Investigating lunar regolith 3D printing with real-time synchrotron X-ray imaging

Additive manufacturing methods such as Laser Powder Bed Fusion (LPBF) are of interest for in situ resource utilization on the Moon. LPBF selectively melts layers of powder using a laser to build 3D objects, and its independence from water or chemical binders makes it a candidate for use in resource-constrained environments, such as the lunar surface.

However, the extreme environmental conditions (e.g., vacuum and reduced gravity) and the intrinsic properties of lunar regolith (e.g., its irregular morphology, broad mineral composition, and low thermal conductivity) present challenges for directly applying LPBF in space. Understanding how lunar regolith behaves during laser melting on Earth is an important step in adapting this technology to lunar applications. 

In this work, operando synchrotron X-ray imaging was used to observe laser melting in a lunar mare regolith simulant (LMS-1). The experiments were conducted at beamline ID19 using a miniaturized, synchrotron-compatible version of an industrial LPBF machine, equipped with X-ray transparent windows for real-time, in situ imaging at micrometre spatial resolution and millisecond temporal resolution (Figure 1) [1].
 

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Fig. 1: Overview of the Quad-ISOPR system and operando imaging configuration. a) Computer-aided design (CAD) model of the Quad Laser – In situ and Operando Process Replicator (Quad-ISOPR), showing: (1) RenAM 500Q scanning head, (2) Additive Manufacturing Process Monitor (AMPM) module, (3) high-speed camera (Photron NOVA S12), (4) Intellilock laser interlock system, (5) laser enclosure compliant with BS EN 60825–1:2014 certification, (6) ISOPR chamber, (7) laser beam, and (8) X-ray beam. b) Rendered cross-sectional view of the laser enclosure during operando synchrotron X-ray imaging, highlighting: (9) Sample holder, (10) ISOPR laser window, and (11) X-ray windows (glassy carbon). c) Representative X-ray imaging result. Adapted from Hocine et al. [1].

The focus was on how LMS-1 powder interacts with different substrates: fused silica and aluminium alloy Al6062. Fused silica, while chemically compatible with LMS-1, showed limited melting, shallow melt pools and poor bonding due to poor thermal conductivity and high laser transparency (Figures 2a-c). Aluminium substrates promoted better bonding with LMS-1 powder at lower energy input but resulted in more spattering and instability (Figures 2d-f).

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Fig. 2: Time-resolved X-ray radiography during LPBF of LMS-1 simulant powder on different substrates. Radiographs were acquired using a 450 W laser and a scan speed of 250mm/s. a-b) Images before and after the first laser scan on a fused silica substrate, showing minimal spattering and no significant melt pool formation. c) By the third laser scan, mild conduction heating and shallow melting are observed. d-e) Corresponding radiographs for an Al6062 substrate, showing (d) the initial state, (e) severe spattering, deep keyhole penetration, large melt pool, and porosity after the first scan, and (f) further degradation and increased porosity after the third scan. g) Time series radiographs depicting powder spatter caused by vapour recoil pressure. h) Melt pool dynamics showing pore movement indicative of reversed Marangoni flow.

Real-time imaging at ID19 revealed key aspects of melt pool behaviour, such as vapour-driven spatter, melt ejection, reversed Marangoni flow and the formation of pores. These defects, common in LPBF, are particularly important to control lunar applications. The data help to identify conditions that affect melt stability and component quality (Figures 2g-h). At high laser powers and scan speeds, the LMS-1 regolith simulant powder vapourized, creating strong recoil pressure and leading to an unstable keyhole that eventually collapsed, forming large pores. Observing imperfections such as spatter [2] can support the development of mitigation strategies to improve component quality.

The study further explored how different processing parameters influence melt pool dynamics and dimensional consistency. These data are key to refining machine-learning models for lunar LPBF [3], which will help predict and control manufacturing outcomes under lunar-like conditions. 

In conclusion, while further work is needed, this study provides useful insights into the behaviour of regolith simulants under laser melting and the role of advanced imaging techniques in supporting the development of lunar manufacturing technologies. 
 

Principal publication and authors
Laser additive manufacturing of lunar regolith simulant: New insights from in situ synchrotron X-ray imaging, C. Iantaffi (a,b,c), C.L.A. Leung (a,b), G. Maddison (d), E. Bele (a), S. Hocine (a,b), R. Snell (d), A. Rack (e), M. Meisnar (c), T. Rohr (f), I. Todd (d), P.D. Lee (a,b), Addit. Manuf. 104711 (2025); https://doi.org/10.1016/j.addma.2025.104711
(a) Mechanical Engineering, University College London, London (UK)
(b) Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire (UK)
(c) European Space Agency, ECSAT, Harwell-Oxford Campus, Didcot (UK)
(d) School of Chemical, Materials and Biological Engineering, The University of Sheffield, Sheffield (UK)
(e) ESRF
(f) European Space Agency, ESTEC, Noordwijk (The Netherlands)

This research was supported by the European Space Agency (ESA) through contract 4000132547 as part of ESA's Discovery Program. 

References
[1] S. Hocine et al., Mater. Des. 252, 113767 (2025).
[2] D. Guo et al., Int. J. Extrem. Manuf. 6, 5, 055601 (2024).
[3] W. Li et al., Virtual Phys. Prototyp. 19, 1, e2325572 (2024).