Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “N2”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Annual and Semiannual Oscillations of Thermospheric Composition in TIMED/GUVI Limb Measurements

The Global UltraViolet Imager (GUVI) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite provides a data set of vertical thermospheric composition (O, N2, and O2 densities) and temperature profiles from 2002–2007. Even though GUVI sampling is limited by orbital constraint, we demonstrated that the GUVI data set can be used to derive the altitude profiles of the amplitudes and phases of annual oscillation (AO) and semiannual oscillation (SAO), thereby providing important constraints on models seeking to explain these features. We performed a seasonal and interannual analysis of GUVI limb O, O2, and N2 densities and volume number density ratio O/N2 at constant pressure levels. These daytime observations of O and O/N2 in the lower thermosphere show a strong AO at midlatitudes and a clear SAO at lower latitudes. The global mean GUVI O/N2 number density ratio shows the AO, with slightly larger values in January than in July and a SAO with O/N2 greater during equinoxes than at the solstices. O and N2 densities on fixed pressure levels in the upper thermosphere are anticorrelated with solar extreme ultraviolet flux. On the other hand, O/N2 is smaller during solar minimum and larger during solar maximum. The thermospheric AO and SAO in composition have a constant phase with altitude throughout the thermosphere.

thermosphere composition↗
NASA NTRS2022

The Titan Haze Simulation (THS) Experiment on COSmIC. Part III. XANES Study of Laboratory Analogs of Titan Tholins

We have used the Titan Haze Simulation (THS) experimental set-up at NASA Ames’ COSmIC 19 facility to produce four laboratory analogs of Titan’s aerosols, or tholins. These tholin samples 20 were produced from four gas mixtures, representative of Titan’s atmosphere, of initial 21 compositions N2:CH4 (90:10 and 95:5) and N2:CH4:C2H2 (89.5:10:0.5 and 94.5:5:0.5) at 150 K, 22 using a plasma discharge in the stream of a jet-cooled gas expansion. Here we present an ex-situ 23 X-ray absorption near-edge structure (XANES) spectroscopy analysis of these four tholin 24 samples. The C- and N-XANES spectra show the presence of various functional groups 25 (aromatic carbon, imines, nitriles, etc.) whose abundances are correlated with (i) the relative 26 proportions between N2 and CH4, and (ii) the presence or absence of C2H2 in the initial mixtures. 27 In particular, mixtures containing C2H2 result in the formation of tholins consisting of more 28 aromatic structures and displaying larger relative amounts of imines and nitriles, but lower 29 overall nitrogen content. XANES spectroscopy also allowed for the determination of the 30 elemental C/N ratios for the four tholins, which were all found to be low (< 2.5) and consistent 31 with those measured for tholins produced in other, independent experimental set-ups. The C/N 32 ratios of tholins produced from gas mixtures that contained C2H2 (2.2–2.4) were found to be 33 about twice as large as those of tholins produced from gas mixtures that did not contain C2H234 (0.9–1.3). These new experimental results from the COSmIC/THS experiment demonstrate the 35 impact initial precursors have on the nitrogen chemistry during the formation of tholins, which 36 may help in the interpretation of observations and the development of models of Titan’s 37 atmosphere.

Titan↗
NASA NTRSDate not supplied

Interfacial thermodynamics of cryogenic fluids: The effect on non-condensable gas on fluid storage

