Sustainable In-Space Manufacturing by Upcycling Metal Space Debris via a Vertically Integrated Processing Paradigm

This study presents a novel approach to upcycling metallic space debris, a growing concern due to the increasing quantity of debris in orbit that poses risks to satellites and future missions. Additive Friction Stir Deposition (AFSD), a solid-state additive manufacturing (SSAM) technique, is proposed for in-space recycling, combining the advantages of additive manufacturing of hard-to-weld metals and post-processing to produce near-net shape components. Simulated space debris, composed of AA6061, were fabricated into rods using continuous casting to create feedstock for twin rod AFSD (TR-AFSD). The resulting TR-AFSD deposit showed a reduction of many of the casting defects inherent in the feedstock material and exhibited a microstructure corresponding to improved material properties. X-ray computed tomography showed a decrease in porosity in the TR-AFSD deposit compared to the cast material. X-ray fluorescence analysis of the as-cast feedstock revealed localized concentrations of alloying elements and contaminants resulting in solidification cracking formation. Electron backscatter diffraction identified that the grains in the as-deposited material had approximately 30 times smaller diameter than those in the as-cast feedstock, suggesting material strengthening due to the Hall-Petch effect. The TR-AFSD process also refined large intermetallic particles, suggesting an increase in fatigue resistance. These findings highlight the potential of AFSD for upcycling space debris through microstructure refinement and homogenization, enabling in-situ fabrication of high-performance components for sustainable space exploration.