Combustion of Solid Propellants

Abstract

A review of the understanding of the combustion mechanisms of solid propellants that the authors have built from their work and from the literature is presented. Such an understanding is an important part of the process carried out to master the behavior of solid propellants and to obtain desired characteristics (with respect to energetic level, burning rate level, sensitivity to pressure and initial temperature, nature of emitted combustion products, vulnerability to various aggressions...). The propellants and propellant components considered are: double-base propellants, based on nitrocellulose and nitroglycerin, • • • • • • • • • • • active binder, based on an inert polymer (or energetic such as PAG) and a liquid nitrate ester, inert binders, such as polybutadiene, ammonium perchlorate, nitramines, such as HMX, RDX and CL20 (HNIW), composite ammonium perchlorate-inert binder propellants, composite propellants based on a nitramine and an active binder, aluminum, with respect to the two previous types of propellants, additives, when appropriate. The features of the combustion zone described are: In the condensed phase, the thickness of the temperature profile and of the decomposition zone, the kinetics of the decomposition, the energy released, the nature of the gases evolved, the surface temperature; In the gas phase, the type of flame structure (diffusion or kinetically controlled), the possibility of staging (such as in double-base propellants), the kinetics of the reaction(s), the energy released, the flame temperature (primary and final, when applicable). It is concluded that a fairly proper knowledge of the combustion of the various components and propellants has been acquired (being now extended to new ingredients, oxidizers or binders). Furthermore, based on this knowledge, a first approach modeling description can be achieved. Such a description is necessary in accompanying the elaboration of new propellants and in preparing the investigation of more complicated regimes such as those of erosive burning and of non-stationary response.