Propellant tanks that contain cryogenic fluids (CFs) in low gravity conditions are usually pressurized with non-condensable (NC) gases for fast extraction. Unfortunately, the presence of NC gases causes CFs to exhibit higher boil-offs compared to pure CF systems. For optimal utilization of the cryogenic fuels, these higher boil-off rates must be minimized. Our goal is to quantify the effects NC gases have on the evaporation and condensation dynamics of CFs to develop strategies that mitigate the higher boil-offs. The hypothesis is that the NC gas accumulates around the CF’s liquid vapor interface in the Knudsen layer, creating a kinetic barrier for both evaporation and condensation. Testing this hypothesis with experimental methods is difficult due to the transient nature of the Knudsen layer, which is only a few nanometers thick. Furthermore, experimental capabilities are limited in low gravity conditions and extremely expensive. Accordingly, we approach this problem from a theoretical perspective. In this study, we employ molecular dynamics (MD) simulations to probe the interfacial mechanisms that affect CF’s evaporation and condensation at varying concentrations of NC gases. Specifically, we use nitrogen (N2) and oxygen (O2) as our CFs and neon (Ne) as our NC gas. Using MD simulations, we show that Ne accumulates at N2 liquid vapor interface across a wide range of Ne concentrations, thereby impeding mass transport of N2. Our simulations allow for direct computation of the molar flux as well as the mass accommodation coefficient (MAC) which can then be used as input parameters to continuum fluid dynamics (CFD) models for optimal storage tank design.

Michael Robert DeLyser↗
NASA NTRS2016

Spatial and Temporal Trends in Precambrian Nitrogen Cycling: A Mesoproterozoic Offshore Nitrate Minimum

Fixed nitrogen is an essential nutrient for eukaryotes. As N2 fixation and assimilation of nitrate are catalyzed by metalloenzymes, it has been hypothesized that in Mesoproterozoic oceans nitrate was limited in offshore environments by low trace metal concentrations and high rates of denitrification in anoxic and episodically euxinic deep water masses, restricting eukaryotes to near-shore environments and limiting their evolutionary innovation. To date this hypothesis has only been tested in the Belt Supergroup (∼1.4 Ga), with results that support an onshore-offshore nitrate gradient as a potential control on eukaryote ecology. Here we present bulk nitrogen and organic carbon isotopic data from non-isochronous cross-basinal facies across the Bangemall (∼1.5 Ga) and the Roper (∼1.4–1.5 Ga) basins to better understand the extent and variability of onshore-offshore nitrogen isotope gradients in the Mesoproterozoic. Both basins show an average ∼1-2‰ enrichment in δ-15N(sub bulk) from deep to shallow facies, with a maximum range from ~1‰ offshore to +7.5‰ onshore. Unlike the Belt basin, the Bangemall and Roper basins show some offshore δ-15N(sub bulk) values that are enriched beyond the isotopic range associated with biological N2 fixation alone. This suggests a mixture of aerobic and anaerobic metabolisms offshore. In shallow waters, where δ-15N(sub bulk) enrichment peaks, an aerobic nitrogen cycle was evidently operating. Even though isotopic signatures of aerobic nitrogen cycling are seen in all parts of the Bangemall and Roper basins, our data are consistent with a lateral gradient in nitrate availability within the photic zone, with higher concentrations in near-shore environments than offshore. The variability in δ-15N(sub bulk) values in each depositional environment and the consistently low δ-15N(sub bulk) values from Mesoproterozoic units compared to the Paleoproterozoic and Neoproterozoic suggest that nitrate concentrations in the global ocean were likely low. This trend is now seen in all three Mesoproterozoic basins so far examined, and contrasts with the Paleoproterozoic and Neoproterozoic where nearly all δ-15N(sub bulk) data plot above the N2 fixation window. Thus, we propose that the Mesoproterozoic ocean was characterized by a nitrate minimum, with the lowest concentrations in offshore environments. This inference is consistent with a Mesoproterozoic O2 decline following a temporary Paleoproterozoic O2 peak, and it further supports the idea that nitrate limitation offshore may have contributed to the restriction of photosynthetic eukaryotes to near-shore environments, delaying their rise to ecological dominance until the Neoproterozoic Era.

Mesoproterozoic↗
NASA NTRS2016

Modeling pN2 Through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures

Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth’s surface is atmospheric N2, but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth’s history with particularly low levels in the Neoarchean—presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N2 pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN2 and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN2 to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO2, and (c) atmospheric oxygenation could have initiated a stepwise pN2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N2 and O2 is a signature of an oxygen-producing biosphere.

