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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.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

An atlas of low-latitude 6300-A forbidden O I night airglow from Ogo 4 observations.

The atomic oxygen emission line at 6300 A as measured in the nadir direction by a photometer on the polar-orbiting satellite Ogo 4 has been plotted between 40 deg N and 40 deg S latitude on a series of maps for the moon-free periods between Aug. 30, 1967, and Jan. 10, 1968. Readily apparent are the longitudinal and local time variations that occur during the northern fall-winter season. The northern tropical arc is more widespread; the southern arc is not present at all longitudes. The arcs in early evening are strong and distinct, separated by very low emission rates at the magnetic equator. The arcs lie generally along magnetic parallels, move toward the magnetic equator as the night progresses, and, in the early morning hours, decrease in emission rate and degenerate into patches.

Reed, E. I.↗
NASA NTRS1974

A rocket borne instrument for the study of soft X-ray emission from cosmic X-ray sources

Details about a rocket-borne instrument designed for studying the various characteristics of soft X-ray emission from cosmic X-ray sources in the energy range of 0.2 to 3 keV are presented. The X-ray detector consists of a bank of four multilayer, wall-less proportional counters, each with an area of 400 sq cm. The detectors are covered by windows of 1.4-micron polypropylene and are maintained at a constant pressure in flight using a gas control system. Two of the detectors are equipped with 0.4- by 10-deg collimators for mapping the spatial distribution of soft X-rays from extended X-ray sources. A pair of balanced filters consisting of oxygen and CF4 are used for detecting oxygen emission lines.

Agrawal, P. C.↗
NASA NTRS1974

Conjugate excitation of atomic oxygen emissions in the far ultraviolet

Rocket observations of far-ultraviolet terrestrial airglow emissions in the 1230- to 1450-A band at night have been carried out from White Sands Missile Range. Three rockets carried 15.4-cm-diam far-ultraviolet telescopes to about 220 km altitude at various times during the night from postsunset to predawn. Postsunset and predawn observations were made when the solar zenith angle at the conjugate ionosphere was about 95 deg, and in both cases positive identification of strong O I 1304-A emissions was made. Evidence that in these cases the 1356/1304 intensity ratio was less than 0.2 is presented. Observations made well into the night yielded only an upper limit to the combined O I 1304- and 1356-A emissions of 20 Rayleighs, consistent with previous observations and theoretical calculations. These results show that meaningful rocket observations of the cosmic far ultraviolet background can be made only when the solar zenith angle at the conjugate ionosphere of the launch site is larger than 105 deg or if atomic oxygen emission lines are excluded from the detectors' bandpass.

Holberg, J.↗
NASA NTRS1975

Permitted iron lines in NGC 7469

Using the Michigan multichannel spectrometer on the 1.3-meter telescope, relatively strong Fe II emission has been detected in the Seyfert galaxy NGC 7469. This object is different from the handful of others with permitted iron lines in that it also exhibits intense forbidden lines of oxygen. The observations do not show the strong He II at 4686 A reported by previous investigators.

Shectman, S. A.↗
NASA NTRS1976

Results and progress on the NASA Lewis H2-O2 MHD program

It was found that flame sprayed ceramic coatings on combustion chamber and nozzle walls permit operation with hot walls, thereby eliminating possible problems associated with seed condensation. However, under the conditions of experiment the net heat transfer was unexpectedly increased over that of cold copper walls. Pressure disturbances associated with oblique pressure waves were measured in a MHD channel. These disturbances are due to a rocket-type nozzle which was designed to achieve low weight rather than perfectly parallel flow at the exit. A new nozzle with parallel flow at the exit was designed. Electrical conductivity measurements agreed well with theory except at low combustion pressures and/or high ratios of seed/oxygen mass flows (seed was injected into oxygen flow line). The discrepancy is believed to be the result of poor atomization of the seed at high ratios of seed/oxygen mass flows which results in droplet sizes which do not completely vaporize the combustor.

Smith, J. M.↗
NASA NTRS1978

Radiometer system to map the cosmic background radiation

A 33-GHz airborne radiometer system has been developed to map large angular scale variations in the temperature of the 3 K cosmic background radiation. A ferrite circulator switches a room-temperature mixer between two antennas pointing 60 deg apart in the sky. In 40 min of observing, the radiometer can measure the anisotropy of the microwave background with an accuracy of plus or minus 1 mK rms, or about 1 part in 3000 of 3 K. The apparatus is flown in a U-2 jet to 20 km altitude where 33-GHz thermal microwave emission from the atmosphere is at a low level. A second radiometer, tuned to 54 GHz near oxygen emission lines, monitors spurious signals from residual atmospheric radiation. The antennas, which have an extremely low side-lobe response of less than -65 dB past 60 deg, reject anisotropic radiation from the earth's surface. Periodic interchange of the antenna positions and reversal of the aircraft's flight direction cancel equipment-based imbalances. The system has been operated successfully in U-2 aircraft flown from NASA-Ames at Moffett Field, Calif.

