Thrust magnitude control for a solid rocket by injection at the throat.

Abstract

^EVERAL authors have proposed fluid injection at the ^ throat of a nozzle as a thrust magnitude control device. Martin and McArdle studied the case of subsonic nozzles, using a vortex sheet model and a flow separation model for the mixing process. Zumwalt and Jackomis, using cold flow experiments, demonstrated that control can be realized by throat injection in a supersonic nozzle. The present work concerns itself with injection just upstream of the throat of a supersonic nozzle, and consists of a theoretical analysis based on a one-dimensional model in which nondissipative mixing takes place. The flow is supposed to originate in the combustion chamber of a solid propellant rocket motor in which the burning rate obeys a power law relationship with the chamber pressure. A portion of the chamber gas is shunted past the nozzle inlet and is injected peripherally just upstream of the nozzle throat, which is presumed choked. The injection creates an effective constriction at the throat, causing the chamber pressure to increase. The analysis will show that a net increase in thrust results.