Determination of the role of the ballistic modifier in propellant combustion using the heat of explosion test

Abstract

The role of the ballistic modifier in the combustion of a nitrocellulose propellant is evaluated using the heat of explosion test. It is shown that differences in heat of explosion caused by the modifier reflect differences in burning rate. This is particularly true at low pressures (below 500 lb/in2), where lead stearate affects the chemistry of the combustion process. Here lead stearate increases the heat of explosion as well as the burning rate. At the higher pressures (beyond the plateau region) lead stearate resembles a low energy (relatively inert) propellant additive; it decreases both the burning rate and the heat of explosion. The plateau can therefore be considered as a transitional region, where lead stearate changes its role from that of an active ingredient and catalyst to the role of an inert ingredient. In order to establish a common level for comparing the results, the burning rate and the heat of explosion tests are analysed in detail.