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

Sustainable In-Space Manufacturing by Upcycling Metal Space Debris via a Vertically Integrated Processing Paradigm | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Sustainable In-Space Manufacturing by Upcycling Metal Space Debris via a Vertically Integrated Processing Paradigm Charlye R. Baker, Ning Zhu, Pruthul Kokkada Ravindranath, Joseph W. Pawelski, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6334841/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract 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. Physical sciences/Materials science/Structural materials Scientific community and society/Business and industry/Engineering Physical sciences/Engineering Physical sciences/Materials science Scientific community and society/Business and industry Social science/Science technology and society Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction The recycling of metal space debris holds significant promise in addressing the growing concern of on-orbit space debris. As of 2024, the European Space Agency (ESA) estimates there are over 35,000 objects larger than 10 cm in Earth's orbit, with millions of smaller fragments that pose significant risks to active satellites, space stations, and future missions (1).This number will continue to grow as space activity increases. By converting this otherwise hazardous material into feedstock for on-orbit manufacturing and repair, space metal recycling provides a critical opportunity to mitigate these risks while simultaneously increasing in-situ resource utilization (ISRU) capabilities. Manufacturing paradigms that utilize space debris present multiple critical functionalities for future space missions. ISRU facilitates the creation of new components and structures in-space from locally available resources, reducing reliance on Earth-based supply chains and the need for costly and logistically challenging launches from Earth. At the same time, space debris upcycling would mitigate some of the immediate dangers posed by space debris and allow decommissioned spacecraft to be removed from orbit and upcycled into high-value components before they become a hazard to other space missions. This method aligns with broader goals of sustainability and self-sufficiency in space exploration through responsible use of space resources (2) and converting potential hazards into valuable resources that can promote further exploration and development. The conventional approach of recycling aluminum alloys through casting presents significant challenges. Heat treatable aluminum alloys are commonly found in space debris due to their extensive use in space exploration applications, such as upper stages of rockets, satellites, landers, and rovers, making them a key material for ISRU (3). However, there are significant barriers to effective recycling of secondary scrap, both terrestrially and in-space, due to the presence of contaminants such as ferrous materials in the scrap material. Casting these materials often leads to defects like solidification cracking and porosity because the impurities create stress concentrations within the material during liquid to solid phase transformations. Furthermore, in traditional manufacturing processes, cast billets are homogenized at high temperatures prior to further processing to improve extrudability and mechanical properties (4). Conventional recycling processes also often require addition of primary aluminum to dilute contaminants to within an allowable range (5). These approaches to improve the properties of recycled material are energy-intensive and require additional feedstock materials, making them challenging to implement for point-of-need manufacturing in austere environments such as space. Therefore, there is a critical need for efficient manufacturing and post-processing methods to convert recycled cast aluminum alloy feedstocks into usable components with robust mechanical behavior for point-of-need applications, without the addition of primary aluminum or energy-intensive thermal processing steps. Additive Friction Stir Deposition (AFSD) offers an efficient way to fabricate near-net-shape components from recycled metals or metal matrix composites, including the removal or mitigation of defects such as porosity and element segregation, resulting in fully dense builds or repairs. AFSD is a solid-state additive manufacturing (SSAM) technique that operates at ambient temperature and atmosphere, making it well-suited for austere environments. During the AFSD process, feedstock, which can consist of a solid rod, machine chips, metal strips, or powder, is fed through a hollow, rotating tool (6). The tool’s rapid rotation generates frictional heat, which softens the feedstock material without melting it. As the tool traverses, this softened material is deposited layer-by-layer through plastic deformation, creating a metallurgical bond at the layer interfaces. Because AFSD is a solid-state process, it is well-suited for on-orbit or other in-space manufacturing applications in which molten metal would present operational and safety challenges. AFSD also inherently avoids the solidification cracking issues commonly associated with rapid cooling rates in beam-based additive manufacturing techniques (7,8). These advantages, combined with AFSD’s significant energy savings due to its reliance on low-power technology and thermomechanical processing (6,9), makes it a more efficient manufacturing method for austere environments. The impact of AFSD on the microstructure and mechanical properties of aluminum alloys, as well as other metals, has been characterized, revealing substantial grain size refinement primarily due to dynamic recrystallization (8,10–12). These refined microstructures translate to improved material performance, further demonstrating AFSD's potential in advanced manufacturing. The technical potential of AFSD for recycling aluminum scrap has been explored for various materials. Two primary approaches exist for depositing machine chips: direct feeding of loose chips through a hopper into the AFSD tool (13,14) or compacting the chips into feedstock (15,16). Beck et al. demonstrated that direct additive recycling (DAR) AFSD AA5083 exhibited nearly identical fatigue performance to wrought material, with comparable ultimate tensile strength, higher yield strength, and slightly lower elongation to failure. Yoder et al. demonstrated the efficacy of utilizing AFSD for upcycling automotive machining chips. Machining chips made of a cast aluminum alloy were compressed into a ~68% dense square feedstock rod and deposited using AFSD. The resulting deposit was fully dense, with fine, equiaxed grains, and the improved properties were attributed to the reduction, spheroidization, and dispersion of second-phase particles induced by AFSD (16). Babaniaris et al. investigated the compaction of machining chips via hot extrusion to create AFSD feedstock. The study found that AFSD, followed by heat treatment, may allow recycling of aluminum with higher levels of Fe contamination compared to other recycling methods (15), potentially mitigating the increased corrosion that typically arises due to Fe contamination in aluminum scrap recycling. Previous AFSD studies have also demonstrated that AFSD is a promising means to fabricate lunar regolith metal matrix composites (MMCs) for point-of-need ISM. Lopez et al. used AFSD to fabricate AA6061-lunar regolith simulant MMCs with 9, 18, and 31% lunar regolith simulant (17). The regolith simulant was refined by approximately 100x from the initial particle size and increased volume fraction of regolith simulant led to an increased hardness in the deposit. However, the regolith was not distributed uniformly throughout the AFSD deposit, leading to inhomogeneities in material properties. A subsequent study focused on AA6061 – 20 wt% regolith simulant MMCs fabricated using AFSD (18). X-ray computed tomography (CT) showed the total porosity of the build was 0.03% and the usable volume of the deposit (19) had a porosity of 0.001%, demonstrating that regolith MMCs fabricated using AFSD are effectively fully dense. The MMC deposit exhibited a higher ultimate stress than AA6061 deposits without regolith particles, confirming that incorporating secondary particulates like lunar regolith can enhance the strength of AFSD deposits while also enabling the use of in-situ resources. The present research presents a novel concept for aluminum space debris recycling, illustrated in Figure 1. Casting is used to consolidate scrap from sources such as space debris to create feedstock for the twin rod AFSD (TR-AFSD) process, which uses offset round feedstock rods. Most prior work on AFSD uses a single square center-fed feedstock. Using multiple offset rods increases deposition rates without widening the deposit and enables the use of round feedstock. This is beneficial for material upcycling, as round rods can be produced through various fabrication methods. A schematic of the TR-AFSD process is shown in Figure 2. The goal of this study is to evaluate the effect of TR-AFSD processing on the microstructure and resulting properties of recycled simulated space debris feedstock fabricated using continuous casting. Specimens of the cast feedstock and as-deposited TR-AFSD build were analyzed using x-ray computed tomography (CT), x-ray fluorescence (XRF), energy dispersive x-ray spectroscopy (EDS), optical microscopy, and electron backscatter diffraction (EBSD). These multiscale characterization results demonstrated that AFSD is an efficient means to refine the microstructure of cast recycled space debris feedstocks to create components with improved material performance. Materials and methods 2.1.1 Materials and AFSD The cast recycled simulated space debris, with a nominal composition equivalent to Aluminum Alloy 6061 (AA6061), was provided by CisLunar Industries, Inc. AA6061 was selected since it represents a ubiquitous model alloy system. Debris simulant was cast using parabolic payload test subsystems from the Modular Space Foundry (MSF), developed by CisLunar Industries. The MSF uses an electromagnetically positioned and heated continuous casting process to produce rods and billets for in space manufacturing, on-orbit and on the lunar surface (23). Casting was selected as the feedstock fabrication method due to the challenges of consolidating a range of scrap material shapes in a low-gravity environment. The electromagnetic induction system employed by the MSF allows for contactless gathering and positioning of the metal scrap, making it suited for manufacturing in a range of gravitational accelerations (24). The recycled space debris simulant was machined into two 12.7 mm diameter round feedstock rods for use in a Bond Technologies GL7 hybrid friction stir welding (FSW) / TR-AFSD system. The rods were spray coated with a graphite lubricant coating to prevent feedstock from jamming in the tool during depositions. The machine was operated at a feed rate of 17 mm/min, traverse velocity of 89 mm/min, and a spindle speed of 500 rpm, and had an initial dwell time of 4 s to generate the initial frictional heat required for plastic flow. The material was deposited on a 6.25 mm thick AA6061-T6 substrate. 