Browsing by Author "Callahan, Michael"
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Item A Review of Baseline Assumptions and Ersatz Waste Streams for Partial Gravity Habitats and Orbiting Microgravity Habitats(51st International Conference on Environmental Systems, 7/10/2022) Muirhead, Dean; Moller, Stacey; Adam, Niklas; Callahan, MichaelHighly efficient water management and recovery systems will be required to support human missions beyond the low Earth orbit of the International Space Station (ISS). A review of baseline assumptions for the human activities and associated water cycle in surface, partial gravity habitats and orbiting, microgravity habitats is conducted. The paper reviews and updates ersatz formulations and water flow rates for the main liquid water waste streams of urine, humidity condensate, hygiene, and laundry. A framework is provided to coordinate development of water recovery systems for 30-day crew occupancies under partial gravity with longer term, continuous occupancy in orbiting microgravity habitats and the Mars transit habitat.Item Assessment of Biocide Impacts on Life Support and Extravehicular Activity Architectures(50th International Conference on Environmental Systems, 7/12/2021) Abney, Morgan; McCarley, Kevin; Campbell, Colin; Callahan, Michael; Williams, Spencer; Gazda, Daniel; Montgomery, Eliza; Delzeit, Lance; Feather, MartinIodine has historically been used to minimize microbial growth in wetted portions of life support and Exploration Extravehicular Mobility Unit (xEMU) systems. Because of challenges with dormancy, the life support water processing team has baselined silver as a biocide for future Exploration missions, but continues to consider iodine, bromine, and chlorine as options. An assessment was conducted to identify and evaluate the trade space for implementation of various biocides in Lunar surface, Mars transit, and Martian surface vehicles. The team identified sixteen possible biocide sources for use in Exploration systems. An evaluation of the effects of each biocide on crew health, life support hardware, and xEMU hardware was conducted and resulted in eleven potential biocide architectures. Here we report the results of the architecture trade study and recommendations for future investigations.Item Baseline Assumptions and Ersatz Waste Streams for Partial Gravity Habitats with Mobile Female and Male Crew(2023 International Conference on Environmental Systems, 2023-07-16) Muirhead, Dean; Marshall, Stacey; Romero, Leopoldo; Adam, Niklas; Callahan, MichaelEffective and reliable water management and recovery systems will be required to sup-port human missions beyond the low Earth orbit (LEO) of the International Space Station (ISS). Lunar and Mars surface missions will introduce new challenges to managing water and associated waste streams from mobile crew members who will be living in up to six shelters in extreme environmental conditions under a range of gravity conditions. A review of baseline assumptions for the human activities and associated air and water cycles in and between the transit vehicle, orbiting station, lander-ascent vehicle, surface habitat, pressurized rover, and suits is conducted. The paper reviews ersatz formulations and water flow rates for the main liquid water waste streams of urine, humidity condensate, hygiene, and laundry. Emphasis is placed on the metabolic emissions partitioning between the six habitat elements and the lunar exosphere during a design reference mission scenario.Item Biologically Pre-Treated Habitation Waste Water as a Sustainable Green Urine Pre-Treat Solution(47th International Conference on Environmental Systems, 2017-07-16) Jackson, William; Thompson, Bret; Sevanthi, Ritesh; Morse, Audra; Meyer, Caitlin; Callahan, MichaelThe ability to recover water from urine and flush water is a critical process to allow long term sustainable human habitation in space or bases on the moon or mars. Organic N present as urea or similar compounds can hydrolyze producing free ammonia. This reaction results in an increase in the pH converting ammonium to ammonia which is volatile and not removed by distillation. The increase in pH will also cause precipitation reactions to occur. In order to prevent this urine on ISS is combined with a pretreat solution. While this process has been successful there are a number of draw backs including: storage and use of highly hazardous solutions, limitations on water recovery (<85%), and production of brine with pore dewatering characteristics. We evaluated the use of biologically treated habitation wastewaters (ISS and early planetary base) to replace the current pretreat solution. We evaluated both amended and un-amended bioreactor effluent. For the amended effluent we evaluated “green” pretreat chemicals including citric acid