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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 433 records · Page 24
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NASA NTRS1982

Multifrequency observations of the quasar 1156+295

The recent outburst in the quasar 1156+295 was discovered in the course of optical monitoring made in preparation for IUE observations in April 1981. Short and long wavelength spectra were obtained on three occasions when the object was very bright, and which were separated in time by intervals of 4 and 60 days. The UV continuum in all cases is a steeply falling power law, with slope close to -2.0. No spectral features are apparent in the UV. Closely simultaneous observations were made by our collaborators at radio, infrared, and optical frequencies. The continuum is less steep at optical and infrared frequencies, and the overall spectra show little change in shape with time.

Glassgold, A. E.↗
NASA NTRS1982

The high velocity symbiotic star AG Draconis after its 1980 outburst

High and low resolution spectra of AG Dra taken in 1981 are analyzed. The UV spectrum of AG Dra is characterized by prominent high ionization emission lines superimposed on a strong continuum. At high resolution, several intense absorption lines of interstellar origin are seen, in spite of the low interstellar extinction. A similar situation is displayed by the high galactic latitude sd0 stars. The radial velocity difference between the emission lines and the i.s. lines is about -105 Km/sec in agreement with the optical observations. The He II 1640 A line appears much stronger than in other symbiotic stars and suggests the presence of a hot source which is variable according to the activity of the star. The line also exhibits broad emission wings which could be formed in a rotating disk. The NV resonance doublet displays a P Cygni profile and is probably formed in a warm wind. Two components in the UV continuum are identified: a steep component dominating the far UV probably associated with the hot source, and a flatter continuum in the near UV which cannot be accounted for by f-f and f-b emission alone, but which is probably emitted by an optically thick region or disk.

Viotti, R.↗
NASA NTRS1982

Math modeling for helicopter simulation of low speed, low altitude and steeply descending flight

A math model was formulated to represent some of the aerodynamic effects of low speed, low altitude, and steeply descending flight. The formulation is intended to be consistent with the single rotor real time simulation model at NASA Ames Research Center. The effect of low speed, low altitude flight on main rotor downwash was obtained by assuming a uniform plus first harmonic inflow model and then by using wind tunnel data in the form of hub loads to solve for the inflow coefficients. The result was a set of tables for steady and first harmonic inflow coefficients as functions of ground proximity, angle of attack, and airspeed. The aerodynamics associated with steep descending flight in the vortex ring state were modeled by replacing the steady induced downwash derived from momentum theory with an experimentally derived value and by including a thrust fluctuations effect due to vortex shedding. Tables of the induced downwash and the magnitude of the thrust fluctuations were created as functions of angle of attack and airspeed.

Sheridan, P. F.↗
NASA NTRS1981

Energetic oxygen and sulfur in the Jovian magnetosphere

Measurements made in the Jovian magnetosphere by the cosmic ray subsystem on Voyager 1 and 2 are reported. Energy spectra of oxygen ions in the energy range 1-20 MeV/nuc between 5 and 20 Jovian radii are presented, and phase space densities are calculated. A steep positive radial gradient in the phase space density of the energetic oxygen ions is observed, indicating an inward diffusive flow. The upper limit on the rate at which oxygen ions with greater than 400 MeV/nuc-G diffuse across 10 Jovian radii is calculated to be 5 x 10 to the 21st ions per second, indicating that about 10 to the -7th of the ions from Io are accelerated to over 400 MeV/nuc-G and diffuse to 10 Jovian radii. Observations also suggest that oxygen and sulfur ions in the Io plasma torus diffuse radially outward, are nonadiabatically accelerated in a region outside 17 Jovian radii, and diffuse inward and outward from the accelerated region.

Gehrels, N.↗
NASA NTRS1981

Compact radio source 1413 + 135 is a far-IR extragalactic object

The radio source 1413 + 135 is shown to be one of the strongest known emitters of millimeter radiation. The energy distribution of this object, measured between meter and X-ray wavelengths, reveals that most of the power emitted by this object comes out at millimeter and far-IR wavelengths. If the emission at 1 mm is due to incoherent synchrotron radiation, then the source must be very compact, with a size around 25 micron arc sec, and contain a magnetic field larger than 10 G. The steep spectral index in the near-IR is attributed to a high-energy cutoff in the distribution of synchrotron emitting electrons at a Lorentz factor of approximately 300.

