Static attitude stability of deep space sample return capsule with thin aeroshell

A sample return mission to deep space has been proposed. The orbital velocity of the deep space sample return capsule (DS-SRC) during atmospheric entry reaches 15 km/s, which results in extremely severe aerodynamic heating to the sample return capsule. We proposed a new concept of the DS-SRC with a lightweight and large-area aeroshell to reduce the severe heating environment at high altitudes through efficient aero-deceleration. The DS-SRC must be aerodynamically stable at all speeds because it is expected to be operated without a parachute at atmospheric entry. First, we showed the flight environment of the DS-SRC along the atmospheric entry trajectory obtained by trajectory analysis. Second, we investigated the aerodynamic characteristics and the static stability in the all-speed range using low-speed, transonic, and supersonic wind tunnels. Last, we used a computational science approach to conduct unsteady turbulent flow simulations to show its stability mechanism. The trajectory analysis indicated that the peak heat flux at the stagnation point of the capsule was kept approximately 10 MW/m2 when decelerating from high altitude because of its low ballistic coefficient. Based on the wind tunnel experimental results, we confirmed that this capsule is statically stable in attitude at all speeds. Furthermore, the computed results suggested that there is a difference in pressures at the windward and leeward sides of the front surface when the capsule is pitched up or down. This difference in pressure distribution acts as a static stability mechanism generating a moment in the direction that restores the pitching motion.