The space transportation system using capsule/rocket configurations such as Apollo and Soyuz are simple compared with Space Shuttle, and have several merits from the viewpoint of reliability. The capsule/rocket system will take over the Space Shuttle, after it retires in 2010. As the Space Shuttle accidents had been caused by several factors, e.g., aerodynamic interaction of shock waves ahead of its wing, advanced abort systems such as LAS (Launch Abort System) are required for the capsule/rocket system. In the present study, as a baseline configuration, a combination of a cone and a cylinder is employed as a CEV (Crew Exploration Vehicle), which consists of a capsule (LAV: Launch Abort Vehicle) and a rocket (SM: Service Module). By changing the relative position of the two components as well as the profile area of the rocket, their effects on the capsule/rocket aerodynamic interaction and characteristics (drag and pitching moment) are experimentally and numerically investigated at a supersonic speed (M∞ = 3.0). It is found from the results that the clearance have little effects on the flow field for the case of the baseline configuration. The capsule always showed a positive drag (CD = 0.34), which means that thrust is required to overcome the drag. Otherwise the capsule will recontact the rocket. However in the case where the rocket contact area is 2.2 times as large as the capsule profile, more favorable effects were obtained. Especially in the case of a certain clearance (h/D = 0.40), the drag coefficient of the capsule is CD = −0.35, which means that the capsule suffers a thrust force from the aerodynamic interaction. Under this condition, if capsule has a pitch angle with 5 degrees instantaneously, then pitching moment coefficient becomes CMp = −0.41 therefore capsule stabilize. However, in the case of a very small clearance (h/D ≈ 0.00), the flow becomes unsteady involving pulsating shock wave, leading to a potentially risky separation of the capsule.

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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.

Supersonic flow fields around Two-Stage-To-Orbit (TSTO) models with different configurations have been experimentally examined in this paper. Four configurations for the orbiter have been considered: A) a hemispherecylinder, B) a hemisphere-cylinder with a flat bottom, C) an obliquely truncated circular cylinder, and D) a cone-cylinder. All the flow fields around these models showed complicated shock/shock and shock/boundary-layer interactions, which can be categorized into three patterns, depending on the extent to which the separation shock wave contributes to these interactions. The models B, C and D were proposed to suppress the pressure rise due to the interactions observed in the model A. As a result, the model B showed almost the same interactions as the model A, while in the model C they did not present. In the model D, a large pressure rise was seen in the case with no clearance, whereas the model undergoes the least aerodynamic interaction at a rather large clearance. It is concluded from these results that the model C is less affected by aerodynamic interactions due to the clearance than the other models.