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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Nitrogen threshold experiment

In order to obtain data on Earth geologic processes associated with wind erosion, Mar's and Venus' atmospheres were simulated. Experiments were designed to observe the effects of pressure, gravity, and density on sand movement. An experiment designed to test the operator variance was a comparative test between nitrogen and carbon dioxide. Pressure and therefore density was increased until threshold was noted. Threshold was determined at precisely the same densities of the two gases. If viscosity were a contributing factor in grain saltation the effect would be noted at low pressures. The experiment showed no such variance between carbon dioxide and nitrogen runs for low pressure (density). The largest difference in viscosity between carbon dioxide and nitrogen occurs at low pressures (densities).

Treat, C. L.↗
NASA NTRS1984

The global distribution of thermospheric odd nitrogen for solstice conditions during solar cycle minimum

A two-dimensional model of odd nitrogen in the thermosphere and upper mesosphere is described. The global distributions of nitric oxide and atomic nitrogen are calculated for the solstice period for quiet and moderate magnetic activity during the solar minimum period. The effect of thermospheric transport by winds is investigated along with the importance of particle-induced ionization in the auroral zones. The results are compared with rocket and satellite measurements, and the sensitivity of the model to eddy diffusion and neutral winds is investigated. Downward fluxes of NO into the mesosphere are given, and their importance for stratospheric ozone is discussed. The results show that the summer-to-winter pole meridional circulation transports both NO and N(S-4) across the solar terminator into the polar night region where there is a downward vertical transport toward the mesosphere. The model shows that odd nitrogen densities at high winter latitudes are entirely controlled by particle precipitation and transport processes.

Gerard, J.-C.↗
NASA NTRS1984

The case for a Martian origin of the shergottites - Nitrogen and noble gases in EETA 79001

Nitrogen and noble gases have been measured in samples of a glass inclusion and its surrounding basaltic matrix in an Antarctic shergottite meteorite (EETA 79001). The nitrogen component was found trapped in the glass, but not the matrix, having a value of delta 15-N = +190 per mil. Ratios between abundances of Ar-40 and N-14, N-15 and N-14 in the glass are consistent with the dilution of a Martian atmospheric component. The trapped noble gases in the glass are similar to elemental and isotopic compositions measured in Mars atmosphere by the Viking lander, and are in general agreement with previous measurements. It is suggested that a sample of Martian atmosphere has been caught in the EETA 79001 glass, and that other shergottite, nakhilite, and chassignite meteorites with similar features probably also originated on Mars. A table is presented which lists the abundances of nitrogen and the noble gases found in the non-glassy matrix and in the EETA 79001 glass.

Becker, R. H.↗
NASA NTRS1984

Powder containing 2H-type silicon carbide produced by reacting silicon dioxide and carbon powder in nitrogen atmosphere in the presence of aluminum

The production of powder which contains silicon carbide consisting of 40% of 2H-type silicon carbide, beta type silicon carbide and less than 3% of nitrogen is discussed. The reaction temperature to produce the powder containing 40% of 2H-type silicon carbide is set at above 1550 degrees C in an atmosphere of aluminum or aluminum compounds and nitrogen gas or an antioxidation atmosphere containing nitrogen gas. The mixture ratio of silicon dioxide and carbon powder is 0.55 - 1:2.0 and the contents of aluminum or aluminum compounds within silicon dioxide is less than 3% in weight.

Kuramoto, N.↗
NASA NTRS1984

Flow of nitrogen-pressurized Halon 1301 in fire extinguishing systems

Halon 1301 which is a halocarbon fire extinguishing agent (CBrF3) used by the U.S. Army for vehicle fire suppression is discussed. Halon 1301 is discharged under nitrogen pressure, and the Halon-nitrogen mixture is a two phase, two component mixture that obeys compressible fluid laws and exhibits choking effects. A computer model was developed to analyze the discharge of Halon and nitrogen from a storage bottle through pipes and nozzles. The model agrees well with data from Halon 1301 discharge tests. The discharge time depends mainly on nozzle area and pipe volume, for given initial conditions. Graphs were developed for estimating discharge times. A nozzle employing multiple concentric converging/diverging nozzles was developed which gave hemispherical coverage.

Elliott, D. G.↗
NASA NTRS1984

Lightning - Estimates of the rates of energy dissipation and nitrogen fixation

The nitrogen needed by plants can normally not be directly obtained from the nitrogen present in molecular form in the atmosphere. The reason for this situation is related to the great energy required to break the N-N bond. Only a few organisms, such as algae and certain bacteria, can 'fix' nitrogen. An abiological process for breaking the N-N bond is provided by lightning. The present investigation is concerned with this possibility. It is found that lightning produces approximately 2.6 x 10 to the 9th kg N per year. There are, however, uncertainties, which are mainly related to the energy of a lightning flash.