Beichman, C. A.↗
NASA NTRS1981

Experimental evaluation of a perspective tunnel display for three-dimensional helicopter approaches

A computer-generated perspective tunnel display for a steep and strongly curved three-dimensional helicopter approach is studied. The necessary control variables for following a curved trajectory are analyzed, the effectiveness of superimposed predictor symbology is investigated, and a suitable predictor law is formulated. The theoretical considerations are validated by an extensive fixed-base simulator program. The tunnel display with a superimposed predictor symbol is shown to outperform conventional-type displays in its abilities to follow a curved trajectory in the presence of gust disturbances, to enter the trajectory from an unknown position outside this trajectory, as well as to monitor automatic approaches. The feasibility of the tunnel display for operation in actual flight has been demonstrated in an exploratory flight test.

Grunwald, A. J.↗
NASA NTRS1981

318-MHz variability of complete samples of extragalactic radio sources

It is found by a low-frequency variability survey, involving two- and three-epoch, 318-MHz observations of extragalactic sources in samples complete to 3 Jy at 1400 MHz and 1 Jy at 5000 MHz, that steep-spectrum sources do not seem to vary while all flat-spectrum sources exhibit low-frequency variability greater than 8% over about 5 yr. It is also found that the flat-spectrum sources with inverted spectra show the largest fractional variations, and that there is a correlation between the incidence of low-frequency variability and the determination that a source is an optically violent variable. These statistical properties are consistent with models which invoke radio and optical emission relativistic beaming.

Dennison, B.↗
NASA NTRS1981

Helical helicopter approaches with microwave landing system guidance

It is desirable that the landing approach of helicopters and V/STOL aircraft into a congested airport equipped with a microwave landing system (MLS) can take place essentially independent of CTOL traffic. The helical approach has been proposed as one way to provide aircraft separation while requiring minimum airspace. A helical descent makes it possible for the helicopter to lose altitude in a confined airspace without descending along an excessively steep glide slope. This avoids helicopter handling problems which occur at slow airspeeds. Preliminary flight-test data are presented regarding the operational feasibility of the helical approach under IFR conditions where the primary guidance information is from an MLS.

Mcgee, L. A.↗
NASA NTRS1981

Influence of the Tibetian Plateau on cumulative and diurnal changes of weather and climate in summer

An investigation of the dynamic and thermodynamic influences of the Tibetian Plateau on the monsoon circulation in southeastern Asia and China is reported. A five-day primitive equation numerical model was used to simulate the influences of the high mountains in the 0-180 deg E and 25-55 deg N region on a typical July day. The equations predicted horizontal motion, heat, the water vapor mixing ratio, and surface pressure. Consideration was given to solar and longwave radiation and the release of latent heat by deep cumulus clouds. A net warming over the Plateau as opposed to the surrounding areas was found to lead to vertical air ascent and the establishment of strong summer monsoon circulation to the south. It is noted that the grid was too coarse to adequately describe the distribution of precipitation on the steep mountains.

Kuo, H. L.↗
NASA NTRS1981

Discovery of a Seyfert 1 galaxy with an unusually soft X-ray spectrum

A newly-discovered Seyfert 1 galaxy, E1615+061, is identified with the bright, soft X-ray source H1613+06. The object possesses a steep X-ray spectrum, an energy index lower than 2.0, and is similar to BL Lac objects' variable soft X-ray components. Such components may be present at times in all compact extragalactic X-ray emitters, and could represent high-luminosity states of the accretion disks around the supermassive black holes that are the underlying power sources. Many of the presently unidentified, bright, soft X-ray sources at high galactic latitudes may fall into the category of these compact extragalactic objects.

Pravdo, S. H.↗
NASA NTRS1981

A new component of hard X-rays in solar flares

High-resolution (approximately 1 keV FWHM) spectral measurements from 13 to 300 keV of a solar flare hard X-ray burst observed on 1980 June 27 by a balloon-borne array of cooled germanium planar detectors are presented. At energies below about 35 keV, a new component of solar flare hard X-rays is identified. This component is characterized by an extremely steep spectrum which fits closely to that from a Maxwellian electron distribution with a maximum temperature of about 34 x 10 to the 6th K and an emission measure of 2.9 x 10 to the 48th per cu cm. This hot isothermal component appears at the peak of the normal power-law-like impulsive X-ray burst component, and it remains isothermal and dominates the X-ray emission below about 30 keV through the decay of the flare event.