and citric acid amended with benzoic acid. We used a mock urine/air separator modeled after the urine collection assembly on ISS. The urine/air separator was challenged continually for ~6 months. Depending on the test point, the separator was challenged daily with donated urine and flushed with amended or un-amended reactor effluent. We monitored the pH of the urine, flush solution and residual pH in the urine/air separator after each urine event. We also evaluated solids production and biological growth. Our results support the use of both un-amended and amended bioreactor effluent to maintain the operability of the urine /air separator. The ability to use bioreactor effluent could decrease consumable cost, reduce hazards associated with current pre-treat chemicals, allow other membrane based desalination processes to be utilized, and improve brine characteristics.Item Cascade Distillation System – A water recovery system for deep space missions(44th International Conference on Environmental Systems, 2014-07-13) Patel, Vipul; Au, Henry; Shull, Sarah; Sargusingh, Miriam J.; Callahan, MichaelHoneywell Aerospace has developed a distillation technology to process wastewater streams in microgravity environments for recovering potable water. The wastewater processing Cascade Distillation System (CDS) utilizes an innovative and proven multi-stage thermodynamic process to produce purified water. The Cascade Distiller (CD) is the core component of the CDS technology. The CD is a Centrifugal Vacuum Distiller (CVD) that processes wastewater as a feed source and purifies it to near potable water. Some volatile substances escape to the purified water. With minimum post processing, the water can be restored as potable for human consumption. The CD was tested at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) with a greater than 90% recovery rate during a technology comparison test. The results were compared with two other technologies. All three systems were challenged with two pretreated test solutions, each intended to represent a feasible wastewater generated in a deep space environment. An expert panel assembled by NASA down-selected the CDS as one of the technologies for further development. NASA internally developed the Vapor Compression Distiller (VCD) technology, which has reached Technology Readiness Level (TRL) 9. The VCD has paved the way for future development of wastewater recovery technologies by identifying critical requirements. However, the VCD has limited distillation capacity when compared to the CD. Currently, Honeywell Aerospace has an Indefinite Delivery, Indefinite Quantity (IDIQ) contract with NASA for further development of the CD.Item Concepts for a Total Organic Carbon Analyzer for Exploration Missions(49th International Conference on Environmental Systems, 2019-07-07) Morrison, Chad; McPhail, Christopher; Callahan, Michael; Pensinger, StuartMonitoring the Total Organic Carbon (TOC) in spacecraft potable water will be of major importance in long-duration human space exploration. In-flight analysis of potable water produced from a regenerative water processor provides immediate feedback on the quality of reclaimed water along with a system health check on the processing hardware. While the International Space Station (ISS) successfully employs a Total Organic Carbon Analyzer (TOCA) to complete these tasks, this device is not configured in a mass and volume form factor most suitable for long-duration missions, nor is it efficiently integrated into the water processing system. This paper summarizes the survey of potential technologies and their feasibility for application in a spaceflight TOC analyzer. The most promising of these technologies have been selected for further evaluation and development with the primary goal to achieve significant reductions in mass, volume, and resupply requirements over the current state-of-the-art TOCA system. Current development is focused on oxidation processes using excimer ultraviolet (UV), photocatalytic UV, or combustion technologies. Carbon dioxide (CO2) detection techniques under development are liquid-phase membrane-transfer conductivity and Raman spectroscopy as well as gas-phase tunable laser spectroscopy. Further work is planned to develop these individual technologies into full-functioning TOC system breadboards followed by selection and advancement to a technology demonstration of a next-generation TOCA on the ISS.Item Considerations for Development of a Total Organic Carbon Analyzer for Exploration Missions(48th International Conference on Environmental Systems, 2018-07-08) Morrison, Chad; McPhail, Christopher; Schumacher, Shawn; Callahan, Michael; Pensinger, StuartMonitoring the Total Organic Carbon (TOC) in spacecraft potable water will be of major importance in long-duration human