Electrostatic transport of regolith particles for sample return mission from asteroids

To achieve reliable and autonomous regolith sampling from asteroids in space, the authors have developed a new sampling system that utilizes electrostatic force. This system consists of electrostatic capture and transport subsystems. Regolith particles on an asteroid are captured through parallel screen electrodes activated by the application of an alternating high voltage. The captured particles are then transported to a collection capsule from side to side basically along the electric flux lines in a zigzag path where an alternating electrostatic field is applied. It has been demonstrated that glass and sand particles can be transported in the horizontal direction that imitates micro-gravity on asteroids. The transport rate was increased by applying a high voltage of appropriate frequency. The demonstrated transport rate was approximately 3 g/min. The configuration of the path was improved to increase the transport performance. Numerical calculation using the discrete element method predicted that the transport of particles is successful if the gravity is less than 0.02-G. The process of sampling particles on asteroids will be easier than that on the Earth, because gravity is extremely low on small asteroids, particles are assumed to be highly charged because of cosmic rays, no air drag is exerted on the particles, and high voltage can be applied in vacuum where no gas discharge occurs.