Browsing by Author "Berger, Gordon"
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Item A Two-Stage Regenerable Filter for Collection and Disposal of Carbon Fines(51st International Conference on Environmental Systems, 7/10/2022) Berger, Gordon; Agui, Juan; Black, Cara; Mehan, Jeff; Holtsnider, John; McCurry, BryanNASA is investigating the use of the Plasma Pyrolysis Assembly (PPA), which is a methane post-processing technology with the goal to recover hydrogen from the Carbon dioxide Reduction Assembly (CRA) currently onboard the International Space Station (ISS). The PPA can theoretically recover 75% of hydrogen from methane produced by the CRA. During methane processing the PPA creates roughly 40 mg/hr of carbon dust when operating at 4 crew member levels. The unwanted fines need to be removed from the stream to prevent any clogging of downstream components. The Regenerable Carbon Filter (RCF) was designed by Umpqua Research Company to address the carbon particulate created in the PPA. The RCF includes two stages. The first is an electrostatic precipitator designed to collect ultrafine particles. The second is a low pressure drop physical filter. Both filters are made of heat tolerant materials to allow regeneration of the filtration capacity by O2 oxidation of captured carbon. This paper will discuss the RCF hardware and test plans.Item Cold Trap Carbon Capture Filter for Carbon Fines Management - In-laboratory Performance and Efficiency Results(2023 International Conference on Environmental Systems, 2023-07-16) Agui, Juan; Berger, GordonCarbon dust management is vital to the continuous operation of the Plasma Pyrolysis Assembly (PPA), which supports the Carbon Dioxide Reduction Assembly (CRA) on the ISS. A developmental filter system known as the Cold Trap Carbon Capture Filter is being prototyped and tested to determine its performance under different challenge aerosols. The filter system employs particle separation through high-speed inertial impaction, centrifugal forces and tortuous flow paths combined with media filtration to remove carbon particulates from the PPA effluent flow. Tests were performed focused on the collection efficiency of the filter system subjecting it to ISO (International Organization for Standardization) Fine Test Dust (FTD) and carbon black. The collection efficiency of the filter system depended on the collective efficiencies of its three filter stages. Efficiencies were measured gravimetrically by determining the accumulated dust mass in each filtration and separation stage. The test data indicated that about 76% of the dust is captured in the first two stages of filtration with ISO FTD. However, the carbon dust was only collected to about 41% collection efficiency. Pressure drop rise with particle loading was gradual to moderate for the first two filter stages in the main filter housing. There was almost no rise in pressure drop across the HEPA filter with ISO FTD loading, but a noticeable pressure drop rise with carbon loading. Improvements in internal filter design can help increase dust holding performance of the system. This paper will report on the experimental technique and results of a series of tests to assess the simulated performance of the filter system.Item Development and Validation of a Model to Account for Gaseous HCl and Aluminum Surface Interactions for Spacecraft Fire Safety Applications(49th International Conference on Environmental Systems, 2019-07-07) Niehaus, Justin; Gokoglu, Suleyman; Mazumder, Sandip; Berger, Gordon; Easton, JohnExperiments and modeling were performed to determine the surface kinetics of gaseous hydrogen chloride (HCl) with aluminum surfaces subjected to various treatments. HCl and other acid gases are a spacecraft fire safety concern as they are commonly found in products from electrical wire pyrolysis. Three types of aluminum surfaces were considered: surface with chromate conversion coating (iridite), anodized, and untreated. A test cell made of Teflon was used to measure the difference in HCl from the inlet to the outlet. Inlet and outlet sensors were used to measure HCl concentrations. A simple one-step global surface reaction model was proposed, and an Arrhenius surface kinetics expression that accounts for active surface sites was employed. The kinetic constants were determined (calibrated) using the measured data. The calibrated model was validated against experiments with different flow rates and HCl inlet concentrations. The results showed that anodized aluminum had the most HCl uptake, followed by the iridite and then the untreated aluminum. The amount of HCl uptake seems to correlate well with the thickness of the oxide layer on aluminum. The relevance of these findings are discussed with respect to the design of large-scale fire safety experiments in space and various fire safety application scenarios.Item Development of an