Simulation and evaluation of a mechanical hopping mechanism for robotic small body surface exploration

The key to understanding the origins of our solar system is likely to be found on small bodies including asteroids, and we are more capable than ever to implement in-situ exploration of their surfaces. Swarms of small hopping robots are an intriguing alternative to traditional multi-wheeled rovers to traverse the extreme environments and low gravity of small solar system bodies (SSSBs), but several challenges must be addressed before utilizing these swarms. Small-body surface vehicle missions have not yet been carried out by NASA, likely in large part due to difficulties navigating in an unfamiliar environment and complications due to low gravity. Our past work has proposed using a small, spherical robot (SphereX) with a mechanical hopping mechanism consisting of a linear actuator system to orient the robot and a spring-foot system to achieve a normal force for hopping. Two key challenges that must be addressed when designing these robots are navigation and the complex interactions between the surface and the hopping mechanism. In this research, the first challenge is addressed by developing a simulated environment in the software package Webots modeled on the asteroid Bennu to test the navigation of a SphereX robot with realistic obstacles. The second challenge is addressed using the N-body code PKDGRAV, adapted for use in planetary science and to compute granular dynamics, to test how the mechanical foot might interact with asteroid-like regolith in order to optimize the mechanism for given conditions. Simulating mechanical hopping robots on asteroids is a novel area of planetary exploration research, and surface contact behaviors are largely unknown. By demonstrating navigation in an asteroid-like environment and numerically modeling low-gravity surface interactions, a mechanical hopping robot can be evaluated as a potential method of surface exploration and mapping on SSSBs.