This paper describes a computational technique for prediction of the flow and thermal environment in the Space Shuttle Solid Rocket Motor field joint cavities. The SRM field joint hardware has been tested with a defect in the insulation. Due to this defect, the O-ring gland cavities are pressurized during the early part of the ignition. A computer model has been developed to predict the flow and thermal environment through the simulated flaw, during the pressurization of the field joint. The transient mass, momentum, and energy conservation equations in the flow passage in conjunction with the thermodynamic equation of state are solved by a fully implicit iterative numerical procedure. Since this is a conjugate flow and heat transfer problem, wall temperatures are calculated by solving the one-dimensional transient heat conduction equation in the solid along with the other governing equations. The pressure and temperature predictions have been compared with the test data.