Search Results

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.

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.

Understanding the effects of dynamic thermal and vacuum regeneration on VOC desorption kinetics is needed for the development of regenerable trace contaminant control air revitalization systems. The effects of temperature and vacuum quality on the desorption kinetics of ethanol from Carbosieve SIII were examined using 1 hour regeneration cycles. The effect of vacuum quality on ethanol desorption was studied by exposing adsorption tubes loaded with ethanol to low pressures (1.0, 0.5, 0.3, and 0.12 atm) at various thermal regeneration temperatures (160, 100, 70, and 25 °C). At 1 atm of pressure, ethanol removal was found to increase from 2% at 25 °C, to 25% at 70 °C, to 55% at 100 °C, and to 77% at 160 °C. Decreasing the atmospheric pressure from 1 to 0.1 atm for 1 hr did not significantly enhance Carbosieve SIII regeneration at ambient temperatures (25 °C). However, heating the adsorbent at low pressures enhanced its regeneration.

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.

A set of contained environment chambers have been designed to study the effects of Volatile Organic Compounds (VOCs) on plant growth and development. The Volatile Organic Compound Analysis (VOCA) system consists of six Lexan chambers, each with independent VOC monitoring and control capacities. The VOC exposure chambers are located within a larger controlled environment chamber (CEC) which provides a common air temperature, photoperiod, and light control. Relative humidity, CO2 concentration, and VOC concentration of the atmosphere are independently controlled in each VOCA exposure chambers. CO2, air temperature, relative humidity and PPF are continuously monitored with software developed using IOControl™ and IODisplay™.

The candidate crops that have been considered by NASA for providing moderate quantities of supplemental food for crew's consumption during near term or long duration missions include minimally processed “salad” species. Lettuce (cv. Flandria), radish (cv. Cherry Bomb II) and green onion (cv. Kinka) plants were grown under cool-white fluorescent (CWF) lamps with light intensities of 8.6, 17.2, or 25.8 mol m−2 d−1, at air temperatures of 25 and 28 °C, 50% relative humidity, and 1200 µmol mol−1 CO2. Following 35 days growth, final edible mass yields were recorded. All three species grown at 25 °C showed an increase in edible fresh mass and growth rates as light intensity increased. When grown at 28 °C however, the edible fresh mass and crop growth rate of radish, lettuce and onion was significantly reduced at all light intensities when compared to yields at 25 °C. Overall, results indicated that all three crops were sensitive to changes in light intensity and temperature.

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.

A continuous leaching device was designed to extract inorganic nutrients from ALS solid wastes for recycling back to hydroponic plant growth systems. The system consists of a conveyor that carries the waste under a water spray. The leacher was used to extract nutrients from hydroponic rice crop residues. The highly aerated and nutrient-rich recirculation liquid supports microbial growth on all surfaces, which leads to biofouling that causes maintenance difficulties. However, it may be better than the standard leaching protocol, as it produces leachate with significantly reduced BOD. This would make it possible to use the leachate from this reactor in hydroponic plant systems without further processing.

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.

Bioreactor technology for bioprocessing graywater solutions in microgravity is under development by NASA at Johnson Space Center and at major aerospace companies. Inoculum sources have been inconsistent. Startup and subsequent operation of ground-based bioreactors may have been adversely affected by this inconsistency and/or by inoculation procedures. The goal of the research reported in this paper is to develop an inoculum that will completely biodegrade Igepon T42 soap to carbon dioxide and water under anaerobic, denitrifying conditions and with process conditions set by bioreactor design requirements for microgravity operation. Potential inoculum sources from two habitats within the KSC-ALS breadboard project were developed for potential use. The effects of pH (7.2 vs. 9.0, buffered) on soap degradation by the two inocula was determined in a flask study. Nearly all of the soap was degraded at pH 7.2 while nearly none was degraded at pH 9.0. Both inocula behaved similarly.

The National Aeronautics and Space Administration (NASA) intends to continue the human exploration of outer space. Long duration missions will require the development of reliable regenerative life support processes. The intent of this paper is to define the Kennedy Space Center Controlled Ecological Life Support System (CELSS) research plan for the development and testing of three candidate biological processors for a hybrid biological and physical-chemical waste recycling system. The system would be capable of reclaiming from inedible plant biomass, human metabolic waste, and gray water those components needed for plant growth (carbon dioxide, water, and inorganic salts), while eliminating noxious compounds and maximizing system closure. We will colaborate with AMES Research Center (ARC), Johnson Space Center (JSC), and academia, to design a functional biological-based waste processing system that could be integrated with the planned Human Rated Test Facility (HRTF) at JSC.