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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Comparative health and safety assessment of the SPS and alternative electrical generation systems

A comparative analysis of health and safety risks is presented for the Satellite Power System and five alternative baseload electrical generation systems: a low-Btu coal gasification system with an open-cycle gas turbine combined with a steam topping cycle; a light water fission reactor system without fuel reprocessing; a liquid metal fast breeder fission reactor system; a central station terrestrial photovoltaic system; and a first generation fusion system with magnetic confinement. For comparison, risk from a decentralized roof-top photovoltaic system with battery storage is also evaluated. Quantified estimates of public and occupational risks within ranges of uncertainty were developed for each phase of the energy system. The potential significance of related major health and safety issues that remain unquantitied are also discussed.

Habegger, L. J.↗
NASA NTRS1982

Ultraviolet and X-ray detection of the 56 Peg system (KO 2p + WD)

Both IUE short and long wavelength exposures of the 56 Peg system are discussed. This mild barium star has an X-ray luminosity of 3 x 10 to the 31st power ergs/1, comparable to the rapidly rotating RS CVn binary systems, yet lies in a region of the HR diagram where stellar X-rays are generally not observed. This cool, bright giant is not a rapid rotator and the key to understanding its emission lies in the recent discovery of its white dwarf companion. Accretion onto the white dwarf of approximately 0.1% of the stellar wind of the primary is sufficient to power an X-ray source of the observed luminosity. Reprocessing of the X-rays in the cool dense stellar wind explains the origin of the UV emission line spectrum, and may explain the time varying asymmetry of the Mg 2 kappa line profile that is observed. Graphs which show observed fluxes and wavelengths are discussed.

Schindler, M.↗
NASA NTRS1981

Global ozone long-term trends from satellite measurements and the response to solar activity variations

Analysis of global ozone variations for the period April 1970 to December 1975 was performed by using the reprocessed Nimbus 4 backscattered ultraviolet (BUV) measurements of total ozone. A correlation coefficient of 0.97 is found between the 6-month running mean of global mean total ozone (filtered for mean semiannual, annual, and quasibiennial variations) and the 10.7-cm solar activity index. Correcting ozone for a time-dependent latitudinal bias relative to Dobson ozone measurements reduces to 2-3% the global mean ozone variation over the solar cycle. The solar ultraviolet variability required in a one-dimensional time-dependent radiative photochemical model to account for the observed ozone variation appears to be consistent with recent solar UV observations.

Keating, G. M.↗
NASA NTRS1981

Kinetic inhibition of CO and N2 reduction in circumplanetary nebulae - Implications for satellite composition

In contrast to the solar nebula, the conversion of CO to CH4 and of N2 to NH3 in the circumplanetary nebulae of the Jovian planets is fast enough relative to radial mixing and nebula cooling rates that CO and N2 are minor constituents in the circumplanetary nebulae. Thus, although the Jovian planets may have accreted carbon and nitrogen from the solar nebula mainly in the form of CO and N2, these species were then reprocessed within the circumplanetary nebulae to form mainly CH4 and NH3. Satellites of the Jovian planets which accreted in sufficiently cool parts of their circumplanetary nebula are therefore predicted to retain large amounts of NH3 and CH4 in the form of clathrate hydrates and also very small but chemically important amounts of HCN.

Prinn, R. G.↗
NASA NTRS1981

BE Ursae Majoris /PG 1155 + 492/ - A unique cataclysmic-variable-like object

The variable spectrum of BE Ursae Majoris, which is similar to that of the cataclysmic variables (CVs), shows (1) an emission-line spectrum with the high-excitation CN 4650 A blend as the strongest optical feature, weaker H and He lines, and a strong Balmer jump, and (2) an absorption spectrum dominated by He. Although the object shows no evidence of photometric variability on either short or long time-scales, it has been shown by Kurochkin (1964, 1971) to have a 2.29-day, sinusoidal, 1.5-mag variation. The luminosity is dominated by a UV power-law component, though the 4000-10000 A continuum is flat. The hypothesis that this object is an active mass transfer binary is not supported by its photometric behavior, energy distribution and long period, despite the spectroscopic variability. Nevertheless, three components whose nature is not understood remain: (1) an ultraviolet source whose energy distribution is explainable neither by a uniform temperature primary star nor by an accretion disk; (2) a reprocessed component powered by the UV star; and (3) a component similar to a CV disk, producing the optically thick Balmer lines.

Ferguson, D. H.↗
NASA NTRS1981

Rapid X-ray and optical flares from Scorpius X-1

A 1 second time structure in X-ray flares from Sco X-1 and simultaneous optical flares with time structures no faster than 20 s are reported. The shortest reported time scale in the X-ray emission from Sco X-1 is decreased by a factor of 10, while remaining consistent with the parameters of the standard plasma model from Sco X-1. Different mechanisms for the production of X-ray flares and optical flares are suggested, and the production of optical flares by reprocessing on the surface of the binary companion of Sco X-1 is ruled out by the X-ray/optical flare time delay.

