Numerical simulation of flow past the multibody Shuttle configuration in ascent mode has been carried out using the USA (unified solution algorithms) code, which is a finite volume, unified time/space marching, zonal, Reynolds-averaged Navier-Stokes solver featuring an implicit, upwind-biased scheme and total variation diminishing discretization for high accuracy. Body conforming elliptic multizonal grids were used in the computation. The agreement between computed and experimental results is reasonable. The interference effects of various components on the surface pressure distribution are discussed. The results show the importance of ensuring simulation of proper blockages due to various components of the mated Space Shuttle vehicle to obtain a reliable prediction of aerodynamic forces. Agreement between computed and experimental results could be improved by refining the definition of various geometric features and by including all geometric complexities.