Inertial and Cold Trap Filter For Carbon Fines Management(51st International Conference on Environmental Systems, 7/10/2022) Agui, Juan; Green, Robert D.; Berger, GordonThe Plasma Pyrolysis Assembly (PPA) is a methane processing technology that integrates with the Sabatier Reactor Assembly (SRA) to further advance oxygen loop closure for spaceflight. A problematic reaction byproduct of the PPA is very fine carbon dust which accumulates on the walls of the reactor and migrates to downstream Environmental Control and Life Support System (ECLSS) components with the effluent flow. The reactor is regenerated periodically by generating a CO2 plasma within the reactor to clean the internal walls and microwave stub. To address the flow of carbon dust to downstream components, the PPA will require an effective carbon capture management system. While various methods have been attempted through prototype testing, the effective filtering and regenerative performance of these devices remains a challenge. A new approach is being explored which will provide large carbon dust holding capacity by flow inertial impaction and recirculation and low temperature particle quenching techniques. The technique involves a custom-designed housing to produce a strong and large recirculating pattern to remove the dust through inertial forces and confine it to a large collection cup. The collection cup is enshrouded in a cold trap to quench the PPA effluent and precipitate the remaining carbon from the reaction. The flow then passes through a single stage baffle and tube filters before exiting through the outlet at the top of the housing. A prototype of this concept was built and is being tested with simulant dust. This report will highlight the design and operation of the prototype and provide preliminary test results.Item Development of Challenge Aerosols for Testing Filters in Spacecraft Air Revitalization Systems(2023 International Conference on Environmental Systems, 2023-07-16) Green, Robert; Berger, Gordon; Sumlin, Benjamin; Vijayakumar, R.; Agui, JuanThe common means for reducing particle concentrations in air in enclosed spaces, including in space habitats, are source prevention and particle removal by air filters. While air filtration and testing is a well-established discipline and industry, testing and classifying filters according to commonly used standards rely on a test aerosol that is often arbitrary and chosen for the convenience of the test method. In space habitats, the particle size distributions are expected to be quite different than the particle size distributions prescribed in test standards, due to the partial or low gravity environment affecting sedimentation of large particulates like hair or cloth fibers, or the introduction of planetary dust to the pressurized volume. This means that the efficacy of the filter will be quite different in the space habitat than specified according to a prevailing standard. This paper will present some initial work in development of a “composite” challenge aerosol to bound the measured and reported particle sizes reported for the International Space Station (ISS), and for expected particulate matter in a Lunar lander, habitat, or orbiting platform susceptible to the intrusion of Lunar dust. Application of this test aerosol is expected to yield filter efficiencies and loading effects closer to what one can expect on these spacecraft and be useful in determining filter lifetime and replacement cycles.Item Effect of Humidity on Surface Interactions of Gaseous HCl and Aluminum for Spacecraft Fire Safety Applications(2020 International Conference on Environmental Systems, 2020-07-31) Niehaus, Justin; Gokoglu, Suleyman; Mazumder, Sandip; Berger, Gordon; Easton, JohnExperiments were performed to understand the interaction of gaseous hydrogen chloride (HCl) with aluminum surfaces in the presence of water vapor. The results show that increasing levels of relative humidity, tested for 10, 25, and 50 percent in air, increase the capacity of HCl adsorption compared to results previously published with dry air flow. A series of tests were performed on individual aluminum samples after they had been saturated with a fixed concentration of HCl in dry air conditions with the goal of determining how their HCl uptake capacity change after various treatments with water relative to the original saturation run. HCl-saturated aluminum samples subjected to a second dry air flow at the same HCl concentration as the original test had an uptake of 23.5% of the original sample. Saturated aluminum samples subjected to an in-between clean-up relative humidity of 90% air flow had an uptake of 35.6% of the original. Saturated aluminum samples submerged in distilled water for 12 hours had an uptake of 82.2% of the original sample. Saturated aluminum subjected to 50% humid air resulted in similar uptake characteristics in multiple