Rocket engine with dual contour nozzle

A method of operating a rocket engine, comprising:

• providing a rocket engine, wherein the rocket engine comprises:
• a primary propulsion subsystem,
• a secondary propulsion subsystem,
• a primary chamber,
• a double contour nozzle attached to the primary chamber, wherein the double contour nozzle comprises:
• an inner contour nozzle comprising a conical contour;
• an outer contour nozzle comprising
• a bell contour, and
• at least one propellant injection orifice, and
• a transition region between the inner contour nozzle and the outer contour nozzle,
• wherein the transition region comprises a radius of curvature of less than 0.75 and a tangency angle of 40 to 90 degrees;
• activating the primary propulsion subsystem;
• activating the secondary propulsion subsystem;
• performing a lift-off operation;
• deactivating the secondary propulsion subsystem;
• performing a mission operation;
• performing a landing operation;
• and
• deactivating the primary propulsion subsystem.