Gorenstein, M. V.↗
NASA NTRS1978

Detached auroral arcs in the trough region

In a previous paper, Moshupi et al. (1977) have reported on the occurrence of rare auroral 'patches' equatorward of the normally well-defined boundary of diffuse aurora. Some less spectacular but more common arclike features were observed in the same 'trough' region (between the plasmapause and the auroral oval) during the period 1972-1975. These 'detached' arcs show some similarities to stable auroral red arcs in terms of their location and occurrence, but are completely different spectroscopically in that the stable auroral red arcs produce almost pure atomic oxygen red line emissions, whereas the detached arcs are deficient in red line emission - a feature implying totally different production mechanisms. The characteristics of the detached lines are described, including their unusual local time/longitude dependence.

Anger, C. D.↗
NASA NTRS1981

Drive mechanism for the shuttle orbiter/external tank propellant disconnect

The Space Shuttle design required development of a large, 0.43-m (17-in.) nominal diameter separable disconnect for the liquid hydrogen and liquid oxygen propellant lines at the orbiter-to-external-tank interface. The disconnect must provide for shutoff of the propellant flow area by simultaneous action of two rotary flapper valves (orbiter and external tank) prior to disconnect separation. In the case of pneumatic system failure, the rotary flapper valves are closed automatically through mechanical interlocking linkage during disconnect separation. The mechanism must meet requirements while accommodating changes in bearing clearances and linkage geometry over a wide temperature range from ambient to 20.37 K (-423°F). The mechanical design of the separable disconnect, kinematics of the drive mechanism, and the analysis and test methods used to verify proper operation and qualification for the Space Shuttle dynamic environments are presented.

E. Thomas↗
NASA NTRS1985

Effects of breaking gravity waves on the chemical composition of the mesosphere and lower thermosphere

Eddy diffusion and momentum forcing in the mesosphere and lower thermosphere arise principally from the effects of breaking gravity and waves. The propagation and dissipation of gravity waves depend strongly on season and latitude because of its relationship to the background zonal wind. These processes have significant effects on the transport of chemical species in that region, so that observations of variations in chemical constituents provide useful tracers for dynamical theory. A parameterization of gravity wave propagation and dissipation was incorporated in the coupled dynamical-chemical model to study these effects. Several easily observable airglow features of the mesosphere-thermosphere region are shown to provide sensitive indications of gravity wave influence. In particular, theoretical predictions of large seasonal and latitudinal variations in the atomic oxygen green line, the Meinal bands of excited OH, and the O3 densities inferred from O2 (delta supra 1 sub g) emission at altitudes from 75 to 90 km are shown to be in remarkably good agreement with observations. Implications of these sensitive chemical tracers for the dynamics of the mesosphere-lower thermosphere region and its relationship to gravity waves are discussed.

Solomon, S.↗
NASA NTRS1985

What we do not know about cometary ices - A review of the incomplete evidence

Only two features seem rather well established about the cometary nucleus: it is an icy conglomerate that contains a large amount of volatile ices, and its major constituent seems to be water ice. The evidence on all the minor constituents is incomplete and fragmentary and there are still major difficulties in establishing a complete list of the parent molecules from the numerous radicals, ions, and atoms observed in the coma. In particular, the case of the forbidden lines of oxygen is discussed here in detail; new arguments are shown to contradict the need for CO2 as a major source of O(1D).

Delsemme, A. H.↗
NASA NTRS1987

The early spectral phase of type Ib supernovae - Evidence for helium

A near-infrared spectrum and several optical spectra of SN 1983N obtained over a period from 10 days before maximum light to about a week after maximum and of SN 1984L from about maximum light to about 60 days later are presented. On the basis of these spectra it is argued that the first definite identification of helium in supernova ejecta near maximum light has been made. The emergence of oxygen emission lines which presage the dramatic transition to the supernebular phase is identified. Supernova atmosphere models which are consistent with the observations are presented, and it is argued that a strong departure of helium level populations from LTE is necessary. The current status of SNe Ib, the arguments that they result from core collapse in moderately massive stars, and some of the immediate work necessary to further clarify the nature of these events are summarized.

Harkness, R. P.↗
NASA NTRS1988

The auroral 6300 A emission - Observations and modeling

A tomographic inversion is used to analyze measurements of the auroral atomic oxygen emission line at 6300 A made by the atmosphere explorer visible airglow experiment. A comparison is made between emission altitude profiles and the results from an electron transport and chemical reaction model. Measurements of the energetic electron flux, neutral composition, ion composition, and electron density are incorporated in the model.