repeated tests. These small-scale tests were run in parallel to a large-scale ground duct test used to mimic the stand-off in the Cygnus spacecraft during a Saffire experiment. Conclusions of this testing will be used in the design of large-scale spacecraft fire safety experiments and to develop a model to account for the interactions of HCl and aluminum surfaces in the presence of water in those tests.Item Evaluation and Performance of a Regenerable Porous Metal Alloy Filter to Remove Carbon Particulates from a Plasma Pyrolysis Reactor Effluent(2020 International Conference on Environmental Systems, 2020-07-31) Agui, Juan; Black, Cara; Jones, Jacob; Berger, GordonNASA is exploring a microwave-based plasma pyrolysis technology to increase oxygen recovery and advance loop closure of life support systems on the International Space Station (ISS) and future manned spacecraft. The Plasma Pyrolysis Assembly (PPA) serves to pyrolyze methane produced from the Carbon Dioxide Reduction Assembly (CRA) into acetylene and hydrogen. A small amount of solid carbon dust is generated that must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. A custom designed filter and housing made from high temperature alloy steel was designed and tested at NASA for its carbon capturing performance from the PPA effluent. The filter consists of seven tubular filter elements made from porous sintered steel, the same steel as in the housing, soldered onto a partition plate on the inside of the cylindrical filter housing. The filtration rated of the tubular filters is 10 µm but the thickness of the tube walls allows for a degree of depth filtration to capture smaller particles. The tolerance to high temperatures, up to 750 ⁰C, permits the high temperature oxidation of the captured carbon during a regeneration phase of operation. The filter has been integrated to the PPA under simulated operating conditions and has undergone several short carbon loading tests of 8 and 20-hour tests, and a long duration test of 100 hour. In this work, we present the experimental results and analysis of performance from these tests.Item Filter efficiency and leak testing of returned ISS bacterial filter elements (BFEs) after 2.5 years of continuous operation(46th International Conference on Environmental Systems, 2016-07-10) Green, Robert; Agui, Juan; Berger, Gordon; Vijayakumar, Rajagopal; Perry, JayThe air quality control equipment aboard the International Space Station (ISS) and future deep space exploration vehicles provide the vital function of maintaining a clean cabin environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of sedimentation. The ISS Environmental Control and Life Support (ECLS) system architecture in the U.S. Segment uses a distributed particulate filtration approach consisting of traditional High-Efficiency Particulate Adsorption (HEPA) filters deployed at multiple locations in each U.S. Segment module; these filters are referred to as Bacterial Filter Elements, or BFEs. As more experience has been gained with ISS operations, the BFE service life, which was initially one year, has been extended to 2-5 years, dependent on the location in the U.S. Segment. In our previous work, we developed a test facility and test protocol for leak testing the ISS BFEs. For this work, we will present results of leak testing of a sample set of returned BFEs with a service life of 2.5 years, along with efficiency and pressure drop measurements. The results can potentially be utilized by the ISS Program to ascertain whether the present replacement interval can be maintained or extended to balance the on-ground filter inventory with extension of the lifetime of ISS beyond 2020. These results can provide meaningful guidance for particulate filter designs under consideration for future deep space exploration missions.Item Filter Efficiency and Pressure Drop Testing of Returned ISS Bacteria Filter Elements (BFEs)(47th International Conference on Environmental Systems, 2017-07-16) Green, Robert; Agui, Juan; Vijayakumar, R.; Berger, Gordon; Perry, JayThe air quality control equipment aboard the International Space Station (ISS) and future deep space exploration vehicles provide the vital function of maintaining a clean cabin environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of sedimentation. The ISS Environmental Control and Life Support (ECLS) system architecture in the U.S. Segment uses a distributed particulate filtration approach consisting of traditional High-Efficiency Particulate Air (HEPA) filters deployed at multiple locations in each U.S. Seg-ment module; these filters are referred to as Bacterial Filter Elements, or BFEs. In our previous work, we presented results of efficiency and pressure drop measurements for a sample set of two returned BFEs with a service life of 2.5 years. In this follow-on work, we present similar efficiency, pressure drop, and