In-Flight Investigation of Floating Beads for Sloshing Mitigation for Liquid-Fueled Rockets

Sloshing, characterized by free-surface wave formation in partially filled tanks under forced excitation, remains a major challenge in aerospace engineering, particularly for propellant tanks in launch vehicles. Laboratory studies have demonstrated that a granular layer placed at the liquid surface can significantly attenuate sloshing waves, provided that the granular medium remains compact. However, the performance of this mitigation strategy under real flight conditions has yet to be assessed. In this work, we investigate sloshing mitigation using a granular surface layer through an in-flight experiment conducted aboard a supersonic sounding rocket. The results show that granular surface damping is effective under realistic launch conditions as long as sufficient apparent gravity preserves the cohesion of the granular layer. Conversely, under near-microgravity conditions, loss of granular compactness leads to a breakdown of the damping mechanism. These findings indicate that granular-based sloshing mitigation is well suited for first-stage launch vehicles and sounding rockets, but is unlikely to remain effective during extended microgravity phases.