Results for “Gas Capture” — Page 9

NASA NTRS2016

Multiparameter Flowfield Measurements in High-Pressure, Cryogenic Environments Using Femtosecond Lasers

Femtosecond laser electronic excitation tagging (FLEET) and Rayleigh scattering (RS) from a femtosecond laser are demonstrated in the NASA Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The measured signals from these techniques are examined for their thermodynamic dependencies in pure nitrogen. The FLEET signal intensity and signal lifetimes are found to scale primarily with the gas density, as does the RS signal. Several models are developed, which capture these physical behaviors. Notably, the FLEET and Rayleigh scattering intensities scale linearly with the flow density, while the FLEET signal decay rates are a more complex function of the thermodynamic state of the gas. The measurement of various flow properties are demonstrated using these techniques. While density was directly measured from the signal intensities and FLEET signal lifetime, temperature and pressure were measured using the simultaneous FLEET velocity measurements while assuming the flow had a constant total enthalpy. Measurements of density, temperature, and pressure from the FLEET signal are made with accuracies as high as 5.3 percent, 0.62 percent, and 6.2 percent, respectively, while precisions were approximately 10 percent, 0.26 percent, and 11 percent for these same quantities. Similar measurements of density from Rayleigh scattering showed an overall accuracy of 3.5 percent and a precision of 10.2 percent over a limited temperature range (T greater than 195 K). These measurements suggest a high degree of utility at using the femtosecond-laser based diagnostics for making multiparameter measurements in high-pressure, cryogenic environments such as large-scale TCT facilities.

Burns, Ross A.↗

NASA NTRS1979

Xenon from intermediate zones of supernovae

The paper examines the photodisintegration and neutron capture in massive stars which show that the bulk of the p-isotopes of Xe is formed during the gamma-process of Woosley and Howard (1978) by stripping of the Xe + Be seeds. The environments in which the chondrites can be formed were determined by the neutron-capture calculations; they show that the Xe-124-rich gas must be associated at the sources with anomalously large overabundances of Nd-142, Sm-144, and possibly Ba-130, and with anomalously small overabundances of the p-isotopes of Se, Kr, Sr, and Mo.

Heymann, D.↗

NASA NTRS1983

NGC 315 - High-velocity H I in an active elliptical galaxy

The detection of high-velocity H I in absorption against the nuclear continuum source in the giant elliptical galaxy NGC 315 is reported. The absorption line is found to be highly blueshifted in the reference frame of the galaxy with a projected velocity toward the galaxy of 490 km/s. The absorption line is very strong (244 + or - 4 mJy), consisting of two components with very narrow velocity widths of 2.5 km/s (FWHM) each and peak optical depths of 0.9 and 0.2. The kinetic temperature must be 150 K if the line widths are due entirely to thermal broadening, while the neutral gas column densities implied are 2-5 x 10 to the 20th hydrogen atoms/sq cm. No OH in absorption was detected in these clouds to a limiting peak optical depth of 0.04, although this result is consistent with either a galactic or extragalactic origin of the clouds. It is suggested that these clouds may have condensed out of a large unobserved galactic halo of gas, or they may reside in or have been captured from the intracluster medium.

Dressel, L. L.↗

NASA NTRS1994

An approximate Riemann solver for thermal and chemical nonequilibrium flows

Among the many methods available for the determination of inviscid fluxes across a surface of discontinuity, the flux-difference-splitting technique that employs Roe-averaged variables has been used extensively by the CFD community because of its simplicity and its ability to capture shocks exactly. This method, originally developed for perfect gas flows, has since been extended to equilibrium as well as nonequilibrium flows. Determination of the Roe-averaged variables for the case of a perfect gas flow is a simple task; however, for thermal and chemical nonequilibrium flows, some of the variables are not uniquely defined. Methods available in the literature to determine these variables seem to lack sound bases. The present paper describes a simple, yet accurate, method to determine all the variables for nonequilibrium flows in the Roe-average state. The basis for this method is the requirement that the Roe-averaged variables form a consistent set of thermodynamic variables. The present method satisfies the requirement that the square of the speed of sound be positive.

