Human life support in permanent lunar base architectures

The future of human space exploration relies on many different requirements that must be fulfilled to expand human presence beyond Low Earth Orbit (LEO). Indeed, a major factor affecting deep space mission architectures resides in the ability to cope with a hostile environment, which is very different from the one found in LEO. With the ultimate goal of taking humans to Mars, several technological limitations need to be overcome in order to sustain human life in such harsh conditions. In the context of an evolutionary path, which would see the incremental employment, testing, and validation of new elements for future Mars expeditions, a lunar mission can be considered as an inevitable and paramount milestone. Even though several astronauts have already set foot on our natural satellite, it was only for short sorties, whose architectures would need to be radically altered for long stays to be envisioned. The present paper investigates enabling factors related to long permanence on the lunar surface, and proposes solutions to support human life. The main aspects to be tackled include crew size, tasks analysis, outpost location, habitable and laboratory modules, and the feasibility of a lunar greenhouse. The crew is sized starting from the analysis of tasks and activities to be performed, as well as accounting for psychological and social aspects. For the assessment of habitat location and configuration, particular attention has been given to geography and illumination of the site. Moreover, the aim is indeed to respond to the need of a self-sustaining lunar outpost, where most of the consumables necessary for life support, such as oxygen, water and food, are produced in-situ: this is why in-situ resource utilization (ISRU) and greenhouse technologies are at the core of our investigation. Additionally, ISRU is also taken into account for radiation shielding purposes: covering the modules with regolith or burying them is in fact the best way to reduce launch masses from the Earth.