We propose a method for in-space manufacturing and construction of large truss structures by direct robotic extrusion of UV-curing polymers. Space solar power call for the availability of large space structures as support for solar arrays and reflectors, while mass and volume constraints are a major bottleneck for this technolgy. The highest packing efficiency can be achieved by transporting the raw material and manufacturing such structures directly in space. A prototype for in-space manufacturing of simple, but reliable, large truss structures has been developed at Munich University of Applied Sciences and was tested in microgravity on a parabolic flight campaign. A viscous photo-reactive resin is extruded through a directed nozzle and simultaneously cured by LED induced UV-light. While conventional 3D-printers operate layer-by-layer, the presented method directly creates three-dimensional structural elements in one continuous movement, providing a very reliable, fast and cost-effective method for manufacturing of large structures. The proposed method mainly consists of an extruder or pump through which a viscous photopolymer can be dispensed. This allows the resin to be ejected through a nozzle with a controlled mass flow and afterwards cured by UV-light. By moving the nozzle, it is possible to produce three-dimensional structures. Unlike with a conventional 3D printer, the resin is not applied layer by layer. Structures are created by direct extrusion through a nozzle and a simultaneous three-dimensional movement, allowing the creation of highly customized structures and components. So far, the technology has been successfully demonstrated under 1g conditions and microgravity. Tests under open space conditions are foreseen on a sounding rocket in Feb. 2021. The main goal of this study is the investigation of applicability and feasibility of currently available technology for development of truss structures in space.
