Adapter device for a rocket engine nozzle having a movable diverging portion

A device, for use with a rocket engine nozzle, including a stationary nozzle throat and the diverging portion that is movably mounted relative to the nozzle throat, under conditions of relatively high, initial external pressure, for minimizing separation of a jet created by the rocket engine nozzle and having a flow section, from an inside surface of said movably mounted diverging portion,

• wherein thrust deflection of said rocket engine nozzle is achieved by adjusting an orientation of said diverging portion and the flow section, to deflect the jet to maximize an area of contact between said jet and diverging portion, the device comprising:
• a structure that is disposed inside of and fixed with respect to said diverging portion and formed separately therefrom, to reduce the diverging nature of the flow section and, when the orientation of the diverging portion is adjusted, to increase the area of contact between said jet and said inside surface of the diverging portion and to decrease jet separation,
• the structure including a plurality of protuberances that are distributed on the inside wall of and along the axis of the structure and that project some radial distance into the flow section to provide additional surface area for deflecting the jet in said flow section, and
• the plurality of protuberances having a streamlined shape whose radial distance of projection into the flow stream substantially increases in an axial direction towards the downstream end of said structure before decreasing proximate said gas outlet portion of said diverging portion.