The aero-thermoelasticity effect on re-entry capsules across Mach 2 and Mach 3 regimes is investigated in this study. Using computational fluid dynamics (CFD), heat transfer analysis, and finite element analysis (FEA), simulations are conducted to analyze the coupled behavior of aerodynamics, thermal effects, and structural deformation. Results reveal significant differences in aerodynamic forces, thermal loads, and structural responses across the different Mach regimes. At Mach 2, moderate stress and strain concentrations are observed, particularly near the fixed ends of the capsule. As the Mach number increases to Mach 3, stress concentrations become more pronounced, with heightened structural strain near both ends of the capsule.