Nonlinear longitudinal combustion instability - Influence of propellant composition

Current stability criteria for longitudinal combustion instability were tested for generality using data from 54 different propellants. These included formulations containing polyurethane and carboxyl-terminated polybutadiene binders, ammonium perchlorate, aluminum, and rate modifiers. The propellants were tested at 70F in 4- and 8-in. diam, tubularly-perforated motors which were pulsed to initiate the instability. It was found that for a particular propellant system, well-defined behavioral trends could be established as the formulation was varied. A considerable variability in such trends was observed, however, for grossly different propellant systems. Consequently, a generalized correlation of motor behavior with the details of propellant formulation was not achieved. Similarly, the stability criterion proposed by Capener, Dickinson, and Kier, which features a power law relation between a 'threshold' burning rate and the corresponding chamber pressure, was found to be invalid in the general case. (Author)