Abstract: An integrated rocket ramjet in which initial acceleration of the rocket is achieved by a rocket fuel propellant and subsequent flight is sustained by a ramjet engine receiving air via a supersonic diffuser from an inlet disposed at the middle of the rocket. The flame for the ramjet combustion system is incorporated into the diffuser so that diffusion and combustion take place simultaneously. The combustion process continues within the space previously occupied by the rocket fuel propellant and the walls bounding this space are the outer casing of the rocket and are directly cooled by free stream air flowing past the rocket.