EXPERIMENTAL DATABASE DESCRIBING PULSE-TRIGGERED NONLINEAR INSTABILITY IN SOLID ROCKET MOTORS

Pulse-triggered combustion instability constitutes a considerable prob lem in the design and operation of solid propellant rocket motors. Res ults from an experimental study involving 45 full-scale motor firings are presented to provide guidance in motor design and a database for c omparison with existing and future nonlinear theories. The repeatabili ty of pulse-triggered instability along with the effect of variations in propellant formulation, operating pressure, grain configuration, mo tor scale, and motor length were evaluated according to the parameters fraction of de shift and wave strength. The stability rating of a con figuration based on these two different parameters was not always cons istent; the fraction of de shift was judged superior. It was shown tha t oxidizer particle size distribution and the presence of a stability additive affected pulse-triggered instability. In addition, it was sho wn that instability tended to increase with pressure, that cylindrical grains tended to be less stable than star grains, that shorter motors tended to be less stable than longer ones, and that smaller motors te nded to be less stable than larger ones.