A unified hybrid DSMC-CFD model will be utilized to assess its applicability to analyze flow fields at all altitudes, from the continuum to the free molecular flow regime. Test cases will be selected to highlight its sound approach in terms of modeling the wall boundary condition as the flow regime changes with increasing altitude. Also, after the assessment of the hybrid method is complete, laminar to turbulent transition phenomenon will be subject to further research with the hybrid model. If the model proves to be an effective and useful tool, a continuing phase II effort will incorporate the DSMC model into an existing government approved aero-propulsive CFD code. A hybrid DSMC-CFD predictive capability will greatly enhance the current limitations experienced by the CFD codes. The fundamental continuum hypothesis embedded in the Navier-Stokes equations which limits the applicability of all CFD codes will be extended into the "slip" and the "transitional" flow regimes. The hybrid approach, if proven to be efficient and accurate, will be available as a module to existing CFD solvers to expand current capabilities
