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NASA NTRS2002

Trends of Measured Climate Forcing Agents

The growth rate of climate forcing by measured greenhouse gases peaked near 1980 at almost 5 W/sq m per century. This growth rate has since declined to approximately equal to 3 W/sq m per century, largely because of cooperative international actions. We argue that trends can be reduced to the level needed for the moderate "alternative" climate scenario (approximately equal to 2 W/M2 per century for the next 50 years) by means of concerted actions that have other benefits, but the forcing reductions are not automatic "co-benefits" of actions that slow CO2 emissions. Current trends of climate forcings by aerosols remain very uncertain. Nevertheless, practical constraints on changes in emission levels suggest that global warming at a rate + 0.15 +/- 0.05 C per decade will occur over the next several decades.

Hansen, James E.↗

NASA NTRS1985

The problem of the Earth's CO2 content and the iron core

The near absence of metallic iron and the presence of magnetite and FeS in the C-1 chondrites imply that metallic iron was a minor phase present during the accretion process that formed the C-1 chondrites. If the C-1 chondrites provided the bulk of the initial planetary growth materials, the carbon reduction model is favored. The above estimates suggest that some 1240 to 227 times as much CO2 may have been produced during the formation of the core than can be accounted for in the crust and mantle. This discrepancy taken to the extreme suggests either that: (1) the Earth has lost more than 99 percent of its initial CO2 during early differentiation (this is highly unlikely) or: (2) the Earth has acquired some 90 percent of its present mass by the accretion of debris from previously reduced and differentiated but subsequently disrupted planetary bodies whereby the associated CO2 would not be captured, or: (3) the C-1 chondrites represent only a trivial fraction of the initial accretion materials present in the nebular cloud or: (4) condensed iron and anhydrous silicate phases were preferentially accreted during the initial formation of the planetary bodies.

Devore, G. W.↗

NASA NTRSDate not supplied

Modeling the Integrated Thermal Amine Scrubber and Air Cooled-Temperature Swing Adsorbent Compressor

As part of a larger CO2 removal architecture study, a model was developed in Aspen Custom Modeler of the Thermal Amine Scrubber (TAS), an ISS flight experiment intended to scrub CO2 from the cabin air. In order to minimize mass losses, it was determined the TAS should work in conjunction with the Air Cooled-Temperature Swing Adsorption Compressor (AC-TSAC) to reduce the CO2 for O2 production. First the TAS removes CO2 from the cabin atmosphere, then the AC-TSAC compresses the CO2 and feeds it in a steady steam to a Sabatier or Bosch process. This document details an effort to add a model of the AC-TSAC to the existing TAS model to determine if the two hardware systems will have deleterious effects on each other’s performance. It was found the AC-TSAC provided sufficient vacuum for the TAS’s desorption to occur, but not the same level of vacuum as space vacuum. This lower quality vacuum led to a reduction in the total cyclical uptake capacity of the TAS and thus a lower CO2 removal under the same conditions. The TAS did not remove enough CO2 to fill the AC-TSAC bed to capacity during the production phase which caused the AC-TSAC to run out of CO2 during production. This renders the addition of the AC-TSAC pointless. It is believed these effects can be overcome with a redesign of one or both systems.

TAS↗

NASA NTRS2015

Chlorophyll Variability in the Oligotrophic Gyres: Mechanisms, Seasonality and Trends

A 16-year (1998-2013) analysis of trends and seasonal patterns was conducted for the 5 subtropical ocean gyres using chlorophyll-a (Chl-a) retrievals from ocean color satellite data, sea surface temperature (SST) obtained from optimally interpolated Advanced Very High Resolution Radiometer (AVHRR) data, and sea-level anomaly (SLA) from Aviso multi-sensor altimetry data. Trend analysis was also performed on mixed-layer data derived from gridded temperature and salinity profiles (1998-2010) from the Simple Ocean Data Assimilation (SODA) model. The Chl-a monthly composites were constructed from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate-resolution Imaging Spectroradiometer (MODIS) on Aqua using two different algorithms: the standard algorithm (STD) that has been in use since the start of the SeaWiFS mission in 1997, and a more recently developed Ocean Color Index (OCI) algorithm that is purported to provide improved accuracy in low chlorophyll waters such as the oligotrophic regions of the subtropical gyres. Trends were obtained for all gyres using both STD and OCI algorithms, which demonstrated generally consistent results. The North Pacific, Indian Ocean, North Atlantic and South Atlantic gyres showed significant downward trends in Chl-a, while the South Pacific gyre has a much weaker upward trend with no statistical significance. Time series of satellite-derived net primary production (NPP) showed downward trends for all the gyres, while all 5 gyres exhibited positive trends in SST and SLA. The seasonal variability of Chl-a in each gyre is tightly coupled to the variability in mixed layer depth (MLD) with peak values in winter in both hemispheres when vertical mixing is more vigorous, reaching depths approaching the nutricline (ZNO3, here defined as the depth of the 0.2 micron nitrate concentration). On a seasonal basis, Chl-a concentrations increase when the MLD approaches or is deeper than the nutricline depth, in agreement with the concept that vertical mixing is the major driving mechanism for phytoplankton photosynthesis in the interior of the gyres. In addition, MLD and SST seasonal changes are well correlated indicating that SST is a reasonable index of vertical mixing in the gyres. The combination of surface warming trends and biomass reduction over the 16-year period has the potential to reduce atmospheric CO2 uptake by the gyres and therefore influence the global carbon cycle.

