Dynamic stability analysis and passive control method developing of a reentry capsule

• Free-to-pitch oscillations of the reentry capsule are simulated numerically.
• Dynamic stability of reentry capsule is focused on.
• Wake flow structures of reentry capsule are analyzed for stability mechanism.
• The unsteady moment generated at aft-body may the source of dynamic instability.
• Modified shapes are proposed to explore passive control method for reentry Capsule.

Dynamic stability of a reentry capsule is analyzed numerically and passive control method is developed to reduce the self-excited free-to- pitch oscillation of the reentry capsule. The coupling equations comprising Navier-Stokes equations and Euler rigid body dynamic equation are employed to govern the free-to-pitch motion of the reentry capsule. By solving these equations, the free-to-pitch problem of reentry capsule is simulated numerically. The wake properties, including pressure distribution, vortex core structure and streamlines, were investigated to understand the flow mechanism of the pitching reentry capsule. For better understand the dynamic behavior of the reentry capsule, the unsteady moment of the fore-body and aft-body of the capsule are evaluated respectively. The results showed that the unstable effect is generated by the aft-body of the pitching reentry capsule. Based on the comprehension above, passive control methods are developed. Six modified reentry capsule models with different aft-body shapes are proposed. Theirs free-to-pitch characteristics, including amplitudes and frequencies, are evaluated numerically. The results showed that the dynamic stabilities of reentry capsule could be effectively improved by modifying the aft-body shape.