Burning surface and internal ballistic calculation of dual-thrust rocket motor with three-dimensional assembling grains

Based on the finite volume method, a general numerical burning surface calculation method was derived for the arbitrarily shaped three-dimensional assembling grains, which is suitable for various grain design such as the multi-propellants, dual burning rate grain, or even the grains containing metal wire. Its numerical procedure requires only the initial and final grain shape, hence the complex geometric analytic relations can be avoided. By using it, the internal ballistic performances of a dual thrust solid rocket motor of 3-D assembling grains were predicted under the condition of throat ablation, and the predicted results are in good agreement with the experimental ones.