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With the installation of the Water Recovery System (WRS) during mission STS-126 in 2008, the International Space Station (ISS) added the capability to recover clean water for reuse from crewmember urine and atmospheric humidity condensate, including EVA (Extravehicular Activity) wastes. The ability to collect, store and process these waste streams is required to increase potable water recovery and support the ISS crew augmentation planned for 2009. During ground testing of the Urine Processing Assembly (UPA), one of two primary component subsystems that comprise the WRS, significant fouling was repeatedly observed in stored urine pretreated with 0.56% of chromium trioxide and sulfuric acid. During initial observation, presumptive microbiological growth clogged and damaged flight-rated hardware under test as part of a risk-mitigation Flight Experiment (FE).

This report describes ground testing of a commercial-off-the-shelf (COTS) water treatment device for contingency recovery of potable liquid from ersatz human urine to support spaceflight testing. The Forward Osmosis Bag (FOB) is a portable, passive water treatment device utilizing osmotic potential to move water across a layered, ultra-filtration membrane to remove pathogens and reject chemical contaminants. The FOB is capable of rejecting ≥90% of the salts, ≥85% of the Total Oxidizable Carbon (TOC), ≥95% of the Total Nitrogen (TN), and ≥93% of Urea-Nitrogen (BUN) in the ersatz urine while completely removing a mixed bacterial population of >108 cells per milliliter.

This report describes proof-of-concept testing of a commercial-off-the-shelf deep ultraviolet LED for future application as a point-of-use or residual disinfection device for spacecraft potable water systems. The electro-optical performance and disinfection efficacy of a 0.5 mW 265nm UV-C LED (UVTOP, Sensor Electronic Technology, Inc., Columbia, SC) was measured in both static and flow environments against five challenge microorganisms inoculated into potable water at an initial concentration ≥ 108 cells per milliliter. The germicidal irradiation from a single UV-C LED array was sufficient to effect > 4-log kill (> 99.99%) of the challenge bacterial population in < 60 minutes contact time.

A sub-scale testbed for characterizing the dynamic performance of regenerable adsorbents for filtering trace contaminants (TCs) from cabin atmospheres was built and tested. Regenerable adsorbents employed in pressure-swing adsorption (PSA) systems operate in a dynamic environment, where they undergo repeated loading / regeneration cycles. Adsorbents have a given chemical specificity for non-methane TCs depending on their composition, and on the humidity and temperature at which they operate. However, their ability to filter TCs is also affected by contact time, cycle time, regeneration vacuum quality and thermal conditioning.

This report describes the design, assembly, and testing of a modified, re-circulating drip flow reactor to quantify the electrical, optical, and thermal performance of solid-state ultraviolet (UV) lighting and semi-conducting photocatalyst for potable water disinfection by advanced oxidation processes. The reactor test assembly incorporates high-output UV-A Light Emitting Diodes (LEDs) with active thermal control to reject heat and generate reactive oxygen species from immobilized titanium dioxide attached to borosilicate glass in the laminar flow stream. Compared with UV-excimer and UV-mercury arc lamps, the UV-A LED system demonstrated excellent thermal stability and good electrical and optical performance.

Carbosieve SIII was used to filter dichloromethane (DCM) from a simulated spacecraft gas stream. This adsorbent was tested as a possible commercial-off-the-shelf (COTS) filtration solution to controlling spacecraft air quality. DCM is a halocarbon commonly used in manufacturing for cleaning and degreasing and is a typical component of equipment offgassing in spacecraft. The performance of the filter was measured in dry and humid atmospheres. A known concentration of DCM was passed through the adsorbent at a known flow rate. The adsorbent removed dichloromethane until it reached the breakthrough volume. Carbosieve SIII exposed to dry atmospheric conditions adsorbed more DCM than when exposed to humid air. Carbosieve SIII is a useful thermally regenerated adsorbent for filtering DCM from spacecraft cabin air. However, in humid environments the gas passes through the filter sooner due to co-adsorption of additional water vapor from the atmosphere.

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 lab-scale testbed for screening and characterizing the chemical specificity of commercial “off-the-shelf” (COTS) polymer adsorbents was built and tested. COTS polymer adsorbents are suitable candidates for future trace contaminant (TC) control technologies. Regenerable adsorbents could reduce overall TC control system mass and volume by minimizing the amounts of consumables to be resupplied and stored. However, the chemical specificity of these COTS adsorbents for non-methane volatile organic compounds (NMVOCs) (e.g., methanol, ethanol, dichloromethane, acetone, etc) commonly found in spacecraft is unknown. Furthermore, the effect of humidity on their filtering capacity is not well characterized. The testbed, composed of a humidifier, an incubator, and a gas generator, delivers NMVOC gas streams to conditioned sorbent tubes.

Volatile organic compounds (VOCs) are important indoor air pollutants, particularly in spaces lacking adequate ventilation and containing off gassing materials. The problem is particularly acute in closed environments, such as spacecraft. The best solution to controlling VOC accumulation in closed environments is eliminating the offending chemicals from the spacecraft design. However, when this is not possible, removal of VOCs from spacecraft air is necessary. Two species of fungi, Paecilomyces lilacinus and Fusarium verticillioides, were tested for the ability to remove tert-butanol from air. The fungi were grown on PCA+C agar and placed into jars with high atmospheric concentrations of t-butanol. The concentration of t-butanol was monitored in the containers for one week. The t-butanol consumption rates were estimated after adjusting for leakage. Leak rates ranged from 0.0003 to 0.0027 h-1.