Solomon, Stanley C.↗
NASA NTRS1989

Dissociative recombination in aeronomy

The importance of dissociative recombination in planetary aeronomy is summarized, and two examples are discussed. The first is the role of dissociative recombination of N2(+) in the escape of nitrogen from Mars. A previous model is updated to reflect new experimental data on the electronic states of N produced in this process. Second, the intensity of the atomic oxygen green line on the nightside of Venus is modeled. Use is made of theoretical rate coefficients for production of O (1S) in dissociative recombination from different vibrational levels of O2(+).

Fox, J. L.↗
NASA NTRS1991

Studies of the chemistry of the nightside ionosphere of Venus

A combination of numerical modeling and analysis of the Pioneer Venus UADS data base is studied, specifically data from the orbiter ion mass spectrometer (OIMS), orbiter neutral mass spectrometer (ONMS), and orbiter electron temperature probe (OETP). A one dimensional model of the Venus nightside ionosphere was set up in which downward fluxes of atomic ions are introduced at the upper boundary to simulate transport of ions from the dayside. The model shows that the densities of mass-28 ions, CO(+) + N(2+), resulting from an influx of atomic ions from the dayside are quite small, due to the high ionization potentials of CO and N2 that make chemical production difficult. A look at the data reveals that the actual densities of mass-28 ions are quite variable, from values near 10 to more than 10(exp 4) cm(exp -3). The excess mass-28 ions are assumed to be produced by electron precipitation and that the presence of high densities of mass-28 ions is a signature of auroral precipitation. A discussion of the atomic oxygen green line in the nightglow of Venus, which is produced mainly by dissociative recombination of O(2+), is presented. Original calculations of production rates of excited states for models based on Pioneer Venus data are also presented.

Fox, J. L.↗
NASA NTRS1991

First results from the Faint Object Camera - Imaging the core of R Aquarii

The Faint Object Camera on the HST was pointed toward the symbiotic long-period M7e Mira variable R Aquarii, and very high resolution images of the inner core, mainly in the ionized oxygen emission lines in the optical, are reported. Both images show bright arcs, knots, and filaments superposed on a fainter, diffuse nebulosity extending in a general SW-NE direction from the variable to the edge of the field at 10 arcsec distance. The core is resolved in forbidden O III 5007 A and forbidden O II 3727 A into at least two bright knots of emission whose positions and structures are aligned with PA = 50 deg. The central knots appear to be the source of a continuous, well-collimated, stream of material extending out to 3-4 arcsec in the northern sector corresponding to a linear distance of about 1000 AU. The northern stream seems to bend around an opaque obstacle and form a spiral before breaking up into wisps and knots. The southern stream is composed of smaller, discrete parcels of emitting gas curving to the SE.

Paresce, F.↗
NASA NTRS1991

Theoretical studies of important processes in planetary and comet atmospheres

This is the fifth semi-annual progress report describing research on dissociative recombination reactions in planetary and comet atmospheres. The Appendix has two papers that describe NASA supported research. Both papers have been recently accepted for publication. The first paper, 'The Generation of O(S-1) from the Dissociative Recombination of O2(+)', describes in detail the Multichannel Quantum Defect (MQDT) theory used for the calculation of dissociative recombination (DR) cross sections and rates. The application to the generation of the upper state of the atomic oxygen green line emission is of great importance to the modelling of planetary atmospheres. The second paper in the Appendix, 'Dissociative Recombination of the Ground State of N2(+)', applies the methods described in the first paper to N2(+). We find remarkable agreement with the prior microwave afterglow experiments for both the total recombination rate and for its electron temperature dependence. However, the results disagree with recent merged beams results which gave cross sections that are a factor of five below the microwave afterglow experiments and the current results. DR of N2(+) is an important mechanism for generating energetic N atoms which can escape the atmosphere of Mars. Currently we are also continuing additional work on the DR of O2(+) which is aimed at calculating both the total DR rate as a function of ion vibrational level and the rate for production of O(D-1).

Guberman, Steven L.↗
NASA NTRS1993

Spectral measurements of shock layer radiation in an arc-jet wind tunnel

Measurements were made of the radiating gas cap of a blunt body in an NASA Ames 20 MW arcjet wind tunnel. The test gas was air. Spectra of the flux incident on a small aperture centered at the stagnation region were obtained. A helium-cooled MgF window transmitted flux into an evacuated collimating system that focused the aperture onto the entrance slit of a spectrometer. Data were obtained with films and by photomultipliers. The range covered was 120 nm to 1000 nm and the resolution was 0.05 nm to 0.5 nm. This paper presents preliminary results from the experiment. Representative spectral records from 200 nm to 1000 nm are shown. The spectra show the atomic lines from oxygen and nitrogen in the IR, as well as the molecular systems of NO, N2, N2(+), and CN. Copper, as a contaminant, and carbon are tentatively identified.

Palumbo, Giuseppe↗