Influence of ambient pressure on laser beam melting of lunar regolith simulant
Tjorben Griemsmann, Joel Patzwald, Chetan Chawda, T. Eismann, Arvid Abel, Nicole Emminghaus, Jörg Hermsdorf, Enrico Stoll, Ludger Overmeyer
Abstract
The construction of a lunar base requires a huge amount of material, which cannot be entirely transported from Earth. Therefore, technologies are needed to build with locally available resources, such as the lunar regolith. One approach is to directly melt the lunar regolith on the surface and under the vacuum condition of the Moon, using laser radiation. In this article, a lunar regolith simulant is laser beam melted to two-dimensional single-layer-structures using different ambient pressures from 0.05 mbar to 2000 mbar, laser process parameters from 60 W to 100 W laser power, and 1 mm s −1 to 3 mm s −1 feed rates. Additionally, the influence of the ambient gas was investigated using argon as an air alternative. The results show that the ambient pressure on the Moon is not negligible when studying the melting processes of lunar regolith on Earth. With decreasing ambient pressure, the appearance of the melted regolith simulant varies from a shiny to a matt surface. At the highest laser energy density, the thickness of a single-layer increases from 2.6 ± 0.4 mm to 5.3 ± 0.3 mm and the porosity of the melted regolith increases from 17.2 % to 52.2 % with decreasing ambient pressure. Additionally, mechanical properties are determined using 3-point bending tests. The maximum bending strength decreases by 60 % with the increased ambient pressure from 10 mbar to 2000 mbar. Consequently, the development of in-situ resource utilization technologies, which process the lunar regolith directly on the lunar surface, must consider the ambient pressure on the Moon. Otherwise, the processes will not work as expected from the experiments in Earth-based laboratories. • Porosity of melted simulant increases by 67 % when reducing pressure. • The thickness of a melted regolith layer increases by 51 % when reducing pressure. • Maximum bending force of the sample is 75 % higher at low-pressure conditions. • The maximum bending stress increases by 60 % at high-pressure conditions. • Argon leads to higher porosity in the sample than air at high-pressure conditions.