Hydrodynamic impact reduction during water entry via a variable damping system

The extreme impact forces encountered during the early moments of water entry are of critical concern in diverse fields, ranging from spacecraft recovery to aircraft ditching. Herein, we systematically investigate a variable damping strategy that uses an internal non-Newtonian fluid damper to regulate the transmission of impulsive loads during water entry. Through a combined experimental and theoretical approach, the dynamic response of dampers filled with shear-thinning and shear-thickening fluids is characterised. We demonstrate that the peak load transmitted to the main body can be reduced by up to 89.7 % compared to a fully rigid counterpart. A coupled dynamic model reveals that, unlike the constant viscosity characteristic of Newtonian fluids, non-Newtonian fluids provide damping responses that vary with the loading rate and regulate the transmission of impulsive loads under highly transient impact conditions. These findings elucidate how the rheology of damping fluid mediates the transmission of hydrodynamic impulse to the protected structure, providing a framework for variable damping protection systems during water entry.