2.2 Material Characterization X-Ray Computed tomography (CT) scans were performed on the cast feedstock and AFSD build using a North Star Imaging (NSI) X-3000 industrial X-ray CT inspection system. The sampling voxel size was 40 µm and the source was set to a focal spot size of 52 µm. After the reconstruction of the CT scan images using the NSI efX-CT software, the image stack of the slices was exported. The three-dimensional volume of the cast and deposit parts were analyzed using the deep learning feature of the Dragonfly image processing software for quantification of porosity volume and location. The voids were segmented and quantified from these regions of interest (ROIs) to measure their volumetric size. X-ray fluorescence (XRF) scans were completed with a Bruker S1 TITAN 800 Handheld XRF scanner using a scan time of 20 seconds. Energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) samples were machined from the AFSD deposit using a Mitsubishi wire cut electrical discharge machine (EDM). These samples were taken from the steady state region of the deposit to ensure experimental results were not affected by the dwell or exit portions of the AFSD process. Cast feedstock samples for EBSD were machined from the remaining feedstock . Because the irregular geometry inhibited clamping for EDM, cast samples were cut manually using a precision metallography saw. All EBSD, EDS, and optical microscopy samples were mounted for microscopy and ground using P600 and P1200 SiC paper, followed by polishing with 3 μm and 1 μm diamond suspension solutions. The samples were then vibratory polished with a 0.02 μm colloidal silica solution for 4 hours. Optical microscopy was completed with a Keyence VHX-7000 digital microscope. A Versa 3D Focused Ion Beam Scanning Electron Microscope (FIB-SEM) equipped with EDAX EDS and EBSD detectors was utilized for further material characterization. EDS scans were conducted at 25 kV, 2000x magnification, a spot size of 6.0, and a nominal working distance of 10 mm. EBSD specimens were positioned with a 70-degree pre-tilt, and all scans were performed at 20 kV, 5.3 nA, and a spot size of 7.0. Cast scans were completed using a 10 μm step size over an approximately 1840 by 1460 μm area. Scans of the as-deposited material were conducted using a step size of 0.25 μm over an approximately 30 x 30 μm area. Data cleanup, visualization, and grain size analysis was conducted using the OIM software by EDAX using the standard grain dilation algorithm and a minimum grain size of 16 pixels. All scans had less than 12% points changed during data cleanup and above 70% CI>0.1. A grain misorientation angle of 10 degrees was used to determine high angle grain boundaries, and misorientation angles between 2 and 10 degrees were classified as low angle grain boundaries. Results The TR-AFSD process was successfully used to create a fully dense, multilayer component using the recycled space debris simulant cast feedstock. Visual inspection of a representative sample of the cast material Figure 3a revealed multiple prominent cracks in the material surface and a high surface roughness. The TR-AFSD build, shown in Figure 3b, had minimal surface defects, albeit with some flash (excess material on the deposit edge that can be machined away and recycled through TR-AFSD again) as typical of the near-net shape AM process. The build consisted of two approximately 1 mm thick, 27 mm wide, 50 mm long layers. CT imaging results demonstrate that the TR-AFSD process effectively reduced the number of defects present in the material, i.e. consolidation of cast porosity and the formation of a more fully dense structure. The total void volume fraction in the cast deposit was 0.63%, and void sizes ranged from 0.01 to 16.5 mm³. A three-dimensional rendering of the CT scan of the cast material, shown in Figures 4a-b, illustrates the distribution of porosity throughout the sample. The total porosity calculated from the scan of the build, shown in Figure 4c-d, was 0.19%. Void sizes in the build ranged from and 0.003 to 0.37 mm³. This porosity was concentrated on the edges of the build, which would likely be machined away during finishing to create the functional component. In a steady-state region of the deposit measuring 20 × 36 mm, 12 voids were detected with volumes ranging from 0.004 to 0.067 mm³. This area approximated the volume that would be usable after finish machining for a final component (19). The usable volume of the deposit had a porosity of 0.016%, equivalent to a 97.4% reduction compared to the cast feedstock. The usable material in the deposit is effectively fully dense, indicating that the level of porosity present in the as-deposited material would not negatively impact the performance of the finished component. Figure 5 shows the XRF sampling locations and composition results. The given nominal values are the upper compositions limits as specified in the American Society for Metals (ASM) standard for AA6061 (25). The analysis shows that the concentrations of several AA6061 alloying elements are higher in the crack region than in the main body of the material. Specifically, the Si, Fe, and Cu concentrations are approximately 1.26%, 2.70%, and 0.34% higher, respectively, in the crack. EDS mapping was utilized to identify the qualitative elemental compositions of the constituent particles and intermetallic compounds in the cast feedstock. Figure 6 shows a backscatter electron (BSE) SEM image of a representative location on a cast feedstock cross section and the corresponding EDS map results for Al, Mg, Si, O, and Fe. The oxygen-rich regions correspond to the locations of large particles in the aluminum matrix, indicating that these particles are likely large oxides. Likewise, the needle-like intermetallics, which appear as white areas in the SEM micrograph, can be classified as Fe- and Si- rich intermetallics. Figure 7 shows optical micrographs of the feedstock and as-deposited material cross sections, taken at 400x magnification. Note that the cast images were taken using the Keyence software’s built-in three-dimensional depth composition feature to provide a clear image of the particles protruding from the sample surface. The oxides and intermetallics present in the EDS sample were distributed throughout the material and can also be seen in the optical micrograph (Figure 7a). In contrast, the AFSD cross-section (Figure 7b) taken from the central, fully dense region of the deposit, has significantly smaller and more evenly dispersed particles. The average particle size in the cast material was 34.7 μm 2 , while the average in the AFSD build was 3.1 μm 2 , corresponding to a 91% reduction. EBSD analysis of the cast material and as-deposited microstructures allows for comparison of texture and grain size due to the deposition process. Figure 8 shows a three-dimensional EBSD representation of the cast material and as-deposited material. The EDAX software reported average grain sizes of approximately 112.9 μm and 3.7 μm for the cast and as-deposited material, respectively, or an approximate 30x reduction. The deposited microstructure also exhibits a high density of low-angle grain boundaries (LAGBs), which are largely absent in the as-cast material. Table 1: Summary of porosity, grain size, intermetallic size, for the as-cast feedstock and usable volume of the TR-AFSD deposit Sample Porosity (volume %) Minimum Detected Pore Volume ( mm³) Maximum Detected Pore Volume ( mm³) Avg. Grain (Diameter, μm) Average Constituent Particle Size (Area, μm 2 ) Cast Feedstock 0.63 0.01 16.5 112.9 34.7 TR-AFSD Usable Volume 0.016 0.004 0.067 3.7 3.1 Discussion A primary goal of this study was to evaluate the effectiveness of a novel vertically integrated materials processing approach that utilizes continuous casting and SSAM to upcycle metallic space debris into functional components. Due to contaminants in the recycled material and the challenges associated with casting in reduced gravity, the as-cast material exhibited high porosity, significant elemental segregation, and a coarse microstructure, which are unsuitable characteristics for providing robust material performance during in-space applications. Microstructural analysis of the cast simulated space debris and the as-deposited TR-AFSD build showed substantial refinement and homogenization, highlighting the potential of this technology to process recycled materials into functional components. The high number of voids present in the cast feedstock (Figure 4a) can be attributed to shrinkage porosity, which is particularly prevalent when casting heat-treatable aluminum alloys. In alloys like AA6061, the lower silicon content compared to aluminum alloys designed for casting restricts fluidity during solidification, limiting the material's ability to fill mold cavities effectively (26). The high Fe level present in the recycled material is also detrimental to material flow. Reduced flowability during casting increases the likelihood of void formation as the molten metal contracts and solidifies. Additionally, factors such as uneven cooling rates and inadequate material feeding can exacerbate porosity, compromising the mechanical properties and structural integrity of the cast material. The stirring mechanism inherent to the AFSD and other friction stir processes results in the reduction of porosity present in the cast feedstock material. Existing work on the influence of friction stir processing on the microstructure and mechanical properties of cast aluminum alloys describes the similar observations (27,28). However, the deposition process results in porosity formation on the deposit edges because on the outer surfaces of the deposit, material flows to a free surface where there is no force driving material consolidation (18). The defects present in the AFSD build are likely due to non-optimized processing parameters given the limited amount of material available for the study. Flash formation on deposit edges is attributed to the material feed rate and excessive heat generation during deposition (29–31). As a result, this defect could be mitigated by further process parameter optimization for this material. However, because the flash and porosity are concentrated on the edges of the deposit, these defects would be removed during finish machining. As illustrated in Figure 2, the TR-AFSD process produces a near-net shape component that requires machining to produce the final component geometry and surface finish. As a result, the edge defects would be machined away and upcycled into new feedstock, meaning they would likely not have a negative impact on material performance. XRF analysis of the cast simulated space debris (Figure 5) revealed higher concentrations of AA6061 constituent elements, primarily Si, Fe, and Cu, in the crack compared to the fully dense region, indicating there is a high level of elemental segregation in the material and the defect is likely due to solidification cracking. The highest concentrations in the crack are Fe and Si. Iron is a common impurity in aluminum alloys, especially for recycled materials. Iron is highly soluble in liquid aluminum alloys but tends to form intermetallic phases during solidification. EDS composition mapping (Figure 6) showed the presence of Fe and Si rich intermetallics, which are likely β-Al 5 FeSi as this is the dominant intermetallic phase formed in AA6061 in the presence of silicon (26). This phase is characterized by higher hardness, increased brittleness, and a thermal expansion coefficient that differs from the aluminum matrix, leading to localized stress concentrations that can become crack nucleation