This project will advance technology for the automated assembly of large truss towers. Assembly of truss-based structures is one of the leading candidates for establishing some of the early lunar infrastructure. Specifically, joining technologies and robotic tools are required to enable autonomous/automated assembly of tall towers as well as shelters, domes and habitats. Automated assembly using fasteners presents challenges related to the management of the large quantity of small parts, whereas an integral joining technique such as Friction Stir Welding (FSW) can reduce the need for a material handling system that feeds rivets or bolts. FSW be more easily integrated into an autonomous assembly process. With a FSW solution for robots, parts can be assembled on 7 axes (as opposed to 3 or 5 on a machining center machine), allowing the entire surface of large parts to be covered and welded in 3 dimensions. A variant of traditional FSW, Refill Friction Stir Spot Welding (RFSSW) was developed for making spot joints in overlapped materials, similar to joints made using fasteners like bolts or rivets. Some work has been done in design of space-based trusses, and also in robotic assembly of space-based structures, but an integrated solution for the assembly and joining process is still needed. This proposal addresses the opportunity to perform automated assembly of tall towers using the energy efficient, low parts count and high joint strength method of RFSSW. It is expected that this project will raise the TRL from 2 to 4. Anticipated
Benefits: Assembly of truss-based structures is one of the leading candidates for establishing some of the early lunar infrastructure—for example, tall towers (50- to 80-m total height, which includes the attached payload height) for solar power generation, blast containment shields for launch and landing pads, shelters, etc. RFSSW is a replacement for a rivet gun or resistance spot welder with appropriate robotic assistance. By proving out usefulness of robotic RFSSW for structural trusses on earth, manufacturing speed and cost of such assemblies can be reduced. Beyond structural elements, target markets are rivet replacement for airplane construction and aluminum bodied ground vehicles such as cars and trucks.
