Recent missions reveal that rubble-pile asteroids usually have a wide distribution of bare rocks in various scales. The dynamical evolution of a lander interacting with such rough surfaces is still an open problem. This article investigates the influence of the explicitly refined rocky terrains on the natural landing motion of a cuboid asteroid lander. The methodology for constructing the local terrains with centimeter-sized to meter-sized rocks is developed based on manipulating the original polyhedron shape model. Local rocky terrains refined with different-sized rocks (20 cm, 40 cm, 80c m, and 1 m) are generated. Moreover, hypothetical local terrains in different numbers of 1-m-sized rocks are presented to assess their influence on the landing motion. Numerical simulations are performed to characterize the dynamical behavior of the lander in rocky terrains. The distributions of the first and second touchdown positions, the transfer time, and the locomotion distance are taken as the three key indicators for examining the motion difference in these rocky terrains. The mechanism for the landing motion is analyzed by considering the collision slope. The results are expected to provide guidelines for the lander deployment and the path planning of a rover on rocky asteroids .

Investigating the impact process between the hopping lander and the regolith surfaces is of great significance for the in situ asteroid explorations. The high-efficiency description of the regolith...

The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM method. This paper applies four different contact force models in the newly-proposed DEM algorithm to analyze their difference and implication. The four contact force models include one linear model and three nonlinear models derived from the complete Mindlin–Deresiewicz equations. By considering the macroscopical results and calculation efficiency, the single-collision and multiple-collision cases are analyzed by comparing the four contact models. Specifically, the restitution coefficient, the angular velocity, the rebound angle, and the kinetic energy are applied as indicators for the single collision. The multiple-collision case is studied under the Brazil nut effect with ellipsoidal granules. Additionally, the softening feasibility is also discussed by decreasing the Young’s modulus of the material, mainly analyzing the outgoing results and the calculation efficiency.

This article investigates the ballistic landing motion and final distribution of the landers in different sizes or shapes near the small celestial body. Three typical shapes, including cubic, cuboid, and cylindrical, are considered for the landers deployed to a tri‐axial ellipsoid model. The Polygonal Contact Model (PCM) is used to detect the contact/collision, where the Hertz model is applied to calculate the continuous contact force. Different‐sized cubic landers (in the edge length of 20, 30, 40, and 50 cm) are numerically simulated to examine how the lander size influences its dynamics. The landing motion of the cuboid‐ and the cylinder‐shaped landers are then analyzed in the same technique. The heights of these asymmetrical landers are assumed to be 25, 30, and 35 cm, respectively, to illustrate the shape effect. Monte Carlo simulations are implemented for various landers to account for the surface motion randomness. The final dispersion, the outgoing velocity after the collision, the horizontal transfer distance, and the settling time are taken to be critical indicators for discussing the landing behavior, which can provide implications for the probe design of future missions.