sites. The elevated levels of Fe and Si in the crack region indicate localized segregation or impurity enrichment, possibly due to differential solidification rates or the accumulation of second-phase particles. The formation of Fe- and Si-rich intermetallics and the subsequent stress concentrations during cooling are also probable contributing factors to solidification cracking (32–35). Visual inspection of optical micrographs taken of the material cross sections (Figure 7) revealed that the TR-AFSD process results in significant refinement of the particles present in the cast aluminum, resulting in a more uniform microstructure. The refinement observed in this work aligns with similar work quantifying the dispersion and refinement of foreign oxide particles (36) and second-phase particulates in AFSD (37–39,17,40), as well as other friction stir processes (41). Qualitative EDS analysis (Figure 5) identified these particles as oxygen rich, meaning they are likely oxide particles. The size reduction of the particles is due to the shear stress induced on the material by the tool rotation during the AFSD process, which may create sufficient force to fracture secondary-phase particles. The unrefined particles in the cast material may be locations of stress concentrations, increasing the risk of crack initiation. The constituent particle refinement observed from the AFSD process reduces the risk of crack initiation, meaning the AFSD build may have increased fatigue resistance, a critical property for many structural and large-scale components. EBSD analysis of the cast material and as-deposited microstructures (Figure 8) demonstrated that the AFSD process leads to significant grain refinement, with an approximate 30-fold reduction in grain diameter compared to the cast material. This grain refinement is primarily attributed to dynamic recrystallization, which occurs due to the severe plastic deformation and high shear strains inherent to AFSD. LAGBs also appeared more frequently in the as-deposited material, suggesting a reduction in dislocation density within the grains (8,37) In cases where there is not significant work hardening, a decrease in grain diameter correlates to an increase in yield strength, independent of other strengthening mechanisms in the material. The observed homogenization of the recycled material microstructure through the AFSD process demonstrates that the vertically integrated manufacturing paradigm investigated in this study is an efficient means to create a more desirable microstructure without thermal processing. The severe plastic deformation inherent to the AFSD process promotes refinement of detrimental intermetallic phases and contaminant particles. Grain refinement due to dynamic recrystallization also contributes to improved material performance through grain boundary strengthening. This results in a more uniform microstructure with a more even distribution of alloying elements and contaminants, resulting in more uniform material behavior. The porosity reduction, intermetallic refinement, and grain refinement observed demonstrates that AFSD can enhance the properties of recycled cast aluminum without the need for post-deposition heat treatment or additional post-processing like hot isostatic pressing (HIP). Potential applications of this manufacturing paradigm include the fabrication of large-scale structural components such as pressure vessels or fuel storage tanks, as well as small components and tools needed during a space mission. Examples of components that can be fabricated using TR-AFSD are shown in Figure 9. Because TR-AFSD can utilize a wide range of feedstock materials, it is possible to create components using in-situ resources beyond metal scrap, such as regolith (17,18). The components depicted in Figure 9 were fabricated from wrought aluminum alloy feedstock and lunar regolith simulant to create metal matrix composites (MMCs) that take advantage of additional in-situ resources on the lunar surface. This ISRU manufacturing paradigm could enable the rapid fabrication of critical components, such as repair tools and medical devices, from scrap material and resources available on the lunar surface. By utilizing in-situ resources for point-of-need manufacturing, this approach could enhance operational efficiency and adaptability for future space missions. The present study represents a critical first step in the development of a novel manufacturing paradigm suitable for large-scale in-space manufacturing and repair operations, but further advancements will be necessary to understand the capabilities of the process and implement it on a future space mission. The in-space casting system used in this study produces feedstock that is not the correct dimensions for TR-AFSD, introducing an additional machining step prior to deposition. Future work could enhance the interfacing between these two processes such that continuously cast material could be fed directly into the TR-AFSD SSAM process, removing the feedstock machining step and increasing resource utilization efficiency. Furthermore, to successfully implement upcycling of space debris using AFSD on future space missions, in-depth quantification of PSPP relationships and process optimization, guided by physics based computational techniques, such as smooth particle hydrodynamics (SPH), will be needed. The influence of in-space environmental conditions, such microgravity, vacuum, cosmic radiation, and extreme temperatures, on the underlying PSPP relationships in this manufacturing paradigm will also be critical in advancing this technology. Future work should also investigate alternative methods of feedstock fabrication to broaden the range of materials and applications for this technology. Based on the prior studies on AFSD lunar regolith MMCs (17,18) and the preliminary work to fabricate the TR-AFSD components shown in Figure 9, feedstock configuration has a significant influence on regolith dispersion in the metal matrix. Solid state metals processing technologies, such as Shear Assisted Processing and Extrusion (ShAPE), have shown promise for direct upcycling of industrial scrap with high levels of iron contamination (43). Using ShAPE or another friction extrusion process to fabricate composite feedstocks with dispersed regolith could enhance the uniformity of regolith dispersion and refinement in the metal matrix. This solid-state approach could also eliminate the need for casting scrap material and allow for the implementation of a fully solid-state debris upcycling paradigm in austere environments. Addressing these challenges and possible improvements will ensure that ISM processes meet operational needs and align with long-term goals for responsible and efficient use of space resources. Conclusions The current work presented a novel concept for sustainable in-space manufacturing and recycling of metallic space debris for in-situ resource utilization for space exploration applications. Simulated space debris fabricated from AA6061 was recycled into feedstock using continuous casting. TR-AFSD was then used to fabricate a fully dense, multilayer near-net shape component. · X-ray CT showed that the AFSD process reduced porosity by 97.4% in the usable volume on the deposit, resulting in an effectively fully dense material. · XRF analysis identified alloying element segregation near defects in the cast material, demonstrating that solidification cracking is a prominent issue in the cast feedstock. · EDS mapping of the cast feedstock identified the needle-like features as silicon- and iron-rich intermetallics, and the larger particles present throughout the material were found to be oxide inclusions. · AFSD refined intermetallics and constituent particles by approximately 91% and created a more uniform microstructure, which may contribute to a higher strength and fatigue resistance in the as-deposited material. · EBSD analysis revealed grain size reduction of approximately 30X in the AFSD deposit compared to the cast feedstock. This refinement is due to dynamic recrystallization that occurs during the AFSD process and suggests an increased material strength via the Hall-Petch effect. This study is the first work to present an investigation of PSPP relations in cast recycled feedstock processed with TR-AFSD for ISRU in-space manufacturing applications. The findings demonstrate that AFSD is a viable method for converting low-quality recycled cast feedstocks into large-scale components with refined and more homogenous microstructures and therefore more desirable material properties. These results highlight the potential of the proposed vertically integrated manufacturing paradigm for point-of-need applications in space exploration. Declarations Acknowledgements A portion of the work was funded by the National Science Foundation (NSF) Future Manufacturing Program, Award 2328383. The funder played no role in study design, data collection, analysis and interpretation of data, or the writing of this manuscript. The authors would like to thank the Center for Microscopy and Imaging (CMI) at Baylor University (Waco, TX) for use of facilities and technical support during microscopy and image analysis. Author Contributions CRB conducted the investigation and formal analysis of the generated data, performed data visualization, created figures, wrote the original draft, and contributed to review and editing. NZ developed the methodology and conducted the formal analysis of the microscopy data, as well as contributed to review and editing. PKR performed the X-ray computed tomography scans and carried out the accompanying data visualization and analysis. JWP contributed to the conceptualization of the study, wrote portions of the original draft, and performed data visualization. CR designed and carried out the manufacturing of the components shown in Figure 9. RS fabricated the deposit characterized in the study. WSM contributed to the study conceptualization and participated in review and editing. 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Beck SC, Williamson CJ, Kinser RP, Rutherford BA, Williams MB, Phillips BJ, et al. Examination of microstructure and mechanical properties of direct additive recycling for Al-Mg-Mn alloy Machine chip waste. Materials & Design. 2023 Apr 1;228:111733. Jordon JB, Allison PG, Phillips BJ, Avery DZ, Kinser RP, Brewer LN, et al. Direct recycling of machine chips through a novel solid-state additive manufacturing process. Materials and Design. 2020 Aug 1;193. Babaniaris S, Jiang L, Varma RK, Farabi E, Dorin T, Barnett M, et al. Precipitation in AA6063 produced from swarf using additive friction stir deposition. Additive Manufacturing Letters. 2022 Dec 1;3:100096. Yoder JK, Hahn GD, Zhao N, Brennan RE, Cho K, Yu HZ. Additive friction stir deposition-enabled upcycling of automotive cast aluminum chips. Additive Manufacturing Letters. 2023 Feb 1;4:100108. Lopez JJ, Williams MB, Rushing TW, Brian Jordon J, Cartwright JA, Thompson GB, et al. Local Resource Utilization of Lunar Regolith for Manufacturing at the Point-of-Need of Metal Matrix Composites. In: Earth and Space 2022 [Internet]. American Society of Civil Engineers; 2023 [cited 2024 Jan 24]. p. 298–307. Available from: https://ascelibrary.org/doi/10.1061/9780784484470.028 Lopez JJ, Williams MB, Ravindranath PK, Rushing TW, Jordon JB, Thompson GB, et al. Friction stir additive manufacturing of regolith metal matrix composite. Advances in Space Research. 