Petro, L. D.↗
NASA NTRS1982

IUE observations of the X-ray burst source 4U/MXB 1735-44

The ultraviolet (1250-1950 A) energy distribution of the X-ray burst source 4U/MXB 1735-44 has been observed with the International Ultraviolet Explorer. The source was detected with an average flux of 1.1 x 10 to the -15th ergs/sq cm per sec per A. The similarity of the optical energy distribution of this source to that of Sco X-1 extends into the far-ultraviolet. Assuming that the optical and ultraviolet emission of MXB 1735-44 is due to reprocessing of X-rays in an accretion disk, the ratio of X-ray to bolometric (optical + ultraviolet) flux has been used to make an estimate of the thickness of the disk. For an assumed X-ray albedo of 0.5, it is found that the disk extends to less than approximately 6 deg from the orbital plane.

Hammerschlag-Hensberge, G.↗
NASA NTRS1981

Characteristics of space and ground based total ozone observing systems investigated by intercomparison of Nimbus 4 Backscattered Ultraviolet /BUV/ data with Dobson and M-83 results

The Nimbus 4 Backscattered Ultraviolet (BUV) experiment data has been reprocessed to provide a near global data set covering the seven years from 1970 to 1977. The data set is the result of a three year effort by the Ozone Processing Team which included review and correction of the spacecraft ephemeris, instrument calibration, and processing algorithms. The accuracy of the resulting total ozone determinations compares well with that of ground based data. An important application of the global BUV data set is to use it in determining long term trends in global total ozone. However, in order to identify long term trends in ozone, it is necessary to eliminate first long-term drift in the instrument calibration. A follow on experiment, the Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer, (SBUV/TOMS), was flown on Nimbus 7 launched in October 1978. The SBUV provides information about both total ozone and vertical ozone profiles for a 200 km square field of view.

Fleig, A. J.↗
NASA NTRS1981

Global ozone - Solar activity relationship from satellite measurements

Global ozone variations are evaluated by analyzing satellite measurements, using the technique of integrating out dynamical effects causing large variations in total ozone at individual locations. Analysis of Nimbus 4 reprocessed BUV data was extended to cover the period from April 1970 through December 1975. Temporal and latitudinal variation of biases and yearly change in global biases between the satellite and ground based ozone measurements are indicated. The bias-corrected 6-month-running filtered global means are shown, and the correlation coefficient between ozone and the solar activity index remains high at 0.94. It is concluded that the results give a strong indication of an ozone-solar activity relationship that is caused by solar UV variability.

Keating, G. M.↗
NASA NTRS1982

Gamma-ray sources as Comptonized X-ray sources

The possible contribution of Compton scattering to the formation of gamma-ray burst spectra is analyzed. Monte Carlo calculations are used to study the spectral distribution emerging from a plasma at temperatures typical of gamma-ray burst spectra (above 100 keV) with an underlying source of photons reprocessed by inverse Compton scattering surrounding a point source of blackbody radiation. Comparison of the computations with the observed spectrum of the burst GB781104 results in a best fit with a blackbody X-ray source at 2.4 keV, plasma temperature of about 150 eV and plasma column density of 4 x 10 to the 24th electrons/sq cm. The Comptonization model is also shown to be capable of accounting for the two-component spectra observed for bursts GB790329 and GB790524, and the moving low-energy spectral cut-off in the burst of November 18, 1978.

Fenimore, E. E.↗
NASA NTRS1982

Shuttle ground turnaround and launch projections

An analysis of factors in the Turnaround Improvement Program intended is presented as a basis for launch rate projections. Noting that a second Shuttle processing facility is in preparation at Kennedy Space Center, details of the initial reprocessing phase, the refurbishing of the SRBs, which are jettisoned about 2 min after lift-off, are described. Until STS-7, Orbiter turnaround begins by configuring the vehicle for flight to KSC on board a 747. The Orbiter Processing Facility at KSC features two identical bays for unloading, inspection, repair, analysis, testing, and preparing for the succeeding flight. The SRBs are repositioned first, then the external tank, and then the Orbiter is fitted back in place. Parallel processing of two Orbiters will begin with STS-5 turnaround, and optimized times are expected to be achieved with the STS-30 flight, with significant test reduction coming with STS-14.

Smith, R. G.↗
NASA NTRS1982

The report of the Gravity Field Workshop

A Gravity Field Workshop was convened to review the actions which could be taken prior to a GRAVSAT mission to improve the Earth's gravity field model. This review focused on the potential improvements in the Earth's gravity field which could be obtained using the current satellite and surface gravity data base. In particular, actions to improve the quality of the gravity field determination through refined measurement corrections, selected data augmentation and a more accurate reprocessing of the data were considered. In addition, recommendations were formulated which define actions which NASA should take to develop the necessary theoretical and computation techniques for gravity model determination and to use these approaches to improve the accuracy of the Earth's gravity model.

