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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.

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.

Silver biocide offers a potential advantage over iodine, the current state-of-the-art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. As such, silver may reduce the overall complexity and mass of future spacecraft potable water systems, particularly those used to support long duration missions. A primary technology gap identified for the use of silver biocide is one of material compatibility. Wetted materials of construction are required to be selected such that silver ion concentrations can be maintained at biocidally effective levels.

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.

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.

The first spaceflight opportunities for Advanced Life Support (ALS) Project testing with plants will likely occur with missions on vehicles in Low Earth Orbit, such as the International Space Station (ISS). In these settings, plant production systems would likely be small chambers with limited electrical power. Such systems are adequate for salad-type crops that provide moderate quantities of fresh, flavorful foods to supplement the crew diet. Successful operation of salad crop systems in the space environment requires extensive ground-based testing with horticultural methodologies that meet expected mission constraints. At Kennedy Space Center, cultivars of radish, onion, and lettuce are being compared for performance under these “flight-like” conditions.

Light-emitting diodes (LEDs) represent an innovative artificial lighting source with several appealing features specific for supporting plants, whether on space-based transit vehicles or planetary life support systems. Appropriate combinations of red and blue LEDs have great potential for use as a light source to drive photosynthesis due to the ability to tailor irradiance output near the peak absorption regions of chlorophyll. This paper describes the importance of far-red radiation and blue light associated with narrow-spectrum LED light emission. In instances where plants were grown under lighting sources in which the ratio of blue light (400–500 nm) relative to far-red light (700–800 nm) was low, there was a distinct leaf stretching or broadening response. This photomorphogenic response sanctioned those canopies as a whole to reach earlier critical leaf area indexes (LAI) as opposed to plants grown under lighting regimes with higher blue:far-red ratios.

NASA's Advanced Life Support Breadboard Project at Kennedy Space Center focuses on biological regeneration of essential commodities for long-term space missions. If plants are grown on these missions, roughly 50% of the biomass will be inedible. Composting can reduce the volume of inedible biomass, reduce levels of leachable soluble organics, and produce a mineral-rich leachate that can be used to provide nutrients to subsequent generations of plants. Other wastes will also be generated on space missions; co-composting of these wastes should increase the rate and extent of degradation and should assist in control of moisture content during composting. To investigate these assumptions, we added simulated human solid waste to freshly harvested inedible wheat biomass and composted the mixture for 21 days.

The Breadboard Project at Kennedy Space Center has focused on the development of the bioregenerative life support components, crop plants for water, air, and food production and bioreactors for recycling of waste. The keystone of the Breadboard Project has been the Biomass Production Chamber (BPC), which is supported by 15 environmentally controlled chambers and 2150 m2 (23,200 ft2) of laboratory facilities. The Project objectives, in support of the ALS Program, utilize these facilities for large-scale testing of components and development of required technologies for the human testbeds at JSC, flight experiments, and ALS research to enable a Mars mission.

Regenerative life support systems are under development to reduce the need for resupply of essential commodities during long duration space missions. If higher plants are used to supply food, oxygen, and potable water, composters could be used to stabilize solid wastes, provide CO2 and nutrients to the plants, and achieve pathogen reduction. Small-scale aerobic composting was used successfully to degrade organic compounds in inedible potato biomass. Soluble nutrients were extracted from the compost at concentrations that supported seed germination. Further work is indicated to understand the inhibitory effects of some leachates. Future composter designs should allow improved performance through better instrumentation and process control.

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.

New information is presented on conceptual designs of bioregenerative life support systems, with subsystems defined, sizes estimated, and configurations developed.1 Components are sized by comparison with design data from Spacelab, the space station, commercial practice, and research on new technologies. Designs were developed on a Microstation CAD system, importing existing models such as space station modules where available. Layouts consider component mass and power as well as connections and access requirements. In addition, current efforts in the NASA CELSS Breadboard Facility (CBF) at Kennedy Space Center are described, which may validate some of these design concepts. Design optimization for the next-generation Breadboard Facility is discussed.

The coupling of plant growth and waste recycling systems is an important step toward the development of bioregenerative life support systems. This research examined the effectiveness of two alternative methods for recycling nutrients from the inedible fraction (residue) of candidate crops in a bioregenerative system; 1) extraction in water, or leaching, and 2) combustion at 550 °C, with subsequent reconstitution of the ash in acid. The effectiveness of the different methods was evaluated by 1) comparing the percent recovery of nutrients, and 2) measuring short- and long-term plant growth in hydroponic solutions, based on recycled nutrients.

Manned space missions require the development of compact, efficient, and reliable life support systems. A number of aqueous biological conversion processes are associated with bioregenerative life support systems. Vessels, or bioreactors, capable of supporting these processes in microgravity must be developed. An annular flow bioreactor has been conceived. It has the potential to incorporate containment, phase separation, gas exchange, and illumination into a single vessel. The bioreactor utilizes capillary fluid management techniques and is configured as a cylindrical tube in which a two-phase liquid-gas flow is maintained. Vanes placed around the inner perimeter enhance capillary forces and cause the liquid phase to attach and flow along the interior surface of the tube. No physical barrier is required to complete phase separation.

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.