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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Mixing and dilution controls on marine CO 2 removal using alkalinity enhancement

Marine CO 2 removal (CDR) using enhanced-alkalinity seawater discharge was simulated in the estuarine waters of the Salish Sea, Washington, US. The high-alkalinity seawater would be generated using bipolar membrane electrodialysis technology to remove acid and the alkaline stream returned to the sea. Response of the receiving waters was evaluated using a shoreline resolving hydrodynamic model with biogeochemistry, and carbonate chemistry. Two sites, and two deployment scales, each with enhanced TA of 2997 mmol m -3 and a pH of 9 were simulated. The effects on air-sea CO 2 flux and pH in the near-field as well as over the larger estuary wide domain were assessed. The large-scale deployment (addition of 164 Mmoles TA yr -1 ) in a small embayment (Sequim Bay, 12.5 km 2 ) resulted in removal of 2066 T of CO 2 (45% of total simulated) at rate of 3756 mmol m -2 yr -1 , higher than the 63 mmol m -2 yr -1 required globally to remove 1.0 GT CO 2 yr -1 . It also reduced acidity in the bay, ΔpH ≈ +0.1 pH units, an amount comparable to the historic impacts of anthropogenic acidification in the Salish Sea. The mixing and dilution of added TA with distance from the source results in reduced CDR rates such that comparable amount 2176 T CO 2 yr -1 was removed over >1000 fold larger area of the rest of the model domain. There is the potential for more removal occurring beyond the region modeled. The CDR from reduction of outgassing between October and May accounts for as much as 90% of total CDR simulated. Of the total, only 375 T CO 2 yr -1 (8%) was from the open shelf portion of the model domain. With shallow depths limiting vertical mixing, nearshore estuarine waters may provide a more rapid removal of CO 2 using alkalinity enhancement relative to deeper oceanic sites.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

A global meta‐analysis of soil organic carbon response to corn stover removal

Corn (Zea mays L.) stover is a global resource used for livestock, fuel, and bioenergy feedstock, but excessive stover removal can decrease soil organic C (SOC) stocks and deteriorate soil health. Many site-specific stover removal experiments report accrual rates and SOC stock effects, but a quantitative, global synthesis is needed to provide a scientific base for long-term energy policy decisions. We used 409 data points from 74 stover harvest experiments conducted around the world for a metaanalysis and meta-regression to quantify removal rate, tillage, soil texture, and soil sampling depth effects on SOC. Changes were quantified by: (a) comparing final SOC stock differences after at least 3 years with and without stover removal and (b) calculating SOC accrual rates for both treatments. Stover removal generally reduced final SOC stocks by 8% in the upper 0-15 or 0-30 cm, compared to stover retained, irrespective of soil properties and tillage practices. A more sensitive meta-regression analysis showed that retention increased SOC stocks within the 30-150 cm depth by another 5%. Compared to baseline values, stover retention increased average SOC stocks temporally at a rate of 0.41 Mg C ha -1 year -1 (statistically significant at $p$ < 0.01 when averaged across all soil layers). Although SOC sequestration rates were lower with stover removal, with moderate (< 50%) removal they can be positive, thus emphasizing the importance of site-specific management. Our results also showed that tillage effects on SOC stocks were inconsistent due to the high variability in practices used among the experimental sites. Finally, we conclude that research and technological efforts should continue to be given high priority because of the importance in providing science-based policy recommendations for long-term global carbon management.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

