Combustion behavior of boron-based BAMO/NMMO fuel-rich solid propellants

Abstract

Combustion characteristics of boron/poly(BA MO/NMMO) fuel-rich solid propellants have been studied due to their potential application to solid-fuel ramjets (SFRJ). For the same boron content, BAMO/NMMO copolymer-based fuels are superior to conventional hydroxyl terminated polybutadien (HTPB) fuels due to their vigorous pyrolysis characteristic for dispersing boron particles into the main reaction zone. However, their specific impulses are generally lower than that of HTPB, in spite of high positive heats of formation. Formation of hexagonal crystalline boron nitride (BN) has been found in the combustion of this family of propellants studied. Favorable conditions for the formation of BN have been identified. BN also has a significant effect on the theoretical performance for high equivalence ratio conditions. The burning rate was found to depend strongly upon pressure and nonmonotonically on boron content. An energy sink hypothesis is proposed to explain this observation. Fine-wire thermocouple measurements support this hypothesis.