Calculation of solid-propellant burning rates from condensed-phase decomposition kinetics

Kinetic rates of thermal decomposition reactions of three ammonium perchlorate composite propellants have been determined by the techniques of differential scanning calorimetry and thermogravimetric analysis at pressures to 500 psi (1 psi=6894.7 Pa=0.068 atm; 1 atm=14.7 psi). The results of these experiments were extrapolated to give heat-evolution rates at temperatures that are believed to prevail at the surface of burning propellants. A semi-empirical condensed-phase combustion model has been used to calculate propellant burning rates from these heat-evolution rates and surface temperatures determined by equilibrium vaporization. Calculated and experimental burning rates are found to agree within an order of magnitude. The differences between these rates were attributed to a gas-phase heat-flux term in the energy balance at the propellant surface.