Theoretical Analysis of Dual-Thrust Rocket Motors with Intermediate Nozzle

摘要

Dual-thrust rocket motors with intermediate nozzles provide a compromise between the two commonly competing design requirements: a high thrust ratio, and a stable motor operation. Depending on the design of the motor and propellant charges, the flow of combustion gas products through the intermediate nozzle during the boosting phase can be sonic, subsonic, or initially reversed. The state of this intermediate nozzle flow dictates the values of equilibrium pressures in both chambers during the boosting phase. In the sustaining phase, the intermediate nozzle maintains a high equilibrium pressure for the sustaining grain while its gas products expand twice, yielding a low sustain thrust. The present Note has been devoted to developing an integrated mathematical treatment for the DTRM with an intermediate nozzle in all possible operation conditions. Starting from the basic physical relations and using justified assumptions, closed-form expressions for equilibrium pressures and thrusts have been deduced.