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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Determination of the sources and sinks of N/+/ ions in the thermosphere

Measurements of atmospheric parameters made by the Atmosphere Explorer-C satellite used to identify mechanisms for the production and loss of N(+) ions in the ionosphere are presented. Photo-dissociative ionization of N2 is the main source below 250 km. Above 250 km the reaction O(+)(4S) + N(2D) yields N(+)(3P) + O(3P) is dominant, and a possible minor source of N(+) is the reaction O(+)(2P) + N2 yields N(+) + NO. Photoionization of N(4S) and dissociative charge exchange of He(+) with N2 constitute detectable sources above 350 km. Charge exchange of N(+) with O is a significant sink above 300 km, and the rate coefficients for these reactions are derived.

Torr, D. G.↗
NASA NTRS1979

Determination of the auroral O/1S/ production sources from coordinated rocket and satellite measurements

This paper examines the auroral excitation mechanisms using data collected in a satellite/rocket/aurora coordination. Past theories considered that variation with altitude of the emission from the O(1S) state is the same as that from the N2(+) first negative band system. Actually, the source function for O(1S) does not covary with N2(+) but has a smaller scale height. The covariation is due to quenching of the source function by O(3P). The steadiness of the aurora in a flight of the Michigan Airglow Payload allows the profile to be differentiated for direct comparison with theory. It is concluded that when most of the relevant variables for production of the O(1S) state are simultaneously measured in aurora, the major source functions are dissociative recombination of O2(+) above 210 km to apogee at 250 km, and below 180 km the energy transfer from N2(A3sigma) in the oxygen atom quenching reaction.

Sharp, W. E.↗
NASA NTRS1979

Some effects of gas adsorption on the high temperature volatile release behavior of a terrestrial basalt, tektite and lunar soil

Mass pyrograms obtained from high-temperature, mass psectrometric pyrolysis of a glassy theoleiitic submarine basalt and a tektite, ground in air to less than 64 microns, have shown N2 and SO release patterns very similar to those from the pyrolysis of mature lunar soil fines. The N2 and CO release behavior from the terrestrial samples reproduces the biomodal, high-temperature (approximately 700 and 1050 C) features from the lunar samples. Unground portions of the basalt and tektite show no release of N2 and CO during pyrolysis. Grinding also alters the release behavior and absolute amounts of H2O and CO2. It is suggested that adsorption of atmospheric gases in addition to solar wind implantation of ions may account for the wide range of values in previously reported concentrations of carbon and nitrogen from lunar fines.

Graham, D. G.↗
NASA NTRS1980

Satellite studies of N/D-2/ emission and ion chemistry in aurorae

The incident particle flux ion and neutral composition data taken on the AE-D satellite have been used to investigate the quantal emission of N2(plus) at 4278 A, N(D-2) at 5200 A, and the ion chemistry in aurorae. The results of a time dependent auroral model have been compared to the data. The calculated 4278 A emission of N2(plus), the 5200 A emission of N(D-2), the densities of O2(plus), NO(plus), N2(plus), O(plus), and the electron density are generally in agreement with the measured values. These results are consistent with the branching ratios and quenching rates deduced from previous studies of the N(D-2) densities in the day-time, mid-latitude ionosphere. It is found that in an auroral arc, the measured atomic oxygen density is lower than predicted by the MSIS model.

Rusch, D. W.↗
NASA NTRS1980

Causes of the F region winter anomaly

Measurements made by the Atmosphere Explorer satellites are used to determine the causes of the F-region winter anomaly, i.e., seasonal variations which result in peak electron densities which are larger in winter than in summer. It is found that for the data examined there are three causes of the winter anomaly: (1) seasonal changes in neutral composition; (2) an increase in the vibrational temperature of N2 and hence in the rate coefficient for the reaction O(+)(4S) + N2 yields NO(+) + N; (3) an increase in winter in the production of O(+)(4S) due to enhanced electron quenching of O(+)(2D). The presence of vibrational excitation is inferred from an increase in the rate coefficient for the reaction O(+) + N2 yields NO(+) + N from winter to summer at heights above 260 km. It is demonstrated quantitatively that the initial increase in electron density produced in winter by causes (1) and (2) results in an increase in the quenching of O(+)(4S), thereby enhancing the source of O(+)(4S) ions. It is estimated that causes (1) to (3) account for approximately 55%, 20% and 25% respectively of the seasonal change in O(+)(4S) from summer to winter at solar minimum.