MODEL 9975 SHIPPING PACKAGE: IMPACT OF CAPLUG REMOVAL ON FIBERBOARD MOISTURE LEVEL

Two 9975 shipping packages were removed from KAC and provided to SRNL for test purposes, after both packages were found to exceed the 1 inch maximum criterion for the axial gap at the top of the package. Package 9975-01818 was found with an axial gap of 1.437 inch, and an estimated 2.5 liters of excess moisture in the lower fiberboard layers. Package 9975-02287 was found with an axial gap of 1.008 inch, and only slightly elevated moisture levels relative to typical packages. Prior data from the 9975 Surveillance Program has shown that the 9975 drum provides a degree of isolation, and will tend to preserve fiberboard moisture levels for an extended period of time. Both packages were provided to SRNL to identify whether removal of the 4 caplugs in each package would allow moisture to escape the package. Following testing with the caplugs removed for approximately 1 year, this report documents the findings from this effort. Two 9975 shipping packages removed from service in K-Area Complex (KAC) due to an excessive axial gap have been tested in SRNL to determine if caplug removal would facilitate the reduction of excess fiberboard moisture. An additional question to be answered through this testing was whether the resulting moisture loss would reduce the axial gap, reversing the effect seen during storage with excess moisture present. These packages have completed approximately 1 year in test, during which time the weight of each package has steadily decreased as a result of moisture migration out of the package. However, elevated moisture levels still remain in the packages. During this test period, the bottom fiberboard layers of package 9975-01818 (which contained the greater amount of excess moisture) experienced further compaction, and the axial gap of both packages has increased. This effort has shown that removal of the caplugs may not be a sufficient measure to rehabilitate packages with excess moisture or excess axial gaps in a timely manner. However, this measure might make a meaningful contribution in combination with other actions (to be determined). It is recommended that the caplug removal tests in SRNL be discontinued at this time.

36 MATERIALS SCIENCE↗
DOE OSTI2012

ORNL Soils Remediation and Slabs Removal - The Bridge from D and D to Redevelopment - 12342

The landscape of the Oak Ridge National Laboratory (ORNL) has dramatically changed over the past 2 years with demolition of aging facilities in the Central Campus. Removal of these infrastructure legacies was possible due to an influx of DOE-Environmental Management funding through the American Recovery and Reinvestment Act of 2009 (ARRA). Facility D and D traditionally removes everything down to the building slab, and the Soils and Sediments Program is responsible for slabs, below-grade footers and sub-grade structures, abandoned waste utilities, and soils contaminated above certain risk levels that must be removed before the site can be considered for redevelopment. DOE-EM has used a combination of base and ARRA funding to facilitate the clean-up process in ORNL's 2000 Area. Demolition of 13 buildings in the area was funded by the ARRA. Characterization of the remaining slabs, underground pipelines and soils was funded by DOE-EM base funding. Additional ARRA funding was provided for the removal of the slabs, pipelines and contaminated soils. Removal work is in progress and consists of removing and disposing of approximately 7,650 cubic meters (m{sup 3}) of concrete, 2,000 m{sup 3} of debris, and 400 m{sup 3} of contaminated soil. Immediately adjacent to the 2000 Area is the Oak Ridge Science and Technology Park and the modernized ORNL western campus. The Science and Technology Park is the only private sector business and technology park located within the footprint of a national laboratory. The completion of this work will not only greatly reduce the risk to the ORNL campus occupants but also allow this much sought after space to be available for redevelopment and site reuse efforts at ORNL. Demolition of aging facilities enabled by injection of ARRA funding has significantly altered the landscape at ORNL while reducing risk to laboratory personnel and operations and providing valuable central campus land parcels for redevelopment to expand and enhance the science mission of the Laboratory. D and D of these infrastructure legacies that were once eyesores that harbored risk in the ORNL Central Campus have been transformed to green spaces and extremely valuable candidate sites for future buildings. The 2000 Area slabs and soils removal marks the first step in creating the bridge between the modernized east and west campus and acts as the cornerstone in the redevelopment of the ORNL Central Campus area which will be a key contributor to ORNL meeting its vision of the future. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Removal of priority and emerging pollutants from aqueous media by adsorption onto synthetic organo-funtionalized high-charge swelling micas

