Browsing by Author "Knox, James"
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Item 4-Bed CO2 Scrubber – From Design to Build(2020 International Conference on Environmental Systems, 2020-07-31) Cmarik, Gregory; Knox, James; Peters, WarrenFour-bed technology is an International Space Station (ISS) mainstay for metabolic Carbon Dioxide (CO2) removal and crew life support. The current generation is known as the Carbon Dioxide Removal Assembly (CDRA) and has a long history of unplanned maintenance as well as obsolete core components. The 4-bed CO2 Scrubber was commissioned to operate with no unplanned maintenance for 3 years while removing 4 crew-equivalents of CO2 at a target inlet concentration of 2 torr CO2. This work goes into detail of the various design aspects which have been undertaken to ensure a successful project design and successful build leading to an upcoming flight. This work will discuss the compromises caught both early and late in the design cycle and the adaptations in response. Finally, the expected performance of the system once launched will be discussed based on summaries of data from the testbed.Item 4BCO2 EDU Performance(50th International Conference on Environmental Systems, 7/12/2021) Peters, Warren; Cmarik, Gregory; Knox, JamesNASA is reducing the power, volume and mass requirements on future CO2 (Carbon Dioxide) removal systems for exploration missions. To meet this goal, a 4BCO2 flight experiment based on 4BMS (Four Bed Molecular Sieve) technology is under construction and will fly to ISS (International Space Station) for on-orbit performance and reliability testing. The 4BCO2 flight experiment was based on the 4BMS-X EDU (Engineering Development Unit) design, which has been modified to incorporate elements of the flight system. This paper will present the operational performance of the 4BCO2 EDU.Item 4BMS-X Design and Test Activation(47th International Conference on Environmental Systems, 2017-07-16) Peters, Warren; Knox, JamesIn support of the AES (Advanced Exploration Systems) goals to reduce power, volume and mass requirements on future CO2 (Carbon Dioxide) removal systems for exploration missions, a 4BMS (Four Bed Molecular Sieve) test bed was fabricated and activated at the NASA Marshall Space Flight Center. The 4BMS-X (Four Bed Molecular Sieve-Exploration) test bed used components similar in size, spacing, and function to those on the flight ISS flight CDRA system, but were assembled in an open framework. This open framework allows for quick integration of changes to components, beds and material systems. The test stand is highly instrumented to provide data necessary to anchor predictive modeling efforts occurring in parallel to testing. System architecture and test data collected on the initial configurations will be presented.Item Analysis of Performance Degradation of Silica Gels after Extended use Onboard the ISS(48th International Conference on Environmental Systems, 2018-07-08) Cmarik, Gregory; Knox, James; Huff, TimothyThe disassembly of two flight desiccant beds from the Carbon Dioxide Removal Assembly (CDRA) revealed significant discoloration of the silica gel near the bed inlet as well as a coincidental performance loss. This material was analyzed for the presence of chemical contaminants, physical porosity changes, and adsorption performance. The material characteristics are compared against the location in the bed from which they were sampled in order to develop profiles through the bed. Additional testing of the beds prior to disassembly provided more data points. Possible mechanisms for the loss of capacity are provided though no root cause has been confirmed. Extrapolation of the performance loss is used to estimate the required oversizing of the silica gel layer for long-term operation.Item Calibration and Sensitivity of a Fixed-Bed Adsorption Model for Atmosphere Revitalization in Space(47th International Conference on Environmental Systems, 2017-07-16) Son, Karen N.; Weibel, Justin A.; Garimella, Suresh V.; Knox, JamesSolid sorbents offer a reliable and efficient means of carbon dioxide separation in space applications. Adsorbent-based technologies are currently used for atmosphere revitalization onboard the International Space Station (ISS) and are a promising candidate for deep-space travel. Ongoing research is maturing the existing ISS system to enable human space exploration beyond low-Earth orbit. These efforts hinge on the development of an accurate predictive model of the adsorbent-based system to act as a virtual laboratory for optimizing design and operation parameters for next-generation systems. In particular, the sensitivities of the model outputs to changes in input parameters must be understood and quantified. This paper analyzes the sensitivity of a one-dimensional fixed-bed adsorption model; specifically, we consider the effects of the linear-driving-force (LDF) mass transfer coefficient, axial dispersion, and sorbent thermal properties on the breakthrough time, total bed capacity, and