Advancing Asteroid Surface Exploration Using Sublimate-Based Regenerative Micropropulsion And 3D Path Planning

Abstract

The advancement of asteroidal surface science necessitates in-situ science collection by robotic landers. The Asteroid Mobile Imager and Geologic Observer (AMIGO) is a conceptualized surface hopping robot relying on miniaturization of avionics, structures, and science equipment to accompany a larger “mothership” type orbiter for surface measurements. The scientific rationale for asteroid surface characterization is explored. Ideally, mobility facilitates more robust data collection from a range of areas on the asteroid surface with fewer robots for maximum coverage. As evidenced by images from asteroid visiting spacecraft, recently Hayabusa II and OSIRIS-Rex, “rock gardens” on asteroid surfaces provide uneven and obstructed terrain from boulders and piles of dust. Two enabling technologies are developed for the CubeSat class AMIGO hopping robot. Hopping is enabled by a high-level path planning algorithm is developed by using a stereo camera that outputs both color images and a depth map for obstruction detection. The depth map allows for objects and adverse terrain to be detected and avoided for safer mobility. The surface boulders present difficulties in both line of site to other areas of the asteroid and in landing safely. These large obstructions and dramatic topology of asteroids reduces the robot’s visibility range and navigating around them provides new scenes to examine. The boulders should also be avoided when hopping such that they do not damage the robot or cause it to tip over to a state where data cannot be collected. Imaging from these new locations and headings can be used to construct surface level maps of the terrain and gather information on boulder distribution. The avoidance algorithm is evaluated on a test model of AMIGO with representative avionics and structure by hopping multiple times to avoid obstacles. The other technology is a micropropulsion system based on cold-gas and microelectromechanical systems (MEMS) technology to provide both lift-off hopping actuation and 2-axis attitude control during a quasi-ballistic, open loop trajectory to a target destination. Hopping from the propulsion system allows the robot to traverse the rough terrain to an area deemed interesting or safe from the hop selection algorithm. The design methodology for the micronozzles and two control valves are shown. Micronozzles are optimized in a quasi-isentropic analysis and compared to computational fluid dynamics simulations.