Experimental study of the burning rates of some solid propellants by using a closed bomb

Abstract

This report represents an attempt to correlate experimental data obtained with a burning rate bomb with the data obtained from the firing of rocket charges, and to obtain burning rate curves for new propellants where insufficient data exists. It was found that very good agreement could be obtained between experimental data obtained in a burning rate bomb and data derived from test firing of rocket charges. A comparison was made among three different propellants which utilized Thiokol LP-3 for the fuel, and potassium perchlorate and ammonium perchlorate, separately or in combination, for the oxidizer. It was found that potassium perchlorate only gave the fastest burning rate, and the ammonium perchlorate only gave the slowest burning rate, while a mixture of the two gave an intermediate value. An investigation was made on the coning of solid propellant charges. Coning is the term applied when the burning of a solid propellant charge forms a conical burning surface. Normally a flat burning surface is expected and desired. It was found that a wide deviation in the burning rates existed between the center of the propellant and the edge in the case of the mixture of the ammonium and potassium perchlorate and the pure ammonium perchlorate oxidizers. The results also showed that the difference in burning rates between the center and edge of the charge increased as the amount of ammonium perchlorate in the oxidizer was increased. The limited investigation seemed to indicate that the fundamental variation in burning rate was the only cause of coning. Best results were obtained from the use of a restricting material similar in nature to the propellant being investigated. In this case, a Thiokol restricting material gave the best results on the Thiokol propellants.