Another flying engine without moving parts is the ramjet [1]. It's a compression engine that doesn't use turbine blades to compress the incoming air, but simpl

Another flying engine without moving parts is the ramjet [1]. It's a compression engine that doesn't use turbine blades to compress the incoming air, but simply the speed of the flying object itself. Since it can't function at speed zero by definition it needs assistance to get to a minimum speed where it function (which is usually Mach 3). For this reason it's usually found in missiles; more recently it showed up in artillery shells [2]. An engine not having moving parts does not mean no noise though. I never heard a ramjet powered missile myself, but I doubt it's very quiet. [1] https://en.wikipedia.org/wiki/Ramjet https://en.wikipedia.org/wiki/Ramjet [2]http://www.thedrive.com/the-war-zone/21531/yes-this-is-a-ramjet-powered-artillery-shell-and-it-could-be-a-game-changer http://www.thedrive.com/the-war-zone/21531/yes-this-is-a-ram...