Laser-based directed energy deposition with mullite: A necessary step for lunar regolith printing

Additive manufacturing (AM) is pivotal in advancing in-situ resource utilization (ISRU) technologies for space exploration, enabling the construction of lunar infrastructure directly from local materials such as lunar regolith. Among the various AM techniques, laser-based directed energy deposition (DED-LB) offers scalability and binder-free processing, making it highly suitable for fabricating large-scale components on the Moon. However, the limited availability of actual lunar regolith necessitates the use of simulants. Mullite, an aluminosilicate ceramic with a chemical composition closely resembling that of highland lunar regolith, is a promising candidate. In this study, synthetic mullite with a spherical morphology was employed as a model feedstock to investigate the feasibility of fabricating multilayer 3D printed components using the DED-LB process. The high thermal stability and round particle morphology of mullite make it an ideal proof-of-concept material to understand the thermal and mechanical challenges associated with lunar regolith printing. A combination of in-situ thermal monitoring and microstructural characterization was used to define optimal process parameters and assess print quality. The results demonstrate the suitability of mullite for DED-LB and contribute to the development of scalable AM processes for future lunar infrastructure. • Statement on Key Findings: This study investigates the feasibility of Laser-based Directed Energy Deposition (DED-LB) for lunar regolith printing , using mullite as a process analog to explore the challenges and opportunities of DED for in-situ resource utilization (ISRU) . Given the scarcity of actual lunar regolith, mullite serves as a stand-in material to assess processing parameters, defect formation, and deposition quality , providing insights into the scalability of DED-based additive manufacturing for extraterrestrial infrastructure. • Key takeaways: • Process optimization identifies a feasible parameter window ( laser power, scanning speed, and substrate material ) to achieve defect-minimized deposition. • Substrate influence plays a significant role in deposition quality: while stainless steel substrates resulted in delamination and warping due to thermal mismatch, a mullite-based geopolymer substrate enabled better adhesion but introduced porosity and outgassing effects. • Microstructural and in-situ analyses assess surface morphology, porosity, and process stability under different conditions. • Multilayer deposition studies reveal the impact of thermal cycling on void migration, layer adhesion, and printability . • In-situ monitoring captures melt pool dynamics, providing insights into process stability and defect formation mechanisms . • The results contribute to the advancement of DED-based AM for lunar applications , laying the groundwork for scalable and sustainable on-site manufacturing solutions in future space exploration.