2024 Apr 23; Gradl PR, Mireles OR, Protz CS, Garcia CP, editors. Metal Additive Manufacturing for Propulsion Applications [Internet]. Reston, VA: American Institute of Aeronautics and Astronautics, Inc.; 2022 [cited 2025 Jan 23]. Available from: https://arc.aiaa.org/doi/book/10.2514/4.106279 Chu J. MIT News | Massachusetts Institute of Technology. 2017 [cited 2024 Sep 13]. Space junk: The cluttered frontier. Available from: https://news.mit.edu/2017/space-junk-shards-teflon-0619 Hoarston J, Strain J, Artzer D, Zettwoch J, Brewer L, Jordon JB, et al. PONI-Baylor-LSAAT [Internet]. Kansas City Nuclear Security Campus (KCNSC), Kansas City, MO (United States); 2023 Jun [cited 2024 Sep 25]. Report No.: NSC-614-5376. Available from: https://www.osti.gov/biblio/1984940 European Space Agency, Technical University of Berlin. European Space Agency. 2021 [cited 2024 Sep 25]. Laser melting to construct infrastructure on the Moon. Available from: https://www.esa.int/ESA_Multimedia/Images/2021/07/Laser_melting_to_construct_infrastructure_on_the_Moon Pawelski JW, Toby Joseph Daniel Mould, Jan Walter Schroeder, Gary Douglas Calnan. Space Foundry [Internet]. Denver, CO; US-11634241-B1, 2023 [cited 2024 Dec 17]. Available from: https://ppubs.uspto.gov/dirsearch-public/patents/html/11634241?source=USPAT&requestToken=eyJzdWIiOiI0NzE3ZjNhYy1iNzhlLT QxYjktOWNkMS0zNjhiZGFmN2Y5YTAiLCJ2ZXIiOiI3NjgxMzQyYS05NmExLTQxNTE tYWI2ZS1iOTU2MTgxMGFjZTUiLCJleHAiOjB9 Schroeder JW, Calnan GD, Bogno AA, Mould TJD, Pecher RP, Pawelski JW, et al. Space Debris Recycling by Electromagnetic Melting. In: Badescu V, Zacny K, Bar-Cohen Y, editors. Handbook of Space Resources [Internet]. Cham: Springer International Publishing; 2023 [cited 2024 Dec 17]. p. 309–34. Available from: https://doi.org/10.1007/978-3-030-97913-3_7 Anderson K, Weritz J, Kaufman JG, editors. 6061 and Alclad 6061: General Structural Alloy. In: Properties and Selection of Aluminum Alloys [Internet]. ASM International; 2019 [cited 2024 Feb 16]. p. 388–93. Available from: http://dl.asminternational.org/handbooks/book/91/chapter/2088303/6061-and-Alclad-6061General-Structural-Alloy Taylor JA. Iron-Containing Intermetallic Phases in Al-Si Based Casting Alloys. Procedia Materials Science. 2012 Jan 1;1:19–33. Santella ML, Engstrom T, Storjohann D, Pan TY. Effects of friction stir processing on mechanical properties of the cast aluminum alloys A319 and A356. Scripta Materialia. 2005 Jul 1;53(2):201–6. Ma ZY, Sharma SR, Mishra RS. Effect of friction stir processing on the microstructure of cast A356 aluminum. Materials Science and Engineering: A. 2006 Oct 15;433(1):269–78. Garcia D, Hartley WD, Rauch HA, Griffiths RJ, Wang R, Kong ZJ, et al. In situ investigation into temperature evolution and heat generation during additive friction stir deposition: A comparative study of Cu and Al-Mg-Si. Additive Manufacturing. 2020 Aug 1;34:101386. Stubblefield GG, Fraser KA, Robinson TW, Zhu N, Kinser RP, Tew JZ, et al. A computational and experimental approach to understanding material flow behavior during additive friction stir deposition (AFSD). Comp Part Mech [Internet]. 2023 Apr 19 [cited 2023 Jul 3]; Available from: https://link.springer.com/10.1007/s40571-023-00578-x Stubblefield GG, Fraser K, Phillips BJ, Jordon JB, Allison PG. A meshfree computational framework for the numerical simulation of the solid-state additive manufacturing process, additive friction stir-deposition (AFS-D). Materials & Design. 2021 Apr;202:109514. Cinkilic E, Moodispaw M, Zhang J, Miao J, Luo AA. A New Recycled Al–Si–Mg Alloy for Sustainable Structural Die Casting Applications. Metall Mater Trans A. 2022 Aug 1;53(8):2861–73. Li S, Apelian D. Hot Tearing of Aluminum Alloys. Inter Metalcast. 2011 Jan 1;5(1):23–40. Liu J, Kou S. Susceptibility of ternary aluminum alloys to cracking during solidification. Acta Materialia. 2017 Feb 15;125:513–23. Ma Z, Samuel AM, Samuel FH, Doty HW, Valtierra S. A study of tensile properties in Al–Si–Cu and Al–Si–Mg alloys: Effect of β-iron intermetallics and porosity. Materials Science and Engineering: A. 2008 Aug 25;490(1):36–51. Zhu N, Avery DZ, Rutherford BA, Phillips BJ, Allison PG, Brian Jordon J, et al. The effect of anodization on the mechanical properties of aa6061 produced by additive friction stir-deposition. Metals. 2021 Nov 1;11(11). Avery DZ, Phillips BJ, Mason CJT, Palermo M, Williams MB, Cleek C, et al. Influence of Grain Refinement and Microstructure on Fatigue Behavior for Solid-State Additively Manufactured Al-Zn-Mg-Cu Alloy. Metall Mater Trans A. 2020 Apr 5;51(6):2778–95. Avery DZ, Rivera OG, Mason CJT, Phillips BJ, Jordon JB, Su J, et al. Fatigue Behavior of Solid-State Additive Manufactured Inconel 625. JOM. 2018 Nov 1;70(11):2475–84. Lopez JJ, Williams MB, Rushing TW, Confer MP, Ghosh A, Griggs CS, et al. A solid-state additive manufacturing method for aluminum-graphene nanoplatelet composites. Materialia. 2022 Jun 1;23:101440. Rutherford BA, Avery DZ, Phillips BJ, Rao HM, Doherty KJ, Allison PG, et al. Effect of thermomechanical processing on fatigue behavior in solid-state additive manufacturing of Al-Mg-Si alloy. Metals. 2020 Jul 14;10(7):1–17. Ma ZY, Sharma SR, Mishra RS. Effect of multiple-pass friction stir processing on microstructure and tensile properties of a cast aluminum–silicon alloy. Scripta Materialia. 2006 May 1;54(9):1623–6. Valiev RZ, Langdon TG. Principles of equal-channel angular pressing as a processing tool for grain refinement. Progress in Materials Science. 2006 Sep 1;51(7):881–981. Whalen S, Overman N, Taysom BS, Bowden M, Reza-E-Rabby Md, Skszek T, et al. Effect of high iron content on direct recycling of unhomogenized aluminum 6063 scrap by Shear Assisted Processing and Extrusion. Journal of Manufacturing Processes. 2023 Jul 7;97:115–24. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 19 May, 2025 Reviews received at journal 18 May, 2025 Reviewers agreed at journal 15 May, 2025 Reviews received at journal 13 May, 2025 Reviewers agreed at journal 12 May, 2025 Reviewers agreed at journal 12 May, 2025 Reviewers agreed at journal 12 May, 2025 Reviewers invited by journal 12 May, 2025 Editor assigned by journal 01 Apr, 2025 Submission checks completed at journal 01 Apr, 2025 First submitted to journal 29 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6334841","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":436972721,"identity":"200c9fe0-40d0-4c4b-b3e4-b40619e559a8","order_by":0,"name":"Charlye R. Baker","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Charlye","middleName":"R.","lastName":"Baker","suffix":""},{"id":436972722,"identity":"6f30c570-5c6d-46c6-8c3b-40764607d402","order_by":1,"name":"Ning Zhu","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Ning","middleName":"","lastName":"Zhu","suffix":""},{"id":436972723,"identity":"e22aa058-791d-4604-b3b7-773d9b8cda4c","order_by":2,"name":"Pruthul Kokkada Ravindranath","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Pruthul","middleName":"Kokkada","lastName":"Ravindranath","suffix":""},{"id":436972724,"identity":"14f62956-f90f-4db8-a666-adf77c9a0264","order_by":3,"name":"Joseph W. Pawelski","email":"","orcid":"","institution":"CisLunar Industries","correspondingAuthor":false,"prefix":"","firstName":"Joseph","middleName":"W.","lastName":"Pawelski","suffix":""},{"id":436972725,"identity":"c7130033-bba7-4610-a60a-4c91dd67761e","order_by":4,"name":"Cole Ritter","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Cole","middleName":"","lastName":"Ritter","suffix":""},{"id":436972726,"identity":"32d831c3-561a-4ae8-8e46-415020c719a8","order_by":5,"name":"Rachel Swinney","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Rachel","middleName":"","lastName":"Swinney","suffix":""},{"id":436972728,"identity":"0253ca35-f2cb-4290-bdac-ca23cc913e89","order_by":6,"name":"Walter Matthews","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Walter","middleName":"","lastName":"Matthews","suffix":""},{"id":436972729,"identity":"675271fa-93b1-48ae-84cb-4c308e452933","order_by":7,"name":"Trevor J. Fleck","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"Trevor","middleName":"J.","lastName":"Fleck","suffix":""},{"id":436972730,"identity":"4532d359-25b6-43ad-b4b2-8f06b565b291","order_by":8,"name":"J. Brian Jordon","email":"","orcid":"","institution":"Baylor University","correspondingAuthor":false,"prefix":"","firstName":"J.","middleName":"Brian","lastName":"Jordon","suffix":""},{"id":436972731,"identity":"cd62248f-d660-453f-a683-e79e8fbfa674","order_by":9,"name":"Paul G. Allison","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/0lEQVRIiWNgGAWjYHACxgMMDBYybCDmxwYGBj6wIBt+PUAtEjwgNYwzG2CKidECYjDzEqPFnP2MwQGGGgkePv7Dxx7b7rBLbGPvfcDwoewwTi2WPTlALceADpNISzfOPZOc2MZz3IBxxjncWgwOgLSwgbTwmEnntjEntkmkAV3YhkfL+TdALf+AWvjPmElbttVDtPzFp+UG0BbGNlCI5ZhJM7YdhmhhxKPFcsazggOMfWC/pEn2njlu3MZzjOFgz7l0nFrM+ZM3PmD4ZiMn33/4mMTPHdWy/extjA9+lFnjdhgQM/9BEnBsYADHFG5ggC5gj0/1KBgFo2AUjEwAAKrETSMcpQxCAAAAAElFTkSuQmCC","orcid":"","institution":"Baylor University","correspondingAuthor":true,"prefix":"","firstName":"Paul","middleName":"G.","lastName":"Allison","suffix":""}],"badges":[],"createdAt":"2025-03-29 15:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6334841/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6334841/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81673470,"identity":"4b76c814-615b-475a-9f31-61cc76fd34f0","added_by":"auto","created_at":"2025-04-30 06:39:44","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":978647,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eVertically integrated process approach for fabrication of large-scale components machined from solid state additive manufacturing of recycled space debris. a) Artistic rendering of on-orbit space debris (20), b) Image of continuous casting system used to create feedstock, c) TR-AFSD process , d) example of large, hollow near-net shape build fabricated using TR-AFSD (21) e) artistic rendering of fuel tanks on the lunar surface, a possible application for the proposed manufacturing paradigm (22).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/b1e3e5f6453647d5e4827dd0.png"},{"id":81672772,"identity":"773006eb-f308-489c-a62b-5ba0c8c1f9bd","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1049532,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea) Schematic showing the TR-AFSD process. A near-net shape component is fabricated by depositing layers of material successively onto a substrate. The final component is machined from the build after deposition. b) Photograph of a wrench partially machined from an AFSD deposit illustrating how a final component is produced from a near-net shape deposit.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/06ab764b57fc09580bbcf885.png"},{"id":81672774,"identity":"6a35189d-a059-406f-90ee-8597883bb45f","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":686749,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea) Top view of cast material sample. b) Two-layer TR-AFSD deposit.