System dynamics and performance factors of a lunar greenhouse prototype bioregenerative life support system

Future habitation of space, including lunar outposts will require special systems capable of performing important tasks such as revitalizing atmosphere (generate oxygen and fix carbon dioxide), purifying water (e.g., via plant transpiration), and growing human food. Bioregenerative Life Support Systems (BLSS) represent a solution to the problem of sustaining human existence in space. The lunar greenhouse (LGH) prototype project funded by NASA Steckler Phase I Space Grant supported collaboration from a multidisciplinary and multinational team to evaluate the scientific and technical merit and feasibility of a lunar greenhouse prototype for BLSS. The LGH system was constructed to be lightweight, collapsible for transport, autonomous for deployment, modular for expansion, with a hydroponic multi-cropping system that could produce NASA candidate crops such as lettuce, strawberry, sweet potato, and tomato. The system was instrumented to continuously monitor all primary resource inputs (feed water, nutrient solution, CO₂, labor, and energy) as well as desired outputs (biomass, condensed water, oxygen generated). This paper reports results of a nine-month research with four repeated closure experiments on production outputs and resource inputs of the LGH system. The Phase I project concluded that the LGH system was capable of producing 2.26±0.33 kg day^-1 biomass, 21.4±1.85 kg day ^-1 of condensed water, and consuming 0.07±0.11 kg day ^-1 fertilizer, 25.7±3.31 kg day^-1 input water, 100.3 kWh day^-1 (361.1 MJ day^-1) as well as 35.9 min day^-1 labor use.