Burning rate of a trimodal composite rocket propellant

Abstract

Some new perceptions in the field of composite propellants are considered. The effects of trimodal oxidizer distribution on the burning rate of composite propellants are considered. It is note that reducing the oxidizer particles in the presence of depressors reduces the burning rate of these propellants. In the formulation of the experimental approach, modern and effective methods of experimental design with the application of extremevertices design were used. SOLID composite propellant is a heterogenous mixture of crystalline oxidizer, polymer as a binder and fuel, metallic powder, burning-rate modifiers, and other additives regulating physico-chemical properties required to meet specific design objectives. For high-energy composite propellants, ammonium perchlorate (AP) is the preferred oxidizer. The polymeric binder, which acts as a fuel in the combustion process, accounts for the mechanical properties of a solid propellant charge. Metal powder improves the energetic characteristics of a propellant by increasing the combustion temperature. Burning-rate modifiers serve to increase (catalysts) and reduce (depressors) burning rates. The most frequently used catalysts are metal oxides and solid and liquid metaboric organic compounds. For the burning-rate depressors, fluorides, oxides, and carbonates of lithium, calcium, strontium, and barium are used. The specific composition is a function of the physical and chemical properties required for each particular missile. This complexity of composite rocket propellant compositions poses a difficult problem to research people in creating and defining compositions having specified properties. Renie et al., 1 Cohen and Strand,2 and Beckstead et al. 3 have analyzed the effect of particle size of ammonium perchlorate on the burning rate. Results were obtained for both unimodal and bimodal propellants with oxidizer particle size ranging from ultrafine 0.7 /xm to coarse 400 fim. For unimodal propellants, it was determined that the burning rate was higher for the smaller oxidizer sizes as would be expected. For the bimodal distributions, the results were consistent with those that could be inferred from the unimodal results. Specifically, the burning rates were strong functions of the coarse-to-fine ratio and the mean diameter of the fine fraction. Miller4 investigated the effects of ammonium perchlorate size distribution in a series of nonaluminized propellants. Burning rates were measured using cured strands and correlated to a characteristic particle size of the ammonium perchlorate. Horton and Rice5 analyzed the effects of different compositions (ammonium perchlorate particle size, copper chromite, and lithium fluoride) on the oscillatory combustion of a polybutyl-acrylic acid propellant. The objective of the current research is to extend these results by investigating the effect of trimodal oxidizer distributions on the burning rate, and the effect of lithium fluoride as a burning-rate depressor. Specifically, statistically designed