Mark M. Weislogel and Rihana Mungin
Effective omni-gravity hydroponics will allow astronauts to supplement nutrition and further close the life cycle of water in orbit, lunar, and Martian conditions. This project determines the operational limits of the test cells for the Plant Water Management Hydroponics mission. A scaled 1-g channel was designed by Rihana Mungin to mimic full-scale performance in microgravity that could be tested terrestrially. This project sought to find the limits of operation of the 1-g test cells and identify failure modes that could pose a safety risk in space. The cells were filled at increments of 20% and cycled from 0.184 to 8.33 mL/s, and the qualitative system stability was characterized.
Several key limits of operation were identified and are detailed in Figure 1 as a function of fill percentage and logarithmic flow rate. At lower fills, the downstream liquid profile approached bubble ingestion on the outlet as flow rates increased. At higher fills and flow rates, embolisms formed on the upstream free surface, indicating a trend toward instability. In some configurations, mass ejections occurred as inertial forces overcame capillary forces. As plants were introduced and the flow disrupted, stable operational limits decreased dramatically.
In the terrestrial demonstrations, new stability regimes were identified. The jetting phenomenon is independent of gravitational effects, and therefore must be taken into consideration as an upper limit to operation in space. These regimes will provide the foundation for experiment crew procedures and safety protocols. The first full-scale flight demonstrations will launch aboard SpaceX-18 in July 2019.
Prevo, Tara M., "Omni-gravity Hydroponics System for Spacecraft" (2019). Undergraduate Research & Mentoring Program. 37.