Biosignatures↗
NASA NTRS2023

First Optical Constants of Laboratory-Generated Organic Refractory Materials (Tholins) Produced in the NASA Ames COSmIC Facility from the Visible to the Near Infrared (0.4–1.6 μm): Application to Titan’s Aerosols

We have measured the complex refractive indices, from 0.4 to 1.6μm, of five laboratory-generated organic refractory materials (tholins) produced at low temperature(150 K)using plasma chemistry in the stream of a supersonic expansion in NASA Ames’ COsmic SImulation Chamber(COSmIC)facility. Three samples were produced from N2:CH4gas precursors(with different voltages inducing different degrees of ionization in the plasma), one sample was produced from N2:CH4:C2H2, and one sample was produced from Ar:CH4in order to produce a purely carbonaceous sample. The optical constants, n and k, of the samples were determined using spectral reflectance measurements. We observe that both n and k appear to be correlated with the nitrogen content in the solid sample, with samples containing more nitrogen having higher n and k. Comparisons to previous laboratory studies and Titan aerosol optical constants derived from observations show that the COSmIC tholins with a higher nitrogen content (higher n and k)are closer analogs of Titan aerosols. We also present a new analysis of Cassini Visible Infrared Mapping Spectrometer observations of Titan’s atmosphere in the visible to near infrared using the COSmIC tholin optical constants in a radiative transfer model. The COSmIC tholin sample produced from N2:CH4with the lowest energy level has a spectral behavior that appears well suited to reproduce the observed Titan aerosol properties. This study has therefore demonstrated that this COSmIC tholin sample has valuable and promising optical properties for the analysis of Cassini’s Titan atmospheric observations.

Optical Constants↗
NASA NTRSDate not supplied

Development, Validation and Approval of A Planetary Extravehicular Activity Prebreathe Protocol: NASA Exploration Atmosphere Tests 1 & 2

INTRODUCTION: Denitrogenation prebreathe protocols used to mitigate DCS risk for Space Shuttle and International Space Station EVAs are validated for the microgravity environment, but the significantly increased risk of DCS during equivalent ambulatory surface EVAs make these protocols inapplicable to planetary/Lunar missions as planned by the Artemis program. Living in an “Exploration Atmosphere” of 56.5 kPa (8.2 psia), 34% O2, 66% N2 has been recommended by NASA for future Moon and Mars missions as a compromise that balances pre-EVA prebreathe duration, hypoxia, and flammability risk, assuming a 29.6 kPa (4.3 psi) spacesuit. A prebreathe validation campaign at NASA’s Johnson Space Center in 2022–2023 has aimed to validate the prebreathe durations and is being operationalized by NASA for use in upcoming Lunar EVAs. METHODS: Twelve volunteers lived in a hyboparic chamber for 11 days with an “exploration atmosphere” of 56.6kPa/34% O2 66% N2. Subjects acclimated to this atmosphere for 48 hrs and thereafter participated in five 6-hour simulated EVAs at 34kPa/85% O2 / 15% N2 over the course of 11 days. Prior to each simulated EVA, subjects underwent a 20-minute prebreathe at 85% O2. The EVA simulation was designed to include tasks that are physically and ergonomically representative of future planetary EVAs, proportionate to the subject’s VO2max. Decompression stress was evaluated during the simulated EVA by serial doppler and echocardiographs alternating every 15 min, as well as clinical monitoring for DCS signs/symptoms. Venous gas emboli (VGE) and DCS outcomes were verified against NASA Standard 3001, which guides allowable prebreathe protocol acceptance criteria. RESULTS AND DISCUSSION: Venous gas emboli (VGE) were identified during EVAs. No Grade IV VGE were observed. Two cases of mild, Type I DCS were identified in the subjects over the course of 50 EVA exposures. Ten planned EVA exposures were eliminated due to mask fit, metabolic rate, or subject safety concerns. One subject was removed from the study due to presence of left ventricular VGE. Additionally, two doppler techs also experienced DCS, and one case of hypoxia was noted. All cases of DCS resolved with treatment. No cases of severe DCS were observed. The observed incidence (4%, 1.1–13.5% at 95% confidence) met the NASA Standard 3001 criteria leading to the transition of this protocol from research to operational use for upcoming Lunar missions.

