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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 415 records · Page 23
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NASA NTRS1974

Relations among low ionosphere parameters and A3 radio wave absorption

Charged particle conductivities measured in the very low ionosphere are compared with atmospheric parameters and high-frequency radio wave absorption measurements. Between 33 and 58 km, positive conductivity is well correlated with neutral atmospheric temperature. Good correlations are found also between high-frequency radio wave absorption and negative conductivity at altitudes as low as 53 km, this fact suggesting that day-to-day variations in absorption may be principally due to variations in electron loss rate. These correlations do not apply to some days of very low or very high radio wave absorption, for which the effects of transport on nitric oxide appear to be important.

Cipriano, J. P.↗
NASA NTRS1974

CH and CH/+/ in interstellar clouds

Recycling and loss rates for a typical interstellar cloud are considered, giving attention to disagreements concerning some of the production rates. It is pointed out that the formation rate of CH(+) via vibrationally excited hydrogen molecules exceeds in many situations rates of other processes. In low density clouds comparable amounts of CH and CH(+) are produced when the fast dissociative recombination rate is used.

Stecher, T. P.↗
NASA NTRS1974

Effect of anode ring arrangement on the spectroscopic characteristics of the NASA Lewis bumpy torus plasma

The modified Penning discharge in the NASA Lewis Bumpy Torus is normally produced by an anode ring at high voltage in each of the 12 magnetic mirror midplanes. For this investigation, the plasma was run with 12, 6, 3, and 1 anode rings. When 3 anode rings were used, the spectroscopically determined relative electron density and mean ion residence time increase by factors of 10 and 5, respectively, in one mode of operation. The discharge is observed to uniformly fill all bumps around the torus regardless of the anode arrangement and number. A plasma density on axis of 10 to the 11th power cm/3 is estimated for the 3 anode case in one mode of operation based on an observed discharge current to ion loss rate correlation and a measured mean ion residence time of .5 msec.

Richardson, R. W.↗
NASA NTRS1974

Effect of anode ring arrangement on the spectroscopic characteristics of the NASA Lewis Bumpy Torus plasma

The modified Penning discharge in the NASA Lewis Bumpy Torus is normally produced by an anode ring at high voltage in each of the 12 magnetic mirror midplanes. For this investigation, the plasma was run with 12, 6, 3, and 1 anode rings. When 3 anode rings were used, the spectroscopically determined relative electron density and mean ion residence time increased by factors of 10 and 5, respectively, in one mode of operation. The discharge is observed to uniformly fill all bumps around the torus regardless of the anode arrangement and number. A plasma density on axis of 100 billion per cu cm is estimated for the 3-anode case in one mode of operation based on an observed discharge current to ion loss rate correlation and a measured mean ion residence time of .5 msec.

Richardson, R. W.↗
NASA NTRS1975

An experimental investigation of multiple ion processes in mercury bombardment thrusters

Utilizing a collimated E x B mass separator probe, the ratio of double to single ion current densities has been measured in the beam of a 30 cm ion thruster over a wide range of beam and discharge conditions. For a specified thruster geometry, the mass utilization efficiency has been found to be the governing parameter in the determination of the doubly-charged ion content. By a reduction in the open area of the accelerator grid, a reduction in the doubly-charged ion ratio could be achieved while maintaining overall efficiency constant. The results are examined in terms of ion densities and neutral loss rates.

Vahrenkamp, R.↗
NASA NTRS1975

Energy loss of relativistic electrons and positrons traversing cosmic matter

Questions of adiabatic expansion are considered along with aspects of Compton scattering, bremsstrahlung, electronic excitation, synchrotron radiation, and electron-positron pair production. It is found that, unless the intergalactic magnetic field is very small, synchrotron radiation will dominate all other energy loss processes at ultrahigh electron and positron energies. The dependence of the loss rates on the cosmic epoch is also discussed.