Borucki, W. J.↗
NASA NTRS1987

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a sampling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less effected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Ingebo, Robert D.↗
NASA NTRS1987

An intercomparison of nitrogen-containing species in Nimbus 7 LIMS and SAMS data

Odd-nitrogen chemistry and transport are analyzed using a two-dimensional model and Nimbus 7 data. The Nimbus 7 data include: measurements of O3, NO2, HNO3, H2O, and temperature by the LIMS instrument; N2O, CH4, and temperature measurements by the SAMS instrument; and O3 data from the SBUV instrument. The characteristics of the two-dimensional model used in the study, a modified Guthrie et al. (1984) model, are described. NO2 and HNO3 are calculated using the two-dimensional model, and the computed data are compared with the LIMS NO2 and HNO3 measurements. The model uncertainties are computed based on the photochemical equilibrium assumption, and the role of stratospheric dynamics in determining NO2 and HNO3 is discussed. It is observed that there is good correlation between the LIMS and model data in the upper stratosphere; however, the data do not correspond in the lower stratosphere. The effect of nitrogen sources, such as lightning, on the stratospheric odd nitrogen distribution is examined.

Jackman, Charles H.↗
NASA NTRS1987

Nitrogen recombination on high-temperature reusable surface insulation and the analysis of its effect on surface catalysis

The energy transfer catalytic recombination coefficients for nitrogen and oxygen on a borosilicate glass are determined in nitrogen and air hypersonic arc jet streams. These data, obtained from a reacting boundary-layer analysis with first-order surface reaction kinetics, compare well with earlier results from a Goulard frozen boundary-layer model up to 1600 K. The apparent surface recombination rates increase up to 1600 K, then begin to decrease. To illustrate the effects of temperature and nitrogen dissociation on energy transfer to the glass, a diffusional heat-flux is calculated using the present results from 1450 K up to 1850 K. This diffusional heat-flux is the contribution to the total heating rate by atom recombination, and is used to compare the present results with coefficients from three previous studies.

Kolodziej, Paul↗
NASA NTRS1987

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop-size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a smapling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less affected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Ingebo, Robert D.↗
NASA NTRS1988

Measurements of air-broadened and nitrogen-broadened half-widths and shifts of ozone lines near 9 microns

Air- and nitrogen-broadened half-widths and line shifts at room temperature for more than 60 individual vibration-rotation transitions in the nu1 fundamental band of (O-16)3 and several transitions in the nu3 band were determined from infrared absorption spectra. These spectra were recorded at 0.005/cm resolution with a Fourier-transform spectrometer. A tunable-diode-laser spectrometer operating in the 1090-1150/cm region was also used to record data on oxygen-, nitrogen-, and air-broadened half-widths for selected individual transitions. The nitrogen- and air-broadened half-widths determined by these two different measurement techniques are consistent to within 4 percent. The results are in good agreement with other published measurements and calculations.

Smith, M. A. H.↗
NASA NTRS1988

Isotopic composition of cosmic-ray boron and nitrogen

New measurements of the cosmic-ray boron and nitrogen isotopes at earth and of the elemental abundances of boron, carbon, nitrogen, and oxygen are presented. A region of mutually allowed values for the cosmic-ray nitrogen source ratios is determined, and the cosmic-ray escape mean free path is determined as a function of energy using a leaky box model for cosmic-ray propagation in the Galaxy. Relative to O-16, a N-15 source abundance consistent with solar system composition and a N-14 source abundance which is a factor of about three underabundant relative to the solar value are found.

Krombel, K. E.↗
NASA NTRS1988

Laboratory studies of irradiated nitrogen-methane mixtures - Applications to Triton

The characteristics of the near-IR spectrum of Triton is addressed in view of 0.8-2.5 micron laboratory transmission spectra obtained for methane dissolved in liquid nitrogen. It is found that, for methane concentrations greater than 3 percent of the saturation value, the collision-induced, 2.152-micron first-overtone band of molecular nitrogen is overshadowed by the methane band centered at 2.3 microns. While gamma-radiolysis of nitrogen-methane mixtures generates an unstable precipitate whose yellowish color is qualitatively similar to the yellow color of Triton, no specific absorption band in the precipitate can be unambiguously identified on Triton.

Piscitelli, J. R.↗
NASA NTRS1988

Remote sensing of canopy chemistry and nitrogen cycling in temperate forest ecosystems

The use of images acquired by the Airborne Imaging Spectrometer, an experimental high-spectral resolution imaging sensor developed by NASA, to estimate the lignin concentration of whole forest canopies in Wisconsin is reported. The observed strong relationship between canopy lignin concentration and nitrogen availability in seven undisturbed forest ecosystems on Blackhawk Island, Wisconsin, suggests that canopy lignin may serve as an index for site nitrogen status. This predictive relationship presents the opportunity to estimate nitrogen-cycling rates across forested landscapes through remote sensing.

