An Untethered Mobile Limb For Modular In-Space Assembly

In-space assembly can enable new types of spacecraft and structures which are too large or fragile to be carried on a rocket in an assembled form, and robotic systems can make in-space assembly feasible and cost-effective. Such systems should be able to assemble large and complex structures while imposing minimal launch mass and mission risk. We propose an autonomous robotic limb, henceforth referred to as "Limbi," which is self-mobile and symmetric. Two identical electromechanical docking mechanisms serve as end-effectors. With either end-effector anchored to a base structure, the other can grab modular elements and attach them to the growing structure. Power and computing are provided by the spacecraft through these docks, enabling Limbi to walk end-over-end across the structure without a battery or tether. We have constructed and tested a prototype system in a planar workspace that demonstrates the mobility and assembly capabilities of the proposed limb. We also introduce the concept of "Limboids," consisting of multiple Limbi robots temporarily attached to each other to form more complex kinematic chains. The resulting configurations are application-specific and can be tailored to the degrees of freedom, range of motion, and general dexterity required by a particular task. Because Limbi and Limboids can assemble large and complex structures with minimal robotic complexity, the development of this class of robots is a critical step forward in low-risk and lightweight assembly.