One-Degree-Of-Freedom Attitude Stability Analysis of a Mars Entry Inflatable Aeroshell Using Fluid-Structure Interaction

This study investigates the dynamic attitude stability of a deployable flexible aeroshell intended for Mars landing missions by developing a fluid–structure–motion coupled simulation framework. Large-eddy simulation is combined with a structural finite-element model through an implicit two-way partitioned coupling, enabling one-degree-of-freedom free-oscillation analysis under Martian atmospheric conditions at Mach 0.3. The rigid-model analysis reveals that the dynamic stability strongly depends on the initial pitch angle: oscillations decay for initial angles of 45° or less, whereas they diverge for 60°, indicating an eventual rollover. A flexible model is then introduced to examine the role of membrane deformation. The aeroshell exhibits swing and axial-stretch deformation modes corresponding to higher-order structural eigenmodes, which occur at frequencies an order of magnitude higher than the pitch oscillation. Although the overall pitch motion remains qualitatively similar between the rigid and flexible models, the flexible model exhibits weaker decay of the oscillation amplitude. This behavior is attributed to a reduction in the effective angle of attack caused by structural deformation, which weakens the aerodynamic restoring moment. These findings provide new insight into the fluid–structure–motion coupling mechanisms governing inflatable aeroshells in Mars-relevant environments and offer guidance for the design of stable deployable entry systems.