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/1d5ee36b416b8f1a7448c21c.png"},{"id":81672775,"identity":"bb3a92df-7923-44cc-8a9a-2e7e837e189b","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1729393,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea, b) 3D CT reconstructions of the cast material. c) Top view of CT reconstruction of the AFSD build. d) isometric view of CT reconstruction of the AFSD build. The substrate was not included in the porosity analysis, and the usable volume of the near-net shape deposit is outlined in the top view. Note the difference in the color scales between a-b) and c-d)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/b202881119654168656b98c9.png"},{"id":81673472,"identity":"fc23b2ac-e58f-4015-bfda-4f22f50deda4","added_by":"auto","created_at":"2025-04-30 06:39:44","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":487971,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea) Top view of representative sample of the cast rod. XRF sampling locations are marked. b) XRF composition results of the cast feedstock for Fe and the major alloying elements of AA6061\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/01827704de0a6c14d034c70e.png"},{"id":81672780,"identity":"61f50bd3-a15b-4910-9688-8a7f2caab812","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2578779,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSEM BSE micrograph of cast feedstock area mapped using EDS, and the EDS map results for Al, Mg, Si, O, and Fe.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/26ab27e85e13fe383ad6d383.png"},{"id":81672777,"identity":"037a2faf-1d61-4333-882d-8b617e0e63f1","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":342133,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptical micrographs of a) cast feedstock and b) TR-AFSD deposit cross section\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/fde540906971a1bc73039baf.png"},{"id":81672779,"identity":"7d37935e-1cdc-46f9-be7c-847a2033abad","added_by":"auto","created_at":"2025-04-30 06:31:44","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1449996,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThree-dimensional inverse pole figure (IPF) orientation map of a) as-received cast material (500 μm scale bar) and b) as-deposited (10 μm scale bar). Low angle grain boundaries (misorientation angles between 2° and 10°) are shown as white lines, and high angle grain boundaries (misorientation greater than 10°) are shown in black. LD, TD, and BD refer to the longitudinal, transverse, and build directions, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/35bd26eb3024604876dce953.png"},{"id":81673471,"identity":"e49737db-1ff2-4815-a5a1-990d7af17054","added_by":"auto","created_at":"2025-04-30 06:39:44","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":651613,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePotential applications of the proposed ISM paradigm utilizing in-situ space resources. The components shown were fabricated from TR-AFSD near-net shape deposits of aluminum alloy 6061 (AA6061) metal matrix composites (MMCs) containing 10 wt.% lunar regolith simulant. (a) 10 mm wrench, (b) ISO-standard scalpel handle, and (c) surgical probe.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/1e1f54045b95a9d649558f5d.png"},{"id":81673693,"identity":"11bc9569-b85e-4b64-89c7-ba5d20c7b162","added_by":"auto","created_at":"2025-04-30 06:47:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":15608216,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6334841/v1/f6023bb8-1e33-40d8-b8ec-5bd3013bcd11.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sustainable In-Space Manufacturing by Upcycling Metal Space Debris via a Vertically Integrated Processing Paradigm","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe recycling of metal space debris holds significant promise in addressing the growing concern of on-orbit space debris. As of 2024, the European Space Agency (ESA) estimates there are over 35,000 objects larger than 10 cm in Earth\u0026apos;s orbit, with millions of smaller fragments that pose significant risks to active satellites, space stations, and future missions\u0026nbsp;(1).This number will continue to grow as space activity increases. By converting this otherwise hazardous material into feedstock for on-orbit manufacturing and repair, space metal recycling provides a critical opportunity to mitigate these risks while simultaneously increasing in-situ resource utilization (ISRU) capabilities.\u003c/p\u003e\n\u003cp\u003eManufacturing paradigms that utilize space debris present multiple critical functionalities for future space missions. ISRU facilitates the creation of new components and structures in-space from locally available resources, reducing reliance on Earth-based supply chains and the need for costly and logistically challenging launches from Earth. At the same time, space debris upcycling would mitigate some of the immediate dangers posed by space debris and allow decommissioned spacecraft to be removed from orbit and upcycled into high-value components before they become a hazard to other space missions. This method aligns with broader goals of sustainability and self-sufficiency in space exploration through responsible use of space resources\u0026nbsp;(2)\u0026nbsp;and converting potential hazards into valuable resources that can promote further exploration and development.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe conventional approach of recycling aluminum alloys through casting presents significant challenges. Heat treatable aluminum alloys are commonly found in space debris due to their extensive use in space exploration applications, such as upper stages of rockets, satellites, landers, and rovers, making them a key material for ISRU\u0026nbsp;(3). However, there are significant barriers to effective recycling of secondary scrap, both terrestrially and in-space, due to the presence of contaminants such as ferrous materials in the scrap material. Casting these materials often leads to defects like solidification cracking and porosity because the impurities create stress concentrations within the material during liquid to solid phase transformations.\u003c/p\u003e\n\u003cp\u003eFurthermore, in traditional manufacturing processes, cast billets are homogenized at high temperatures prior to further processing to improve extrudability and mechanical properties (4). Conventional recycling processes also often require addition of primary aluminum to dilute contaminants to within an allowable range (5). These approaches to improve the properties of recycled material are energy-intensive and require additional feedstock materials, making them challenging to implement for point-of-need manufacturing in austere environments such as space. Therefore, there is a critical need for efficient manufacturing and post-processing methods to convert recycled cast aluminum alloy feedstocks into usable components with robust mechanical behavior for point-of-need applications, without the addition of primary aluminum or energy-intensive thermal processing steps.\u003c/p\u003e\n\u003cp\u003eAdditive Friction Stir Deposition (AFSD) offers an efficient way to fabricate near-net-shape components from recycled metals or metal matrix composites, including the removal or mitigation of defects such as porosity and element segregation, resulting in fully dense builds or repairs. AFSD is a solid-state additive manufacturing (SSAM) technique that operates at ambient temperature and atmosphere, making it well-suited for austere environments. During the AFSD process, feedstock, which can consist of a solid rod, machine chips, metal strips, or powder, is fed through a hollow, rotating tool (6). The tool\u0026rsquo;s rapid rotation generates frictional heat, which softens the feedstock material without melting it. As the tool traverses, this softened material is deposited layer-by-layer through plastic deformation, creating a metallurgical bond at the layer interfaces.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBecause AFSD is a solid-state process, it is well-suited for on-orbit or other in-space manufacturing applications in which molten metal would present operational and safety challenges. \u0026nbsp;AFSD also inherently avoids the solidification cracking issues commonly associated with rapid cooling rates in beam-based additive manufacturing techniques (7,8). These advantages, combined with AFSD\u0026rsquo;s significant energy savings due to its reliance on low-power technology and thermomechanical processing (6,9), makes it a more efficient manufacturing method for austere environments. The impact of AFSD on the microstructure and mechanical properties of aluminum alloys, as well as other metals, has been characterized, revealing substantial grain size refinement primarily due to dynamic recrystallization (8,10\u0026ndash;12). These refined microstructures translate to improved material performance, further demonstrating AFSD\u0026apos;s potential in advanced manufacturing.\u003c/p\u003e\n\u003cp\u003eThe technical potential of AFSD for recycling aluminum scrap has been explored for various materials. Two primary approaches exist for depositing machine chips: direct feeding of loose chips through a hopper into the AFSD tool (13,14) or compacting the chips into feedstock (15,16). \u0026nbsp;Beck et al. demonstrated that direct additive recycling (DAR) AFSD AA5083 exhibited nearly identical fatigue performance to wrought material, with comparable ultimate tensile strength, higher yield strength, and slightly lower elongation to failure. Yoder et al. demonstrated the efficacy of utilizing AFSD for upcycling automotive machining chips. Machining chips made of a cast aluminum alloy were compressed into a ~68% dense square feedstock rod and deposited using AFSD. The resulting deposit was fully dense, with fine, equiaxed grains, and the improved properties were attributed to the reduction, spheroidization, and dispersion of second-phase particles induced by AFSD (16). Babaniaris et al. investigated the compaction of machining chips via hot extrusion to create AFSD feedstock. The study found that AFSD, followed by heat treatment, may allow recycling of aluminum with higher levels of Fe contamination compared to other recycling methods (15), potentially mitigating the increased corrosion that typically arises due to Fe contamination in aluminum scrap recycling.\u003c/p\u003e\n\u003cp\u003ePrevious AFSD studies have also demonstrated that AFSD is a promising means to fabricate lunar regolith metal matrix composites (MMCs) for point-of-need ISM. Lopez et al. used AFSD to fabricate AA6061-lunar regolith simulant MMCs with 9, 18, and 31% lunar regolith simulant (17). The regolith simulant was refined by approximately 100x from the initial particle size and increased volume fraction of regolith simulant led to an increased hardness in the deposit. However, the regolith was not distributed uniformly throughout the AFSD deposit, leading to inhomogeneities in material properties. A subsequent study focused on AA6061 \u0026ndash; 20 wt% regolith simulant MMCs fabricated using AFSD (18). X-ray computed tomography (CT) showed the total porosity of the build was 0.03% and the usable volume of the deposit (19) had a porosity of 0.001%, demonstrating that regolith MMCs fabricated using AFSD are effectively fully dense. The MMC deposit exhibited a higher ultimate stress than AA6061 deposits without regolith particles, confirming that incorporating secondary particulates like lunar regolith can enhance the strength of AFSD deposits while also enabling the use of in-situ resources.