leak tests results for a larger sample set of six returned BFEs. The results of this work can aid the ISS Program in managing BFE logistics inventory through the station’s planned lifetime as well as provide insight for managing filter element logistics for future exploration missions. These results also can provide meaningful guidance for particulate filter designs under consideration for future deep space exploration missions.Item Filtration of carbon particulate emissions from a Plasma Pyrolysis Assembly Reactor(46th International Conference on Environmental Systems, 2016-07-10) Agui, Juan; Green, Robert; Vijayakumar, R.; Berger, Gordon; Greenwood, Zach; Abney, Morgan; Peterson, ElspethThe ISS presently recovers oxygen from crew respiration via a Carbon Dioxide Reduction Assembly (CRA) that utilizes the Sabatier chemical process to reduce captured carbon dioxide to methane (CH4) and water. In order to recover more of the hydrogen from the methane and increase oxygen recovery, NASA Marshall Space Flight Center (MSFC) is investigating a technology, plasma pyrolysis, to convert the methane to acetylene. The Plasma Pyrolysis Assembly (or PPA), achieves 90% or greater conversion efficiency, but a small amount of solid carbon particulates are generated as a side product and must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. We discuss developmental work on several options for filtering out the carbon particulate emissions from the PPA exit gas stream. We also present supporting characterization results of the carbon particulates that help to define filter requirements.Item Flight Environment HEPA Filter Testing for Lunar Dust Removal Capability(2023 International Conference on Environmental Systems, 2023-07-16) Walcker, Andrew; Turner, Zach; Agui, Juan; Green, Robert; Berger, GordonLunar dust is an abrasive compound that can cause critical damage to hardware and crew. The mechanical and chemical makeup various from typical earth dust due to weathering effects. Current space missions require extensive air filtration of lunar dust to ensure mission success; as such filtration testing is paramount in verifying the dust-removal capabilities of the system. Previous testing at NASA GRC consisted of two stages: testing a flat high efficiency particulate air (HEPA) media sheet at various pressure ranges (Stage 1) and testing a pleated HEPA filter at different humidity and dust levels (Stage 2). This testing was done to buy-down risk when testing the flight-qualification HEPA filter for the proposed Stage 3 test. Stage 3 testing consisted of using a flight-ready HEPA filter thereby determining the performance characteristics to verify programmatic requirements. This includes measuring lunar dust loading vs. pressure drop performance and determining a maximum capacity based on the allowable pressure drop, determining the HEPA filter efficiency utilizing two separate methodologies, and assessing if the lunar dust caused the HEPA filter to experience any damage. Additionally, dust removal from the HEPA filter was performed using a vacuum to determine if the filter life can be prolonged. These test results will aid the program in verifying programmatic requirements and ensuring risk buydown before this HEPA filter takes flight.Item Modeling the Uptake of Hydrogen Chloride onto Interior Spacecraft Materials(50th International Conference on Environmental Systems, 7/12/2021) Niehaus, Justin; Mazumder, Sandip; Gokoglu, Suleyman; Berger, Gordon; Easton, JohnHydrogen chloride (HCl) is a major combustion product from the pyrolysis of polyvinyl chloride (PVC) insulated electrical wires, a common spacecraft fire safety concern. Models at two different scales were developed to predict HCl uptake on anodized, chromate conversion coated (Iridite), and bare aluminum surfaces, as well as on Nomex fabric: a macroscopic one-step global surface reaction model where all the active sites are on the exterior surface, and a pore model where the interior active sites deeper into the oxide layer can also be accessed by HCl. Experiments were performed to calibrate kinetic and diffusion constants in the models. A cast acrylic test cell was used to measure the differences between the inlet and outlet concentration of HCl after inserting a sample rod of the test material. For the materials with a thin (< 200 �m) or no oxide layer, the macroscopic surface reaction model adequately predicts the experimental measurements. For the anodized aluminum with a thicker oxide layer, the pore model provided a better match to experimental results. The results will be discussed with respect to the spacecraft fire safety project (Saffire).Item Particle Loading Tests on HEPA Flat Sheet Media at Sub-Ambient Pressures Using a Lunar Dust Simulant(50th International Conference on Environmental Systems, 7/12/2021) Agui, Juan; Green, Robert; Berger, Gordon; Johnson, Matthew; Brown, GaryWhen