Long-term trends↗

NASA NTRS2000

Ammonia Formation by the Reduction of Nitrite/Nitrate by FeS: Ammonia Formation Under Acidic Conditions

FeS reduces nitrite to, ammonia at pHs lower than the corresponding reduction by aqueous Fe+2. The reduction follows a reasonable first order decay, in nitrite concentration, with a half life of about 150 min (room temperature, CO2, pH 6.25). The highest ammonia product yield measured was 53%. Under CO2, the product yield decreases from pH 5.0 to pH 6.9. The increasing concentration of bicarbonate at higher pH interferes with the reaction. Bicarbonate interference is shown by comparing runs under N2 and CO2. The reaction proceeds well in the presence of such species as chloride, sulfate, and phosphate though the yield drops significantly with phosphate. FeS also reduces nitrate and, unlike with Fe+2, the reduction shows more reproducibility. Again, the product yield decreases with increasing pH, from 7% at pH 4.7 to 0% at pH 6.9. It appears as if nitrate is much more sensitive to the presence of added species, perhaps not competing as well for binding sites on the FeS surface. This may be the cause of the lack of reproducibility of nitrate reduction by Fe+2 (which also can be sensitive to binding by certain species).

Summers, David P.↗

NASA NTRS2006

Rapid Cycling CO2 and H2O Removal System for EMU

NASA's planned future missions set stringent demands on the design of the Portable Life Support Systems (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the EMU is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The CO2 and humidity control unit in the existing PLSS design is relatively large, since it has to remove 8 hours worth of CO2. If the sorbent regeneration can be carried out during the extravehicular activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. (TDA) is developing a compact, regenerable sorbent-based system to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all duration-limiting elements in the life support system. This paper summarizes the results of the sorbent development and testing, and evaluation efforts. The results of a preliminary system analysis are also included, showing the size and volume reductions provided by the new system.

Alptekin, Gokhan↗

NASA NTRS1995

The role of sea ice in 2 x CO2 climate model sensitivity. Part 1: The total influence of sea ice thickness and extent

As a first step in investigating the effects of sea ice changes on the climate sensitivity to doubled atmospheric CO2, the authors use a standard simple sea ice model while varying the sea ice distributions and thicknesses in the control run. Thinner ice amplifies the atmospheric temperature senstivity in these experiments by about 15% (to a warming of 4.8 C), because it is easier for the thinner ice to be removed as the climate warms. Thus, its impact on sensitivity is similar to that of greater sea ice extent in the control run, which provides more opportunity for sea ice reduction. An experiment with sea ice not allowed to change between the control and doubled CO2 simulations illustrates that the total effect of sea ice on surface air temperature changes, including cloud cover and water vapor feedbacks that arise in response to sea ice variations, amounts to 37% of the temperature sensitivity to the CO2 doubling, accounting for 1.56 C of the 4.17 C global warming. This is about four times larger than the sea ice impact when no feedbacks are allowed. The different experiments produce a range of results for southern high latitudes with the hydrologic budget over Antarctica implying sea level increases of varying magnitude or no change. These results highlight the importance of properly constraining the sea ice response to climate perturbations, necessitating the use of more realistic sea ice and ocean models.

Rind, D.↗

NASA NTRS1983

Signal averaging limitations in heterodyne- and direct-detection laser remote sensing measurements

The improvement in measurement uncertainty brought about by the averaging of increasing numbers of pulse return signals in both heterodyne- and direct-detection lidar systems is investigated. A theoretical analysis is presented which shows the standard deviation of the mean measurement to decrease as the inverse square root of the number of measurements, except in the presence of temporal correlation. Experimental measurements based on a dual-hybrid-TEA CO2 laser differential absorption lidar system are reported which demonstrate that the actual reduction in the standard deviation of the mean in both heterodyne- and direct-detection systems is much slower than the inverse square-root dependence predicted for uncorrelated signals, but is in agreement with predictions in the event of temporal correlation. Results thus favor the use of direct detection at relatively short range where the lower limit of the standard deviation of the mean is about 2 percent, but advantages of heterodyne detection at longer ranges are noted.

