Browsing by Author "Hudson, Edgar"
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Item Changes in Chemical Composition of ISS Archive Water Samples from Collection to Analysis(49th International Conference on Environmental Systems, 2019-07-07) Wallace, William; Hudson, Edgar; Dunbar, Brandon; Hamilton, Tanner; Wallace, Sarah; Gazda, DanielAnalysis of archive water samples from the International Space Station provides important insight into the performance of the U.S. Water Processor Assembly (WPA). Ensuring the results from these samples accurately represent the chemical composition of the samples as collected on orbit is essential, as this data is used to make decisions regarding the use of on-orbit replacements for WPA components. Recently, samples of effluent from the Multifiltration (MF) beds were collected to determine if the expected breakthrough products (acetate/bicarbonate) were responsible for increased conductivity measured by in-line sensors. Initial results showed the presence of acetate, but the bicarbonate concentration was lower than expected based on the sensor readings, suggesting the possibility of CO2 diffusing through the sample bags. To assess this possibility, a second set of samples were collected in both the standard archive bags and smaller Teflon bags that were subsequently sealed in Mylar to minimize gas permeation. The MF bed 1 effluent sample collected in the standard bags showed breakthrough of a number of expected species, though many were present at lower than anticipated levels. Analysis of samples sealed in Mylar confirmed that gas diffusion had occurred in the standard bag, as the bicarbonate and conductivity readings were both higher than the standard bags. Interestingly, the acetate concentration was also significantly higher. A repeat analysis of the same sample aliquot performed to verify these findings showed no carboxylate species. A fresh aliquot obtained from the sample bag refrigerated in the Mylar pouch showed acetate results close to the original concentrations, but repeat analysis of this aliquot four days later showed no detectable carboxylates. Here, we will discuss efforts to understand the mechanisms that could lead to the compositional changes seen in the archive samples of MF bed effluent, which appear to be dependent on gas diffusion and temperature.Item Chemical Challenge Tests on ISS Fire Cartridges(2023 International Conference on Environmental Systems, 2023-07-16) Muko, Cristina; Beck, Steven; Wallace, William; Hudson, Edgar; Barrett, Lawrence; Korona, Adam; Williams, Spencer; Gazda, Daniel; Rabel, EmilyFollowing a confirmed combustion event onboard the International Space Station (ISS), crew members will don Emergency Masks, each fitted with 2 ISS fire cartridge filters. As the crew member breathes through the filters, combustion products in the cabin air are either filtered or catalyzed by the fire cartridge media to minimize crew exposure to harmful levels of contaminants. Rigorous certification, acceptance, and surveillance programs for the fire cartridges ensure that each lot meets stringent performance requirements throughout the service life of the cartridges. In accordance with the Quality/Acceptance Test Plan, multiple fire cartridges from each lot undergo chemical challenge tests involving one or more chemicals at specified concentrations. These tests are conducted at specific temperatures, humidity levels, and gas flow rates intended to mimic the worst-case conditions for fire cartridge performance. These challenge tests are conducted by the Environmental Chemistry Laboratory at the NASA Lyndon B. Johnson Space Center. Many of the challenge tests focus on carbon monoxide (CO), but other gases include hydrogen cyanide (HCN), hydrogen chloride (HCl), cyclohexane, acrolein, ammonia (NH3), and acetaldehyde. A fire cartridge is exposed to the test gas in a chamber at the specified conditions, and the outlet is monitored for breakthrough during the 2.5-hour test. This paper will briefly introduce fire cartridges and how they work and will then discuss details of the challenge gas delivery and exposure system, breakthrough monitoring methods, and discussion of issues that have arisen during the course of the test program. Although the focus of this paper will be on the challenge tests, a general summary of the performance of the fire cartridges will also be provided.Item Effects of Ambient Alcohol Levels on the Real-time Monitoring of the Atmosphere of the International Space Station(51st International Conference on Environmental Systems, 7/10/2022) Wallace, William; Limero, Thomas; Clark, Kenneth; Gazda, Daniel; Hudson, EdgarMonitoring of the spacecraft environment is required to ensure the health of the crew and the vehicle systems. For the ISS atmosphere, routine volatile organic compound (VOC) monitoring has been performed for almost a decade by Air Quality Monitors (AQMs). The target compounds measured by the AQMs include three types of chemicals: 1) those compounds that would be harmful to crew, 2) those compounds that have been detected regularly in archival samples, and 