humans return to the moon under NASA�s Artemis program, their activities on the lunar surface will inevitably lead to the intrusion of some level of lunar dust into the lander cabin and subsequently its potential transfer into orbiting segments after docking. The spacecraft�s cabin filtration system will need to be effective at removing the airborne lunar dust to properly purify the breathable cabin air and minimize subsequent dust transfer for the duration of the mission. The fine nature of the lunar dust will require high efficiency filtration, such as HEPA filtration. A series of tests were performed in a specially designed recirculating sealed flow loop, for testing filter media and filter elements at the NASA GRC. The flow loop was used to assess the performance and capacity of flat sheet filter media at representative cabin pressures using JSC-1AF lunar simulant and at high rates of particle loading. The pressure drop across the filter media was measured as a function of accumulated particle mass load at ambient pressure and at two sub-ambient pressures, 70.3 kPa and 56.4 kPa, and at a media velocity that was scaled relative to its pleated configuration. The challenge particle flows were generated by a custom designed particle generator that introduces dispersed particles of the lunar simulant at high concentrations. In addition, an optical particle counting instrument provided filter efficiency measurements within the sealed environment. The pressure drop was found to increase linearly with the amount of dust load on the media in all cases for this test range, but the rate of pressure drop increase was lower in the sub-ambient pressure cases. High filter efficiency was maintained even with high particle loads on the media.Item Particulate Filtration from Emissions of a Plasma Pyrolysis Assembly Reactor Using Regenerable Porous Metal Filters(47th International Conference on Environmental Systems, 2017-07-16) Agui, Juan; Berger, Gordon; Vijayakumar, R.; West, Philip; Mitchell, Karen; Abney, Morgan; Greenwood, ZachMicrowave-based plasma pyrolysis technology is being studied as a means of supporting oxygen recovery in future spacecraft life support systems. The process involves the conversion of methane produced from a Sabatier reactor to acetylene and hydrogen, with a small amount of solid carbon particulates generated as a side product. The particles must be filtered before the acetylene is removed and the hydrogen-rich gas stream is recycled back to the CRA. We discuss developmental work on porous metal media filters for removing the carbon particulate emissions from the PPA exit gas stream and to provide in situ media regeneration capability. Because of the high temperatures involved in oxidizing the deposited carbon during regeneration, there was particular focus in this development on the materials that could be used, the housing design, and heating methods. This paper describes the design and operation of the filter and characterizes their performance from integrated testing at the Environmental Chamber (E-Chamber) at MSFC.Item Performance of a Regenerable Carbon Filter for the Plasma Pyrolysis Assembly(2024 International Conference on Environmnetal Systems, 2024-07-21) Berger, Gordon; Agui, Juan; Mehan, Jeff; Crawford, KagenOxygen recovery will be a key element of advanced Environmental Control and Life Support Systems (ECLSS) on future deep space missions. The Plasma Pyrolysis Assembly (PPA) works in conjunction with a Sabatier Reactor, which is a leading oxygen recovery technology. The function of the PPA is to recover hydrogen from the Sabatier reactor products. The 3rd generation PPA processes the methane, produced by the Sabatier Reactor, at a 4 crew-member flow rate to produce hydrogen, acetylene, other trace gases and solid carbon fines. A Regenerable Carbon Filter (RCF) was developed under a SBIR by Umpqua Research Company to capture the nuisance carbon fines and was put through integrated ground testing with a 3rd generation PPA unit at the NASA Marshall Space Flight Center�s ECLSS Environmental Chamber (E-Chamber). The filter system consists of three separate in-series components: a regenerable electrostatic precipitator, a regenerable fibrous media filter, and a passive HEPA filter. Oxidation is used to regenerate the two regenerable components by flowing a small amount of oxygen through the regenerable components at 750 C. The tests consisted of carbon loading from the PPA and regeneration stages. Two different duration carbon loading cycle were performed corresponded to a typical loading cycle of the PPA, 8 hours, before the PPA reactor requires regeneration, and a 20-hour loading cycle to test for performance under longer carbon build up. The effectiveness of regeneration was checked visually inside the electrostatic precipitator component through borescope inspection. In addition, the