Exploration Atmosphere↗
NASA NTRSDate not supplied

Trace Oxygen Measurements of Asteroid Sample Storage Desiccators

The Astromaterials Curation facility at the NASA Johnson Space Center is currently curating more than 120 g of carbonaceous asteroid Bennu material as well as over 500 mg of asteroid Ryugu [1 and 2]. These astromaterials are stored in isolating desiccators and gloveboxes under a continuous purge of pure (<1 ppm O 2 ) gaseous nitrogen. The oxygen and moisture concentrations in our OSIRIS-REx sample processing gloveboxes are continuously monitored via integrated sensors; however, our sample storage desiccators lack integrated oxygen and humidity sensors. In previous studies, we used PreSens Fibox 4 trace oxygen meters and optochemical PSt9 spot sensors to measure the oxygen concentrations in candidate asteroid sample containers that had been sealed in nitrogen; we determined that Eagle stainless steel containers inhibit the ingress of external oxygen for several weeks [3]. This optochemical sensor technology allowed us to take precise, contactless measurements within a trace range of 0 to 200 ppmv O 2 . The effectiveness of the trace oxygen sensors in our container experiments inspired us to utilize them to assess the performance of our desiccators that previously lacked trace oxygen monitoring. In this study, our goal was to determine the quality of the nitrogen purge in the isolating desiccator under normal operating conditions by measuring the trace oxygen content. Utilizing optochemical sensor technology, we determined how long the oxygen concentration takes to reach an equilibrium in the desiccator; that is, determine the rate at which the oxygen diffusion into the desiccator equals the rate at which oxygen diffuses out of the desiccator via N2 purge. Additionally, we wanted to determine the oxygen concentration at this equilibrium, the state in which our desiccators are in during normal operating conditions. We tested a custom three chamber desiccator manufactured by Germfree using a PSt9 trace oxygen sensor spot that was mounted into a ¼” National Pipe Tapered (NPT) metal flow-through cell and attached it to the desiccator exhaust. The desiccator consists of top, middle, and bottom isolating chambers. The top chamber door was opened for several minutes to simulate a sample exchange, it was sealed, and then purged ~15 Standard Cubic Feet per Hour (SCFH). Oxygen measurements were automatically recorded via the Fibox 4 trace oxygen meter in 5-minute intervals over the course of a 24-hour period. Our results indicate the desiccator reached an equilibrium value of 10-15 ppm O 2 after ~5 hours (Fig. 1). This data allows us to explore standards for purging and exchange protocols that can be applied to similar types of desiccators in Hayabusa2, OSIRIS-REx, and for sample return collections. The assessment of the internal gaseous compositions of desiccators also allows us to share with the community the N 2 environment in which many of our asteroid samples and hardware are securely curated. Future measurements will include other nitrogen flow rates and measuring the trace oxygen concentration as a function of time for the levels of the previous commercial desiccator in which the Hayabusa2 sample collection was stored. We will also analyze how long the desiccators hold N2 after being disconnected from their N2 source, an extended measurement for sample security reassurance.

Curation↗
NASA NTRS1971

Gain and power of CO2 gasdynamic lasers.

This paper presents experimental and theoretical studies of the small signal gain and the radiant power for one configuration of CO2 gasdynamic lasers to define the optimum-gas temperature, pressure and gas compositions for the gain and the laser power. The laser was operated with two gas mixtures (CO2-N2-He and CO2-N2-H2O) at temperatures of 800-2200 deg K, pressures of 2-16 atm, and a wide range of gas compositions. For this laser optimum gas temperatures were roughly 1500-1600 deg K for gain and more than 2200 deg K for power. It was found that the gasdynamic laser would not oscillate for He or H2O concentrations of less than 10% and 1%, respectively. The various kinetic processes for establishing gain and the various laser cavity parameters that determine laser power were examined. The theories were assessed for their ability to predict gain and power. In most cases, the gain theory gave excellent quantitative results whereas the power theory gave only qualitative results. Laser power of nearly 2 kw was obtained.

