A research program has been carried out to validate a numerical simulation of the flow and combustion process in the combustion chamber of a solid fuel ramjet with experimental results. Operating conditions were chosen to represent a sustained missile flight at Mach 4 at an altitude of 13 km. Experimental data were obtained by burning cylindrical fuel grains made of polyethylene and hydroxyl terminated polybutadiene in a solid fuel ramjet using a connected pipe facility. For numerical simulation a computer code was developed, describing rotational symmetric steady-state turbulent reacting flows through channels with and without a sudden expansion. Calculations were carried out using polyethylene as a fuel. For the validation emphasis was laid on the regression rate. The results show that the computer code predicts the mean regression rate with reasonable accuracy. The value for the effective heat of gasification is found to be very important. The experiments and the calculations carried out show the feasibility to apply a solid fuel ramjet for sustained hypersonic flight at these conditions.