Some embodiments of the present disclosure are directed to a rocket engine, comprising a primary chamber and a double contour nozzle attached to the primary chamber. In some embodiments, 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 contour break point between the inner contour nozzle and the outer contour nozzle. Ins some embodiments, the outer contour nozzle comprises a radius of curvature of less than 0.75 and a tangency angle of 40 to 90 degrees on a surface adjacent to the contour break point.