Gould, R. J.↗
NASA NTRS1975

Plasma confinement by a picket-fence

It is shown that a current-produced line cusp field in a 'picket fence' configuration will confine both primary ionizing electrons and plasma. The 'picket fence' consists of a planar array of equally spaced water-cooled copper tubing with the current alternating in direction. The loss rates of both plasma and primary electrons are shown to be inversely proportional to the fence current. Plasma confinement is found to be much weaker than electron confinement.

Leung, K. N.↗
NASA NTRS1975

The origin of the nonthermal radiation of quasi-stellar objects and galactic nuclei

The supermassive-star model for the origin of the nonthermal luminosity of quasars and nuclei of Seyfert galaxies is analyzed. In the general model, a moving magnetic field is the accelerating mechanism for ultrarelativistic particles and gravitational collapse is the energy source. Several specific models are considered for the magnetic field, including a frozen-in field that is twisted about the axis of a rotating supermassive star, a tightly wound magnetic spiral, and the rotating field of a giant pulsar. In the general model, an accelerating efficiency close to unity is assumed. However, it is found that observational and theoretical evidence indicate an accelerating efficiency of less than 0.01 for the specific magnetic-field models. Mass-loss rates of quasars and Seyfert nuclei are calculated on the basis of the lower efficiency value and found to be reasonable.

Opher, R.↗
NASA NTRS1975

A sensitive search for soft X-rays from Arcturus and Procyon

Sensitive X-ray observations have been obtained of alpha Boo and alpha CMi using rocket-borne large area proportional counters. No flux was detected from either star, yielding limits on intrinsic luminosity in the 75-2000 eV band (6-165 A) as stringent as 10 to the 28-th power ergs per sec depending upon assumed coronal temperature. These are at least an order of magnitude better limits than previously reported values. Upper limits are also set on a mass loss rate of three billionths solar mass per year and on an emission measure of less than 3 times 10 to the 53-rd power per cu cm. If these stars are typical, then giants and subgiants cannot be responsible for a significant fraction of the soft component of the diffuse X-ray background.

Cruddace, R.↗
NASA NTRS1976

Helium isotopes in an aurora

Aluminum and platinum foils were flown into two bright auroras and subsequently recovered. They were then analyzed for traces of trapped noble gases in a sensitive high-resolution mass spectrometer. In this paper we report the detection of He-3 and confirm measurements of the He-4 flux reported in a previous paper. The He-4:He-3 ratio in the first (brighter) aurora was 2950 plus or minus 250. This ratio is only slightly higher than the average solar wind ratio of 2350 and since the atmospheric ratio is grossly different (250 times larger), establishes the solar wind as the principal source of auroral helium, at least in the aurora concerned. The result supports earlier suggestions that auroral precipitation is one of the main sources of the He-3 in the terrestrial atmosphere. Current estimates of He-3 sources and loss rates are found to be consistent with a balanced atmospheric He-3 budget.

Buehler, F.↗
NASA NTRS1976

Evidence for mass loss at moderate to high velocity in Be stars

Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

Snow, T. P., Jr.↗
NASA NTRS1976

Mass loss in red giants and supergiants

The circumstellar envelopes surrounding 13 late-type giants and supergiants have been studied using a homogeneous collection of high-resolution, photoelectric scans of strong optical resonance lines. Various properties of the envelopes, including the mass loss rate, dilution factor, hydrogen density, and degree of ionization, have been determined quantitatively.

Sanner, F.↗
NASA NTRS1975

Monte Carlo simulation of astronaut light flash observations on Apollo and Skylab missions

Monte Carlo calculations are performed to study the relation between cosmic ray nuclei and visual flashes observed by astronauts, in space. A satisfactory overall fit to all available data excluding the Skylab observations in the South Atlantic Anomaly (SAA) has been achieved by varying three visual system parameters: effective retinal thickness, minimum projected track length inside retina and minimum energy loss rate. All light flash data from space excluding the SAA observations can be understood fully upon the basis of the primary cosmic ray charge and energy spectra together with the fitted values of the three visual system parameters. Monte Carlo simulations of the SAA observations suggest the existence of a previously unobserved multiply-charged component of the inner radiation belt.