3) compounds that, while not necessarily harmful to crew health, could present problems for Environmental Control and Life Support Systems (ECLSS). Following the docking of SpaceX-Demo1 (SpX-DM1), the AQMs began to report high levels of isopropanol (IPA). While elevated IPA is routinely observed with visiting vehicles, the level measured by the AQM, and its continued presence following multiple days of scrubbing, caused concerns regarding the U.S. Water Recovery System. Following the departure of SpX-DM1, the IPA levels decreased to nominal levels, allowing the team to investigate the cause of the elevated measurements. Based on the changes in the shape of the gas chromatograph (GC) traces in the IPA region during docked operations, it appeared that an unknown coeluting species was causing problems with quantification. However, with the docking of Northrup-Grumman-11 (NG-11), the elevated IPA returned, as well as the changes in GC traces. In contrast to the SpX-DM1 results, the AQM IPA results did not return to nominal levels following the departure of NG-11, suggesting that the changes could not be tied directly to the visiting vehicle. In this paper, we will discuss a number of potential causes for both the genuine (measured in archival samples) increases in IPA as well as the much higher levels measured by the AQM. Additionally, we will discuss methods being explored to decrease the potential for a reoccurrence in the future.Item Effects of Material Choice on Biocide Loss in Orion Water Storage Tanks(46th International Conference on Environmental Systems, 2016-07-10) Wallace, William; Castro-Wallace, Sarah; Kuo, C.K. Mike; Loh, Leslie; Hudson, Edgar; Gazda, Daniel; Lewis, JohnWhen preparing for long-duration spaceflight missions, maintaining a safe supply of potable water is of the utmost importance. One major aspect of that is ensuring that microbial growth is minimized. Historically, this challenge has been addressed through the use of biocides. When using biocides, the choice of materials for the storage containers is important, because surface reactions can reduce biocide concentrations below their effective range. In the water storage system baselined for the Orion vehicle, the primary wetted materials are stainless steel (316 L) and a titanium alloy (Ti6Al4V). Previous testing with these materials has shown that the biocide selected for use in the system (ionic silver) will plate out rapidly upon initial wetting of the system. One potential approach for maintaining an adequate biocide concentration is to spike the water supply with high levels of biocide in an attempt to passivate the surface. To evaluate this hypothesis, samples of the wetted materials were tested individually and together to determine the relative loss of biocide under representative surface area-to-volume ratios after 24 hours. Additionally, we have analyzed the efficacy of disinfecting a system containing these materials by measuring reductions in bacterial counts in the same test conditions. Preliminary results indicate that the use of titanium, either individually or in combination with stainless steel, can result in over 95% loss of biocide, while less than 5% is lost when using stainless steel. In bacterial testing, viable organisms were recovered from samples exposed to the titanium coupons after 24 hours. By comparison, no organisms were recovered from the test vessels containing only stainless steel. These results indicate that titanium, while possessing some favorable attributes, may pose additional challenges when used in water storage tanks with ionic silver biocide.Item A Study of the Kinetics of the CO Oxidation Catalyst in a Human Spaceflight Fire Cartridges as a Method to Understand and Predict Performance(2023 International Conference on Environmental Systems, 2023-07-16) Barrett, Lawrence; Korona, Adam; Rabel, Emily; Muko, Cristina; Beck, Steven; Hudson, EdgarFire Cartridges (FC) are an integral part of fire response on ISS, Orion and Gateway. When a pair of FCs are integrated with an Emergency Mask, they can be used to provide safe breathing air on these vehicles in a post-fire environment. The FCs have two primary mechanisms for removing contaminants from the air, an activated carbon (AC) bed which adsorbs the majority of fire byproducts, and a catalyst bed consisting of gold nanoparticles supported on iron oxide which oxidized CO to CO2 under near ambient conditions. While the FC catalyst has proven its ability to convert CO under relevant conditions, this paper attempts to address the apparent inconsistent performance of the catalyst seen in testing. Numerous variables effect the performance of the catalyst, including but not limited to: reaction environment, reactant gas composition, inert gas composition, catalyst age, and catalyst lot. This paper discusses the importance of these variables and attempts a fundamental mechanistic explanation for the effects of each variable. The fundamental mechanisms are then used to establish the magnitude of expected performance variability, which were validated against real test data of flight quality FCs.