An Exploration of Requirements and Techniques Enabling Small Object Capture Around Low Gravity Asteroids

Abstract

The appropriation of regolith from rubble pile asteroids provides science with direct access to material essentially unchanged since the formation of the solar system. Sample and return missions to these bodies enable chemical and radioisotope studies which not only provide evidence for the formation of the solar system, but also a basic understanding of where resources might be found for future exploitation. The touch-down and sample techniques established by Hayabusa-2 and OSIRIS-REx accomplish this mission by physically touching down on the asteroid and collecting samples into a basket extended via a probe from the bottom of the spacecraft. This technique has been demonstrated to work, but contains a high cost in both mission operations as well as the size and complexity of the collection mechanism itself. This dissertation explores an alternative sample and return technique by exploiting the recent discovery of regolith particle ejections from Bennu. Particles ejected from the surface of Bennu are typically 1-10 cm in size and spend several hours in flight, suggesting the possibility that swarm nanospacecraft deployed from a notional mother-spacecraft could chase down, collect and return such particles with minimal sensor and delta-V capability. Key aspects of this mission are developed to reduce risk, including techniques for navigation, guidance, grappling and testing, while an overall mission requirements for rubble pile asteroids (and then Centaurs) are developed to establish plausibility. Finally, as an extension of this work, the tendency of these ejected particles to shape the asteroids themselves is explored as an alternative approach to explain the prevalence of top-shaped asteroids.