Prabhu, Ramadas K.↗

NASA NTRS1995

A new technique for ground simulation of hypervelocity debris

A series of hypervelocity damage experiments were preformed on spacecraft materials. These experiments employed a technique which accelerates micro flyer plates simulating space debris traveling at 3 to 8 km/sec. The apparatus used to propel the micro flyer plates was compact and fit well into a space environmental chamber equipped with instrumentation capable of analyzing the vapor ejected from the sample. Mechanical damage to the sample was also characterized using optical and scanning electron microscpopy. Data for this work was obtained from hypervelocity impacts on a polysulfone resin and a graphite polysulfone composite. Polysulfone was selected because it was flown on the Long Duration Exposure Facility (LDEF) which spent several years in low earth orbit (LEO). Chemistry of the vapor produced by the impact was analyzed with a time of flight mass spectrometer, (TOFMS). This represents the first time that ejected vapors from hypervelocity collisions were trapped and analyzed with a mass spectrometer. With this approach we are able to study changes in the vapor chemistry as a function of time after impact, obtain a velocity measurement of the vapor, and estimate a temperature of the surface at time of impact using dynamic gas equations. Samples of the vapor plume may be captured and examined by transmission electron microscopy. Studies were also conducted to determine mechanical damage to a graphite polysulfone composite and a polysulfone resin. Impact craters were examined under optical and scanning electron microscopes. The collision craters in the matrix were typical of those shown in conventional shock experiments. However, the hypervelocity collisions with the graphite polysulfone composite were remarkably different than those with the resin.

Roybal, R.↗

NASA NTRS2012

Cascade Storage and Delivery System for a Multi Mission Space Exploration Vehicle (MMSEV)

NASA is developing a Multi Mission Space Exploration Vehicle (MMSEV) for missions beyond Low Earth Orbit (LEO). The MMSEV is a pressurized vehicle used to extend the human exploration envelope for Lunar, Near Earth Object (NEO), and Deep Space missions. The Johnson Space Center is developing the Environmental Control and Life Support System (ECLSS) for the MMSEV. The MMSEV s intended use is to support longer sortie lengths with multiple Extra Vehicular Activities (EVAs) on a higher magnitude than any previous vehicle. This paper presents an analysis of a high pressure oxygen cascade storage and delivery system that will accommodate the crew during long duration Intra Vehicular Activity (IVA) and capable of multiple high pressure oxygen fills to the Portable Life Support System (PLSS) worn by the crew during EVAs. A cascade is a high pressure gas cylinder system used for the refilling of smaller compressed gas cylinders. Each of the large cylinders are filled by a compressor, but the cascade system allows small cylinders to be filled without the need of a compressor. In addition, the cascade system is useful as a "reservoir" to accommodate low pressure needs. A regression model was developed to provide the mechanism to size the cascade systems subject to constraints such as number of crew, extravehicular activity duration and frequency, and ullage gas requirements under contingency scenarios. The sizing routine employed a numerical integration scheme to determine gas compressibility changes during depressurization and compressibility effects were captured using the Soave-Redlich-Kwong (SRK) equation of state. A multi-dimensional nonlinear optimization routine was used to find the minimum cascade tank system mass that meets the mission requirements. The sizing algorithms developed in this analysis provide a powerful framework to assess cascade filling, compressor, and hybrid systems to design long duration vehicle ECLSS architecture. 1

Yagoda, Evan↗

NASA NTRS2020

Human influence on joint changes in temperature, rainfall and continental aridity

