Review of research progress and key technologies of foldable-wing trans-medium vehicles

Foldable-wing trans-medium vehicles combine rapid aerial maneuverability with covert underwater navigation. However, the substantial differences between air and water pose complex adaptability challenges in vehicle configuration, propulsion, and trans-medium transition. To address these challenges, representative vehicles and related studies in China and abroad are reviewed, and their technical characteristics are analyzed in terms of wing-folding modes, propulsion modes, and water-exit and water-entry modes. Key issues concerning folding mechanisms, motion control, propulsion systems, and impact-load mitigation during water entry are also discussed. On this basis, the applicable conditions and current limitations of different technical approaches are summarized, providing a reference for further research on foldable-wing trans-medium vehicles.