<p>In this study, the effects of atmospheric entry capsule forebody geometry on aerodynamic performance and thermal loads were systematically investigated through computational analysis under hypersonic flow conditions in which thermochemical nonequilibrium effects are dominant. In particular, this study quantitatively demonstrates how geometric parameters of axisymmetric heatshields, represented by spherical section and sphere-cone geometries, alter the design trade-off relationship between drag and heat transfer. Various axisymmetric heatshield geometries were defined, focusing on geometric parameters such as the ratio of nose radius to base radius and cone half-angle, and computational fluid dynamics analyses considering thermochemical nonequilibrium were performed for flight conditions along Earth re-entry trajectories. Through the analyses, a ratio between the dimensionless average heat transfer parameter and drag coefficient was defined, and correlations across the design space with respect to nose radius ratio were derived. The ratio of the average heat transfer parameter to drag coefficient exhibited a good linear correlation with the square root of the nose radius ratio, thereby presenting a practical design correlation method that enables rapid prediction of aerodynamic and thermal performance for intermediate geometries even when analyzing only a few representative configurations. The proposed correlation is valid within the specific range of Earth reentry trajectory conditions and axisymmetric geometries investigated here, and extension to other flow environments would require further validation.</p>