Despite the pervasive impact of drought on human and natural systems, the large-scale mechanisms conducive to regional drying remain poorly understood. Here we use a multivariate approach to identify two distinct externally forced fingerprints from multiple ensembles of Earth system model simulations. The leading fingerprint, F(M1)(x), is characterized by global warming, intensified wet–dry patterns and progressive large-scale continental aridification, largely driven by multidecadal increases in greenhouse gas (GHG) emissions. The second fingerprint, F(M2)(x), captures a pronounced interhemispheric temperature contrast, associated meridional shifts in the intertropical convergence zone and correlated anomalies in precipitation and aridity over California, the Sahel and India. F(M2)(x) exhibits nonlinear temporal behaviour: the intertropical convergence zone moves southwards before 1975 in response to increases in hemispherically asymmetric sulfate aerosol emissions, and it shifts northwards after 1975 due to reduced sulfur dioxide emissions and the GHG-induced warming of Northern Hemisphere landmasses. Both fingerprints are statistically identifiable in observations of joint changes in temperature, rainfall and aridity during 1950–2014. We show that the reliable simulation of these changes requires combined forcing by GHGs, direct and indirect effects of aerosols, and large volcanic eruptions. Our results suggest that GHG-induced aridification may be modulated regionally by future reductions in sulfate aerosol emissions.

Human influence↗

NASA NTRSDate not supplied

Observation of Trace Gases Seasonal Variability in the Marine Boundary Layer over the Atlantic Ocean during the ACTIVATE Field Campaign

High resolution in-situ measurements of carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and water vapor (H2O) were made onboard the NASA HU-25 aircraft during the ACTIVATE (Aerosol Cloud meteorology Interactions oVer the western Atlantic Experiment) campaign during 2020 and 2021 in different seasons (winter through summer) over the mid-latitude western Atlantic Ocean. As most of the flights focused on the marine boundary layer (MBL) during the campaign, these trace gas observations are an excellent data set to examine seasonal variability of trace gas background values in the MBL without the influence of localized point sources. We will describe the variability of these trace gases in the MBL background by filtering out concentrated point sources using back trajectory analysis along with trace gas ratios. Additionally, the ocean is a significant sink of anthropogenic CO2 capturing about one quarter of total anthropogenic carbon. By looking at the MBL CO2 variation as a function of season, we discuss observed changes in CO2 uptake over the ocean. These high accuracy observations of trace gas backgrounds in the MBL along with characterizing seasonal effects on oceanic sequestering of anthropogenic CO2 will improve the understanding of seasonal variations and change in climate and inverse modelling over the ocean.

Yonghoon Choi↗

NASA NTRSDate not supplied

New Methods to Determine the Electromagnetic Effects from Precipitation Static

The Electrostatics and Surface Physic Laboratory has devised a new method to determine the electromagnetic effects from precipitation static or p-static as its commonly called. P-static occurs as a result of triboelectric charging of granular materials or ice crystals bombarded onto the surfaces of air and/or space vehicles at high speeds. The electrostatic charge that builds up on the outer surface can have deleterious effects that arise during discharge events. These discharges can cause loss of communication to and from the vehicle from ground stations, EMI interference, radio frequency noise, etc… There are even cases of total loss of vehicles caused by p-static charging. We have developed a method to simulate the extensive tribocharging of insulating materials that occurs during p-static through the use of corona charging which allows testing to occur within a lab environment. These tests simulate the discharges that occur on rocket vehicles during ascent as a result of gas breakdown by performing the corona charging tests inside a vacuum chamber and subsequently removing the air. The simultaneous gas discharges emit electromagnetic interference (EMI) which can be captured and monitored.

Charles R Buhler↗

NASA NTRSDate not supplied

Modeling of a Solid Oxide Fuel Cell as Part of a Predictive Functional Model for Aerospace Fuel-Cell Systems

This paper will discuss initial efforts at modeling a solid oxide fuel cell (SOFC) for aerospace applications. Fuel cells historically have been used in spacecraft from the Gemini to the Shuttle era for providing spacecraft power with the added benefit of producing water for crew use. However, there are many potential applications for fuel cells and electrolyzers in spaceflight, including oxygen generation, in-situ resource utilization (ISRU) and propellant production. This proof-of-concept model has been developed using a commercial multiphysics modeling software package. Two-dimensional and one-dimensional isothermal models were created based on a certain SOFC design and results were compared to test data from the real system. Local Butler-Volmer kinetic relations were adjusted, and an effective porous medium approach was taken in order to capture how the many interconnects between cells in the gas channels affected fluid flow. The model was able to reproduce polarization curves derived from test data within around 0.02 Volts for a given current density. This model could be adapted to model a solid oxide electrolyzer, proton exchange membrane fuel cell, or other type of fuel cell technology in order to understand how these types of technologies could fit into broader spacecraft designs and advance the capabilities of spaceflight systems.

