General method for internal ballistic analysis of complex propellant grain

Using finite volume and stagger grid, a general method is derived to calculate burning-area of grain that has complex configuration. The entire grain region is covered by a three-dimensional orthogonal grid. The material that occupied each grid volume is relatively distinguished as propellant, burned-cavity and incombustible material. During the combustion process, burning points expand at all directions, resulting a change in the volume of burned cavity. The average burning area is obtained by application of differential medium theorem. The procedure requires only the initial and final grain shape. Complicated analytic expressions for burning-area are not needed. Perspective drawing of grain can be obtained simultaneously. Internal ballistic performance of dual thrust motor with segmented grains is predicted under the condition of ablation. Predicted chamber pressure is in good agreement with experiment.