level of carbon oxidation during regeneration was monitored by measuring gaseous products with a gas chromatograph. The results of the two loading tests and multiple regeneration tests will be presented in this paper.Item Proposed protocols for defining requirements and sizing of media-based filters for spacecraft and planetary lander applications(51st International Conference on Environmental Systems, 7/10/2022) Green, Robert; Vijayakumar, Rajagopal; Agui, Juan; Berger, Gordon; Johnson, MatthewThe air quality control equipment aboard future deep space exploration vehicles provide the vital function of maintaining a clean cabin environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of sedimentation in low gravity, and can experience short durations of peak dust loading from planetary surfaces for Lunar or Mars landers. The filter industry has established methods to properly size filters for a given particulate load, but requirements for the space or planetary application introduce additional considerations. In this work, a methodology for evaluating and sizing particulate filters for a Lunar surface pressurized environment will be presented, including estimating the loading and particle size distributions of the loading based on mission requirements. In addition, a scaling analysis from single filter media sheet to full-scale filters for this application, based on recent testing, will also be presented. The results of this study may provide meaningful guidance in early design phase for air revitalization systems utilizing media-based particulate filters for deep space exploration missions.Item Spacecraft Smoke Detector Characterization with Reference and Smoke Aerosols(2020 International Conference on Environmental Systems, 2020-07-31) Wang, Xiaoliang; Chow, Judith; Watson, John; Meyer, Marit; Ruff, Gary; Easton, John; Berger, Gordon; Mudgett, PaulPerformance testing of consumer smoke detectors requires specific facilities and experiments with smoldering and flaming emissions from different fuels. Smoke detectors for use in spacecraft are tested using similar setups with representative fuel materials. To simplify smoke detector testing, this study explored the use of laboratory-generated reference aerosols as transfer standards to evaluate smoke detector performance. Among the three tested reference aerosols, mineral oil particles were reproducibly generated with a Gemini smoke detector tester, dioctyl sebacate (DOS) particles were generated with a wide concentration range and flexible size distributions using an atomizer, while polystyrene latex (PSL) particles were difficult to produce with the high concentrations needed for smoke detector testing. Reference aerosols generated from 1.5%–100% DOS solutions and mineral oil covered the response range of six types of smoke aerosols generated by oxidative pyrolysis of spacecraft-relevant materials. Although no single reference aerosol can be used to simulate the response of different smoke detection technologies to different smoke aerosols within ±10% error, the relationship between reference and smoke aerosols derived from this study can be used to predict smoke detector responses to combustion aerosols.Item Updated Scroll Filter System for Deep Space Missions(2024 International Conference on Environmnetal Systems, 2024-07-21) Agui, Juan; Berger, Gordon; Green, RobertNASA is developing a cabin air filtration system, known as the Scroll Bacterial Filter Element (BFE), which provides up to three stages of filtration. The Scroll BFE will be of the same form and fit as the current ISS BFE filters, from which the term BFE is derived. A previous version of this filter consisted of two stages. The current updated filter consists of two main components, the filter frame and a replaceable cassette that inserts into the filter frame. These components provide up to three stages of filtration. The cassette is a new design consisting of a first stage pre-filter using a mesh screen roller assembly to automate the change-out (or scrolling) of the screen media, and a second stage inertial impactor filter. The third and finishing stage is provided by a passive HEPA filter element installed in filter frame. With the same volume and dimensional format of the ISS BFE�s, the Scroll BFE could be deployed as a potential future flight technology demonstration on board the ISS. Ground tests are under way to assess the filter system�s performance in a custom designed filtration test stand. Previous benchtop tests were performed to test the scrolling operation, its performance effectiveness and power draw, by loading the filter with simulated deposited layers of fibrous particulate matter (PM). This paper provides details of the new design and its performance. Preliminary results of an optical technique for detecting the buildup of PM debris over the screen mesh is also included in this paper.