Controlled motion of a asteroid hopping rover

Previous missions have revealed that small Solar System bodies are topographically diverse, which raises an immense challenge to a lander that aims to perform scientific measurements at different locations on the surface of the target. In recent years, hopping mechanism has attracted considerable attention due to its adaptability to the granular regolith and the low gravity environment. However, the hopping dynamics related to granular materials remains to be explored, which will contribute not only to future space missions but also to the understanding of the dynamical behavior of granular systems under low gravity.

Several small body rovers utilizing the hopping mechanism.

In this paper, we studied the hopping locomotion of a cuboid lander on the regolith surface of an asteroid. Numerical simulations are performed based on the soft-sphere discrete element method code DEMBody. We systematically explored the effects of the controlled parameter and physical properties of the regolith particles. The results show that the hopping outcomes (velocity, angle and morphology of the cavity left in the regolith) are strongly dependent on these parameters. The high resistance improves the robustness of granular force networks, therefore, the lander hops farther in gravel-like media than less frictional media. When the cohesion between regolith particles is included, the cavity left after the hop becomes a mild indentation, differing from the noncohesive cases that give distinct crater-like cavities.

The hopping process of a rover under controled torque on a granular bed.

Crater-like cavity left by a hopping rover.

Related paper: Cheng, B., Yu, Y., & Baoyin, H. Numerical simulations of the controlled motion of a hopping asteroid lander on the regolith surface, Monthly Notices of the Royal Astronomical Society, 2019, https://doi.org/10.1093/mnras/stz633