\u003c/p\u003e\n\u003cp\u003eThe present research presents a novel concept for aluminum space debris recycling, illustrated in Figure 1. Casting is used to consolidate scrap from sources such as space debris to create feedstock for the twin rod AFSD (TR-AFSD) process, which uses offset round feedstock rods. Most prior work on AFSD uses a single square center-fed feedstock. Using multiple offset rods increases deposition rates without widening the deposit and enables the use of round feedstock. This is beneficial for material upcycling, as round rods can be produced through various fabrication methods. A schematic of the TR-AFSD process is shown in Figure 2. The goal of this study is to evaluate the effect of TR-AFSD processing on the microstructure and resulting properties of recycled simulated space debris feedstock fabricated using continuous casting. Specimens of the cast feedstock and as-deposited TR-AFSD build were analyzed using x-ray computed tomography (CT), x-ray fluorescence (XRF), energy dispersive x-ray spectroscopy (EDS), optical microscopy, and electron backscatter diffraction (EBSD). These multiscale characterization results demonstrated that AFSD is an efficient means to refine the microstructure of cast recycled space debris feedstocks to create components with improved material performance.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e\u003cstrong\u003e2.1.1\u0026nbsp; \u0026nbsp;\u0026nbsp;Materials and AFSD\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe cast recycled simulated space debris, with a nominal composition equivalent to Aluminum Alloy 6061 (AA6061), was provided by CisLunar Industries, Inc. AA6061 was selected since it represents a ubiquitous model alloy system. Debris simulant was cast using parabolic payload test subsystems from the Modular Space Foundry (MSF), developed by CisLunar Industries. The MSF uses an electromagnetically positioned and heated continuous casting process to produce rods and billets for in space manufacturing, on-orbit and on the lunar surface\u0026nbsp;(23).\u0026nbsp;Casting was selected as the feedstock fabrication method due to the challenges of consolidating a range of scrap material shapes in a low-gravity environment. The electromagnetic induction system employed by the MSF allows for contactless gathering and positioning of the metal scrap, making it suited for manufacturing in a range of gravitational accelerations (24).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe recycled space debris simulant\u0026nbsp;was machined\u0026nbsp;into two 12.7 mm diameter round feedstock rods for use in a Bond Technologies GL7 hybrid friction stir welding (FSW) / TR-AFSD system. The rods were\u0026nbsp;spray coated with a graphite lubricant coating to prevent feedstock from jamming in the tool during depositions. The machine was operated at a feed rate of 17 mm/min, traverse velocity of 89 mm/min, and a spindle speed of 500 rpm, and had an initial dwell time of 4 s to generate the initial frictional heat required for plastic flow.\u0026nbsp;The material was deposited on a 6.25 mm thick AA6061-T6 substrate.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2\u0026nbsp;\u003c/strong\u003e \u003cstrong\u003eMaterial Characterization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eX-Ray Computed tomography (CT) scans were performed on the cast feedstock and AFSD build using a North Star Imaging (NSI) X-3000 industrial X-ray CT inspection system. The sampling voxel size was 40 \u0026micro;m and the source was set to a focal spot size of 52 \u0026micro;m. After the reconstruction of the CT scan images using the NSI efX-CT software, the image stack of the slices was exported. The three-dimensional volume of the cast and deposit parts were analyzed using the deep learning feature of the Dragonfly image processing software for quantification of porosity volume and location. The voids were segmented and quantified from these regions of interest (ROIs) to measure their volumetric size. X-ray fluorescence (XRF) scans were completed with a Bruker S1 TITAN 800 Handheld XRF scanner using a scan time of 20 seconds.\u003c/p\u003e\n\u003cp\u003eEnergy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) samples were machined from the AFSD deposit using a Mitsubishi wire cut electrical discharge machine (EDM). These samples were taken from the steady state region of the deposit to ensure experimental results were not affected by the dwell or exit portions of the AFSD process. Cast feedstock samples for EBSD were machined from the remaining feedstock\u003cstrong\u003e.\u0026nbsp;\u003c/strong\u003eBecause the irregular geometry inhibited clamping for EDM, cast samples were cut manually using a precision metallography saw.\u003c/p\u003e\n\u003cp\u003eAll EBSD, EDS, and optical microscopy samples were mounted for microscopy and ground using P600 and P1200 SiC paper, followed by polishing with 3 \u0026mu;m and 1 \u0026mu;m diamond suspension solutions. The samples were then vibratory polished with a 0.02 \u0026mu;m colloidal silica solution for 4 hours. Optical microscopy was completed with a Keyence VHX-7000 digital microscope. A Versa 3D Focused Ion Beam Scanning Electron Microscope (FIB-SEM) equipped with EDAX EDS and EBSD detectors was utilized for further material characterization. EDS scans were conducted at 25 kV, 2000x magnification, a spot size of 6.0, and a nominal working distance of 10 mm. EBSD specimens were positioned with a 70-degree pre-tilt, and all scans were performed at 20 kV, 5.3 nA, and a spot size of 7.0. Cast scans were completed using a 10 \u0026mu;m step size over an approximately 1840 by 1460 \u0026mu;m area. Scans of the as-deposited material were conducted using a step size of 0.25 \u0026mu;m over an approximately 30 x 30 \u0026mu;m area. Data cleanup, visualization, and grain size analysis was conducted using the OIM software by EDAX using the standard grain dilation algorithm and a minimum grain size of 16 pixels. All scans had less than 12% points changed during data cleanup and above 70% CI\u0026gt;0.1. A grain misorientation angle of 10 degrees was used to determine high angle grain boundaries, and misorientation angles between 2 and 10 degrees were classified as low angle grain boundaries.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe TR-AFSD process was successfully used to create a fully dense, multilayer component using the recycled space debris simulant cast feedstock. Visual inspection of a representative sample of the cast material Figure 3a revealed multiple prominent cracks in the material surface and a high surface roughness. The TR-AFSD build, shown in Figure 3b, had minimal surface defects, albeit with some flash (excess material on the deposit edge that can be machined away and recycled through TR-AFSD again) as typical of the near-net shape AM process. The build consisted of two approximately 1 mm thick, 27 mm wide, 50 mm long layers.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCT imaging results demonstrate that the TR-AFSD process effectively reduced the number of defects present in the material, i.e. consolidation of cast porosity and the formation of a more fully dense structure. The total void volume fraction in the cast deposit was 0.63%, and void sizes ranged from 0.01 to 16.5 mm\u0026sup3;. A three-dimensional rendering of the CT scan of the cast material, shown in Figures 4a-b, illustrates the distribution of porosity throughout the sample. The total porosity calculated from the scan of the build, shown in Figure 4c-d, was 0.19%. Void sizes in the build ranged from and 0.003 to 0.37 mm\u0026sup3;. This porosity was concentrated on the edges of the build, which would likely be machined away during finishing to create the functional component. In a steady-state region of the deposit measuring 20 \u0026times; 36 mm, 12 voids were detected with volumes ranging from 0.004 to 0.067 mm\u0026sup3;. This area approximated the volume that would be usable after finish machining for a final component (19). The usable volume of the deposit had a porosity of 0.016%, equivalent to a 97.4% reduction compared to the cast feedstock. The usable material in the deposit is effectively fully dense, indicating that the level of porosity present in the as-deposited material would not negatively impact the performance of the finished component.\u003c/p\u003e\n\u003cp\u003eFigure 5\u0026nbsp;shows the XRF sampling locations and composition results.\u0026nbsp;The given nominal values are the upper compositions limits as specified in the American Society for Metals (ASM) standard for AA6061\u0026nbsp;(25). The analysis shows that the concentrations of several AA6061 alloying elements are higher in the crack region than in the main body of the material. Specifically, the Si, Fe, and Cu concentrations are approximately 1.26%, 2.70%, and 0.34% higher, respectively, in the crack. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEDS mapping was utilized to identify the qualitative elemental compositions of the constituent particles and intermetallic compounds in the cast feedstock.\u0026nbsp;Figure 6\u0026nbsp;shows a backscatter electron (BSE) SEM image of a representative location on a cast feedstock cross section and the corresponding EDS map results for Al, Mg, Si, O, and Fe. The oxygen-rich regions correspond to the locations of large particles in the aluminum matrix, indicating that these particles are likely large oxides. Likewise, the needle-like intermetallics, which appear as white areas in the SEM micrograph, can be classified as Fe- and Si- rich intermetallics.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 7\u0026nbsp;shows optical micrographs of the feedstock and as-deposited material cross sections, taken at 400x magnification. Note that the cast images were taken using the Keyence software\u0026rsquo;s built-in three-dimensional depth composition feature to provide a clear image of the particles protruding from the sample surface. The oxides and intermetallics present in the EDS sample were distributed throughout the material and can also be seen in the optical micrograph (Figure 7a). In contrast, the AFSD cross-section (Figure 7b) taken from the central, fully dense region of the deposit, has significantly smaller and more evenly dispersed particles. The average particle size in the cast material was 34.7 \u0026mu;m\u003csup\u003e2\u003c/sup\u003e, while the average in the AFSD build was 3.1 \u0026mu;m\u003csup\u003e2\u003c/sup\u003e, corresponding to a 91% reduction. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEBSD analysis of the cast material and as-deposited microstructures allows for comparison of texture and grain size due to the deposition process. Figure 8 shows a three-dimensional EBSD representation of the cast material and as-deposited material. The EDAX software reported average grain sizes of approximately 112.9 \u0026mu;m and 3.7 \u0026mu;m for the cast and as-deposited material, respectively, or an approximate 30x reduction. The deposited microstructure also exhibits a high density of low-angle grain boundaries (LAGBs), which are largely absent in the as-cast material.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1: Summary of porosity, grain size, intermetallic size, for the as-cast feedstock and usable volume of the TR-AFSD deposit\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSample\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePorosity (volume %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMinimum Detected Pore Volume (\u003c/strong\u003e\u003cstrong\u003emm\u0026sup3;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum Detected Pore Volume\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(\u003c/strong\u003e\u003cstrong\u003emm\u0026sup3;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAvg. Grain (Diameter,\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026mu;m)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage Constituent Particle Size (Area,\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026mu;m\u003csup\u003e2\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003eCast Feedstock\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0.01\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e16.