Impacts of 'Pick-and-Eat' Plant Growth Systems on the ISS and Gateway

Experience with plant growth in micro-gravity is limited and plants have not yet experienced deep space radiation outside of the Earth’s magnetic field. NASA intends to address these knowledge gaps by performing plant research on present and future habitats. Incorporating plants into the physical chemical life support systems of the International Space Station (ISS) or the future Deep Space Gateway (DSG) poses a new challenge for the systems that must be analyzed beforehand. The simulation tool V HAB is used to study the impact and analyze possible feedback loops between the physical chemical systems and 'Pick-and-Eat' plant systems. The studied plant systems range from the size of two current Veggie experiments to a larger version using a complete International Standard Payload Rack for tomatoes and lettuce. The study for the ISS focuses on the effects of plants on the cabin atmosphere and other life support systems, while for the DSG, the main tradeoff is a comparison between an ‘open-loop’ approach using an Orion CAMRAS and a ‘closed loop’ using ISS components. The results consistently show that the main impacts of small-scale cultivation areas are caused by transpiration. Thus, increasing the water loop closure of the DSG is identified as the most important task. The study then analyzes different viable solutions to close the water loop, like adding a CHX to the cabin of the DSG or to a mostly closed plant growth chamber. The results indicate that the optimal solution depends on the size of the plant growth chamber, and a break even point between the two alternatives is estimated.