Dynamical Analysis of Low-Velocity Impact Landing on Asteroid Gravel Particle Layers

Landing on small bodies presents significant challenges due to the structural and dynamic inhomogeneity of their gravel layers, further complicated by microgravity conditions. These factors lead to highly nonlinear interactions between the lander and the gravel. In this study, the nonspherical discrete element method is applied to investigate the landing dynamics, focusing on the macroscopic behavior of the lander through the evolution of mesoscale force chains within the gravel. Our results show that the force chains quickly form during the initial penetration phase, causing a sharp increase in resistance, which is subsequently reduced as energy is dissipated. A key finding is the decoupling between peak resistance and the onset of rebound, which highlights the temporal discrepancy in the interactions between the lander and the particles. The study also finds that the particle size significantly affects the force chain structure and landing stability: larger particles form stronger force chains, resulting in higher resistance and rebound, while smaller particles dissipate more energy, promoting more stable landings. These findings offer new insights into the mechanics of asteroid surfaces and suggest practical strategies for optimizing landing procedures, such as selecting regions with smaller particles and minimizing lateral velocity to reduce rebound.