Experimental and theoretical study on a dual-thrust rocket motor with subsonic intermediate nozzle

Dual-thrust rocket motors, with proper designs, can yield the desired boost-sustain thrust profiles for a variety of applications. Of the various designs that a dual-thrust rocket motor can have, the one with an intermediate nozzle provides a high boost-to-sustain thrust ratio as well as a stable operation. Depending on the internal conditions, the flow through the intermediate nozzle in the boost phase can be sonic, subsonic, or initially reversed. The present paper discusses the operation and performance of Dual-thrust rocket motors with subsonic intermediate nozzle. A mathematical model describing the internal ballistics of these dual-thrust rocket motors is derived from the basic governing equation. In addition, a set of experiments is conducted using a developed test motor to explore the physics of dual-thrust rocket motors with subsonic intermediate nozzle and assess the mathematical model validity. Results of the theoretical and experimental investigations explain most of the internal ballistics characteristics that were not discussed before in the open literature.