Twenty-Five Years of Ramjet Development

T ramjet engine is the youngest of the family of jet propulsion devices that includes the squid, the rocket, the turbojet, and the pulsejet. Because the ramjet depends on its forward motion to achieve compression of the intake air, the engine itself employs no moving parts and is therefore capable of a simplicity and lightness of construction not possible in other air-breathing engines. This, plus the high thermal efficiency it can achieve, makes the ramjet a favored choice for propulsion of aircraft at supersonic speeds. In the present article the history of ramjet development is briefly reviewed. This is followed by a summary of the design principles of ramjet engines. In the final section performance data for ramjets are compared with data for other jet engines.