Plant Water Management in Microgravity

The NASA Plant Water Management (PWM) experiments conducted aboard the ISS are a set of technology development demonstrations that apply recent advances in microgravity capillary fluidics research towards the mundane yet problematic challenges of simply watering plants in space. Plant growth in a low-g environment is often hampered by inadequate aeration and over-saturation of the root zone. The PWM effort aims to exploit the passive capillary forces of poorly wetting liquids (i.e., contaminated water) within unique system geometries that effectively replace the role of gravity in providing sufficient aeration and hydration for simulated plants. Fourteen ISS operations supported by nine crew members were completed on-orbit in 2021, including approximately six days of soil-based and eight days of hydroponic models in single and parallel channel networks. Supportive terrestrial and low-g drop tower tests were conducted to aid in experiment design via small scale- and full-scale demonstrations. To date, the experiments demonstrate proofs-of-concept, limits of operation, system stability, and more. Applications are discussed in relation to plant growth facilities for both near-term microgravity plant science research and long duration human exploration missions.