Control Forces in Rocket Nozzles Produced by a Secondary Gas Stream Inclined at Various Angles to the Nozzle Axis

Abstract

The side force produced by the injection of secondary gas into the supersonic regime of a main nozzle is investigated with particular reference to the effect of the angle between the secondary jet and the main nozzle axis. In the experiments, downstream and upstream injection angles at one secondary port location in the main nozzle were examined. It is shown that there is a definite advantage to be gained by injecting the secondary gas in an upstream direction. An analytical analysis of the results indicates that for moderate secondary mass flows maximum side force is produced when the angle between the axis of the secondary port and the normal to the axis of the main nozzle is in the range 40-50°. When injecting a given secondary mass flow at the angle for maximum side force the axial thrust augmentation is almost zero. As the angle of injection is reduced from upstream values to downstream values the side force reduces and the thrust augmentation increases, indicating that thrust augmentation can be used to determine how effectively a given mass flow of secondary fluid is being utilized in the production of side force.