Abstract: After some treatment of the ignition process, the MacCormark explicit prediction-correction schemes can be adapted to predicting the one-dimensional unsteady flow field and interior ballistics in a nozzleless rocket motor from ignition to the end. The interior ballistics of cylindrical proforated and slab charges in the nozzleless rocket motor are calculated and compared with each other. The predicted results are in agreement with the experimental data. Moreover, the computations reveal that the choking position appears somewhat downstream to the geometric throat position and the thrust increases as the angle of divergence decreases and vice versa.