Abstract: The combined propulsion engine comprises an air-breathing jet engine and a non-air-breathing rocket engine, the jet engine comprising an air inlet device and an external nozzle which, in association with a central body, defines an air-breathing combustion chamber, while the rocket engine comprises a non-air-breathing annular combustion chamber and at least one turbo pump for feeding it with propellant. The combustion chamber of the rocket engine is disposed inside a central body towards the rear thereof and is situated at the downstream end of the air-breathing combustion chamber, the rocket engine combustion chamber being itself delimited by a streamlined portion extending the central body and constituting a spike which penetrates into the throat of the external nozzle while ensuring aerodynamic continuity for the stream of combustion gases leaving the air-breathing combustion chamber.

Abstract: The diverging portion of discontinuous curvature is fitted with a controlled injection device for controlled injection of an additional jet of gas into the diverging portion in the same direction as the main flow of gas ejected by the nozzle, and said controlled injection device is disposed outside the diverging portion in the vicinity of the join zone between the first and second lengths in order to inject a determined flow of said additional gas into the diverging portion along a direction which is not tangential to the wall of the diverging portion.