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e112.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e34.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003eTR-AFSD Usable Volume\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.016\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0.004\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e3.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Discussion","content":"\u003cp\u003eA primary goal of this study was to evaluate the effectiveness of a novel vertically integrated materials processing approach that utilizes continuous casting and SSAM to upcycle metallic space debris into functional components. Due to contaminants in the recycled material and the challenges associated with casting in reduced gravity, the as-cast material exhibited high porosity, significant elemental segregation, and a coarse microstructure, which are unsuitable characteristics for providing robust material performance during in-space applications. Microstructural analysis of the cast simulated space debris and the as-deposited TR-AFSD build showed substantial refinement and homogenization, highlighting the potential of this technology to process recycled materials into functional components.\u003c/p\u003e\n\u003cp\u003eThe high number of voids present in the cast feedstock (Figure 4a) can be attributed to shrinkage porosity, which is particularly prevalent when casting heat-treatable aluminum alloys.\u0026nbsp;In alloys like AA6061, the lower silicon content compared to aluminum alloys designed for casting restricts fluidity during solidification, limiting the material\u0026apos;s ability to fill mold cavities effectively (26). The high Fe level present in the recycled material is also detrimental to material flow. Reduced flowability during casting increases the likelihood of void formation as the molten metal contracts and solidifies. Additionally, factors such as uneven cooling rates and inadequate material feeding can exacerbate porosity, compromising the mechanical properties and structural integrity of the cast material.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe stirring mechanism inherent to the AFSD and other friction stir processes results in the reduction of porosity present in the cast feedstock material. Existing work on the influence of friction stir processing on the microstructure and mechanical properties of cast aluminum alloys describes the similar observations (27,28). However, the deposition process results in porosity formation on the deposit edges because on the outer surfaces of the deposit, material flows to a free surface where there is no force driving material consolidation (18).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe defects present in the AFSD build are likely due to non-optimized processing parameters given the limited amount of material available for the study. Flash formation on deposit edges is attributed to the material feed rate and excessive heat generation during deposition\u0026nbsp;(29\u0026ndash;31).\u0026nbsp;As a result, this defect could be mitigated by further process parameter optimization for this material. \u0026nbsp;However, because the flash and porosity are concentrated on the edges of the deposit, these defects would be removed during finish machining.\u0026nbsp;As illustrated in Figure 2, the TR-AFSD process produces a near-net shape component that requires machining to produce the final component geometry and surface finish. As a result, the edge defects would be machined away and upcycled into new feedstock, meaning they would likely not have a negative impact on material performance.\u003c/p\u003e\n\u003cp\u003eXRF analysis of the cast simulated space debris (Figure 5) revealed higher concentrations of AA6061 constituent elements, primarily Si, Fe, and Cu, in the crack compared to the fully dense region, indicating there is a high level of elemental segregation in the material and the defect is likely due to solidification cracking. The highest concentrations in the crack are Fe and Si. Iron is a common impurity in aluminum alloys, especially for recycled materials. Iron is highly soluble in liquid aluminum alloys but tends to form intermetallic phases during solidification. EDS composition mapping (Figure 6) showed the presence of Fe and Si rich intermetallics, which are likely \u0026beta;-Al\u003csub\u003e5\u003c/sub\u003eFeSi as this is the dominant intermetallic phase formed in AA6061 in the presence of silicon (26). This phase is characterized by higher hardness, increased brittleness, and a thermal expansion coefficient that differs from the aluminum matrix, leading to localized stress concentrations that can become crack nucleation sites. The elevated levels of Fe and Si in the crack region indicate localized segregation or impurity enrichment, possibly due to differential solidification rates or the accumulation of second-phase particles. The formation of Fe- and Si-rich intermetallics and the subsequent stress concentrations\u0026nbsp;during cooling are also probable contributing factors to solidification cracking\u0026nbsp;(32\u0026ndash;35).\u003c/p\u003e\n\u003cp\u003eVisual inspection of optical micrographs taken of the material cross sections (Figure 7) revealed that the TR-AFSD process results in significant refinement of the particles present in the cast aluminum, resulting in a more uniform microstructure. The refinement observed in this work aligns with similar work quantifying the dispersion and refinement of foreign oxide particles (36) and second-phase particulates in AFSD (37\u0026ndash;39,17,40), as well as other friction stir processes (41).\u003cem\u003e\u0026nbsp;\u003c/em\u003eQualitative EDS analysis (Figure 5) identified these particles as oxygen rich, meaning they are likely oxide particles. The size reduction of the particles is due to the shear stress induced on the material by the tool rotation during the AFSD process, which may create sufficient force to fracture secondary-phase particles. The unrefined particles in the cast material may be locations of stress concentrations, increasing the risk of crack initiation. The constituent particle refinement observed from the AFSD process reduces the risk of crack initiation, meaning the AFSD build may have increased fatigue resistance, a critical property for many structural and large-scale components.\u003c/p\u003e\n\u003cp\u003eEBSD analysis of the cast material and as-deposited microstructures (Figure 8) demonstrated that the AFSD process leads to significant grain refinement, with an approximate 30-fold reduction in grain diameter compared to the cast material. This grain refinement is primarily attributed to dynamic recrystallization, which occurs due to the severe plastic deformation and high shear strains inherent to AFSD. LAGBs also appeared more frequently in the as-deposited material, suggesting a reduction in dislocation density within the grains (8,37)\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\"\u003e\u003c/p\u003e\n\u003cp\u003eIn cases where there is not significant work hardening, a decrease in grain diameter correlates to an increase in yield strength, independent of other strengthening mechanisms in the material.\u003c/p\u003e\n\u003cp\u003eThe observed homogenization of the recycled material microstructure through the AFSD process demonstrates that the vertically integrated manufacturing paradigm investigated in this study is an efficient means to create a more desirable microstructure without thermal processing. The severe plastic deformation inherent to the AFSD process promotes refinement of detrimental intermetallic phases and contaminant particles. Grain refinement due to dynamic recrystallization also contributes to improved material performance through grain boundary strengthening. This results in a more uniform microstructure with a more even distribution of alloying elements and contaminants, resulting in more uniform material behavior. The porosity reduction, intermetallic refinement, and grain refinement observed demonstrates that AFSD can enhance the properties of recycled cast aluminum without the need for post-deposition heat treatment or additional post-processing like hot isostatic pressing (HIP).\u003c/p\u003e\n\u003cp\u003ePotential applications of this manufacturing paradigm include the fabrication of large-scale structural components such as pressure vessels or fuel storage tanks, as well as small components and tools needed during a space mission. Examples of components that can be fabricated using TR-AFSD are shown in Figure 9. Because TR-AFSD can utilize a wide range of feedstock materials, it is possible to create components using in-situ resources beyond metal scrap, such as regolith (17,18). The components depicted in Figure 9 were fabricated from wrought aluminum alloy feedstock and lunar regolith simulant to create metal matrix composites (MMCs) that take advantage of additional in-situ resources on the lunar surface. This ISRU manufacturing paradigm could enable the rapid fabrication of critical components, such as repair tools and medical devices, from scrap material and resources available on the lunar surface. By utilizing in-situ resources for point-of-need manufacturing, this approach could enhance operational efficiency and adaptability for future space missions.\u003c/p\u003e\n\u003cp\u003eThe present study represents a critical first step in the development of a novel manufacturing paradigm suitable for large-scale in-space manufacturing and repair operations, but further advancements will be necessary to understand the capabilities of the process and implement it on a future space mission. The in-space casting system used in this study produces feedstock that is not the correct dimensions for TR-AFSD, introducing an additional machining step prior to deposition. Future work could enhance the interfacing between these two processes such that continuously cast material could be fed directly into the TR-AFSD SSAM process, removing the feedstock machining step and increasing resource utilization efficiency. Furthermore, to successfully implement upcycling of space debris using AFSD on future space missions, in-depth quantification of PSPP relationships and process optimization, guided by physics based computational techniques, such as smooth particle hydrodynamics (SPH), will be needed. The influence of in-space environmental conditions, such microgravity, vacuum, cosmic radiation, and extreme temperatures, on the underlying PSPP relationships in this manufacturing paradigm will also be critical in advancing this technology.