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RESPONSE OF A BURNING PROPELLANT SURFACE TO EROSIVE TRANSIENTS
STANFORD RESEARCH INST MENLO PARK CA POULTER LABS
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The report describes an investigation of high-amplitude axial-mode solid rocket combustion instability which arises in the form of an oscillating shock wave in the combustion chamber. Experimental studies have provided an evaluation of the influence of compositional factors, oxidizer type, and deflagration characteristics on the incidence of axial instability. The stability characteristics of a wide range of ammonium perchlorate and potassium perchlorate propellants were determined in motors ranging from 15 to 82 in. in length, using an explosive pulse to initiate a traveling shock wave. Differential thermal analysis of these propellants, and experiments incorporating fiber-optic devices with high-speed photography, indicated that surface-coupled heat release is a key factor underlying the different stability behavior observed with various propellants. A theoretical combustion model was proposed and a mathematical analysis was developed that predicts the response of a burning propellant to the pressure pulse imposed by a traveling shock wave as it passes over the propellant surface. Also considered theoretically was the interaction mechanism through which this burning rate response supports the shock wave. The resulting theory predicts the limits of the stable operating regime for individual propellants in terms of thermochemical parameters and the degree of surface-coupled heat release associated with the propellant type. The theory provides a consistent explanation of all stability characteristics observed experimentally during this program and established guidelines for avoiding axial instability.
APPROVED FOR PUBLIC RELEASE