Dean L. Muirhead | Search NASA

NASA NTRS2020

Chemistry of Ionic Silver and Implications for Design of Potable Water Systems

Ionic silver (Ag+) at approximately 400 µg/L is proposed as an ingestible biocide for potable water systems in future human spacecraft. This paper investigates the underlying chemistry of the silver ion at potable concentrations and its interactions with other solutes and surfaces. This chemistry evaluation will elucidate ionic silver behavior in potable water systems and enable design optimization to minimize ionic silver depletion during long duration crewed and uncrewed segments of missions. Ionic silver can be lost from the water phase to the water-solid interface via adsorption as the cation and oxidation-reduction reactions with passivation defects. The adsorption and oxidation-reduction reactions of heritage piping materials used on spacecraft – stainless steel 316L, titanium, Inconel 718, and Teflon flex hoses – are considered. Conceptual models of adsorption isotherms and pH adsorption edges are applied to understand the role of pH and the surface-to-volume ratio of pipes and tanks on the partitioning of ionic silver between the aqueous and the solid phase during aging. The effect of repeated exposure-aging to an Ag+ containing solution of two passivated alloys (316L and Inconel 718) is evaluated to determine if an equilibrium concentration of ionic silver in the potable range is attainable for a given alloy and surface-to-volume ratio. Aging unpassivated and passivated 316L reduced the ionic silver depletion rate relative to first time exposures, but the same beneficial effect was not observed for Inconel 718.

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NASA NTRSDate not supplied

Clothes Cleaning Research for Space Exploration

As the National Aeronautics and Space Administration (NASA) plans to establish a sustainable presence on the Moon to prepare for missions to Mars, there is an increased need to find effective and sustainable laundry solutions that are compatible with space travel and reduce the need for clothing resupply. Research and development to overcome resource constraints in space can lead to new products and practices on Earth. This paper describes a collaboration between NASA and Procter & Gamble (P&G) to advance their individual goals as well as provide additional benefits to humanity through more sustainable use of resources. In particular, the two organizations have been working together since August 2020 to advance state-of-the-art, environmentally friendly laundry solutions. Both traditional and novel approaches are being considered and held up against strict resource constraints that may exist in space missions or on Earth in the future. The results of this work are expected to contribute to NASA’s strategic goal of extending human presence deeper into space and to the Moon for sustainable long-term exploration and utilization. Likewise, the collaboration will advance one of P&G’s 2030 corporate sustainability goals by promoting water savings among its 5 billion consumers.

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