Wessman, Carol A.↗
NASA NTRS1989

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen

One of the most striking differences between the conditions on early Mars and earth was a low (18 mb) partial pressure of N2 (pN2) on early Mars, as opposed to 780 mb N2 on earth. To investigate the possibility of biological nitrogen fixation under conditions of early Mars, experiments were carried out on the growth of Azotobacter vinelandii and Azomonas agilis in nitrogen-free synthetic medium under various partial pressures of N2 (ranging from 780 to 0 mb). It was found that, although the biomass, cell number, and growth rate of these bacteria decreased with decreasing pN2 values below pN2 of 400 mb, both microorganisms were capable of growing at pN2 as low as 5 mb (but not at of below 1 mb), indicating that biological fixation of nitrogen could have occurred on primordial Mars.

Klingler, J. M.↗
NASA NTRS1990

Acquisition and correlation of cryogenic nitrogen mass flow data through a multiple orifice Joule-Thomson device

Liquid nitrogen mass flow rate, pressure drop, and temperature drop data were obtained for a series of multiple orifice Joule-Thomson devices, known as Visco Jets, over a wide range of flow resistance. The test rig used to acquire the data was designed to minimize heat transfer so that fluid expansion through the Visco Jets would be isenthalpic. The data include a range of fluid inlet pressures from 30 to 60 psia, fluid inlet temperatures from 118 to 164 R, outlet pressures from 2.8 to 55.8 psia, outlet temperatures from 117 to 162 R and flow rate from 0.04 to 4.0 lbm/hr of nitrogen. A flow rate equation supplied by the manufacturer was found to accurately predict single-phase (noncavitating) liquid nitrogen flow through the Visco Jets. For cavitating flow, the manufacturer's equation was found to be inaccurate. Greatly improved results were achieved with a modified version of the single-phase equation. The modification consists of a multiplication factor to the manufacturer's equation equal to one minus the downstream quality on an isenthalpic expansion of the fluid across the Visco Jet. For a range of flow resistances represented by Visco Jet Lohm ratings between 17,600 and 80,000, 100 percent of the single-phase data and 85 percent of the two-phase data fall within + or - 10 percent of predicted values.

Papell, S. Stephen↗
NASA NTRS1990

Cost-effective use of liquid nitrogen in cryogenic wind tunnels, phase 2

Cryogenic seal tests were performed and Rulon A was selected for the subject nutating positive displacement expander. A four-chamber expander was designed and fabricated. A nitrogen reliquefier flow system was also designed and constructed for testing the cold expander. Initial tests were unsatisfactory because of high internal friction attributed to nutating Rulon inlet and outlet valve plates. Replacement of the nutating valves with cam-actuated poppet valves improved performance. However, no net nitrogen reliquefaction was achieved due to high internal friction. Computer software was developed for accurate calculation of nitrogen reliquefaction from a system such as that proposed. These calculations indicated that practical reliquefaction rates of 15 to 19 percent could be obtained. Due to mechanical problems, the nutating expander did not demonstrate its feasibility nor that of the system. It was concluded that redesign and testing of a smaller nutating expander was required to prove concept feasibility.

Mcintosh, Glen E.↗
NASA NTRS1990

Orbital transfer vehicle oxygen turbopump technology. Volume 2: Nitrogen and ambient oxygen testing

The testing of a rocket engine oxygen turbopump using high pressure ambient temperature nitrogen and oxygen as the turbine drive gas in separate test series is discussed. The pumped fluid was liquid nitrogen or liquid oxygen. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas which will be demonstrated in a subsequent test series. Following bearing tests, the TPA was finish machined (impeller blading and inlet/outlet ports). Testing started on 15 February 1989 and was successfully concluded on 21 March 1989. Testing started using nitrogen to reduce the ignition hazard during initial TPA checkout. The Hydrostatic Bearing System requires a Bearing Pressurization System. Initial testing used a separate bearing supply to prevent a rubbing start. Two test series were successfully completed with the bearing assist supplied only by the pump second stage output which entailed a rubbing start until pump pressure builds up. The final test series used ambient oxygen drive and no external bearing assist. Total operating time was 2268 seconds. There were 14 starts without bearing assist and operating speeds up to 80,000 rpm were logged. Teardown examination showed some smearing of silverplated bearing surfaces but no exposure of the underlying monel material. There was no evidence of melting or oxidation due to the oxygen exposure. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The only anomaly was higher than predicted flow losses which were attributed to a faulty ring seal. The TPA will be refurbished prior to the 400 F oxygen test series but its condition is acceptable, as is, for continued operating. This was a highly successful test program.

Brannam, R. J.↗