the hot gases can only leave through the engine's tailpipe, thus creating forward thrust. The second type is the valveless pulsejet.^[5] The technical terms for this engine are acoustic-type pulsejet, or aerodynamically valved pulsejet.

One notable line of research includes the pulse detonation engine, which involves repeated detonations in the engine, and which can potentially give high compression and reasonably good efficiency.