Smith, D. E.↗
NASA NTRS1982

Infrared photometry of the X-ray binary 2A 1822-371 - A model for the ultraviolet, optical, and infrared light curve

The X-ray source 2A 1822-371 may be prototypical of a class of accreting close binary systems in which the X-ray emission is diffused by a cloud of ionized material which is associated with the accretion disk. The present investigation provides a report on infrared photometry of 2A 1822-371 in the J (1.25 micrometer), H (1.65 micrometer), and K (2.2 micrometer) bands. A complete 5.57 hr light curve has been obtained at J which makes it possible to extend the investigations of the energy dependence of the ultraviolet and optical curve begun by Mason and Cordova (1982). The work conducted by White and Holt (1982) is extended to the long wavelength light curve by incorporating the influence of emission from the inner and outer rim of the disk and from the companion star. Including such effects, and assuming that reprocessed X rays are the major source of light at wavelengths greater than 1100 A, it is found possible to reproduce the morphology and energy dependence which is observed in the light curve of 2A 1822-371 from the far-ultraviolet to the near-infrared.

Mason, K. O.↗
NASA NTRS1982

Einstein Observatory pulse-phase spectroscopy of Hercules X-1

Spectra of the Her X-1 pulsations from 0.15 to 4.5 keV have been obtained with the Objective-Grating and Solid State Spectrometers on the HEAO 2 Einstein Observatory. The spectra show no distinct atomic emission or absorption features, except for broad emission near 1 keV possibly due to unresolved Fe L shell emission lines. Spectrally resolved pulse waveforms show a dramatic 240 deg phase shift for E less than 0.85 keV. The soft X-rays are interpreted as the result of the reprocessing of the hard X-ray beam by the inner disk at the magnetospheric boundary of the neutron star, and several spectroscopic and phase observations are suggested which could provide further knowledge of these structures.

Mccray, R. A.↗
NASA NTRS1982

X-ray observations of AM Herculis in its low state

AM Her was observed with the Einstein Imaging Proportional Counter during the low state of 1980 August. The light curve shows an eclipse at phi sub m = 0.0 similar to the one observed in the customary high state. The spectral distribution of the X-ray photons does not show any soft component. The IPC flux suggests that the intensity of the hard component in the low state is about one-tenth of the intensity of the hard component during the high state, similar to the variation in the optical magnitude. The comparison of the present data with a previous SAS 3 X-ray observation of AM Her in the low state suggests that the soft component is different in similar accretion regimes. The possibility that this component originates from reprocessing of the hard flux becomes then more unlikely.

Fabbiano, G.↗
NASA NTRS1982

Optical bursts from 4U/MXB 1636-53

The results of observations of 15 and 26 optical bursts detected during June and July 1979 and June and July 1980, respectively, from the X-ray burst source 4U/MXB 1636-53 in a 'white light' passband are presented. The maximum burst fluxes above the persistent optical flux and integrated burst fluxes are correlated, and it appears that the maximum optical and X-ray burst fluxes are related according to a power law, consistent with optical emission from blackbody reprocessing of X-rays. The approximately linear relationship between the integrated optical and X-ray burst fluxes argues against this simple picture. The correlation of burst fluxes with waiting time since the previous burst suggests that large optical bursts come after a long waiting time. Short burst intervals observed both for optical and X-radiation suggest that not all available nuclear fuel is consumed in the thermonuclear flash which gives rise to the X-ray burst.

Pedersen, H.↗
NASA NTRS1982

Visual and infrared observations of the distant Comets P/Stephan-Oterma /1980g/, Panther /1980u/, and Bowell /1980b/

The paper reports combined visual imagery and spectroscopy, near-infrared spectroscopy, and broadband infrared photometry of comets P/Stephan-Oterma (1980g), Bowell (1980b), and Panther (1980u) at intermediate heliocentric distances. The visual data indicate the existence of solid grains in extended halos around the nuclei of the three comets. Broadband near-infrared and thermal infrared measurements of Comet Panther suggest the presence of 2-4-micron-radius particles in the coma which most likely contain molecules incorporating the N-H bond, but which are more complex and less volatile than NH3. Such molecules can be produced in the grains by cosmic-ray reprocessing. Near infrared spectral features identical to those seen in comet Panther similary suggest the presence of a molecule incorporating the N-H bond in comet Bowell.

Jewitt, D. C.↗
NASA NTRS1983

Accretion onto magnetized neutron stars - X-ray pulsars with intermediate rotation rates

Assuming that the accreting material originates in a wind or envelope and therefore carried no net angular momentum, the Kevin-Helmholtz instability is applied to the transport of accreting plasma across the magnetopause of a rotating and magnetized neutron star for the case in which this surface is interchange-stable. Magnetopause location is determined, and the blackbody emission temperature is estimated. A possible period-dependence is noted in the X-ray temperature data which is in approximate agreement with the present model calculations. The magnetopause is found to be insufficiently stable to support an optically thick sheath of plasma surrounding the source, so that neither shrouding of the X-ray source nor significant reprocessing of the radiation field is possible in the model presented. It is concluded that while the flow structure at the magnetopause can control accretion column geometry, the emerging pulse profile and spectra are only indirectly altered, through a dynamical influence on emission region geometry.

Burnard, D. J.↗