Determining Dynamic Stability of a Re-entry Capsule at Free Fall

Abstract

Re-entry capsules, designed with blunt-body shapes to endure hypersonic air velocities and heat, encounter instability in the low subsonic regime during the final descent phase. Ensuring a controlled descent with the appropriate attitude for deploying deceleration systems becomes paramount. To address this challenge, we employ a cost-effective approach to investigate the dynamic stability of a typical re-entry capsule in free fall. This study involves formulating the aerodynamic model of the system and hypothesizing associated coefficients. A meticulously designed and instrumented prototype is dynamically scaled and subjected to low altitude drop tests to recreate the desired scenario. Subsequently, the data collected during these tests is processed, and stability derivatives are estimated using system identification techniques. Our research contributes to a deeper understanding of the dynamic stability of re-entry capsules during free fall, shedding light on their behavior and providing insights essential for improving their performance and safety during descent.