Highlights: • Adsorption occurs in the interlayer space (C{sub 18}-Mica-4: 49.9 Å). • Pollutants remained sorbed into C{sub 18}-Mica-4 at least 7 days after treatment. • No sample pH adjustment neither NaCl addition is required. • Removal rates from 70% to 100% for most of the 18 pollutants in 24 h. • Applicability to wastewater, surface and tap water samples demonstrated. In this work, the removal of different types of emerging pollutants (four perfluoroalkyl compounds, two preservatives, three surfactants and nine pharmaceutical compounds) from aqueous solution by adsorption onto two novel synthetic clays, a high-charge swelling mica (Na-Mica-4) and an organo-functionalized mica (C{sub 18}-Mica−4), was evaluated. Na-Mica-4 and C{sub 18}-Mica− 4 were prepared and characterized by X-Ray diffraction, Zeta potential, specific surface area, thermogravimetric analysis and transmission electron microscopy, before and after adsorption experiments. The influence of the aqueous sample pH, salt addition and extraction time in the removal were evaluated. The results showed the high adsorption affinity of C{sub 18}-Mica-4 for most of the emerging pollutants analysed after a removal time of 24 h (14 out of 18 pollutants were effectively removed [70–100%]). A high correlation was observed between the log K{sub ow} of the selected emerging pollutants and the adsorption onto C{sub 18}-Mica-4. The results also indicate that adsorption occurs in the interlayer space. While the removal rates with Na-Mica-4 were in the range 8–97% after seven days, some of the compounds, perfluorobutanoic acid and most of pharmaceutically active compounds, were not adsorbed onto the high-charge mica. C{sub 18}-Mica− 4 was effectively used for the removal of contaminants from four types of water samples.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

DeSelenator: A Se-Removal Process for Environmental Decontamination of Wastewaters from Coal-Burning Power Plants

Selenium may become a toxic contaminant of freshwater systems when released into the environment through industrial wastewaters from mining, coal-burning power plants, or oil refining. Efficient and cost-effective Se-removal technologies are therefore necessary to reduce Se concentrations in these wastewaters to below the regulatory discharge limits. In this study, we have demonstrated an effective process that removes Se, mostly as selenate anions, from wastewaters generated by coal-burning power plants. This process, dubbed DeSelenator, leverages the high concentration of sulfate relative to selenate in the wastewater and the propensity of these oxyanions to cocrystallize with benzene-bis-iminoguanidinium (BBIG) cations into extremely insoluble salts (on par with BaSO 4 ). The SO 4 2− /SeO 4 2− cocrystallization with BBIG removes over 90% of S and Se from the wastewater. Following removal of the precipitate by filtration, the filtrate is passed over an anion-exchange resin that further reduces selenium concentration to 5 ppb, the EPA’s regulatory limit for freshwater systems. Finally, the effluent is passed over an activated carbon column, which removes 99.8% of the residual BBIG ligand remaining after crystallization, allowing for the safe discharge of the treated water into the environment. The Se-removal process was first optimized in the lab at the bench scale and then tested in the field at the Tennessee Valley Authority’s Bull Run coal-burning power plant. A technoeconomic assessment found the cost of water treatment with DeSelenator is on par with that of the active biological method, which is currently considered a state-of-the-art Se-removal technology.

anions↗
DOE OSTI2024

Trade-offs in land-based carbon removal measures under 1.5 °C and 2 °C futures

Land-based carbon removals, specifically afforestation/reforestation and bioenergy with carbon capture and storage (BECCS), vary widely in 1.5 °C and 2 °C scenarios generated by integrated assessment models. Because underlying drivers are difficult to assess, we use a well-known integrated assessment model, GCAM, to demonstrate that land-based carbon removals are sensitive to the strength and scope of land-based mitigation policies. We find that while cumulative afforestation/reforestation and BECCS deployment are inversely related, they are both typically part of cost-effective mitigation pathways, with forestry options deployed earlier. While the CO 2 removal intensity (removal per unit land) of BECCS is typically higher than afforestation/reforestation over long time horizons, the BECCS removal intensity is sensitive to feedstock and technology choices whereas the afforestation/reforestation removal intensity is sensitive to land policy choices. Finally, we find a generally positive relationship between agricultural prices and removal effectiveness of land-based mitigation, suggesting that some trade-offs may be difficult to avoid.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