Torr, D. G.↗
NASA NTRS1980

The chemistry of excited NO/+/ in an aurora

The six most significant production and seven most significant loss mechanisms are identified for NO(+)(a3 Sigma) in the aurora. Rate constants are given for these reactions as well as for the 14 most important reactions competing with the production of NO(+)(a). Using available data and certain crucial deductions on chemical reaction rates to simulate a number of altitude profiles, it is concluded that the two predominant sources of NO(+)(a3 Sigma) are probably N(+) + O2 yields NO(+)(a) + O and N2(+) + NO yields NO(+)(a) + N2. Radiative decay is not the primary loss mechanism but can dominate above 150 km. Destruction via charge exchange with N2 and O are most important below 150 km.

Young, E. R.↗
NASA NTRS1982

Spectroscopic requirements for HALOE: An analysis of the HCl and HF channels

Spectral line parameters that have absorption features within the HCl and HF channels of the Halogen Occultation Experiment (HALOE) were evaluated. Line positions and identification of stratospheric and solar absorption features in both channels are presented based on an analysis of high-resolution, balloon-borne solar occultation spectra. For the relevant HCl and HF lines and for transitions of the interfering species, the accuracy of the following spectral parameters was assessed: line positions, line strengths, lower state energies, air-broadened collisional half-widths, and temperature dependence of the air-broadened half-widths. In addition, since the HALOE instrument and calibration cells are filled with mixtures of HCl in N2 and HF in N2, the self-broadened and N2-broadened HF and HCl half-widths were also considered.

Rinsland, C. P.↗
NASA NTRS1981

Energy accommodation of 5-50 eV ions within an enclosure

Beams of 5-50 eV He(+), Ar(+), Ne(+), O(+), and N2(+) ions were directed into an aluminum sphere, and the equilibrium number density of the atom or molecules was measured inside the sphere using a quadrupole mass spectrometer and signal averaging techniques. The equilibrium number density is inversely proportional to the average speed of the atoms; thus, the results are expressed in terms of the speed ratio, R = V(i)/V(s), where V(i) is the average speed within the enclosure, and V(s) is the average speed of atoms fully accommodated to the temperature of the wall. The speed ratios vary between 1.0 and 1.8. For N2, several values of R were less than 1; this was largely due to desorbed N2. There was no detectable number density for O, which is explained by the reaction of O with the surface.

Humphris, R. R.↗
NASA NTRS1982

EUV emission from Titan's upper atmosphere - Voyager 1 encounter

Most of the observed emission short of Lyman-alpha is shown to be accounted for by electron impact on N2 above 3600 km, in an analysis of Titan's EUV emission spectra obtained at the Voyager 1 encounter. It is determined that N2 is the major component of Titan's upper atmosphere, with 3900-km upper limit mixing ratios of NeI, ArI, CO, H2, and HI of 0.01, 0.06, 0.05, 0.06 and 0.1, respectively. Magnetospheric electron precipitation produces an average dayside electron density of about 3000/cu cm between 3600 and 4000 km, which is the region of bright limb emission, and magnetospheric electron impact dissociation of N2 generates an N atom escape rate of 3 x 10 to the 26th/sec from Titan's exosphere when Titan is within Saturn's magnetosphere.

Strobel, D. F.↗
NASA NTRS1982

Conversion of blackbody radiation into laser energy

By employing detailed kinetic models, three concepts which utilize a blackbody cavity for the conversion of solar energy into laser energy using a CO2 lasant are analyzed and compared. In the first, the blackbody radiation is used to excite flowing CO2 directly. The second and third employ a mixing laser concept with CO and N2 being the donor gases. The CO is optically pumped while thermal heating excites the N2. Blackbody temperatures ranging from 1500 deg K - 2500 deg K are considered. Based on calculated laser power output per unit flow rate of CO2, it appears that the N2-CO2 mixing laser is the most attractive system.

