Some experimental results on the L-star instability of metallized composite propellants

Experimental results are reported on the L-star instability characteristics of three AP/composite propellants. The metal content of the propellants is 2, 16, and 16%. Chuffing, bulk mode oscillations, and time-independent combustion are observed with all three of these propellants. The stability boundary, defined as the boundary between time-independent and unstable combustion, is found to be well defined for two of the propellants in agreement with recognized trends available in the literature on other propellants. The frequency of bulk mode oscillations is presented as a function of the chamber characteristic length. One of the propellants tested has shown bulk mode instability at as high a pressure as 217 psia.