K–Co–Mo–S x chalcogel: high-capacity removal of Pb 2+ and Ag + and the underlying mechanisms

Chalcogenide-based aerogels, known as chalcogels, represent a novel class of nanoparticle-based porous amorphous materials characterized by high surface polarizability and Lewis base properties, exhibiting promising applications in clean energy and separation science. This work presents a K–Co–Mo–S x (KCMS) chalcogel as a highly efficient sorbent for heavy metal ions and details its sorption mechanisms. Its incoherent structure comprises Mo 2 V (S 2 ) 6 and Mo 3 IV S(S 6 ) 2 anion-like clusters with four- and six-coordinated Co–S polyhedra, forming a Co–Mo–S covalent network that hosts K + ions through electrostatic attraction. The interactions of KCMS with heavy metal ions, particularly Pb 2+ and Ag + , reveal that KCMS is exceptionally effective in removing these ions from ppm concentrations down to trace levels (≤5 ppb). KCMS rapidly removes Ag + (≈81.7%) and Pb 2+ (≈99.5%) within five minutes, achieving >99.9% removal within an hour, with a distribution constant K d ≥10 8 mL g -1 . KCMS exhibits an impressive removal capacity of 1378 mg g -1 for Ag + and 1146 mg g -1 for Pb 2+ , establishing it as one of the most effective materials known to date for heavy metal removal. This material is also effective for the removal of Ag + and Pb 2+ along with Hg 2+ , Ni 2+ , Cu 2+ , and Cd 2+ from various water sources even in the presence of highly concentrated and chemically diverse cations, anions, and organic species. Analysis of the post-interacted KCMS by synchrotron X-ray pair distribution function (PDF), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) revealed that the sorption of Pb 2+ , Ag + , and Hg 2+ mainly occurs by the exchange of K + and Co 2+ . Despite being amorphous, this material exhibits unprecedented ion-exchange mechanisms both for the ionically and covalently bound K + and Co 2+ , respectively. In conclusion, this discovery advances our knowledge of amorphous gels and guides material synthesis principles for the highly selective and efficient removal of heavy metal ions from water.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Modeling and Simulating Diffused Aeration for Hydrogen Removal from Expansion Tanks of Parabolic Trough Solar Thermal Power Plants

High-temperature decomposition of organic heat transfer fluids (HTFs) can cause hydrogen build-up in the receiver annulus of parabolic trough power plants. This build-up increases the receiver thermal losses and results in a decline in power output. Prior work has shown that removal of hydrogen from the expansion tank can be an effective mitigation strategy. This paper presents a modeling methodology and simulation results for passive and diffused aeration removal of hydrogen from the expansion tank. Focus is on estimating the mass transfer of hydrogen from the HTF into the headspace gas across the surface and bubble liquid/gas interfaces. Simulations for the operation conditions and expansion tank geometry of the Nevada Solar One power plant (located near Las Vegas, Nevada, USA) show that passive removal (surface mass transfer only) may be sufficient to obtain hydrogen removal rates of 1.7 x 10-4 mol/s (minimal removal rate necessary). A diffused aeration system (surface plus bubble mass transfer) with gas injection volume rates up to 100 L/s may be necessary to obtain a hydrogen removal rate of 2.0 x 10-4 mol/s (optimal removal rate).

