The objective of this project is to verify that the second- order Godunov upwind scheme is a robust, efficient, accurate, and high-resolution methodology for 3D supersonic flowfields involving complex nonlinear wave motion. Phase I work will be limited to inert polytropic gases and simple geometries, with the goal to calculate and analyze the results for a few cases of the analogue oblique shock-wave reflection problem. Groundwork will be laid for Phase II work by implementing the scheme in a highly modular fashion, so that future code development work will build on preceding work.