space exploration. In-flight analysis of potable water produced from a regenerative water processor provides immediate feedback on the quality of reclaimed water along with a system health check on the processing hardware. While the International Space Station (ISS) successfully employs a Total Organic Carbon Analyzer (TOCA) to complete these tasks, this device is not configured in a mass and volume form factor most suitable for long-duration missions nor is it efficiently integrated into the water processing system. A TOC analyzer that is designed to fit the specified mission requirements would benefit mass, volume, crew time, and resupply needs. This paper discusses the challenges presented by exploration requirements, the status of commercially available technologies, and the research and development progress toward the goal of a next generation, exploration Total Organic Carbon Analyzer.Item Design Status of the Capillary Brine Residual in Containment Water Recovery System(46th International Conference on Environmental Systems, 2016-07-10) Sargusingh, Miriam; Callahan, MichaelOne of the goals of the AES Life Support System (LSS) Project is to achieve 98% water loop closure for long duration human exploration missions beyond low Earth orbit. To meet this objective, the AES LSS Project is developing technologies to recover water from wastewater brine; highly concentrated waste products generated from a primary water recovery system. The state of the art system used aboard the International Space Station (ISS) has the potential to recover up to 85% water from urine wastewater, leaving a significant amounts of water in the waste brine, the recovery of which is critical technology gap that must be filled in order to enable long duration human exploration. Recovering water from the urine wastewater brine is complicated by the concentration of solids as water is removed from the brine, and the concentration of the corrosive, toxic chemicals used to stabilize the urine which fouls and degrades water processing hardware, and poses a hazard to operators and crew. Brine Residual in Containment (BRIC) is focused on solids management through a process of “in-place” drying - the drying of brines within the container used for final disposal. Application of in-place drying has the potential to improve the safety and reliability of the system by reducing the exposure to crew and hardware to the problematic brine residual. Through a collaboration between the NASA Johnson Space Center and Portland Status University, a novel water recovery system was developed that utilizes containment geometry to support passive capillary flow and static phase separation allowing free surface evaporation to take place in a microgravity environment. A notional design for an ISS demonstration system was developed. This paper describes the testing performed to characterize the performance of the system as well as the status of the system level design.Item Development of a Foam Based Capillary Driven Brine Residual in Containment (BRIC) Processor(47th International Conference on Environmental Systems, 2017-07-16) Pensinger, Stuart; Weislogel, Mark; Viestenz, Kyle; Campbell, Melissa; Callahan, MichaelOne of the goals for the AES Life Support System (LSS) project is to achieve 98% water loop closure for long duration human exploration missions beyond low Earth orbit. Critical to this goal is development of a brine water recovery system that can extract the remaining 10 to 25% of the water left behind from primary urine and wastewater processing. For the last several years, NASA Johnson Space Center has been developing and evolving Brine Residual in Containment (BRIC) systems that are specifically designed to handle the corrosive and toxic residual chemicals added to stabilize the urine and protect hardware from fouling during collection and water recovery process. Since last reported at the 2016 International Conference on Environmental Systems (ICES), capillary-based BRIC concepts have continued to be evolved. The capillary-based BRIC (CapiBRIC) designs focus on the use of capillary forces in microgravity to manage fluid movement and phase separation within the BRIC device. This paper addresses the continued collaboration between the NASA Johnson Space Center and IRPI Inc. to evolve the CapiBRIC design from a radial veined capillary structure device (ICES 2016), to a thin film woven cell design and finally to a foam based CapiBRIC brine drying system. Design, testing, and manufacturing challenges as the system evolved will be discussed as part of the design evolution.Item Development of an Electrolytic Silver Biocide Dosing System for Use in a Spacecraft Potable Water Bus(47th International Conference on Environmental Systems, 2017-07-16) Gossel, Cody; Callahan, Michael; Raskovic, DejanMaintaining