Laser Melting of Extraplanetary Rock under Lunar Conditions (LEGUM) - System Progress and First Tests

In the LEGUM project, the additive manufacturing of lunar regolith using laser powder bed fusion under vacuum and lunar gravity is being investigated. In cooperation with the Laser Zentrum Hannover e.V. and the Leibniz University Hannover, a test stand is being developed that consists at its core of a vacuum chamber with a powder bed and a laser that is directed at the powder bed via a scanner.

To generate lunar gravity, the experimental setup is integrated into the Einstein-Elevator (EE) at Leibniz University Hannover, Germany. The Einstein-Elevator is a new type of drop tower that can generate defined gravitational accelerations and thus any gravitational conditions by means of a rail-guided actively driven gondola system [1,2]. To make optimal use of the EE's high repetition rate of up to 300 experiments (flights) per day, the vacuum chamber holds up to 20 powder beds, which are placed on a sample carousel. This eliminates the need to open the vacuum chamber to change the powder bed and the associated reevacuation after each experiment.

During the test time of approx. 4 seconds, two-dimensional specimens are produced fully automatically from various regolith simulants. Three-dimensional specimens can also be produced by manually applying further layers of regolith simulant. The process is monitored with high-speed and thermal imaging cameras. The recording of thermal test data will contribute to a better understanding of the manufacturing process and the resulting material properties. The samples produced under reduced gravity are examined for their mechanical properties and metallographically for their microstructure. The influence of reduced gravity on the material properties is thus determined by comparison with samples produced under Earth’s gravity.

In addition to the experimental studies, the process of laser melting regolith under lunar gravity and vacuum is simulated to improve the understanding of the process. The progress of the system design, the first tests and the gained knowledge will be discussed in this presentation.

Acknowledgments:

The LEGUM project is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – under project number 458595944.

References:

[1] Raudonis M. et al. (2023) Quantum Sci. And Techn. 8, 2, 044001. [2] Reitz B. et. al. (2021) Microgravity Sci. Technol. 33, 25. [3] Raupert M. et al. (2023) LUH Repo., DOI: /10.15488/15680