In the context of a sustainable long-term human presence on the Moon, solutions for habitat radiation and thermal protection with regolith are investigated. Regolith compression is studied to choose the optimal density-thickness combination in terms of radiation shielding and thermal insulation. The applied strategy is to protect the whole habitat from the hazards of galactic cosmic rays and design a dedicated shelter area for protection during solar particle events, which eventually may be a lava tube. Simulations using NASA’s OLTARIS tool show that the effective dose equivalent decreases significantly when a multilayer structure mainly constituted of regolith and other available materials is used instead of pure regolith. The computerised anatomical female model is considered here because future missions will be mixed crews, and, generally, more sex-specific data are required in the field of radiation protection and human spaceflight. This study shows that if reasonably achievable radioprotection conditions are met, mixed crews can stay safely on the lunar surface. Compressed regolith demonstrates a significant efficiency in thermal insulation, requiring little energy management to keep a comfortable temperature inside the habitat. For a more complete picture of the outpost, the radiation protection of lunar rovers and extravehicular mobility units is considered.

This chapter discusses regolith utilization in habitat construction mainly from the point of view of radiation protection of humans on missions of long duration. It also considers other key properties such as structural robustness, thermal insulation, and micrometeoroid protection that all have to be considered in parallel when proposing regolith-based solutions. The biological hazards of radiation exposure on the Moon are presented and put in the context of lunar exploration-type missions and current astronaut career dose limits. These factors guide the research in radiation protection done with lunar regolith simulants, which are used in research and development activities on Earth due to the reduced accessibility of returned lunar samples. The ways in which regolith can be used in construction influence its protective properties. Areal density, which plays a key role in the radiation shielding capacity of a given material, can be optimized through different regolith processing techniques. At the same time, density will also affect other important properties of the construction, e.g. thermal insulation. A comprehensive picture of regolith utilization in habitat walls is drawn for the reader to understand the main aspects that are considered in habitat design and construction while maintaining the main focus on radiation protection.