Comprehensive Study of Ammonium Perchlorate Particle Size/Concentration Effects on Propellant Combustion

The effects of altering ammonium perchlorate (AP) particle size or concentration in composite AP/hydroxyl-terminated polybutadiene (HTPB) solid propellants are well documented. Existing propellant burning rate datasets include these variations, but they have significant holes in their current data span. In the current study, isophorone diisocyanate-cured composite AP/HTPB propellants were manufactured with AP mass concentrations between 70 and 87.5% and unimodal AP sizes between 20 and 500 μm; and propellant burning rates were evaluated at pressures of 3.4–21 MPa (500–3000 psia). Decreasing the AP particle size or increasing the AP concentration yielded increases in burning rate, as expected. The AP particle size effect is more drastic than that of the AP concentration. The resulting dataset was coupled with several existing propellant datasets from the literature to develop, for the first time, a simple, empirical correlation that captures these effects. The developed correlation accurately predicts the propellant burning rates for a large span of AP particle sizes and concentrations over a wide range of pressures.