The chemical specificity of several adsorbents, capable of being recycled by thermal desorption, was determined using volatile organic compounds (VOCs) found in ISS cabin air. These VOC adsorbents will be used to design a reusable filter to control ethylene in plant growth chambers and other STS/ISS biological payloads. A reusable filter to remove plant-produced ethylene from plant growth chambers could help minimize the mass and power use of plant flight hardware. Spaceflight-rated plant growth chambers employ either passive or active catalytic scrubbers for maintaining acceptable levels of VOCs. Passive systems require consumables, while active systems require power and their performance can be degraded in high humidity environments. Each adsorbent was loaded with known amounts of VOCs at a known flow rate. The filtering capacity and chemical specificity of each compound was determined from measurements pre- and post-filter VOC concentration.

The development of a spaceflight-rated Porous Tube Insert Module (PTIM) nutrient delivery tray has facilitated a series of studies evaluating various aspects of water and nutrient delivery to plants as they would be cultivated in space. We report here on our first experiment using the PTIM with a software-driven feedback moisture sensor control strategy for maintaining root zone wetness level set-points. One-day-old wheat seedlings (Tritium aestivum cv Apogee; N=15) were inserted into each of three Substrate Compartments (SCs) pre-packed with 0.25–1 mm Profile™ substrate and maintained at root zone relative water content levels of 70, 80 and 90%. The SCs contained a bottom-situated porous tube around which a capillary mat was wrapped. Three Porous Tubes were planted using similar protocols (but without the substrate) and also maintained at these three moisture level set-points. Half-strength modified Hoagland’s nutrient solution was used to supply water and nutrients.

The PESTO (Photosynthetic Experiment System Testing and Operation) experiment flew in the Biomass Production System (BPS) to International Space Station (ISS) on STS-110 (Atlantis) April 8, 2002, and returned on STS-111 (Endeavour) June 19, 2002, after 73 days in space. The ground control was conducted on a two-week delay at Kennedy Space Center in a BPS unit under environmental conditions comparable to ISS. Wheat (Triticum aestivum cv Apogee) and Brassica rapa cv Astroplant were independently grown in root modules for multiple grow-outs. On-orbit harvests, root modules exchanges and primings, seeds imbibitions, and gas and water samplings occurred at periodic intervals; all were replicated in ground controls. Many operations required crew handling and open access to individual chambers, allowing the exchange of microorganisms between the crew environment and the BPS modules.

Spacecraft cabin air quality is influenced by a variety of factors. Beyond normal equipment offgassing and crew metabolic loads, the vehicle's operational configuration contributes significantly to overall air quality. Leaks from system equipment and payload facilities, operational status of the atmospheric scrubbing systems, and the introduction of new equipment and modules to the vehicle all influence air quality. The dynamics associated with changes in the International Space Station's (ISS ) configuration since the launch of the U.S. Segment's laboratory module, Destiny, is summarized. Key classes of trace chemical contaminants that are important to crew health and equipment performance are emphasized. The temporary effects associated with attaching each multi-purpose logistics module (MPLM) to the ISS and influence of in-flight air quality on the post-flight ground processing of the MPLM are explored.

The PESTO (Photosynthesis Experiment and System Testing and Operation) spaceflight experiment is designed to directly measure gas exchange of developing stands of wheat (Triticum aestivum L.) on the International Space Station (ISS). Gas exchange measurements will characterize photosynthesis and transpiration in microgravity at different stages of development. The Biomass Production System (BPS), a double middeck-sized plant growth will be the plant growth hardware used to support this experiment on-board ISS. This report presents results from a 10-day functional test of PESTO protocols in the BPS. Wheat canopy CO2 assimilation rate for 14-24 day-old plants grown in the BPS chambers was 6-7 μmol m-2 s-1 during this test. Plant responses to CO2 and photosynthetic photon flux (PPF) response curves were obtained at different stages of development by altering CO2 and light conditions.

The objectives of these experiments were two fold: 1) to determine if accepted tissue fixation procedures can be adapted for long-term storage on-board the International Space Station (ISS) and 2) to test whether they are suitable for KSC Fixation Tubes (KFTs). Three tissue fixation parameters were tested: time, temperature and sample size.Fixation time:samples are normally fixed from several minutes to several hours, but because of the duration of the UF-1 mission to ISS, the tissue will be in fixative for up to 3 months. Super dwarf wheat tissue samples were fixed in either FAA (a fixative normally used for storage of plant tissues) or a glutaraldehyde-based fixative and stored for 100 days.

Because of mass and power constraints in spacecraft, plant growth units designed for spaceflight have limited volume and low photosynthetic photon flux (PPF). Sufficient lighting and nutrient delivery are basic challenges to the success of supporting long-term plant growth in space. At the Kennedy Space Center, plant lighting and nutrient delivery hardware currently under NASA-sponsored development are being evaluated to define some of the fundamental issues associated with producing different fresh salad crops. Lettuce crops performed well under all nutrient delivery systems and lighting sources tested. Spinach and radish yields were lower in the presence of zeoponic media (using an ASTROCULTURE™ root tray) relative to plant grown in conventional NFT systems. Within each nutrient delivery system, yields of salad crops under red LEDs + blue light were similar to those crops grown under conventional white light.