14 SOLAR ENERGY↗
DOE OSTI2020

Responses of tundra plant community carbon flux to experimental warming, dominant species removal and elevation

1. Rising temperatures can influence ecosystem processes both directly and indirectly, through effects on plant species and communities. An improved understanding of direct versus indirect effects of warming on ecosystem processes is needed for robust predictions of the impacts of climate change on terrestrial ecosystem carbon (C) dynamics. 2. To explore potential direct and indirect effects of warming on C dynamics in arctic tundra heath, we established a warming (open top chambers) and dominant plant species (Empetrum hermaphroditum Hagerup) removal experiment at a high and low elevation site. We measured the individual and interactive effects of warming, dominant species removal and elevation on plant species cover, the normalized difference vegetation index (NDVI), leaf area index (LAI), temperature, soil moisture and instantaneous net ecosystem CO 2 exchange. 3. We hypothesized that ecosystems would be stronger CO 2 sinks at the low elevation site, and that warming and species removal would weaken the CO 2 sink because warming should increase ecosystem respiration (ER) and species removal should reduce gross primary productivity (GPP). Furthermore, we hypothesized that warming and species removal would have the greatest impact on processes at the high elevation where site temperature should be most limiting and dominant species may buffer the overall community to environmental stress more compared to the low elevation site where plants are more likely to compete with the dominant species. 4. The instantaneous CO 2 flux, which reflected a weak CO 2 sink, was similar at both elevations. Neither experimental warming nor dominant species removal significantly changed GPP or instantaneous net ecosystem CO 2 exchange even though species removal significantly reduced ER, NDVI and LAI. 5. Our results show that even the loss of dominant plant species may not result in significant landscape-scale responses of net ecosystem CO 2 exchange to warming. They also show that NDVI and LAI may be limited in their ability to predict changes in GPP in these tundra heaths systems. Our study highlights the need for more detailed vegetation analyses and ground-truthed measurements in order to accurately predict direct and indirect impacts of climatic change on ecosystem C dynamics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Investigation on nanoscale material removal process of BK7 and fused silica glass during chemical‐mechanical polishing

Abstract Understanding the nanoscale material removal process in chemical mechanical polishing (CMP) is of fundamental importance for the operation and further development of CMP. In this study, the nanoscale material removal processes of both fused silica glass and BK7 glass were investigated based on single‐pad‐asperity polishing experiments. The results indicate that the material removal characteristics are highly dependent on the composition and structure of glass materials. In the mechanically induced chemical bonding removal mode, only atoms locate near the outermost several layers can participate in the formation and breakage of interfacial bridge bonds. Moreover, the force on the abrasive particle must exceed a threshold value to induce significant removal of Si atoms from the glass substrate, because as the breakage of Si glass –O backbonds does not occur in low‐stress conditions. We reveal for the first time that the chemical and mechanical properties of the topmost layer, which is recognized as densification, hydrated, or redeposition layer, have not been significantly affected by the mechanical action of the abrasive particles when polishing in this kind of material removal mode. The results are expected to provide a deeper insight into the nanoscale material removal mechanism during glass CMP.

Wang, Lin↗
DOE OSTI2020

Modeling Molten Salt Reactor Fission Product Removal with SCALE

Liquid-fuel Molten Salt Reactors (MSRs) allow for continuous online fuel treatment and processing using a variety of subsystems. Among these subsystems, the off-gas system (OGS) continuously removes fission products from the primary fuel salt through a helium sparging process. Accurately modeling fission product behavior is paramount for the development of MSRs; while there are a variety of depletion modeling and simulation tools that allow for removal of material from a defined system, most of them work in a semicontinuous, batch-wise manner. The new tools implemented into TRITON, in the SCALE suite for reactor analysis and design, aim to address this issue by implementing truly continuous material feeds and removals. In addition, material accountancy is enhanced in these tools, which enable tracking of removed material in user-specified mixtures. These continuous depletion tools provide a way to model material transport throughout systems more efficiently and accurately. This report validates the new SCALE MSR modeling capabilities using data from the Molten Salt Reactor Experiment (MSRE). After a framework was established for deriving realistic removal rates based on design specifications, these rates were used by TRITON to continuously remove specific elements while performing burnup calculations. Results were compared to those obtained in MSRE, with a focus on the 135 Xe poison fraction. After these capabilities were validated, the learned concepts and best practices were applied to model the Molten Salt Breeder Reactor (MSBR) and the Molten Salt Demonstration Reactor (MSDR) to study the effects of continuous fission product removal in fuel salt reactivity, as well as the lifetime effects.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

