Transonic aeroelastic stability analysis of launch vehicles using reduced-order model

With the development of launch vehicles, their increasing size of payload fairing approaches the limits of existing aeroelastic stability criteria. Within critical design conditions, the aerodynamic configuration may cause flutter during transonic flight phases, thereby increasing the risk of aeroelastic instability. This study systematically investigates the mechanism and parameters influence of flutter through numerical simulations and ARX-based reduced-order modeling (ROM) method. Various fairing shapes with different diameter ratio are designed under current criteria and numerical simulations results show larger diameter ratio increase pressure fluctuation, enhancing unsteady flow effects. Further analysis focuses on the launch vehicle configuration with the most significant unsteady effects. Both CFD-CSD simulations and ROM predictions confirm the occurrence of frequency lock-in phenomena. ROM-based root locus analysis further indicates that the flutter originates from single-degree-of-freedom (SDOF) flutter induced by fluid-structure mode interaction. Research on node position effects shows front node shifting forwards lead to the occurrence of flutter. The natural frequency has minimal influence on aeroelastic stability, except for a front node located at the boattail, where an increase leads to system instability. This work reveals the transonic aeroelastic instability mechanism and offers design guidance for launch vehicles.