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 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 long-term human space missions.

中文翻译：

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太空 3D 打印的闭环：真空、回收和紫外线老化对通过长丝挤出增材制造生产的高性能热塑性塑料的影响

太空探索的前景以及人类在太空的长期可持续存在都依赖于现场制造能力的进步。太空增材制造 (AM) 因其生产备件和促进维修以延长太空任务的潜力而受到广泛关注。然而，迄今为止，还没有能够在不受控制的空间条件（即重力降低、真空和辐射环境）下加工高性能工程热塑性聚合物的增材制造系统。此外，紫外线 (UV) 辐射对打印部件的影响仍未得到探索。在这项工作中，我们开发并测试了定制的长丝挤出增材制造面包板，能够制造工程热塑性聚合物，机器被放置在真空室内以部分模拟恶劣的太空环境。在暴露于紫外线老化之前和之后，对印刷样品进行机械（拉伸和弯曲）和热（热重分析、差示扫描量热法和动态机械分析）测试。此外，打印的几何形状经历了回收过程，包括粉碎原始3D打印聚合物样品、干燥所得颗粒，最后挤出可3D打印长丝。然后，对回收的聚合物 3D 打印样本进行进一步的机械和热测试，为了解空间增材制造的可行性以及增强打印部件的圆形度的潜力提供了宝贵的见解。手稿中提供了机械和热测试的结果，以及真空印刷、紫外线老化和回收的效果。这项工作巩固了可持续推进在轨和太空基础设施的基本构件，并为长期载人航天任务铺平了道路。