Design and ground testing of a Zero-Discharge plant growth system for microgravity Applications

Plant-based bioregenerative life-support systems play an essential role for long-duration space missions, offering a renewable source of fresh, nutritious food and psychological benefits for crew members. As human space missions extend further and last longer, developing efficient technologies for space agriculture becomes increasingly critical. In microgravity, altered fluid dynamics change water, nutrient, and gas distribution within the root-zone, potentially limiting plant growth. The Utah Reusable Root Module (URRM) system housed within NASA’s Ohalo III Crop Production System addresses these challenges through five root modules equipped with automated fertigation, redundant moisture sensors, and media containment materials. Designed to support repetitive harvests of pick-and-eat vegetables with minimal crew intervention, the URRM advances water and nutrient management strategies for space-based agriculture. Preliminary ground tests with Mizuna (Brassica rapa var. nipposinica) demonstrated that the URRM maintained optimal root-zone conditions and uniform resource distribution, yielding more than 1 kg of fresh biomass over 17 days. The use of different top cover designs and materials across root modules affected plant establishment and yield, as well as evapotranspiration, whereas water use efficiency (WUE) exceeded 2 g L^-1 across the system. These findings highlight the URRM’s ability to support crop production using automated state-of-the-art technologies, strengthening the feasibility of long-term human space exploration.