microbial control in spacecraft potable water storage and delivery systems is a significant challenge for long-duration human space exploration. Simple, robust biocide systems are needed that are capable of continuous dosing while offering low-equivalent system mass. Use of silver as a biocide is of particular interest. Silver has been successfully implemented as a biocide in spacecraft systems and is an effective microbial control agent at concentrations suitable for direct human consumption. In addition, silver lends itself to strategies for on-orbit dosing. This is a critical need for long-duration missions, where silver must be added to purified water recycled back through a closed-loop water recovery system. In addition, on-orbit dosing may be needed to add back silver that may be lost through chemical reactions with materials found/used in spacecraft potable water systems. This paper reports on the development of an in-line electrolytic-based silver biocide dosing system employing closed-loop feedback control. The overall design of the system is small, lightweight, and can be optimized for low power consumption. A prototype of the system has been built and tested, demonstrating control of ionic silver at 300 ± 40 ppb for 7 weeks in a simulated sub-scale metallic water bus system. The test system volume was approximately 10 liters and incorporated about 1.5 sq. meters of wetted surface area. Results and observations from the development and test of the prototype dosing system are provided herein.Item Effects of Surface Treatments on Stainless Steel 316 Exposed to Potable Water Containing Silver Disinfectant(49th International Conference on Environmental Systems, 2019-07-07) Li, Wenyan; Buhrow, Jerry; Diaz, Angie; Irwin, Tesia; Calle, Luz; Callahan, MichaelSilver has been selected as the forward disinfectant candidate for potable water systems in future space exploration. To develop a reliable antibacterial system that requires minimal maintenance, it is necessary to address relevant challenges to preclude issues for future missions. One such challenge is silver depletion in potable water systems. When in contact with various materials, silver ions can be easily reduced to its metallic state or form insoluble compounds. The same chemical properties that make silver a powerful antimicrobial agent also result in its quick inactivation or depletion in various environments. Different metal surface treatments, such as thermal oxidation and electropolishing, have been investigated for their effectiveness in reducing the depletion of silver disinfectant from potable water. However, their effects on the metal surface microstructure and chemical resistance have not often been included in the studies. This paper reports the effect of surface treatments on SS316 exposed to potable water containing silver ion disinfectants. Early experimental results showed that thermal oxidation, when compared to electropolishing, resulted in a thicker oxide layer and a compromised corrosion resistance of the SS316.Item Feasibility of Ultraviolet Technology to Disinfect Spacecraft Water Systems(49th International Conference on Environmental Systems, 2019-07-07) Almengor, Audry; Gilbert, Susan; Todd, Kristina; Adam, Niklas; Callahan, Michael; Ott, C. Mark; Hanford, AnthonyAs the National Aeronautics and Space Administration (NASA) expands its scope and begins to venture into long-duration, manned space flights, the function and maintenance of spacecraft water systems becomes increasingly critical and difficult to achieve. New mission requirements will limit opportunities for resupply and demand extended periods of uncrewed operations. Based on lessons learned from the International Space Station (ISS), one particular challenge of future spacecraft water systems will be maintaining adequate microbial control, especially in water sub-systems and component-level elements where effective long-duration biocontrol strategies do not currently exist. To ensure the reliability and redundancy in these systems, new technologies will be needed in order to ensure mission success. This paper summarizes a feasibility study conducted to look into commercial-off-the-shelf (COTS) Ultraviolet (UV) reactor systems intended to aid in slowing the progress of microbial and biofilm growth via the implementation of a single pass, point of use and/or recirculation UV device. Using this technology may reduce the need for consumable resupply, such as filters or biocides, as well as minimize crew time needed to make the repairs on exhausted and/or compromised systems. The ultimate rationale behind developing a UV disinfection system is to increase the stability of water systems as requirements for sterility and microbial control become more stringent for deep space missions. The resulting