Farming on the Moon

Abstract

As international interest in lunar exploration gains momentum, the question of how to provide astronauts with a reliable food supply becomes increasingly important. This thesis investigates under which conditions in-situ food production on the Moon can be a thermodynamically favourable alternative to resupply from Earth. Exergy analysis is used to evaluate the food supply chain, including terrestrial production where data allow, transport to the lunar surface, and local food production on the Moon. In doing so, the work addresses a gap between existing studies of space agriculture, which often focus on production-system design or equivalent system mass, and exergy-based studies of terrestrial agriculture and space systems.

Two lunar agriculture systems are considered: a greenhouse for crop cultivation and an algae-based photobioreactor. Their performance is simulated to quantify the mass flows, energy demands, exergy inputs, and life-support interactions associated with the production of edible nutritional energy. In parallel, the exergy costs of launch, lunar transfer, and lunar landing are evaluated for different launch vehicles and mission architectures. The results are combined into scenario-level analyses comparing Earth resupply with food production using currently feasible lunar agriculture systems.

The comparison is performed both on a food-only basis and with habitat coupling, where oxygen production, carbon dioxide uptake, and water exchanges are credited when they reduce life-support resupply requirements. For the currently feasible systems considered, neither the greenhouse crop mixes, any individual greenhouse crop case, nor the photobioreactor reaches an exergy break-even relative to Earth resupply, even when these life-support interactions are included. Although selected single-crop greenhouse cases can reach a long-duration break-even point in uploaded mass for the habitat-coupled comparison, this advantage is offset once the continuing electrical work required to operate the lunar production system is accounted for. This shows that exergy provides a stricter criterion than uploaded mass alone, since life-support mass credits do not necessarily imply a net reduction in thermodynamic resource use.

Process improvements are then evaluated, including the extraction of water from the lunar environment, higher subsystem efficiencies, and improved internal recovery of waste-water streams. When these improvements are combined into an advanced habitat-coupled architecture, finite exergy break-even times are obtained: approximately 4.3 years for the greenhouse equal-area crop mix, 3.5 years for the photobioreactor, and 2.3 years for the best single-crop greenhouse case. The decisive improvement is the reduction of recurring water imports, while subsystem efficiency improvements alone are insufficient to make most cases favourable. The thesis therefore concludes that near-term lunar agriculture is not yet exergetically favourable as a food supply strategy, but can become so for sustained lunar habitation if it is embedded in a broader, resource-recovering lunar base architecture.