Dynamic Instability Analysis with Different Reentry Capsule Shapes at Subsonic and Transonic Speeds

Transonic wind tunnel experiments were conducted using the one-degree-of-freedom rotation method, with Hayabusa capsule model and a next-generation sample return capsule (DS-SRC) proposed for deep space exploration. Pitch angle and wake pressure measurements showed that the amplitude of the oscillation was amplified at Mach number, where the correlation between pitch oscillation and wake pressure fluctuation was stronger, suggesting that wake pressure fluctuation affect pitch oscillation at both transonic and subsonic speeds. Surface pressure measurements on the base surface of the capsule were also performed using the pressure-sensitive paint (PSP) technique. The PSP results indicated that the pitch angle at which the pitching moment transitions from stable to unstable affects the model's oscillation amplitude. Furthermore, an unstable moment always acts on the base surface of the DS-SRC model, suggesting that the dynamic instability was led by a mechanism different from that of the Hayabusa capsule model.