data from this study will be used to narrow down possible technology demonstrations for selected ISS locations in order to assess the use of UV technology on future exploration-class spacecraft systems.Item Feasibility of UV LEDs in a Spacecraft Wastewater Application: Exploring Biofilm Control in the WPA Wastewater Tank(50th International Conference on Environmental Systems, 7/12/2021) Adam, Niklas; Gilbert, Susan N.; Kelley, Christopher; Almengor, Audry; Harris, Jacob; Callahan, Michael; Hanford, Anthony; Toon, Katherine; Ott, C. MarkAs the National Aeronautics and Space Administration (NASA) expands its scope and begins to venture into long-duration, manned space flights, the function and maintenance of spacecraft water systems becomes increasingly critical and difficult to achieve. New mission requirements will limit opportunities for resupply and demand extended periods of uncrewed operations. Based on lessons learned from the International Space Station (ISS), one particular challenge of future spacecraft water systems will be maintaining adequate microbial control, especially in water subsystems and component-level elements where effective long-duration biocontrol strategies do not currently exist. To ensure the reliability and redundancy in these systems, new technologies will be needed in order to ensure mission success. After proving feasibility of commercial off-the-shelf (COTS) ultraviolet (UV) light emitting diodes (LEDs) disinfection devices in flow through applications in 2018, our current work has focused on the development of UV LED technology for microbial control in bellows-style spacecraft wastewater tank. Two primary strategies were developed used to determine initial feasibility. The strategies included, (1) flow into, continuous recirculation, and flow out of the tank volume through a standalone UV reactor system, and (2) direct UV irradiation on the wetted tank surfaces using an integrated UV-tank array. This paper summarizes the feasibility of these approaches through benchtop and subscale tank testing and outlines the proposed development pathway of these technologies for biofilm control in a wastewater tank applications.Item Graphene-Based Filtration Media for Spacecraft Potable Water Systems: An Early Investigation(2024 International Conference on Environmnetal Systems, 2024-07-21) Fernandez, Rogelio Garcia; Callahan, Michael; Gurtowski, LukeGraphene-based materials have allowed fundamental advances in fields such as energy storage, electronics development, material science, optics, medicine, and water processing due to its unique two-dimensional structure, mechanical robustness, large surface, and high conductivity. However, little to no effort has been devoted to exploiting and studying these materials to develop new water technologies suited for spacecraft applications. One such application is the potential use of graphene-based materials as filtration media for reclaimed water. Therefore, studying the adsorptive performance of these new materials becomes crucial in identifying the opportunity to replace/upgrade State-of-the-Art filtration media currently used in space vehicles with water-recovery capability; especially if consumable requirements can be lessened as a result of extended filtration capacity. This early life-support-systems investigation pioneers in graphene-research by testing a number of graphene-based materials in comparative adsorption and antimicrobial experiments where contaminant removal efficiency, maximum adsorption capacity, and log reduction are probed. This preliminary investigation informs on the practicability of using graphene-based materials as filtration media and provides a discussion on the scaling-up and optimization of this prospective filtration technology for spacecraft potable water systems.Item Hybrid Life Support System Full Scale Testing: Integrated bioreactor-desalination for an early planetary base(51st International Conference on Environmental Systems, 7/10/2022) Jackson, William; Hooshyari, Ghaem; Gray, Evan; Callahan, Michael; Salehi Pour Bavarsad, MaryamFuture life support architectures for habitats on the moon or Mars will require higher reliability and reduced consumables. These habitats will likely have a wider diversity of wastewaters including showers, other hygiene activities, and showers. These wastewaters similar to humidity condensate are relatively low strength compared to urine and flush water. As such it may be beneficial to separate the urine from other wastewaters and treat using technologies optimized for each waste. This research evaluated a hybrid wastewater processing system that included separate biological pretreatment of urine and the combined hygiene, laundry, and humidity condensate (grey water). Biologically pretreated grey water was processed