Regolith-based lunar habitats: an engineering approach to radiation shielding

Sustainable human exploration of the Moon will largely rely on in-situ resource utilisation, such as using regolith in habitat construction. This paper investigates the relative effectiveness of a polymer-enriched regolith brick versus a multilayer configuration of bare regolith and successive polyethylene layers as a passive shielding solution, when irradiated with Galactic Cosmic Ray (GCR) protons. Radiation–matter interactions are simulated with RayXpert ® software and the dose equivalent in the ICRU sphere behind a representative habitat wall is calculated. The secondary emission of neutrons and protons from the shielding solution is studied as well. This work provides a quantitative insight into how much polymer is required to achieve a significant improvement in terms of radiation protection when compared to a bare regolith wall. At least 30–50% of polyethylene by mass is required to be added to a regolith mix to achieve a significant advantage in radiation protection capability vis-à-vis bare regolith. Multilayer solutions are far better in terms of radiation protection than the polymer-enriched regolith. For example, the thinnest polyethylene layer tested (0.78 cm), reduces the total dose equivalent by about 3.3%. Thicker polyethylene layers added behind a bare regolith brick reduce the total dose equivalent and the dose equivalent due to protons significantly. For instance, a multilayer with 23.4 cm of polyethylene reduces the total dose equivalent by 19%. The equivalent case of polymer–regolith mix (with 30% of polyethylene by mass) reduces the total dose equivalent only by 3%.