Mcinville, R. M.↗
NASA NTRS1982

SUMS calibration test report

Calibration was performed on the shuttle upper atmosphere mass spectrometer (SUMS). The results of the calibration and the as run test procedures are presented. The output data is described, and engineering data conversion factors, tables and curves, and calibration on instrument gauges are included. Static calibration results which include: instrument sensitive versus external pressure for N2 and O2, data from each scan of calibration, data plots from N2 and O2, and sensitivity of SUMS at inlet for N2 and O2, and ratios of 14/28 for nitrogen and 16/32 for oxygen are given.

Robertson, G.↗
NASA NTRS1982

The spectrum of Titan in the far-infrared and microwave regions

The pressure-induced absorptions of gaseous nitrogen (N2) and methane (CH4) are computed on the basis of the collisional lineshape theory of Birnbaum and Cohen (1976). Laboratory data at 300 and 124 K for N2 and at 296 and 195 K for CH4 are used to determine the collisional time constants and their temperature dependence. The spectrum of Titan from the microwave to the far-infrared region (0.1-600/cm) is then modeled using these opacities and a temperature profile of Titan's atmosphere derived from the Voyager 1 radio occultation experiment. The model atmosphere is composed of N2 and CH4, their relative proportions being determined by the vapor pressure law of CH4. A model with gaseous opacity alone is ruled out by the far-infrared observations. An additional opacity, thought to be associated with a methane cloud, is confirmed. The effective temperature of Titan is estimated at 83.2 plus or minus 1.4 K.

Courtin, R.↗
NASA NTRS1983

Collision-induced absorption in the far infrared spectrum of Titan

The effects of collision-induced absorption on the far infrared spectrum of Titan have been investigated. After a review of the procedure for the theoretical calculation of the N2 translation-rotational spectrum, new results for the temperature range o 70 to 120 K are reported. These are used as input data for a simple atmospheric model in order to compute the far infrared radiance, brightness temperature, and specral limb function. This source of opacity alone is not capable of explaining the Voyager results. When the collision-induced methane is included, the results are in closer agreement in the range between 200 and 300/cm, suggesting that a more complete treatment of collision-induced absorption including particularly CH4-N2, N2-H2, and H2-H2 results, may provide sufficient opacity to reduce or obviate the need for opacities due to clouds or aerosols in order to explain the observed spectra.

Hunt, J. L.↗
NASA NTRS1984

Evaluation of propellant tank insulation concepts for low-thrust chemical propulsion systems

An analytical evaluation of cryogenic propellant tank insulations for liquid oxygen/liquid hydrogen low-thrust 2224N (500 lbf) propulsion systems (LTPS) was conducted. The insulation studied consisted of combinations of N2-purged foam and multilayer insulation (MLI) as well as He-purged MLI-only. Heat leak and payload performance predictions were made for three Shuttle-launched LTPS designed for Shuttle bay packaged payload densities of 56 kg/cu m, 40 kg/cu m and 24 kg/cu m. Foam/MLI insulations were found to increase LTPS payload delivery capability when compared with He-purged MLI-only. An additional benefit of foam/MLI was reduced operational complexity because Orbiter cargo bay N2 purge gas could be used for MLI purging. Maximum payload mass benefit occurred when an enhanced convection, rather than natural convection, heat transfer was specified for the insulation purge enclosure. The enhanced convection environment allowed minimum insulation thickness to be used for the foam/MLI interface temperature selected to correspond to the moisture dew point in the N2 purge gas. Experimental verification of foam/MLI benefits was recommended. A conservative program cost estimate for testing a MLI-foam insulated tank was 2.1 million dollars. It was noted this cost could be reduced significantly without increasing program risk.

