An approach for performing microscale simulations of porous spacecraft thermal protection systems (TPS) is presented. This approach uses the Direct Simulation Monte Carlo (DSMC) method to accurately model the flow of gas through the porous media, which in many cases is rarefied. Here we present this method applied to two cases of porous media flow. The first is flow through idealized two-dimensional cylinders. Here, we found very good agreement between both CFD and DSMC calculations and an empirical relation from the literature. For the second case, we simulate flow through an approximation of a realistic three-dimensional microstructure. Here we also present a method for creating complex random fibrous microstructures. In our analysis, we find reasonably good agreement with experiment. However, discrepancies in the experimental data prevent definitive validation using this dataset.