In this study, we investigate thermal characteristics of nitrous oxide (N2O) decomposition in a catalyst igniter with metal-foam configuration for hybrid rocket propulsion system or monopropellant thruster. For the purpose of the investigation, we opted to use a so-called porous medium approach for modeling the N2O catalytic igniter with metal-foam geometry. Using the Brinkman-extended Darcy equation with the Ergun term and the two-equation model, we calculated velocity and temperature distributions. To ensure the validity of the approach, we compared the calculated Nusselt number ranges with previous experimental data. Based on the results, we identified parameters of engineering importance such as porosity, pore diameter, pumping power, and ratio of length to diameter of the catalytic igniter. We systematically presented the effects of these parameters on thermal performance of the catalytic igniter, using an effective volume flow rate to determine the optimum geometry and porosity values that deliver maximum performance. (C) 2013 Published by Elsevier Ltd.