effluent temperature profile. The model is first calibrated with data from a small-diameter, cylindrical breakthrough test using intra-bed centerline concentration measurements to find the LDF coefficients. We then use this LDF coefficient to extract axial dispersion coefficients from mixed, downstream concentration measurements for both the small-diameter bed and a large-diameter bed. These two test stands represent the extremes of purely pellet-driven dispersion in large-diameter beds versus wall channeling dominated dispersion in small-diameter beds. We find that the model is most sensitive to the LDF coefficient, sorbent density, and bed void fraction. This paper contributes to the discussion on the role of predictive adsorption models in designing systems for space travel.Item CDRA-4EU Testing in Support of ISS(46th International Conference on Environmental Systems, 7/10/2016) Peters, Warren; Stanley, Christine; Knox, JamesNASA's Marshall Space Flight Center (MSFC) recently conducted tests on two desiccant beds of the four-bed molecular sieve carbon dioxide removal assembly (CDRA) returned from the International Space Station (ISS). MSFC had previously characterized the relationship between CDRA-4EU inlet conditions and the dewpoint at the desiccant bed exit and between the compressor and accumulator that make up the Carbon Dioxide Management Assembly (CDMA). MSFC installed the flight desiccant beds into the existing Exploration Test Chamber (E-chamber) using a suite of instrumentation not available on orbit to investigate the orbital performance of the desiccant beds. Test objectives, facility design and test results are presented.Item CDRA-4EU Testing to Assess Increased Number of ISS Crew(47th International Conference on Environmental Systems, 2017-07-16) Peters, Warren; Knox, JamesThe ISS (International Space Station) program is investigating methods to increase CO2 (carbon dioxide) removal on ISS in order to support an increased number of astronauts at a future date. The CDRA-4EU (Carbon Dioxide Removal Assembly – Engineering Unit) system at NASA MSFC (Marshall Space Flight Center) was tested at maximum fan settings to evaluate CO2 removal rate and power consumption at those settings.Item Co-Adsorption of Carbon Dioxide on Zeolite 13X in the Presence of Preloaded Water(48th International Conference on Environmental Systems, 2018-07-08) Cmarik, Gregory; Knox, JamesEnvironmental Control and Life Support requires highly effective CO2 removal systems. The current system onboard the International Space Station is known as Carbon Dioxide Removal Assembly. Recent high-fidelity simulation of this system predicted a major efficiency gain via reduction of desiccant zeolite. Commercial beaded 13X zeolite is used in the desiccant bed to scrub water below 1 ppm but is also a highly active CO2 sorbent. The simultaneous adsorption of water vapor and CO2 is known to strongly favor water, but more accurate measurements are needed. This work details the characterization of the zeolite to be used in the next-generation CO2 removal system for co-adsorption of water and CO2.Item CO2 Capacity Sorbent Analysis Using Volumetric Measurement Approach(47th International Conference on Environmental Systems, 2017-07-16) Huang, Roger; Belancik, Grace; Jan, Darrell; Knox, James; Richardson, Tra-My JustineIn support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0°C, 10°C, 25°C, 50°C, and 75°C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.Item CO2 Removal for the International Space Station – 4-Bed Molecular Sieve Material Selection and System Design(49th International Conference on Environmental Systems, 2019-07-07) Cmarik, Gregory; Knox, JamesEfforts over the past three years have focused on the study of candidate sorbent materials for use in a 4BMS molecular sieve system. The accumulation of knowledge has been invaluable for further decisions and for reflecting on the conclusions of past decisions. The goal of the next generation CO2 removal system is continuous, failure-free operation for nearly 20,000 hours, but no complex life support system has yet reached this lofty goal. In addition to reliability, CO2 removal performance improvements have been intensively studied. The achievements toward this end include highly detailed isotherm measurements which drive system simulations as well as testing physical design improvements. Looking back on the successes and failures of past systems, correlating data from long-duration tests, and carefully projecting future results are all needed for the success of the next system. This work intends to reveal the path we have taken and illuminate the steps to come for CO2 removal life support with the 4BCO2 flight demonstration.Item Computer Simulation and Modeling of CO2 Removal Systems for Exploration(45th International Conference on Environmental Systems, 2015-07-12) Coker, Robert F.; Knox, James; Schunk, Greg; Gomez, CarlosThe Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project was initiated in September of 2011 as part of the