Large-scale numerical simulations of axisymmetric, supersonic base flows were conducted at various Reynolds numbers. Direct Numerical Simulations (DNS) were employed to investigate the hydrodynamic stability behavior of the near-wake region. As a consequence of physical flow instabilities, large coherent structures evolve that have a significant impact on the mean flow wand and are responsible for a considerable amount of base-drag. It is demonstrated that the deliberate exclusion or reinforcement of certain helical modes can lead to a rise in bas -pressure and thus decrease the drag of a blunt body at supersonic speed. For these investigations, a high-order accurate compressible Navier-Stokes solver in cylindrical coordinates with high parallel efficiency was developed and employed on the SGI Origin 3900 shared memory complex at the ERDC MSRC. In addition to providing vital insight into the physical mechanisms in supersonic base flows, the DNS results are intended for use as benchmark data for the development of a Flow Simulation Methodology (FSM) for high Reynolds number turbulent flows.