Kramer, T.↗
NASA NTRS1984

Evaluation of propellent tank insulation concepts for low-thrust chemical propulsion systems: Executive summary

Cryogenic propellant tank insulations or liquid oxygen/liquid hydrogen low-thrust 2224N (500 lbf) propulsion systems (LTPS) were assessed. The insulation studied consisted of combinations of N2-purged foam and multilayer insulation (MLI) as well as He-purged MLI-only. Heat leak and payload performance predictions were made for three shuttle-launched LTPS designed for shuttle bay packaged payload densities of 56 kg cu/m (3.5 lbm/cu ft), 40 kg/cu m (2.5 lbm/cu ft) and 24 kg/cu m (1.5 lbm/cu ft). Foam/MLI insulations were found to increase LTPS payload delivery capability when compared with He-purged MLI-only. An additional benefit of foam/MLI was reduced operational complexity because orbiter cargo bay N2 purge gas could be used for MLI purging. Maximum payload mass benefit occurred when an enhanced convection, rather than natural convection, heat transfer was specified for the insulation purge enclosure. The enhanced convection environment allowed minimum insulation thickness to be used for the foam/MLI interface temperature selected to correspond to the moisture dew point in the N2 purge gas. Experimental verification of foam/MLI benefits was recommended. A conservative program cost estimate for testing a MLI-foam insulated tank was 2.1 million dollars. This cost could be reduced significantly without increasing program risk.

Kramer, T.↗
NASA NTRS1984

Low-frequency sound absorption measurements in air

Thirty sets of sound absorption measurements in air at a pressure of 1 atmosphere are presented at temperatures from 10 C to 50 C, relative humidities from 0 to 100 percent, and frequencies from 10 to 2500 Hz. The measurements were conducted by the method of free decay in a resonant tube having a length of 18.261 m and bore diameter of 0.152 m. Background measurements in a gas consisting of 89.5 percent N2 and 10.5 percent Ar, a mixture which has the same sound velocity as air, permitted the wall and structural losses of the tube to be separated from the constituent absorption, consisting of classical rotational and vibrational absorption, in the air samples. The data were used to evaluate the vibrational relaxation frequencies of N2 and/or O2 for each of the 30 sets of meteorological parameters. Over the full range of humidity, the measured relaxation frequencies of N2 in air lie between those specified by ANSI Standard S1.26-1978 and those measured earlier in binary N2H2O mixtures. The measured relaxation frequencies could be determined only at very low values of humidity, reveal a significant trend away from the ANSI standard, in agreement with a prior investigation.

Zuckerwar, A. J.↗
NASA NTRS1985

Velocity visualization in gaseous flows

Techniques are established for visualizing velocity in gaseous flows. Two approaches are considered, both of which are capable of yielding velocity simultaneously at a large number of flowfield locations, thereby providing images of velocity. The first technique employs a laser to mark specific fluid elements and a camera to track their subsequent motion. Marking is done by laser-induced phosphorescence of biacetyl, added as a tracer species in a flow of N2, or by laser-induced formation of sulfur particulates in SF6-H2-N2 mixtures. The second technique is based on the Doppler effect, and uses an intensified photodiode array camera and a planar form of laser-induced fluorescence to detect 2-d velocities of I2 (in I2-N2 mixtures) via Doppler-shifted absorption of narrow-linewidth laser radiation at 514.5 nm.

Hanson, R. K.↗
NASA NTRS1984

Rate constant for the OH + CO reaction - Pressure dependence and the effect of oxygen

The effect of pressure on the rate constant of the OH + CO reaction has been measured for Ar, N2, and SF6 over the pressure range 200-730 torr. All experiments were at room temperature. The method involved laser-induced fluorescence to measure steady-state OH concentrations in the 184.9 nm photolysis of H2O-CO mixtures in the three carrier gases, combined with supplementary measurements of the CO depletion in these same carrier gases in the presence and absence of competing reference reactants. The effect of O2 on the pressure effect was determined. A pressure enhancement of the rate constant was observed for N2 and SF6, but not for Ar, within an experimental error of about 10 percent. The pressure effect for N2 was somewhat lower than previous literature reports, being about 40 percent at 730 torr. For SF6 a factor of two enhancement was seen at 730 torr. In each case it was found that O2 had no effect on the pressure enhancement. The roles of the radical species HCO and HOCO were evaluated.

Demore, W. B.↗