Advanced Exploration Systems (AES) program. Under the ARREM project and the follow-on Life Support Systems Project (LSSP), testing of sub-scale and full-scale systems has been combined with multiphysics computer simulations for evaluation and optimization of subsystem approaches. In particular, this paper will describe the testing and 1-D modeling of the combined water desiccant and carbon dioxide sorbent subsystems of the carbon dioxide removal assembly (CDRA), as well as initial 3-D modeling and test validation approaches for vacuum desorption. The goal is a full system predictive model of CDRA to guide system optimization and development.Item Development of Carbon Dioxide Removal Systems for Advanced Exploration Systems 2015-2016(46th International Conference on Environmental Systems, 2016-07-10) Knox, James; Coker, Robert; Howard, David; Peters, Warren; Watson, David; Cmarik, Gregory; Miller, LeeA long-term goal for NASA is to enable crewed missions to Mars: first to the vicinity of Mars, and then to the Mars surface. These missions present new challenges for all aspects of spacecraft design in comparison with the International Space Station, as resupply is unavailable in the transit phase, and early return is not possible. Additionally, mass, power, and volume must be minimized for all phases to reduce propulsion needs. Mass reduction is particularly crucial for Mars surface landing and liftoff due to the challenges inherent in these operations for even much smaller payloads. In this paper we describe current and planned developments in the area of carbon dioxide removal to support future crewed Mars missions. Activities are also described that apply to both the resolution of anomalies observed in the ISS CDRA and the design of life support systems for future missions.Item Development of Carbon Dioxide Removal Systems for NASA’s Deep Space Human Exploration Missions 2016-2017(47th International Conference on Environmental Systems, 2017-07-16) Knox, JamesNASA has embarked on an endeavor that will enable humans to explore deep space, with the ultimate goal of sending humans to Mars. This journey will require significant developments in a wide range of technical areas as resupply is unavailable in the Mars transit phase, and early return is not possible. Additionally, mass, power, and volume must be minimized for all phases to reduce propulsion needs. Among the critical areas identified for development are life support systems, which will require increases in reliability and reduced resource requirements. This paper discusses current and planned developments in the area of carbon dioxide removal to support crewed Mars-class missions.Item Development of Carbon Dioxide Removal Systems for NASA’s Deep Space Human Exploration Missions 2017-2018(48th International Conference on Environmental Systems, 2018-07-08) Knox, JamesNASA has embarked on an endeavor that will enable humans to explore deep space, with the ultimate goal of sending humans to Mars. This journey will require significant developments in a wide range of technical areas as resupply is unavailable in the transit phase, and early return is not possible. Additionally, mass, power, and volume must be minimized for all phases to reduce propulsion needs., Among the critical areas identified for development are life support systems, which will require increases in reliability and reduced resource requirements. This paper discusses current and planned developments in the area of carbon dioxide removal to support crewed Mars-class missions.Item Evaluation of Heritage Hardware for Use in Cabin Environments with Reduced Pressure and Increased Oxygen Concentration(51st International Conference on Environmental Systems, 7/10/2022) Abney, Morgan; Bagdigian, Robert; Hopkins, Chase; Pedley, Michael; Macatangay, Ariel; Cagle, Holly; Knox, JamesOn the International Space Station (ISS), the crew perform pre-breathe procedures prior to Extravehicular Activity (EVA) to prevent decompression sickness as their bodies transition from the ISS ambient environment of ~14.7 psia and ~21% oxygen (O2), to the ~4.3 psia and 100% oxygen environment of the suits. To reduce or eliminate the time required for this transition, exploration missions with high-frequency EVA, such as Lunar surface or Martian surface missions, are considering cabin environments of 10.2 psia and 26.5% O2 and 8.3 psia and 34% O2. Although beneficial to EVA operations, these new environments will have consequences on cabin hardware including the environmental control and life support systems (ECLSS), the crew health care system (CHeCS), and crew habitation systems. Given the agency focus on crewed exploration missions within the next decade and incentives to utilize flight-proven cabin hardware, a comprehensive assessment of hardware suitability is needed to begin retrofit and development of exploration cabin hardware. Here we report the results of a study to evaluate the effects of reduced pressure and increased cabin oxygen concentration on the operational