Researchers at Baylor University and CisLunar Industries have developed a vertically integrated method to transform cast aluminum space debris into fully dense, structurally sound components using solid-state additive manufacturing. Their combined system—electromagnetic continuous casting followed by twin-rod additive friction stir deposition (TR-AFSD)—refines grain structure, consolidates defects, and produces pre-machined parts suitable for orbital or lunar applications. Results were published in Nature Communications.
CisLunar Industries, a company focused on in-space metallurgical infrastructure, provided the feedstock using its Modular Space Foundry. This system uses electromagnetic positioning and induction heating to gather and melt scrap metal without physical contact, enabling casting in low-gravity environments. Originally tested under parabolic flight conditions, the Foundry produced AA6061 aluminum rods, 12.7 mm in diameter, used as input for TR-AFSD.
The TR-AFSD setup feeds two offset round rods through a rotating toolhead, generating frictional heat that softens the material and extrudes it in a layer-by-layer fashion without melting. Unlike conventional center-fed methods, this configuration supports higher deposition rates while maintaining part geometry. In the study, researchers printed a bilayer structure composed of two 27 mm wide, 50 mm long, 1 mm-thick layers on an AA6061-T6 substrate, forming a machinable intermediate part.
Computed tomography revealed a porosity reduction from 0.63% in the cast feedstock to 0.016% in the usable machined volume. The cast material contained voids as large as 16.5 mm³, while the TR-AFSD deposit featured only 12 small voids (<0.07 mm³), all confined to edge zones removed during final machining. Flash formation, attributed to excess material flow at high feed rates, was also confined to perimeters and can be recycled.
X-ray fluorescence analysis of the cast material showed significant segregation of alloying elements in cracked regions, with Fe, Si, and Cu levels 2.70%, 1.26%, and 0.34% higher than in adjacent areas. These variations promote the formation of β-Al₅FeSi intermetallics, confirmed through energy-dispersive spectroscopy. Optical and SEM imaging showed that oxygen-rich oxide particles and needle-like Fe-Si intermetallics were widely dispersed throughout the cast structure.
TR-AFSD disrupted these inclusions. Microscopy showed an average particle size reduction from 34.7 μm² in the cast state to 3.1 μm² post-deposition—a 91% decrease. This is attributed to shear-induced fragmentation and dispersion caused by the rotating toolhead. Electron backscatter diffraction revealed additional transformation: grain size decreased from 112.9 μm to 3.7 μm, with increased low-angle grain boundary density. These features indicate dynamic recrystallization and suggest higher yield strength via the Hall–Petch effect.
Recycling aluminum alloys like AA6061 is critical for space-based in-situ resource utilization (ISRU), especially when dealing with orbital debris. The European Space Agency reports more than 35,000 objects larger than 10 cm in orbit—hazards that can be converted into structural components. By eliminating the need for molten processing or additional alloying, TR-AFSD offers a path toward closed-loop recycling with minimal energy input.
This work extends earlier efforts in fabricating aluminum–lunar regolith metal matrix composites using AFSD. Prior studies demonstrated that regolith loading increased hardness, but particle dispersion was inconsistent. The current study resolves this by consolidating scrap through electromagnetic casting before deposition, resulting in uniform structures with minimal porosity. Compatibility with round feedstock also reduces post-casting processing requirements.
Examples of functional parts fabricated include a 10 mm wrench, ISO-standard scalpel handle, and a surgical probe. All were machined from TR-AFSD-printed AA6061 blended with 10 wt% lunar regolith simulant. These results confirm the system’s suitability for manufacturing essential tools and hardware during extended space missions.
One limitation was the need to machine cast rods prior to deposition. Researchers aim to streamline this by directly integrating casting and deposition into a continuous system. Additional work will involve tensile and fatigue testing to characterize mechanical performance beyond microstructure.
To understand the system’s behavior in space, future studies will investigate how vacuum, radiation, and microgravity affect thermal gradients and defect evolution during deposition. Computational tools like smooth particle hydrodynamics will be used to simulate process–structure–property–performance (PSPP) relationships under non-terrestrial conditions. Techniques such as Shear Assisted Processing and Extrusion (ShAPE) may also be evaluated as alternative feedstock routes that bypass casting entirely.
By combining solid-state grain refinement, oxide fragmentation, and porosity elimination, TR-AFSD enables point-of-need fabrication from non-pristine aluminum scrap. This lowers energy costs, reduces material waste, and aligns with long-term goals for circular manufacturing in austere environments. Applications range from orbital infrastructure repair to planetary surface fabrication of pressure vessels, tools, and equipment.
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Featured Photo shows Potential applications of the proposed ISM paradigm utilizing in-situ space resources. Photo via Nature Communications.
