Greenhouse production analysis of early mission scenarios for Moon and Mars habitats

The establishment of planetary outposts and habitats on the Moon and Mars will help foster further exploration of the solar system. The crews that operate, live, and work in these artificial constructions will rely on bio-regenerative closed-loop systems and principles, such as algae reactors and higher plant chambers, in order to minimize resupply needs and improve system resiliency. Greenhouse modules will play a major role in closing not only the oxygen, carbon-dioxide, and water supply loops, but also by providing fresh food for the crew. In early mission scenarios, when the habitat is still in its build-up phase, only small greenhouse systems will be deployed, providing a supplemental food strategy. Small quantities of high water content crops (e.g. lettuce, cucumber, tomato) will be cultivated, improving the crew’s diet plan with an add-on option to the pre-packed meals. The research results of a 400-day biomass and crew time simulation of an adapted EDEN ISS Future Exploration Greenhouse are presented. This greenhouse is an experimental cultivation system that will be used in an analogue test mission to Antarctica (2018-2019) to test plant cultivation technologies for space. The Future Exploration Greenhouse is a high-level analogue for cultivation systems of early mission scenarios on Moon/ Mars. Applying a net cultivation area of 11.9 m², 11 crops have been simulated. Biomass output values were tailored to a tray cultivation (batch) strategy, where 34 trays (0.4x0.6 m) have been integrated into the overall production plan. Detailed work procedures were established for each crop according to its production lifecycle requirements. Seven basic crew time requiring work procedures (e.g. seeding, pruning and training, harvesting, cleaning, post-harvesting) were simulated. Two cultivation principles were the focus of the analysis: The In-Phase Cultivation approach where all trays start at the same time, and the Shifted Cultivation approach, where trays start in a specific sequential manner. Depending on the approach, different biomass output patterns emerged and were analysed with respect to crew consumption, crop shelf-life, and the risk of food spoilage. Crew time estimates were performed with respect to the overall production process, which resulted into 208.9 min per day for the planned cultivation area. When applying normal terrestrial work-times, this equates to approximately 50% of a crew member day for system operation. Biomass and crew time results were analysed in relation to each other, creating specific productivity factors for each crop type. This way, future mission planning, crop selection, and greenhouse design studies can better tailor the implementation challenges of small greenhouse modules into the habitat infrastructure.