performance, the thermal performance, and the material flammability of ISS heritage systems. A discussion of possible mitigations for negative effects and their relative impact on mission planning is provided.Item Experimental Validation of Vacuum Desorption in 1-D Model of CO2 Removal(46th International Conference on Environmental Systems, 2016-07-10) Son, Karen N.; Gomez, Carlos; Paragon, Matthew; Knox, JamesResearchers at NASA’s Marshall Space Flight Center are refining a system-level model of the Carbon Dioxide Removal Assembly (CDRA) which will aid in the design of the next generation four-bed molecular sieve for human exploration beyond low earth orbit. A vacuum characterization test-stand (VCTS) has been built to study sorbent thermal and sorption characteristics in support of this modeling effort. This paper describes the VCTS and presents experimental results of hydraulic and thermal characterization, CO2 breakthrough, and vacuum desorption tests on the VCTS. We then compare experimental results with the one-dimensional model.Item Four Bed Carbon Dioxide Scrubber Engineering Development Unit Cabin Air Inlet Testing(2023 International Conference on Environmental Systems, 2023-07-16) Knox, James; Cmarik, Gregory; Garr, JohnItem Full System Modeling and Validation of the Carbon Dioxide Removal Assembly(44th International Conference on Environmental Systems, 2014-07-13) Coker, Robert; Knox, James; Gauto, Hernando; Gomez, CarlosThe Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project was initiated in September of 2011 as part of the Advanced Exploration Systems (AES) program. Under the ARREM project, testing of sub-scale and full-scale systems has been combined with multiphysics computer simulations for evaluation and optimization of subsystem approaches. In particular, this paper describes the testing and modeling of various subsystems of the carbon dioxide removal assembly (CDRA). The goal is a full system predictive model of CDRA to guide system optimization and development. The development of the CO2 removal and associated air-drying subsystem hardware under the ARREM project is discussed in a companion paper.Item Integrated CO2 Removal and Compression System Performance(46th International Conference on Environmental Systems, 2016-07-10) Richardson, Tra-My Justine; Jan, Darrell; Hogan, John; Huang, Roger; Samson, Jason; Palmer, Gary; Knox, JamesThe CO2 Removal and Compression System (CRCS) is designed to perform both the CO2 removal function of the four-bed molecular sieve (4BMS) system currently employed on the International Space Station (ISS), as well as additional integrated ability to purify and thermally compress CO2 to supply downstream CO2 recovery units. The CRCS approach will reduce cost and improve reliability for future long-duration missions. Previously, data has been presented for testing of a single unit of the 2-Stage Compressor. Data from those tests was used in the assembly a second unit and integration into a two unit system. Operation of the integrated two unit system will be described.Item Investigation of desiccants and CO2 sorbents for advanced exploration systems 2015-2016(46th International Conference on Environmental Systems, 2016-07-10) Knox, James; Cmarik, Gregory; Watson, David; Miller, Lee; West, Philip; Wingard, CharlesDesign of advanced carbon dioxide removal systems begins with the study of sorbents. Specifically, new CO2 sorbents and desiccants need to be studied to enable greater productivity from existing and future spaceflight systems. This presentation will discuss the studies used as input for selecting future CO2 sorbent materials. Also, the adjoining issues of understanding the effects of water co-adsorption and material selection for desiccant beds will be discussed. Current sorbents for CO2 removal are based on 5A zeolites, but a transition to sorbents derived from 13X will be necessary as CO2 levels in cabin air become leaner. Unfortunately, these 13X zeolites are more susceptible to long-term performance loss due to water co-adsorption than 5A due at achievable regeneration temperatures. A study on how impactful the presence of trace water will be to the cyclic operation of small-scale beds will be discussed. Also, methods to recover the performance of beds in a space environment after a major moisture adsorption event will be discussed. The information obtained from the water co-adsorption studies will play a major part in selecting a CO2 sorbent for advanced removal systems. Pellet structural properties play another major role in the selection process. One factor for long-term, hands-off operation of a system is pellet integrity. Maintaining integrity means preventing pellet fracture and the generation of fines due to various thermal and mechanical means which would eventually clog filters or damage downstream systems. Either of these problems require significant shutdowns and maintenance operations and must be avoided. Therefore, study of high-integrity pellets and design of new pellets will be discussed.