Mary Lou Nadeau↗

NASA NTRSDate not supplied

Modeling of a Solid Oxide Fuel Cell as Part of a Predictive Functional Model for Aerospace Fuel-Cell Systems

This paper will discuss initial efforts at modeling a solid oxide fuel cell (SOFC) for aerospace applications. Fuel cells historically have been used in spacecraft from the Gemini to the Shuttle era for providing spacecraft power with the added benefit of producing water for crew use. However, there are many potential applications for fuel cells and electrolyzers in spaceflight, including oxygen generation, in-situ resource utilization (ISRU) and propellant production. This proof-of-concept model has been developed using a commercial multiphysics modeling software package. Two-dimensional and one-dimensional isothermal models were created based on a certain SOFC design and results were compared to test data from the real system. Local Butler-Volmer kinetic relations were adjusted, and an effective porous medium approach was taken in order to capture how the many interconnects between cells in the gas channels affected fluid flow. The model was able to reproduce polarization curves derived from test data within around 0.02 Volts for a given current density. This model could be adapted to model a solid oxide electrolyzer, proton exchange membrane fuel cell, or other type of fuel cell technology in order to understand how these types of technologies could fit into broader spacecraft designs and advance the capabilities of spaceflight systems.

Mary Lou Nadeau↗

NASA NTRSDate not supplied

Modeling of a Solid Oxide Fuel Cell as Part of a Predictive Functional Model for Aerospace Fuel-Cell Systems

This paper will discuss initial efforts at modeling a solid oxide fuel cell (SOFC) for aerospace applications. Fuel cells historically have been used in spacecraft from the Gemini to the Shuttle era for providing spacecraft power with the added benefit of producing water for crew use. However, there are many potential applications for fuel cells and electrolyzers in spaceflight, including oxygen generation, in-situ resource utilization (ISRU) and propellant production. This proof-of-concept model has been developed using a commercial multiphysics modeling software package. Two-dimensional and one-dimensional isothermal models were created based on a certain SOFC design and results were compared to test data from the real system. Local Butler-Volmer kinetic relations were adjusted, and an effective porous medium approach was taken in order to capture how the many interconnects between cells in the gas channels affected fluid flow. The model was able to reproduce polarization curves derived from test data within around 0.02 Volts for a given current density. This model could be adapted to model a solid oxide electrolyzer, proton exchange membrane fuel cell, or other type of fuel cell technology in order to understand how these types of technologies could fit into broader spacecraft designs and advance the capabilities of spaceflight systems.

Mary Lou Nadeau↗

NASA NTRSDate not supplied

Modeling of a Solid Oxide Fuel Cell as Part of a Predictive Functional Model for Aerospace Fuel-Cell Systems

This paper will discuss initial efforts at modeling a solid oxide fuel cell (SOFC) for aerospace applications. Fuel cells historically have been used in spacecraft from the Gemini to the Shuttle era for providing spacecraft power with the added benefit of producing water for crew use. However, there are many potential applications for fuel cells and electrolyzers in spaceflight, including oxygen generation, in-situ resource utilization (ISRU) and propellant production. This proof-of-concept model has been developed using a commercial multiphysics modeling software package. Two-dimensional and one-dimensional isothermal models were created based on a certain SOFC design and results were compared to test data from the real system. Local Butler-Volmer kinetic relations were adjusted, and an effective porous medium approach was taken in order to capture how the many interconnects between cells in the gas channels affected fluid flow. The model was able to reproduce polarization curves derived from test data within around 0.02 Volts for a given current density. This model could be adapted to model a solid oxide electrolyzer, proton exchange membrane fuel cell, or other type of fuel cell technology in order to understand how these types of technologies could fit into broader spacecraft designs and advance the capabilities of spaceflight systems.

