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This work describes the microbiological assessment and materials compatibility of a silver-based biocide as an alternative to iodine for the Crew Exploration Vehicle (CEV) and future spacecraft potable water systems. In addition to physical and operational anti-microbial counter-measures, the prevention of microbial growth, biofilm formation, and microbiologically induced corrosion in water distribution and storage systems requires maintenance of a biologically-effective, residual biocide concentration in solution and on the wetted surfaces of the system. Because of the potential for biocide depletion in water distribution systems and the development of acquired biocide resistance within microbial populations, even sterile water with residual biocide may, over time, support the growth and/or proliferation of bacteria that pose a risk to crew health and environmental systems.

Our long term objective is to utilize the photocatalytic property of titanium dioxide (TiO2) to convert volatile organic compounds (VOC) in contaminated air to carbon dioxide as a measure of total organic carbon (TOC) for risk assessment in space crafts. Photocatalytically active TiO2 surfaces prepared using Degussa P25 and sol-gel methods were evaluated for this purpose. Photocatalytic oxidation (PCO) of representative air contaminants (e.g. ethanol, toluene, dichloromethane, and acetaldehyde) by Degussa P25 immobilized on aluminum substrate revealed several shortcomings that are not suitable for our intended application. A series of experiments were conducted to optimize parameters during TiO2 sol preparation and thin film deposition.

This project sought to develop a photocatalytic oxidation (PCO) based total organic carbon (TOC) analyzer for real time monitoring of air quality in spacecraft. Specific requirements for this application were to convert volatile organic contaminants (VOC) into CO2 stoichiometrically in a single pass through a small reactor with low power requirement. One of the greatest challenges of this TiO2-mediated PCO was the incomplete oxidation of some recalcitrant VOCs leading to less reactive intermediates that deactivate the catalyst over time. Dichloromethane (DCM) is one of these VOCs. The effect of some design factors (e.g. TiO2 catalyst surface area to volume ratio and UV photon flux field) as well as operating conditions of an annular reactor (e.g. VOC residence time and relative humidity) on the efficiency in converting DCM to CO2 were investigated.

The Porous Ceramic Tube - Nutrient Delivery System (PCT-NDS) offers means to control water availability to plants under non-standard gravities. It is hypothesized that control can be obtained by applying suction pressure within the ceramic tubes. The research objectives include verifying the presented control equation for the PCT-NDS under micro-(less than 1 g) and hyper- (greater than 1 g) gravities. Experiments were conducted on a KC-135 subjecting the system to near-zero to 2 g's and to sustained hyper-gravities upto 10 g's using a centrifuge. Results indicated that the water availability can be controlled through applied suction pressure.

A research project has begun to identify the best cultivar for strawberry production as part of an advanced life support system for space. For the cultivar trials, hydroponic systems will be used, so the plants can be grown optimally under controlled environmental conditions and without water stress. The objectives of this project were to determine changes in nutrient solution characteristics, specifically dissolved oxygen (DO), electrical conductivity (EC), hydrogen ion concentration (pH), and temperature, versus four different flow rates (0.5, 1.0, 2.0, and 3.6 L·min−1) at fixed distances in the hydroponic channel with and without media. Three media treatments were used: 1) no media, 2) arcillite, and 3) perlite. The results showed that the highest flow rate (i.e., 3.6 L min−1) exhibited the most uniform conditions of all nutrient solution characteristics and for each of the media treatments over the 7.92 m length of channel.

An atmospherically sealed chamber has been constructed for the purpose of studying gas, liquid, and microbial contaminants produced by growing food crops. This chamber is designed to provide suitable biomass for evaluation of quality, yield, volume, and energy for different environments and nutrient delivery systems.