Effects of thermal radiation on the acoustic response of solid propellants

Theoretical calculations are given for the propellant response function when thermal radiation of the burnt gases is taken into account. Under the assumption that the gas radiates as a gray body, it is found that radiation effects may significantly alter the response function at low frequencies for the low propellant burning rates which are commonly found at low pressures. Thus, this mechanism may offer a partial explanation of the fact that experimental values for the response function at low frequencies and low burning rates tend to be larger than is expected from existing theories. The method of calculation is based on a second order perturbation scheme where the perturbation parameter is a measure of the ratio of energy transfer by radiation to convective energy transfer. (Author)