Mary Lou Nadeau↗

NASA NTRS2016

New Approach to Characterize CO2 and CH4 Emissions over Sacramento, California Using an Airborne Aircraft Measurement

Emission fluxes of carbon dioxide (CO2) and methane (CH4) over Sacramento, California, USA, are estimated using an aircraft equipped with a cavity ring-down greenhouse gas sensor through the Alpha Jet Atmospheric eXperiment (AJAX). To better quantify the emission fluxes over the entire city and two small point sources within the area, we designed flights in a cylindrical pattern and computed the emission fluxes from 9 flights over all seasons using the Kriging method based on Gausss divergence theorem. The concentrations at the downwind side of Sacramento show somewhat persistent patterns among the 9 flights, but the magnitudes and locations of the fluxes vary depending on the individual weather conditions and seasonality on a given flight day. The net emission fluxes tend to be smaller in summer (July) than winter (November). Both trace gas mixing ratios as well as the wind speed and direction show high spatial variability both horizontally and vertically. The local maximum emission fluxes over a landfill and a rice field measured on July 29, 2015, were 2-3 times lower than the maximum measured over the entire city. These low emission fluxes suggest that not only the local source but also the transport of greenhouse gases due to diurnal and seasonal variation in winds have a strong effect on the CO2 and CH4 flux estimation of the both local emissions and city-size emissions. Our results highlight that the aircraft-based approach is effective and useful for capturing city-size emission fluxes and estimating the greenhouse gas emissions and its sources.

airborne↗

NASA NTRS1993

An intercomparison of aircraft instrumentation for tropospheric measurements of carbonyl sulfide, hydrogen sulfide, and carbon disulfide

This paper reports results of NASA's Chemical Instrumentation and Test Evaluation (CITE 3) during which airborne measurements for carbonyl sulfide (COS), hydrogen sulfide (H2S), and carbon disulfide (CS2) were intercompared. Instrumentation included a gas chromatograph using flame photometric detection (COS, H2S, and CS2), a gas chromatograph using mass spectrometric detection (COS) and CS2), a gas chromatograph using fluorination and subsequent SF6 detection via electron capture (COS and CS2), and the Natusch technique (H2S). The measurements were made over the Atlantic Ocean east of North and South America during flights from NASA's Wallops Flight Center, Virginia, and Natal, Brazil, in August/September 1989. Most of the intercomparisons for H2S and CS2 were at mixing ratios less than 25 pptv and less than 10 pptv, respectively, with a maximum mixing ratio of about 100 pptv and 50 pptv, respectively. Carbonyl sulfide intercomparisons were at mixing ratios between 400 and 600 pptv. Measurements were intercompared from data bases constructed from time periods of simultaneous or overlapping measurements. Agreement among the COS techniques averaged about 5%, and individual measurements were generally within 10%. For H2S and at mixing ratio greater than 25 pptv, the instruments agreed on average to about 15%. At mixing ratios less than 25 pptv the agreement was about 5 pptv. For CS2 (mixing ratios less than 50 pptv), two techniques agreed on average to about 4 pptv, and the third exhibited a bias (relative to the other two) that varied in the range of 3-7 pptv. CS2 mixing ratios over the ocean east of Natal as measured by the gas chromatograph-mass spectrometer technique were only a few pptv and were below the detection limits of the other two techniques. The CITE 3 data are used to estimate the current uncertainty associated with aircraft measurements of COS, H2S, and CS2 in the remote troposphere.

