Purpose Despite growing advances in reusable launch technologies, vertical takeoff and vertical landing (VTVL) rockets increasingly depend on accurate attitude transitions; nevertheless, the aerodynamic principles controlling stability and passive control effectiveness during crucial turnover maneuvers are still not fully understood. In particular, the nonlinear aerodynamic behavior and flow-structure interactions associated with curved-fin topologies during horizontal-to-vertical reorientation have received little theoretical attention, despite earlier research emphasizing trajectory optimization, guidance laws, and pose estimation. With a focus on lift, drag, pitching moments, and vortex-driven stability during turnover maneuvers, the current study seeks to close this gap by developing a rigorous, mechanistic, and theory-driven framework for nonlinear aerodynamic stability and passive control effectiveness in VTVL curved-fin rockets. Design/methodology/approach Geometric abstraction, quasi-steady aerodynamic modeling, flow-structure interaction principles, and systematic modifications of fin curvature and cant angle are combined in an integrated conceptual, analytical, and parametric approach. The formulation is based on a reduced-order aerodynamic modeling strategy, where coefficient-level response functions, including the lift coefficient, drag coefficient, and pitching moment coefficient, are used as primary descriptors of nonlinear aerodynamic behavior under turnover conditions. Under large-angle, transient flight conditions, the proposed framework enables predictive interpretation of nonlinear aero-fluid coupling mechanisms. Findings Curved fins generate nonlinear couplings through pressure redistribution, pitch-rate-dependent flow separation, and transient vortex formation, improving passive damping, stabilizing moments, and reducing overshoot during attitude transitions. Geometric and boundary effects govern intrinsic stability limits and passive control effectiveness. The observed nonlinear response trends are consistent with reduced-order aerodynamic signatures reported in the aerodynamic literature for high-angle-of-attack regimes. Originality/value Overall, the study presents a theory-grounded predictive framework that enhances understanding of aero-fluid interactions in VTVL rockets and provides design-relevant insights for improving turnover maneuver performance in future reusable launch systems.
Stephanie Kew Yen Nee (Sat,) studied this question.