A microspine tool: Grabbing and anchoring to boulders on the Asteroid Redirect Mission

NASA's proposed Asteroid Redirect Mission (ARM) plans to change an asteroid's orbit, showing the ability to, in the future, deflect an object headed for a collision with the Earth. The mission plans to extract a boulder from the asteroid's surface and use the combined mass of the spacecraft and boulder to slowly change the parent asteroid's orbit using a gravity tractor technique. ARM would then return this boulder to the Earth-Moon system for future human exploration. ARM would also mature several critical technologies needed for human missions to Mars including high power solar electric propulsion, dexterous robotics and autonomy, and support technologies for human exploration beyond low-Earth orbit. ARM has baselined two Microspine Tools for grasping, anchoring to, and helping extract the boulder from the asteroid. These tools must operate in the microgravity environment of the asteroid with the ability to grip and drill in microgravity. Another challenging constraint is the large uncertainty in the physical properties of the boulder. This paper describes the Microspine Tool's architecture, detailed design, and the fabrication and testing of a development unit. Three subsystems comprise the Microspine Tool: microspine gripper, anchoring drill, and the drivetrain, each of which expands the state of the art in space mechanisms.