using reverse osmosis (RO) at 90% recovery and the brine was combined with biologically pretreated urine and flush water and processed using a static distillation system. Details of the greywater pretreatment and RO system are presented in a companion paper. This paper focuses on the performance of urine pretreatment and distillation of the urine+ RO brine. We evaluated the impact of pH, volume processed, and other operational variables on distillate quality and recovery. We also evaluated the ability to store brine/ brine solids in the distiller over multiple processing events and subsequent impacts on recovery and brine quality. Distillation of RO brine and pretreated urine produces a distillate similar to that produced by chemical pretreatment. Using the static distillation vessel at least 15 continuous days (2 crew/d) of produced wastewater (>100 L) could be distilled without solids or brine removal leading to total water recoveries > 99%. Distillate water quality was dependent on the pH of the biological pretreated wastewater and RO brine. Our results support the ability to use biological pretreatment of urine to produce a stable effluent that when distilled produces a high quality distillate and low odor easily handled brine.Item Hybrid Life Support System Full Scale Testing: Integrated Bioreactor-Desalination Long Term Testing(2023 International Conference on Environmental Systems, 2023-07-16) Hooshyari, Ghaem; Bose, Arpita; La-Grenade, Jessica; Kad, Siddhi; Callahan, Michael; Jackson, WilliamAs space habitats are developed in reduced gravity environments, life support systems will be able to evolve to harness the gravity present enabling a wider diversity of treatment systems that can be more robust and reduce consumable mass. Hybrid life support systems that combine biological regenerative processors with physio-chemical systems are one system that could provide such benefits. In this effort, gravity-dependent bioreactors were tested for extended periods for their capacity to treat space-based greywater and urine + flush water (U+F), separately. Effluent from the greywater biological reactor was further processed using a small-scale low-pressure reverse osmosis (RO) unit. Effluent from the urine biological reactor was desalinated using a static distillation system. Our objectives were to demonstrate if 1) the bioreactor could be used as the RO recycle tank, reducing the system mass and volume; and 2), if operating the urine bioreactor to produce NO3- instead of NO2- as the oxidized NH3 product would improve distillate quality. Using the greywater biological reactor as the RO system recycle tank reduced the life of the prefilter and RO membrane but had no effect on water quality. Operating the urine bioreactor to produce NO3- did reduce NOx- carryover to the distillate. Our results support the ability to use biological pretreatment in concert with desalination systems to eliminate the need for storage tanks, brine processing, reduce system mass and complexity, consumable mass, and provide robust systems.Item Initial Trade Study for In-line Silver Sensor for Spacecraft Potable Water Systems(49th International Conference on Environmental Systems, 2019-07-07) Hicks, Phillip; Nelson, Jason; Callahan, MichaelIonic silver is currently baselined as the biocide for microbial control in potable water systems for future space exploration missions. In-line monitoring of silver ion concentration is desired for system feedback control to introduce and maintain sufficient and safe levels of biocide in the water. To date, NASA testing of silver biocide system prototypes has made use of an Ion-Selective Electrode (ISE) for in-line silver concentration measurements. However, known issues with ISE technology have continued to motivate a search for alternate sensor systems. Although devices capable of detecting silver are available for terrestrial applications, these systems are generally not well-suited for the unique demands of spaceflight. Desired attributes include: low weight, volume, and power consumption; stable, autonomous, and in-line measurement capability; long calibration lifetime; and limited maintenance requirements. This paper provides the results from a preliminary trade study conducted on three candidate silver sensor technologies: ISEs, Anodic Stripping Voltammetry (ASV), and Fiber Optic Chemical Sensors (FOCS). The review of these technologies includes the rationale for their selection, an overview of the principles of their operation, and a detailed assessment of their strengths and weaknesses relative to the anticipated requirements of future spacecraft applications. The study concluded that none of the currently-available versions of these technologies is suitable for immediate application to spacecraft systems; further technology development