Removal of Tc-99, Zr-95, and Nb-95, From Solutions Obtained After Dissolution of Irradiated Mo Targets

Decontamination of 99 Tc, Nb, and Zr impurities in dissolved irradiated Mo disks can be accomplished using Fe(II) precipitation. Here, we report bench-scale experiments and large-scale demonstrations on removal of 99 Tc (0.1 mM), 95 Nb, and 95 Zr from dissolved Mo disk simulant solutions. Tc removal is accomplished through the reduction and simultaneous immobilization of Tc(VII) by Fe(II), producing an insoluble, Tcincorporated Fe(II)-Fe(III) solid that is removed by filtration. Large-scale testing showed that Tc (97.6% ± 1.7%) is removed without affecting 99 Mo yields. Other important side reaction product impurities in irradiated Mo targets, namely various isotopes of Nb and Zr, are also removed (>99%) in this process. The effects of metal (Fe, Tc, Mo) concentrations, Fe(II)/Fe(III) ratio, pH, temperature, Fe addition method, and hydrogen peroxide addition were tested. The minimum amount of Fe(II) needed to remove up to 99% Tc is 10 mM and the optimal pH value for simultaneous removal of Tc, Nb, and Zr impurities is pH 13.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Enhanced Rock Weathering for Carbon Dioxide Removal: Life Cycle Analysis and Techno-Economic Assessment

The study models enhanced rock weathering (ERW) using minerals such as basalt and olivine in terrestrial environments. Our analysis shows potential for ERW CO2 removal and storage costs to approach US$ 100 per tonne (t) of CO2 removed and stored under certain conditions (2023 dollars). In the environmental analysis, the 100-year global warming potential impact with igneous rock and industrial waste materials ranges from 34–263 and 23–180 kg CO2-eq per tonne of CO2 removed and stored, respectively (these values result in overall emissions (removed minus emitted) between –977 and –737 kg CO2-eq net removed per tonne of CO2 removed and stored, meaning for every tonne of CO2 removed by ERW, after accounting for the CO2 equivalent emissions from the GWP, the overall emissions are negative.

Priyadarshini, NFN [NETL Site Support Contractor, ↗
NASA NTRS1986

A description of the active and passive sidewall-boundary-layer removal systems of the 0.3-meter transonic cryogenic tunnel

Results are presented for an operational checkout and shakedown of the active sidewall-boundary-layer removal system newly installed in the Langley 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT). Prior to the installation of this active removal system, the sidewall-boundary layer was removed passively by exhausting directly to the atmosphere (i.e., no reinjection). With the active removal system using the reinjection compressor, the removal capability is greatly expanded to cover the entire operating envelope of the 0.3-m TCT. Details of the active removal system are presented including the compressor reinjection circuit, the compressor pressure ratio/surge control, and the compressor recirculation loop. The control logic and features of the compressor surge control are explained. Initial tests covering critical operating conditions show mass flow removal rates of about 5 percent at lower Mach numbers can be obtained with the active system. Measured performance characteristics of the compressor are presented. As part of the validation of the active system, limited airfoil tests were made using the new system.

