RESEARCH ON UNSTABLE COMBUSTION IN SOLID PROPELLANT ROCKETS

Abstract

Abstract : Initiation of axial combustion instability in an experimental combustor, 40 inches long by 50 inches I.D., containing a radial burning grain, has been studied utilizing a wide variety of composite propellants. Where instability occurred, a correlation was found between the threshold pressure at which instability was first observed and propellant ballistic parameters, notably the linear burning rate. Fast burning propellants, containing either a catalyst or potassium perchlorate, did not sustain axial mode combustion instability. Transverse instability was observed for most non-aluminized propellants in pressure regimes where they were stable to axial combustion instability. An explanation of combustion stability criteria has been sought in terms of either mixing processes within a granular diffusion flame or a thermal explosion process. The granular diffusion flame concept appears thus far to be the more promising explanation; it predicts the stability trends observed in large solid propellant rocket motors.