The present invention provides a regenerative superheater system for an ejector ramjet engine. The invention includes a superheater in thermal communication with the combustion chamber of the ramjet engine. The superheater transfers thermal energy from combustion chamber to an ejectant which is then redirected upstream to the ramjet ejector. In one embodiment of the invention the temperature of the ejectant is modulated by a variable geometry cooler that controls the amount of thermal energy removed from the superheater system by ambient air. In an alternate embodiment of the invention, the temperature of the ejectant is modulated by a variable geometry superheater that controls the amount of thermal energy added to the superheater system through combustion gas.