ramjetscramjet

A ramjetscramjet is a theoretical or experimental air-breathing propulsion concept that combines ramjet and scramjet functionality within a single engine to provide propulsion across a broad Mach range.

In principle, the engine operates as a conventional ramjet at lower speeds, decelerating incoming air in an intake and mixing it with fuel before combustion. As flight speed increases and the flow becomes highly supersonic, the combustor maintains supersonic combustion characteristic of a scramjet, enabling continued efficiency at higher Mach numbers. The goal is to avoid a complete system change as speed rises, allowing a vehicle to transition smoothly from ramjet to scramjet-like operation.

Engine design for a ramjetscramjet typically features an inlet with variable geometry, a combustion chamber capable of both subsonic and supersonic combustion, and fuel injection and mixing systems suitable for different flow regimes. Transition between modes presents control challenges, requiring precise timing, inlet pressure management, and thermal protection for the structure. Materials and cooling must withstand wide ranges of temperature and pressure as the flow regime shifts.

The concept has appeared mainly in theoretical discussions and early-stage research. It is not yet deployed in production vehicles. Potential applications include high-speed missiles and launch systems where an air-breathing propulsion system would operate from moderate to very high speeds, but significant technical hurdles remain, including efficient mode transition, stability of combustion across regimes, and material limits.