Random packs and their use in modeling heterogeneous solid propellant combustion

It is shown that random packs of spheres of various sizes can be constructed that model ammonium-perchloratein-binder propellants in the sense that both the size distributions and the packing fractions of industrial propellant packs can be matched, Strategies for dealing with fractional numbers of large particles are addressed, as are strategies for dealing with a large number of very fine particles (fine powder), Fine powder is necessary in a three-dimensional pack to achieve the required stoichiometric ratio of ammonium perchlorate to fuel binder, but is not necessary in a two-dimensional (disk) pack, Some preliminary calculations of the two-dimensional combustion field supported by a disk pack are presented, in which full coupling between the gas phase, the condensed phase, and the retreating nonplanar propellant surface is accounted for.