Pulsejet propulsion is a type of gas turbine engine that operates on the principle of intermittent combustion to generate thrust. There are several alternative terms that can be used to describe this propulsion system. For example, pulsejet engines are sometimes called pulse detonation engines, intermittent combustion engines, or valved pulsejets. Pulsejet engines have also been referred to as flying stovepipes, because of their distinctive tubular shape. Additionally, pulsejets are sometimes described as simple or primitive engines, since they typically have fewer moving parts than other types of turbines. Despite their simplicity, pulsejets can be highly efficient, and have been used in a variety of applications, including rocket boosters, drones, and model airplanes.