To explore future RLVs, a hypersonic flowfield around a Two-Stage-To-Orbit (TSTO) configuration is analyzed in this paper. This study also demonstrates how CFD, as a powerful tool, can be applied to investigate such a complex flowfield involving a shock/shock interaction and a boundary-layer separation. First, the hypersonic flow around two bodies of the TSTO model has been numerically simulated, and then, the results are validated by comparing with experimental data taken at the UT-Kashiwa Hypersonic Tunnel. Finally, the detailed, computed flowfield is shown to have pairs of streamwise vortices (including horseshoe vortices) with alternating signs of rotation around the TSTO body surfaces.