Air-breathing jet engine that operates with no major moving parts.
It relies on the craft's forward motion to draw in air and on a specially shaped intake passage to compress the air for combustion. After fuel sprayed into the engine has been ignited, combustion is self-sustaining. As in other jet engines, forward thrust is obtained as a reaction to the rearward rush of hot exhaust gases. Ramjets work best at speeds of Mach 2 (twice the speed of sound) and higher. See also turbojet .