The burning rate of solid propellants is essential to the design of rockets. However, good experimental data are expensive to come by. During the past several months, I have been part of a project seeking to model the combustion of solid propellants. Specifically, the aim of my work has been to apply existing propellant models to ammonium perchlorate (AP). The model we use splits the problem into three parts, namely the solid propellant, a reacting melt layer on the surface, and a reacting gas phase. We use detailed kinetics to model the gas phase combustion. The surface melt layer is modeled with global kinetics. Mass and heat transfer are also taken into account. My task has been to adjust the kinetics of the condensed phase and verify the validity of the gas phase kinetics until the model outputs match experimental data. The most important output of our model is the burning rate, although temperature profiles and species profiles are also used to validate the model. This work on monopropellants lays the groundwork for modeling much more complex propellant mixtures.