Osborne, W. Z.↗
NASA NTRS1976

Photodissociation of methyl chloride and methyl bromide in the atmosphere

Methyl chloride (CH3Cl) and methyl bromide (CH3Br) have been suggested to be significant sources of the stratospheric halogens. The breakup of these compounds in the stratosphere by photodissociation or reaction with OH releases halogen atoms which catalytically destroy ozone. Experimental results are presented for ultraviolet photoabsorption cross sections of CH3Cl and CH3Br. Calculations are presented of loss rates for the methyl halides due to photodissociation and reaction with OH and of mixing ratios of these species in the stratosphere.

Robbins, D. E.↗
NASA NTRS1976

On the masses of the quasi-stellar objects

Current estimates of quasar masses are based on the idea that the objects are outbursts involving galaxies or on the argument that the conversion of mass into radiant energy requires a minimum mass. These estimates are contrasted with those that can be obtained by considering the dynamics of the gas in the regions surrounding the highly compact nonthermal central source. In the analysis, it is assumed that absorption arises in gas clouds associated with quasars and that the emission- and absorption-line regions are being driven by radiation pressure. The results demonstrate that the masses of cosmologically distant quasars must lie between 50 million and 2 billion solar masses and that the mass-loss rate should be about one ten-millionth part per year. If the quasars are local objects, the upper mass limit is reduced to about 20 million solar masses. It is noted that these masses are significantly less than the masses of galaxies, but might be appropriate for galactic nuclei.

Burbidge, G.↗
NASA NTRS1976

Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime-delta eutectic

An experimental study was carried out to evaluate the effect of cyclic thermal exposures on the mechanical properties of a gamma/gamma prime-delta eutectic alloy parallel to the growth direction. The alloy had a nominal composition by weight of Ni-20 Nb-6 Cr-2.5 Al and was directionally solidified at 3 cm/hr in a furnace with a thermal gradient of at least 200 C/cm. Bars of the alloy were exposed in a Mach 0.3 burner rig and cycled 300 times between 1100 and 425 C. Oxidation-erosion characteristics of the alloy were determined by weight loss measurements at 300-cycle intervals. After cyclic exposure, stress rupture and tensile tests were performed at both 760 and 1040 C. Microstructural changes from cyclic exposure were determined. Thermal cycling resulted in gamma prime coarsening and Widmanstaetten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. These microstructural changes did not affect the mechanical properties of the eutectic. High oxidation-erosion weight loss rate was observed.

Gray, H. R.↗
NASA NTRS1977

The energy balance of the nighttime thermosphere

The discrepancy between the input from the day hemisphere and the observed loss rates is discussed in terms of ion-neutral processes and gravity wave inputs. There has been considerable speculation as to the energy balance of the thermosphere and in particular about the fraction of the total energy input supplied by ultraviolet radiation. The problem is considerably simplified by considering the energy balance of the nighttime hemisphere alone. Sunrise and sunset vapor trail measurements provide data on the wind systems at the terminator boundary, and temperature measurements provide information on the vertical energy conduction. North-south winds from high latitude vapor trail measurements provide a measure of the energy input from auroral processes.

Glenar, D. A.↗
NASA NTRS1976

New upper limits on Jovian X rays

The paper presents results of a comprehensive search for X-ray emission from the Jovian magnetosphere, using data obtained with an X-ray telescope aboard OSO 3. This satellite scanned Jupiter for 33 days from a distance of 4.4 AU during a maximum phase of solar activity. No transient X-ray fluxes were observed to accompany decameter-wave radio bursts, but upper limits on the steady X-ray emission over the energy range from 7.7 to 210 keV are estimated. These limits are shown to be consistent with the fluxes measured by Pioneer 10 as well as with the trapped-particle fluxes predicted by recent precise modeling of the Jovian trapped radiation. Upper limits are determined for the energy dissipated on Jupiter in bremsstrahlung-producing collisions and also for the electron loss rate. The energy limit is found to be approximately equal to the total solar radiant energy intercepted by the Jovian disk. It is concluded that Jovian X-rays are unlikely to be detected by near-earth observations with sensitivities currently conceivable.

Peterson, L. E.↗