should be considered. To that end, recommendations for forward development work have been proposed and provided herein.Item Investigation into Simulated Microgravity Techniques Used to Study Biofilm Growth(51st International Conference on Environmental Systems, 7/10/2022) Diaz, Angie; Li, Wenyan; Irwin, Tesia; O'Rourke, Aubrie; Calle, Luz; Hummerick, Mary; Khodadad, Christina; Gleeson, Jonathan; Callahan, MichaelBacterial growth in liquid media in microgravity conditions is not well understood. Trends such as a shortened lag phase, longer log phase, slower growth rate, and a higher final population concentration have been noted but the underlying cause remains unclear. At the single cell level, it is predicted that bacteria are less gravity-sensitive than larger species. The effects on their immediate environment, including the lack of cell settlement and slower mass transfer of nutrients due to lack of density driven convection, could help explain the trends. Ground-based spaceflight analogs, or simulated microgravity devices, are often employed to achieve different attributes of weightlessness to study effects on bacterial growth. Though these technologies could isolate gravity�s role in various biological processes, they cannot replicate all its effects and underlying mechanisms. Hence, interpretation of results could be misleading, even if similar to spaceflight. In this study two common simulated microgravity devices were investigated to determine whether they could simulate relevant microgravity conditions for bacterial growth. A bioreactor, the high aspect ratio vessel (HARV), was used with dyes of different density mounted on a random positioning machine (RP machine) or a rotating wall vessel (RWV). The RP machine displayed higher mixing rates than the RWV. The RWV was further tested at different rotations per minute (RPM). The range to minimize effects of density driven convection (low speeds) or centrifugal forces (high speeds) was between a range of 15-20 RPM. These results will help inform the selection of simulated microgravity device as well as interpretation of subsequent biofilm growth results.Item Investigation of Biofilm Formation and Control for Spacecraft - An Early Literature Review(49th International Conference on Environmental Systems, 2019-07-07) Diaz, Angie; Li, Wenyan; Calle, Luz; Callahan, Michael; Irwin, TesiaBacterial biofilms are an important and often problematic aspect of life on earth and in space. Biofilms of opportunistic pathogenic bacteria can lead to severe and costly contamination problems that directly affect human health and long-term mission planning. Microbial contamination on board the International Space Station (ISS) continues to pose mission risks, both to crew health and hardware reliability. In order to optimize the design of future space exploration vehicles, a thorough understanding of biofilm formation and control technologies is needed to control the habitat’s microbial environment. This paper provides a literature review on microbial behavior, biofilm formation in spacecraft or simulated spacecraft environments, and the state of the art of biofilm prevention mechanisms.Item Investigation of Silver Biocide as a Disinfection Tehcnology for Spacecraft – An Early Literature Review(48th International Conference on Environmental Systems, 2018-07-08) Li, Wenyan; Calle, Luz; Hanford, Anthony; Stambaugh, Imelda; Callahan, MichaelAn ideal spacecraft water disinfection system should prevent or control microbial growth, inhibit or prevent biofilm formation, and prevent microbial-induced corrosion. In addition, the selected biocide system should be chemically compatible with materials used in the water storage and distribution system, have minimal maintenance requirement, especially for long-duration missions, and should be safe for crew consumption at levels appropriate for biocidal control. Silver ion is a proven broad spectrum biocide. Terrestrially, there has been an increased interest in the biocidal function of silver, both due to its potential to control bacterial resistant species and due to advances in silver and nano-silver biocide technologies. NASA is considering silver as the future biocide for exploration over the current iodine state-of-the-art (SOA) biocide system. In order to select and design a successful silver biocide delivery system to meet NASA’s requirements, it is essential to understand the advantages and disadvantages of moving to a silver disinfection system. To enhance the knowledge base for the application of silver biocides in spacecraft water systems, this paper provides a first compilation of review data related to: (1) Silver as a biocide technology, (2) Options and concepts for silver biocide delivery, and (3) Silver biocide compatibility studies for spacecraft systems.