CFD simulations using three-dimensional compressible Navier-Stokes equations are carried out for the establishment of the reliability of the CFD tools for the aerodynamic evaluation of space transportation systems. Simulations for Apollo-type capsule show that the simulations with typical number of grid points can give us reasonable result and CFD analysis can be a useful tool for the initial estimation of aerodynamic characteristics. Simulations for the FTB configuration show the dependency of the aerodynamic data on the order of accuracy of the simulations. The flow field near the base alters the characteristics. The example for the delta and double-delta wings which may be a candidate for the future TSTO systems shows that the success of the CFD simulations for delta wings does not necessarily justify the CFD results for similar configurations.