Closing the loop in space 3D printing: Effect of vacuum, recycling, and UV aging on high performance thermoplastics produced via filament extrusion additive manufacturing

The outlook for space exploration, and the long-term sustainable presence of humans in space, rely upon the advancement of in -situ manufacturing capabilities. In -space additive manufacturing (AM) has gained significant attention due to its potential to produce spare parts in -situ and facilitate repairs for extending space missions. However, to date, there is no AM system capable of processing high-performance engineering thermoplastic polymers within uncontrolled space conditions (i.e., reduced gravity, vacuum, and radiation environment). Additionally, the effect of ultra -violet (UV) radiation on printed parts has remained unexplored. In this work, a custom-built filament extrusion AM breadboard has been developed and tested enabling the fabrication of engineering thermoplastic polymers, whereby the machine was placed inside a vacuum chamber to partly mimic the harsh space environment. Mechanical (tensile and flexural) and thermal (thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis) tests were conducted on the printed specimens before and after exposure to UV aging. Moreover, the printed geometries underwent a recycling process involved the shredding of the pristine 3D -printed polymeric samples, the drying of the obtained granulates and finally the extrusion of 3D -printable filaments. The polymeric recycled 3D -printed specimens were then subjected to further mechanical and thermal testing, offering valuable insights into the feasibility of in -space AM and the potential to augment the circularity of the printed parts. The results of the mechanical and thermal tests, together with the effect of vacuum printing, UV aging, and recycling, are provided within the manuscript. This work cements the basic building blocks to sustainably advance on -orbit and in -space infrastructure, and paves the way for longterm human space missions.