The application of computational fluid dynamics (CFD) methods which offer feasible solution for accelerating and refining the space-transportation design process, is discussed. CFD methods and simplfying analytical modeling are used to determine critical wind velocities for the launcher structure on the launch pad. They predict the effect of the complex flow in the ducts that divert the exhaust plumes on the launch pad. The three-dimensional computational results such as wall stream lines and velocity vector plots near the nozzle exit, as well as experimental data obtained both on ground and in flight, are essential for an in-depth understanding of the flow physics and ultimately for shape improvements that reduce the loads to an acceptable level.@en