Lee, G.↗
NASA NTRS1972

Foreign-gas broadening of nitrous oxide absorption lines.

We have measured the foreign-gas broadening coefficients for collisional broadening of lines in the nu-3 fundamental of N2O by He, Ne, Ar, Kr, Xe, H2, D2, and CH4. These coefficients, which give the ratio of the line-broadening ability of these gases to the line-broadening ability of N2, can be used with recent measurements and calculations of N2 broadening to obtain optical collision cross sections.

Tubbs, L. D.↗
NASA NTRS1972

Magnetic storm characteristics of the thermosphere

Energy and diffusive mass transport associated with the thermospheric circulation are considered in a self-consistent, though mathematically relatively simple form to describe in a three-dimensional two-constituent model magnetic storm characteristics in composition (N2, O, and He), temperature and mass-density. It is shown that during disturbed conditions the latitudinal variations of composition and gas temperature T sub g reflect the local nature of the magnetic storm heat input assumed to be primarily confined to the auroral zones. Thereby T sub g and N2 increase, He decreases and O remains constant through the auroral zones at exospheric heights (due to the superposition of temperature and diffusion effects) in agreement with OGO-6 mass spectrometer measurements. In contrast, the magnetic storm response in the total mass density is characterized by a strong world-wide component and a relatively insignificant increase toward the poles with the density peak occurring between two (poles) and eight (equator) hours after the maximum energy input, in substantial agreement with satellite drag data.

Mayr, H. G.↗
NASA NTRS1973

Evaluation of an electrochemical N2/H2 gas separator

A program was successfully completed to evaluate an electrochemical nitrogen/hydrogen (N2/H2) separator for use in a spacecraft nitrogen (N2) generator. Based on the technical data obtained a N2/H2 separator subsystem consisting of an organic polymer gas permeator first stage and an electrochemical second and third stage was estimated to have the lowest total spared equivalent weight, 257 kg (566 lb), for a 15 lb/day N2 generation rate. A pre-design analysis of the electrochemical N2/H2 separator revealed that its use as a first stage resulted in too high a power requirement to be competitive with the organic polymer membrane and the palladium-silver membrane separation methods. As a result, program emphasis was placed on evaluating the electrochemical. A parametric test program characterized cell performance and established second- and third-stage electrochemical N2/H2 separator operating conditions. A design verification test was completed on the second and third stages. The second stage was then successfully endurance tested for 200 hours.

Marshall, R. D.↗
NASA NTRS1972

Hydrogen and oxygen sensor development

A reliable and low cost gas sensor was investigated for instantaneously detecting H2 in N2, H2 in air, and O2 in N2. The major portion of the research was spent in developing a sensor which would instantaneously detect H2 to + or - 50 ppm even in the presence of trace amounts of other gases. The experimental procedures used to provide the performance characteristics for the various oscillators are discussed describing the equipment with help of schematics and photographs where applicable. The resulting performance is given in graphical form. In some cases both hydrogen and helium may be present and since both of them effect gas sensors similarly, a method was found to determine the concentration of each. The methods developed are grouped into the following four broad categories: pure metal response, variation in heat conductivity, reduction methods, and exotic processes. From the above it was decided for the present to use a copper oxide reduction process as this process was demonstrated to be capable of determining the concentrations of hydrogen and helium respectively in a gas mixture with air or nitrogen.

Farber, E. A.↗
NASA NTRS1972

Microphysical, microchemical, and adhesive properties of lunar material. III - Gas interaction with lunar material.