\u003c/p\u003e\n\u003cp\u003eFuture work should also investigate alternative methods of feedstock fabrication to broaden the range of materials and applications for this technology. Based on the prior studies on AFSD lunar regolith MMCs (17,18) and the preliminary work to fabricate the TR-AFSD components shown in Figure 9, feedstock configuration has a significant influence on regolith dispersion in the metal matrix. Solid state metals processing technologies, such as Shear Assisted Processing and Extrusion (ShAPE), have shown promise for direct upcycling of industrial scrap with high levels of iron contamination (43). Using ShAPE or another friction extrusion process to fabricate composite feedstocks with dispersed regolith could enhance the uniformity of regolith dispersion and refinement in the metal matrix. This solid-state approach could also eliminate the need for casting scrap material and allow for the implementation of a fully solid-state debris upcycling paradigm in austere environments. Addressing these challenges and possible improvements will ensure that ISM processes meet operational needs and align with long-term goals for responsible and efficient use of space resources.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe current work presented a novel concept for sustainable in-space manufacturing and\u0026nbsp;recycling of metallic space debris for in-situ resource utilization for space exploration applications. Simulated space debris fabricated from AA6061 was recycled into feedstock using continuous casting. TR-AFSD was then used to fabricate a fully dense, multilayer near-net shape component.\u003c/p\u003e\n\u003cp\u003e\u0026middot; X-ray CT showed that the AFSD process reduced porosity by 97.4% in the usable volume on the deposit, resulting in an effectively fully dense material.\u003c/p\u003e\n\u003cp\u003e\u0026middot; XRF analysis identified alloying element segregation near defects in the cast material, demonstrating that solidification cracking is a prominent issue in the cast feedstock.\u003c/p\u003e\n\u003cp\u003e\u0026middot; EDS mapping of the cast feedstock identified the needle-like features as silicon- and iron-rich intermetallics, and the larger particles present throughout the material were found to be oxide inclusions.\u003c/p\u003e\n\u003cp\u003e\u0026middot; AFSD refined intermetallics and constituent particles by approximately 91% and created a more uniform microstructure, which may contribute to a higher strength and fatigue resistance in the as-deposited material.\u003c/p\u003e\n\u003cp\u003e\u0026middot; EBSD analysis revealed grain size reduction of approximately 30X in the AFSD deposit compared to the cast feedstock. This refinement is due to dynamic recrystallization that occurs during the AFSD process and suggests an increased material strength via the Hall-Petch effect.\u003c/p\u003e\n\u003cp\u003eThis study is the first work to present an investigation of PSPP relations in cast recycled feedstock processed with TR-AFSD for ISRU in-space manufacturing applications. The findings demonstrate that AFSD is a viable method for converting low-quality recycled cast feedstocks into large-scale components with refined and more homogenous microstructures and therefore more desirable material properties. These results highlight the potential of the proposed vertically integrated manufacturing paradigm for point-of-need applications in space exploration.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA portion of the work was funded by the National Science Foundation (NSF) Future Manufacturing Program, Award 2328383. The funder played no role in study design, data collection, analysis and interpretation of data, or the writing of this manuscript. \u0026nbsp;The authors would like to thank the Center for Microscopy and Imaging (CMI) at Baylor University (Waco, TX) for use of facilities and technical support during microscopy and image analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCRB conducted the investigation and formal analysis of the generated data, performed data visualization, created figures, wrote the original draft, and contributed to review and editing. NZ developed the methodology and conducted the formal analysis of the microscopy data, as well as contributed to review and editing. PKR performed the X-ray computed tomography scans and carried out the accompanying data visualization and analysis. JWP contributed to the conceptualization of the study, wrote portions of the original draft, and performed data visualization. CR designed and carried out the manufacturing of the components shown in Figure 9. RS fabricated the deposit characterized in the study. WSM contributed to the study conceptualization and participated in review and editing. TJF, JBJ, and PGA contributed to the conceptualization of the study, secured funding, managed the project, and participated in review and editing of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eESA\u0026rsquo;s Annual Space Environment Report [Internet]. ESA Space Debris Office; 2024 [cited 2025 Jan 21]. Available from: https://www.esa.int/Space_Safety/Space_Debris/ESA_Space_Environment_Report_2024\u003c/li\u003e\n\u003cli\u003eMo W, Kinsey B, Vickers J, Helvajian H, Cozmuta I, Herron M, et al. 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Available from: https://www.esa.int/ESA_Multimedia/Images/2021/07/Laser_melting_to_construct_infrastructure_on_the_Moon\u003c/li\u003e\n\u003cli\u003ePawelski JW, Toby Joseph Daniel Mould, Jan Walter Schroeder, Gary Douglas Calnan. Space Foundry [Internet]. Denver, CO; US-11634241-B1, 2023 [cited 2024 Dec 17]. Available from: https://ppubs.uspto.gov/dirsearch-public/patents/html/11634241?source=USPAT\u0026amp;requestToken=eyJzdWIiOiI0NzE3ZjNhYy1iNzhlLT\u003cbr\u003eQxYjktOWNkMS0zNjhiZGFmN2Y5YTAiLCJ2ZXIiOiI3NjgxMzQyYS05NmExLTQxNTE\u003cbr\u003etYWI2ZS1iOTU2MTgxMGFjZTUiLCJleHAiOjB9\u003c/li\u003e\n\u003cli\u003eSchroeder JW, Calnan GD, Bogno AA, Mould TJD, Pecher RP, Pawelski JW, et al. Space Debris Recycling by Electromagnetic Melting. In: Badescu V, Zacny K, Bar-Cohen Y, editors. Handbook of Space Resources [Internet]. Cham: Springer International Publishing; 2023 [cited 2024 Dec 17]. p. 309\u0026ndash;34. Available from: https://doi.org/10.1007/978-3-030-97913-3_7\u003c/li\u003e\n\u003cli\u003eAnderson K, Weritz J, Kaufman JG, editors. 6061 and Alclad 6061: General Structural Alloy. In: Properties and Selection of Aluminum Alloys [Internet]. ASM International; 2019 [cited 2024 Feb 16]. p. 388\u0026ndash;93. Available from: http://dl.asminternational.org/handbooks/book/91/chapter/2088303/6061-and-Alclad-6061General-Structural-Alloy\u003c/li\u003e\n\u003cli\u003eTaylor JA. Iron-Containing Intermetallic Phases in Al-Si Based Casting Alloys. Procedia Materials Science. 2012 Jan 1;1:19\u0026ndash;33. \u003c/li\u003e\n\u003cli\u003eSantella ML, Engstrom T, Storjohann D, Pan TY. Effects of friction stir processing on mechanical properties of the cast aluminum alloys A319 and A356. Scripta Materialia. 2005 Jul 1;53(2):201\u0026ndash;6. \u003c/li\u003e\n\u003cli\u003eMa ZY, Sharma SR, Mishra RS. Effect of friction stir processing on the microstructure of cast A356 aluminum. 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A study of tensile properties in Al\u0026ndash;Si\u0026ndash;Cu and Al\u0026ndash;Si\u0026ndash;Mg alloys: Effect of \u0026beta;-iron intermetallics and porosity. Materials Science and Engineering: A. 2008 Aug 25;490(1):36\u0026ndash;51. \u003c/li\u003e\n\u003cli\u003eZhu N, Avery DZ, Rutherford BA, Phillips BJ, Allison PG, Brian Jordon J, et al. The effect of anodization on the mechanical properties of aa6061 produced by additive friction stir-deposition. Metals. 2021 Nov 1;11(11). \u003c/li\u003e\n\u003cli\u003eAvery DZ, Phillips BJ, Mason CJT, Palermo M, Williams MB, Cleek C, et al. Influence of Grain Refinement and Microstructure on Fatigue Behavior for Solid-State Additively Manufactured Al-Zn-Mg-Cu Alloy. Metall Mater Trans A. 2020 Apr 5;51(6):2778\u0026ndash;95. \u003c/li\u003e\n\u003cli\u003eAvery DZ, Rivera OG, Mason CJT, Phillips BJ, Jordon JB, Su J, et al. Fatigue Behavior of Solid-State Additive Manufactured Inconel 625. 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Progress in Materials Science. 2006 Sep 1;51(7):881\u0026ndash;981. \u003c/li\u003e\n\u003cli\u003eWhalen S, Overman N, Taysom BS, Bowden M, Reza-E-Rabby Md, Skszek T, et al. Effect of high iron content on direct recycling of unhomogenized aluminum 6063 scrap by Shear Assisted Processing and Extrusion. Journal of Manufacturing Processes. 2023 Jul 7;97:115\u0026ndash;24. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-advanced-manufacturing","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [npj Advanced Manufacturing](https://www.nature.com/npjadvmanuf/)","snPcode":"44334","submissionUrl":"https://submission.springernature.com/new-submission/44334/3","title":"npj Advanced Manufacturing","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"NPJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6334841/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6334841/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"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.","manuscriptTitle":"Sustainable In-Space Manufacturing by Upcycling Metal Space Debris via a Vertically Integrated Processing Paradigm","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-30 06:31:39","doi":"10.21203/rs.3.rs-6334841/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-05-19T07:49:25+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-18T10:29:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"305986958757594201174207852537782748327","date":"2025-05-15T05:38:28+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-13T08:21:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"77914665167908756109705961029063077478","date":"2025-05-12T19:40:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"255901301336884264412351707549046398349","date":"2025-05-12T17:34:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"108711155556295190700986943116312712246","date":"2025-05-12T16:44:38+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-12T16:27:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-01T15:06:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-01T04:51:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"npj Advanced Manufacturing","date":"2025-03-29T15:00:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"npj-advanced-manufacturing","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [npj Advanced Manufacturing](https://www.nature.com/npjadvmanuf/)","snPcode":"44334","submissionUrl":"https://submission.springernature.com/new-submission/44334/3","title":"npj Advanced Manufacturing","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"NPJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"344885a7-bbfa-4ed1-8b1a-26ac14bcd643","owner":[],"postedDate":"April 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":46529566,"name":"Physical sciences/Materials science/Structural materials"},{"id":46529567,"name":"Scientific community and society/Business and industry/Engineering"},{"id":46529568,"name":"Physical sciences/Engineering"},{"id":46529569,"name":"Physical sciences/Materials science"},{"id":46529570,"name":"Scientific community and society/Business and industry"},{"id":46529571,"name":"Social science/Science technology and society"}],"tags":[],"updatedAt":"2025-06-03T02:23:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-30 06:31:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6334841","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6334841","identity":"rs-6334841","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}