Menyuk, N.↗

NASA NTRS1999

A Study of Mars Dust Environment Simulation at NASA Johnson Space Center Energy Systems Test Area Resource Conversion Test Facility

The dust environment on Mars is planned to be simulated in a 20 foot thermal-vacuum chamber at the Johnson Space Center, Energy Systems Test Area Resource Conversion Test Facility in Houston, Texas. This vacuum chamber will be used to perform tests and study the interactions between the dust in Martian air and ISPP hardware. This project is to research, theorize, quantify, and document the Mars dust/wind environment needed for the 20 foot simulation chamber. This simulation work is to support the safety, endurance, and cost reduction of the hardware for the future missions. The Martian dust environment conditions is discussed. Two issues of Martian dust, (1) Dust Contamination related hazards, and (2) Dust Charging caused electrical hazards, are of our interest. The different methods of dust particles measurement are given. The design trade off and feasibility were studied. A glass bell jar system is used to evaluate various concepts for the Mars dust/wind environment simulation. It was observed that the external dust source injection is the best method to introduce the dust into the simulation system. The dust concentration of 30 Mg/M3 should be employed for preparing for the worst possible Martian atmosphere condition in the future. Two approaches thermal-panel shroud for the hardware conditioning are discussed. It is suggested the wind tunnel approach be used to study the dust charging characteristics then to be apply to the close-system cyclone approach. For the operation cost reduction purpose, a dehumidified ambient air could be used to replace the expensive CO2 mixture for some tests.

Chen, Yuan-Liang Albert↗

NASA NTRS2015

Self-Cleaning Boudouard Reactor for Full Oxygen Recovery from CO2 Project

Oxygen recovery from respiratory CO2 is an important aspect of human spaceflight. Methods exist to sequester the CO2, but production of oxygen needs further development. The current ISS Carbon Dioxide Reduction System (CRS) uses the Sabatier reaction to produce water (and ultimately breathing air). Oxygen recovery is limited to 50% because half of the hydrogen used in the Sabatier reactor is lost as methane, which is vented overboard. The Bosch reaction is the only real alternative to the Sabatier reaction, but in the last reaction in the cycle (Boudouard) the resulting carbon buildup will eventually foul the nickel or iron catalyst, reducing reactor life and increasing consumables. To minimize this fouling, find a use for this waste product, and increase efficiency, we propose testing various self-cleaning catalyst designs in an existing MSFC Boudouard reaction test bed and to determine which one is the most reliable in conversion and lack of fouling. Challenges include mechanical reliability of the cleaning method and maintaining high conversion efficiency with lower catalyst surface area. The above chemical reactions are well understood, but planned implementations are novel (TRL 2) and haven't been investigated at any level.

Technology Portfolio System↗

NASA NTRS2021

The Climate Response to Emissions Reductions due to COVID-19: Initial Results from CovidMIP

Many nations responded to the COVID-19 pandemic by restricting travel and other activities during 2020, resulting in temporarily reduced emissions of CO2, other greenhouse gases and ozone and aerosol precursors. We present the initial results from a coordinated Intercomparison, CovidMIP, of Earth system model simulations which assess the impact on climate of these emissions reductions. Twelve models performed multiple initial-condition ensembles to produce over 300 simulations spanning both initial condition and model structural uncertainty. We find model consensus on reduced aerosol amounts (particularly over southern and eastern Asia) and associated increases in surface shortwave radiation levels. However, any impact on near-surface temperature or rainfall during 2020-2024 is extremely small and is not detectable in this initial analysis. Regional analyses on a finer scale, and closer attention to extremes (especially linked to changes in atmospheric composition and air quality) are required to test the impact of COVID- 19-related emission reductions on near-term climate.

Chris D. Jones↗

NASA NTRS1991

Thermal analysis, optimization and design of a Martian oxygen production plant

The objective is to optimally design the thermal components of a system that uses carbon dioxide (CO2) from the Martian atmosphere to produce oxygen (O2) for spacecraft propulsion and/or life-support. Carbon dioxide is thermally decomposed into carbon monoxide (CO) and O2 followed by the electrochemical separation of O2. The design of the overall system and its various individual components depends on, among other things, the fraction of the stoichiometric yield of O2 that can be realized in the system and the temperature of operation of the electrochemical separation membrane. The analysis indicates that a substantial reduction could be obtained in the mass and power requirements of the system if the unreacted CO2 were to be recycled. The concepts of an optimum temperature of the zirconia cell and impracticality of plant operation at low cell efficiencies are also discussed. The design of the thermal equipment is such that the mass and power requirements of the individual components and of the overall system are optimized.