Gregory, Gerald L.↗

NASA NTRSDate not supplied

Development and Validation of a Slosh-Based Ullage Collapse Model

Ullage collapse modeling is an essential tool for the success of spacecraft powered by cryogenic propellants. The degree of ullage collapse can have a major impact on the design of cryogenic propellant tanks as well as the mission’s concept of operations. Additional commodities (e.g., helium gas for pressure control) and their quantities are dependent on the amount of heat transfer and phase change of propellants expected during flight. Currently, high-fidelity computational fluid dynamics (CFD) with heat transfer and phase change is the most accurate method for predicting ullage collapse. CFD simulations of this kind, however, can become very costly for problems requiring large domains, long simulation times, or significant liquid motion. Consequently, there is a need for a reduced order model to provide fast responses which can be used in engineering design decisions. The proposed numerical model is a nodal approach, augmented by outputs from CFD analyses that are generated rapidly and reliably. These outputs include transient values for liquid-vapor interface area, interface velocity, and liquid position using a volume of fluid (VoF) method. There are several benefits of combining a nodal approach with slosh predictions from CFD simulations: leveraging of the Loci/STREAM-VoF solver that has been validated in high-g and low-g environments, rapid modeling of VoF with isothermal propellant simplifications and relatively coarse meshes, and improved model predictions from the nodal tool. The nodal approach, informed by the slosh predictions from CFD, assumes uniform conditions in the liquid and gas domains. Modifications to account for temperature stratification in the liquid and gas may be implemented as a future improvement. Thermodynamic changes within the tank are solved at user-defined timesteps. First, impacts due to mass entering or leaving the control volume are captured. Second, heat transfer impacts are accounted for by tracking the volume of the gas which has been contacted by liquid in that timestep and rebalancing the internal energy. Finally, phase change is approximated using the area and velocity of the interface. The tank conditions are re-computed by conserving mass and energy. Calibration of the model to several test flights and experiments are required to baseline the predictive power and uncertainty. The final product will enable designers and engineers to create quick-turnaround predictions for ullage collapse and inform design feasibility.

Computational Fluid Dynamics↗

NASA NTRS1987

Nucleogenic noble gas components in the Cape York iron meteorite

The paper reports data on neutron capture products of the secondary cosmic ray component, the inferred proton and neutron fluences, and the identification of double beta decay of Se-82 in heavily shielded samples of the Cape York iron meteorite. One purpose of this study is to develop a new chronometer for cosmic ray exposure, based on the nuclides I-129 (16 My half-life) and Xe-129 from low energy cosmic ray reactions on Te. The abundance ratio of these two nuclides permits the determination of an (effective) exposure age of 93 + or - 16 My, which represents the first exposure age datum of Cape York. The very small concentrations of spallogenic Ar-38 = 6.5 x 10 to the -10th cu cm STP/g in the metal and troilite (per g Fe) document the heavily shielded locations of the sample. An excess of Xe-129 in the troilite is shown to be entirely due to the decay of cosmic-ray-produced I-129. On the other hand, an inclusion in the troilite reveals the presence of Xe-129 from extinct I-129 and documents its about 4.5 Gy formation age. Mono-isotopic excess of Kr-82 is identified as due to beta-beta-decay of Se-82 with an inferred half-life of 1.0 x 10 to the 20th y. This represents the first beta-beta-decay product observed in a meteorite.

Murty, S. V. S.↗

NASA NTRS1991

Aerodynamic design of gas and aerosol samplers for aircraft

The aerodynamic design of airborne probes for the capture of air and aerosols is discussed. Emphasis is placed on the key parameters that affect proper sampling, such as inlet-lip design, internal duct components for low pressure drop, and exhaust geometry. Inlet designs that avoid sonic flow conditions on the lip and flow separation in the duct are shown. Cross-stream velocities of aerosols are expressed in terms of droplet density and diameter. Flow curvature, which can cause aerosols to cross streamlines and impact on probe walls, can be minimized by means of a proper inlet shape and proper probe orientation, and by avoiding bends upstream of the test section. A NASA panel code called PMARC was used successfully to compute streamlines around aircraft and probes, as well as to compute to local velocity and pressure distributions in inlets. A NACA 1-series inlet with modified lip radius was used for the airborne capture of stratospheric chlorine monoxide at high altitude and high flight speed. The device has a two-stage inlet that decelerates the inflow with little disturbance to the flow through the test section. Diffuser design, exhaust hood design, valve loss, and corner vane geometry are discussed.

Soderman, Paul T.↗