Johnson, C. B.↗
NASA NTRS2001

Advanced CO2 Removal Technology Development

The Advanced CO2 Removal Technical Task Agreement covers three active areas of research and development. These include a study of the economic viability of a hybrid membrane/adsorption CO2 removal system, sorbent materials development, and construction of a database of adsorption properties of important fixed gases on several adsorbent material that may be used in CO2 removal systems. The membrane/adsorption CO2 removal system was proposed as a possible way to reduce the energy consumption of the four-bed molecular sieve system now in use. Much of the energy used by the 4BMS is used to desorb water removed in the device s desiccant beds. These beds might be replaced by a desiccating membrane that moves the water from [he incoming stream directly into the outlet stream. The approach may allow the CO2 removal beds to operate at a lower temperature. A comparison between models of the 4BMS and hybrid systems is underway at Vanderbilt University. NASA Ames Research Center has been investigating a Ag-exchanged zeolites as a possible improvement over currently used Ca and Na zeolites for CO2 removal. Silver ions will complex with n:-bonds in hydrocarbons such as ethylene, giving remarkably improved selectivity for adsorption of those materials. Bonds with n: character are also present in carbon oxides. NASA Ames is also continuing to build a database for adsorption isotherms of CO2, N2, O2, CH4, and Ar on a variety of sorbents. This information is useful for analysis of existing hardware and design of new processes.

Finn, John E.↗
NASA NTRS2005

Development of a Low-Power CO2 Removal and Compression System for Closed-Loop Air Revitalization in Future Spacecraft

The current CO2 removal technology of NASA is very energy intensive and contains many non-optimized subsystems. This paper discusses the design and prototype development of a two-stage CO2 removal and compression system that will utilize much less power than NASA s current CO2 removal technology. This integrated system contains a Nafion membrane followed by a residual water adsorber that performs the function of the desiccant beds in the four-bed molecular sieve (4BMS) system of the International Space Station (ISS). The membrane and the water adsorber are followed by a two-stage CO2 removal and compression subsystem that satisfies the operations of the CO2 adsorbent beds of the 4BMS aid the interface compressor for the Sabatier reactor connection. The two-stage compressor will utilize the principles of temperature-swing adsorption (TSA) compression technology for CO2 removal and compression. The similarities in operation and cycle times of the CO2 removal (first stage) and compression (second stage) operations will allow thermal coupling of the processes to maximize the efficiency of the system. In addition to the low-power advantage, this processor will maintain a lower CO2 concentration in the cabin than that can be achieved by the existing CO2 removal systems. The compact, consolidated, configuration of membrane gas dryer and CO2 separator and compressor will allow continuous recycling of humid air in the cabin and supply of compressed CO2 to the reduction unit for oxygen recovery. The device has potential application to the International Space Station and future, long duration, transit, and planetary missions.

Mulloth, Lila M.↗
NASA NTRS2005

Microgravity Experiments on Bubble Removal in the Hydrodynamic Focusing Bioreactor - Space (HFB-S)

The Hydrodynamic Focusing Bioreactor-Space (HFB-S) is being developed as a possible replacement for the Rotating Wall Perfused Vessel (RWPV) bioreactor currently planned for use on the International Space Station (ISS). The HFB-S is being developed with the ability to remove gas bubbles that may inadvertently enter the system during long duration experiments (approx. 1-3 months). The RWPV has been used in the past with great success on Shuttle flights and Mir missions, but has occasionally experienced problems with gas bubbles entering the fluid-filled vessel. These bubbles are harmful to the cell science, and bubble removal in the RWPV is problematic. The HFB-S has an access port on the rotation axis that allows for bubble removal under specific operating conditions without detrimentally affecting the cell tissue. Experiments on bubble removal with the HFB-S were conducted in the microgravity environment on NASA's KC-135 Reduced Gravity Aircraft. The first set of flights provided useful data on bubble trajectories that are validating computational predictions. The second set of flights free-floated the apparatus and tested the most recent configuration of the bioreactor while focusing on the bubble removal process itself. These experiments have shown that gas bubbles can successfully be driven to the removal port and purged in microgravity. The last day's experiments had an excellent microgravity environment due to calm air, and the experience gained in previous flights allowed successful bubble removal 18 out of 35 tries, remarkable given the microgravity time constraints and g-jitter on the KC-135.

Nahra, H. K.↗