Iyer, Venkatesh A.↗

NASA NTRS1991

Compression of Martian atmosphere for production of oxygen

The compression of CO2 from the Martian atmosphere for production of O2 via an electrochemical cell is addressed. Design specifications call for an oxygen production rate of 10 kg per day and for compression of 50 times that mass of CO2. Those specifications require a compression rate of over 770 cfm at standard Martian temperature and pressure (SMTP). Much of the CO2 being compressed represents waste, unless it can be recycled. Recycling can reduce the volume of gas that must be compressed to 40 cfm at SMTP. That volume reduction represents significant mass savings in the compressor, heating equipment, filters, and energy source. Successful recycle of the gas requires separation of CO (produced in the electrochemical cell) from CO2, N2, and Ar found in the Martian atmosphere. That aspect was the focus of this work.

Lynch, D. C.↗

NASA NTRS2018

Co-Adsorption of Carbon Dioxide on Zeolite 13X in the Presence of Preloaded Water

Environmental 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.

Cmarik, Gregory E↗

NASA NTRS2001

Biogenic Methane and the Rise of Oxygen

Oxygenic photosynthesis does not make the rise of oxygen inevitable. What is required is that reductant and oxygen be separated and permanently segregated. The usual picture for Earth is that oxygenic photosynthesis split CO2 into carbon and oxygen, with the carbon buried in sediments and the oxygen mostly taken up by oxides of iron and sulfur. The relatively small atmospheric reservoir of O2 is regulated by the carbon burial rate, reaction with volcanic and metamorphic gases, and oxidation of reduced carbon released as old sediments weather. Absent from this picture is a distinction between the Archean and modern times: on average, carbon burial fluxes would have been matched by oxygen losses then as now. Separation of reductant from oxidant is only provisional. No net oxidation of the continents occurs, and so no change of diagenetic, metamorphic, or volcanic gases is expected. Nor would any change in oxidative weathering be expected. Something more than carbon burial is required to make the Archean different. The escape of hydrogen to space permanently separates the reductant from the oxidant. Hydrogen escape is widely believed to have led to the present highly oxidized states of Mars and Venus. Hydrogen escape has usually been thought small for Archaean Earth, because water vapor is cold-trapped at the troposphere and thus held to levels of a few ppmv in the stratosphere. This cold trapping renders hydrogen escape negligible. However, methane is not cold trapped, and its expected abundance in the Archaean, given low oxygen levels and a biogenic source, would have been high, probably more than 100 times present. At such levels methane would have driven geologically significant levels of hydrogen escape. Additional information is contained in the original extended abstract.

Catling, David↗

NASA NTRS2010

International Space Station (ISS) Internal Active Thermal Control System (IATCS) New Biocide Selection, Qualification and Implementation

The Internal Active Thermal Control System (IATCS) aboard the International Space Station (ISS) is primarily responsible for the removal of heat loads from payload and system racks. The IATCS is a water based system which works in conjunction with the EATCS (External ATCS), an ammonia based system, which are interfaced through a heat exchanger to facilitate heat transfer. On-orbit issues associated with the aqueous coolant chemistry began to occur with unexpected increases in CO2 levels in the cabin. This caused an increase in total inorganic carbon (TIC), a reduction in coolant pH, increased corrosion, and precipitation of nickel phosphate. These chemical changes were also accompanied by the growth of heterotrophic bacteria that increased risk to the system and could potentially impact crew health and safety. Studies were conducted to select a biocide to control microbial growth in the system based on requirements for disinfection at low chemical concentration (effectiveness), solubility and stability, material compatibility, low toxicity to humans, compatibility with vehicle environmental control and life support systems (ECLSS), ease of application, rapid on-orbit measurement, and removal capability. Based on these requirements, ortho-phthalaldehyde (OPA), an aromatic dialdehyde compound, was selected for qualification testing. This paper presents the OPA qualification test results, development of hardware and methodology to safely apply OPA to the system, development of a means to remove OPA, development of a rapid colorimetric test for measurement of OPA, and the OPA on-orbit performance for controlling the growth of microorganisms in the ISS IATCS since November 3, 2007.

Wilson, Mark E.↗

NASA NTRS2011

International Space Station (ISS) Internal Active Thermal Control System (IATCS) New Biocide Selection, Qualification and Implementation

Wilson, Mark E.↗

NASA NTRS1986

Utilization of ammonium as a nitrogen source: effects of ambient acidity on growth and nitrogen accumulation by soybean

Dry matter accumulation of plants utilizing NH4+ as the sole nitrogen source generally is less than that of plants receiving NO3- unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4+ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4+ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 +/- 0.1 by automatic additions of 0.01 N H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4+ uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4+ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4+, which were initially about 50% lower at pH 4.1 than at 6.1 continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.

NASA Discipline Number 61-10↗