Gas adsorption measurements on an Apollo 12 ultrahigh vacuum-stored sample and Apollo 14 and 15 N2-stored samples, show that the cosmic ray track and solar wind damaged surface of lunar soil is very reactive. Room temperature monolayer adsorption of N2 by the Apollo 12 sample at 0.0001 atm was observed. Gas evolution of Apollo 14 lunar soil at liquid nitrogen temperature during adsorption/desorption cycling is probably due to cosmic ray track stored energy release accompanied by solar gas release from depths of 100-200 nm.

Grossman, J. J.↗
NASA NTRS1973

Magnetic storm characteristics of the thermosphere.

Energy and diffusive mass transport associated with the thermospheric circulation are considered in a self-consistent, though mathematically relatively simple, form to describe in a three-dimensional two-constituent model magnetic storm characteristics in composition (N2, O, and He), temperature, and mass-density. It is shown that during disturbed conditions the latitudinal variations of composition and gas temperature reflect the local nature of the magnetic storm heat input assumed to be primarily confined to the auroral zones. Thereby gas temperature and N2 increase, He decreases, and O remains constant through the auroral zones at exospheric heights (due to the superposition of temperature and diffusion effects) in agreement with Ogo 6 mass spectrometer measurements. In contrast, the magnetic storm response in the total mass density is characterized by a strong worldwide component and a relatively insignificant increase toward the poles.

Mayr, H. G.↗
NASA NTRS1973

Equatorial phenomena in neutral thermospheric composition.

Several interesting phenomena relating to the equatorial ionosphere have been observed in the data from the OGO-6 mass spectrometer. The diurnal variations during equinox at an altitude of 450 km show the N2 and O densities peaking near 1500 hr while He peaks near 1000 hr. The latitudinal variation in N2 during the day is very similar to the F-region electron density exhibiting the well known features of the ionospheric anomaly. During periods of intense geomagnetic disturbance (e.g. the large storm of 8 March 1970), the low latitude thermospheric temperature increases on the order of 50-150 K, while at mid latitudes, increases of more than 1000 K are observed.

Reber, C. A.↗
NASA NTRS1973

Composition of the earth's atmosphere by shock-layer radiometry during the PAET entry probe experiment.

A determination of the composition of the earth's atmosphere obtained from onboard radiometer measurements of the spectra emitted from the bow shock layer of a high-speed entry probe is reported. The N2, O2, CO2, and noble gas concentrations in the earth's atmosphere were determined to good accuracy by this technique. The results demonstrate unequivocally the feasibility of determining the composition of an unknown planetary atmosphere by means of a multichannel radiometer viewing optical emission from the heated atmospheric gases in the region between the bow shock wave and the vehicle surface. The spectral locations in this experiment were preselected to enable the observation of CN violet, N2(+) first negative and atomic oxygen emission at 3870, 3910, and 7775 A, respectively. The atmospheric gases were heated and compressed by the shock wave to a peak temperature of about 6100 K and a corresponding pressure of 0.4 atm. Complete descriptions of the data analysis technique and the onboard radiometer and its calibration are given.

Whiting, E. E.↗
NASA NTRS1974

Design development and test: Two-gas atmosphere control subsystem

An atmosphere control subsystem (ACS) was developed for NASA-IBJSC which is designed to measure the major atmospheric constituents in the manned cabin of the space shuttle orbiter and control the addition of oxygen and nitrogen to maintain the partial pressures of these gases within very close limits. The ACS includes a mass spectrometer sensor (MSS) which analyzes the atmosphere of a shuttle vehicle pressurized cabin, and an electronic control assembly (ECA). The MSS was built and tested to meet the requirements for flight equipment for the M-171 Metabolic Analyzer experiment for the Skylab flight program. The instrument analyzes an atmospheric gas sample and produces continuous 0-5 vdc analog signals proportional to the partial pressures of H2, O2, N2, H2O, CO2 and total hydrocarbons having a m/e ratio between 50 and 120. It accepts signals from the MSS proportional to the partial pressures of N2 and O2 and controls the supply of these gases to the closed cabin.

Jackson, J. K.↗