Modeling and Design of Optimal Growth Media from Plant - Based Gas and Liquid Fluxes 2005-01-2949

Design solutions for robust and optimal supply of water, nutrients, and gases within plant root media in micro-and reduced-gravity are essential for successful integration of plants as an important bioregenerative component of advanced life support systems. Many of the confounding and ‘unknown’ microgravity effects associated with previous plant research on Mir and on the International Space Station (ISS), may be attributed to inadequate media selection, and lack of monitoring and modeling capability. Our objectives are to: (i) develop a modeling approach for optimizing liquid and gas fluxes to plant roots under extreme volume constraints and reduced gravity conditions, (ii) extend this approach to design engineered porous media that satisfy plant root metabolic requirements in reduced gravity. Building upon recent microgravity porous media research, we can characterize and model appropriate scale-dependent processes of liquid and gas fluxes based on gravitational force and target design parameters [1]. The two key new design principles for future engineered plant growth media (EPGM) are: (1) the segregation of supply pathways and storage zones for liquids and gases; and (2) the use of porous media with prescribed and stable pore spaces for reliable management. Possible design examples include use of liquid retention zones, hydrophobic wells for stabilized gas exchange, nutrient storage capsules, limited mechanical impedance materials, reduced evaporation surfaces, water/tension control systems, and recyclable materials. Considerations for reduced gravity include parent materials and novel designs to optimize water use and root zone size. Verification of the optimized design will include ground-based plant growth studies comparing conventional growth media with the novel porous media design.