Velocity slip boundary conditions were implemented in continuum, perfect gas solver developed at AFRL and compared with the results of a Direct Simulation Monte Carlo solver, called HAP-DSMC. A Mach 7 flow past a blunted wedge and Mach 12 flow past a double cone were studied. For continuum flows, it was found that for the Maxwell's velocity slip model to be accurate, the Knudsen layer must be mesh-resolved. The AFRL solver was vectorized making use of modern GPU hardware. It was found that for the GPU implementation to be effective, large computational meshes need to be used to optimally load the processing units.