The aim of the present paper is to expose the performance simulation of a small sounding rocket that operates with a solid propellant motor. In order to contribute in the understanding of solid propellant rocket engines, this work analyses the basic functioning of this type of motor and simulates its performance in the experimental rocketry field. In a solid propellant rocket, the combustion is clearly determined by the grain shape, which establishes the burning surface as a function of time. It affects directly the chamber pressure and, along with burn rate, it determines thrust. So, as well as propellant characteristics, burning surface is an essential parameter and the engineer can modify it in order to obtain the desired performance. The simplicity of the solid motor and the large number of possible grain burning shapes make solid propellants an interesting option for a rocket engine design. Therefore, the focus of this study is to build a complete model of solid combustion, with a specific burning shape, that simulates the rocket performance. The motor dimensions have been based on an Aerotech engine used in experimental rocketry. It has served as a model for the first calculations and its real performance has proved to be a good comparison tool for the results obtained. The simulation has been carried out in Hopsan, a multi-domain software developed at the Linkoping University. Once the simulation is completely built, an optimization of the engine has been done in order to improve the performance and to increase the altitude reached by the rocket. Finally, the results obtained with the optimization of the system are compared with different case dimensions. Hence, the comparison gives an idea of how this parameter affects rocket performance. (C) 2018 The Authors. Published by Elsevier B.V.