Lin, R. P.↗
NASA NTRS1982

A first look at the eclipsing cataclysmic variable Lanning 10

Photometry and spectroscopy of a new cataclysmic variable star, Lanning 10 are presented. The star is shown to be an eclipsing binary with a 7h 42m orbital period. Blue flickering is observed to occur on a time scale of 10 minutes. The light curve is analyzed with a numerical simulation of the eclipse of the accretion disk by the lobe-filling star. The disk nearly spans the Roche lobe of the white dwarf, and its surface brightness is a steep function of radius. Spectra show broad H alpha and He I 6678 A emission lines from the accretion disk and a weak absorption feature from the red dwarf. Radial velocity measurements of the H alpha emission line vary systematically with binary phase. The observed velocity amplitude 240 km/s, gives the mass function 0.46 solar masses. A phase shift of the velocity curve relative to the eclipse ephemeris indicates that a brightness asymmetry exists in the inner parts of the disk.

Horne, K.↗
NASA NTRS1982

The luminosity of serendipitous X-ray QSOs

The optical counterparts of 47 X-ray sources with previously unreported quasi-stellar objects are identified. The mean ratio of X-ray to optical luminosity of the sample agrees with that derived from X-ray observations of previously known QSOs, although the mean redshift of the sample is z=0.42, and thus the main luminosity of the objects (Mv=24) differs significantly from that of previous QSO surveys with similar optical thresholds. The steep luminosity function inferred indirectly from optical counts is confirmed. Reconciliation of the observed QSO luminosity function with optically and radio-selected QSO samples requires one of two significant stipulations. Either the space and luminosity distributions of QSOs become quite well specified, or the X-ray luminosity of the typical QSO falls short of that inferred by Zamorani et al. (1981).

Margon, B.↗
NASA NTRS1982

Observations of Paschen alpha in the broad-line radio galaxy 3C 445

P alpha line flux measurements of the broad-line radio galaxy 3C 445 made at the NASA IR Telescope Facility in September 1981 are discussed. Broad-band measurements were obtained at H of 1.65 micron and K of 2.2 microns. A line flux of P alpha was found at 3.4 times 10 to the -13th ergs/sq cm sec. No discernable variation was detectable regarding measurements made in 1976. Substantial reddening was concluded to exist, although the H gamma lines observed were not due to reddening. The total H alpha luminosity was determined to be 4 x 10 to the 43rd ergs/sec. Steep Balmer line decrements are concluded to be due to interposed dust.

Rudy, R. J.↗
NASA NTRS1981

A data base approach for prediction of deforestation-induced mass wasting events

A major topic of concern in timber management is determining the impact of clear-cutting on slope stability. Deforestation treatments on steep mountain slopes have often resulted in a high frequency of major mass wasting events. The Geographic Information System (GIS) is a potentially useful tool for predicting the location of mass wasting sites. With a raster-based GIS, digitally encoded maps of slide hazard parameters can be overlayed and modeled to produce new maps depicting high probability slide areas. The present investigation has the objective to examine the raster-based information system as a tool for predicting the location of the clear-cut mountain slopes which are most likely to experience shallow soil debris avalanches. A literature overview is conducted, taking into account vegetation, roads, precipitation, soil type, slope-angle and aspect, and models predicting mass soil movements. Attention is given to a data base approach and aspects of slide prediction.

Logan, T. L.↗
NASA NTRS1982

Applications of parameter estimation in the study of spinning airplanes

Spinning airplanes offer challenges to estimating dynamic parameters because of the nonlinear nature of the dynamics. In this paper, parameter estimation techniques are applied to spin flight test data for estimating the error in measuring post-stall angles of attack, deriving Euler angles from angular velocity data, and estimating nonlinear aerodynamic characteristics. The value of the scale factor for post-stall angles of attack agrees closely with that obtained from special wind-tunnel tests. The independently derived Euler angles are seen to be valid in spite of steep pitch angles. Estimates of flight derived nonlinear aerodynamic parameters are evaluated in terms of the expected fit error.

W Taylor, L., Jr.↗
NASA NTRS1982

Stratigraphic relationships within Martian polar cap deposits

It is found that layered ice and dust deposits accumulate on the smooth and banded terrains of the north and south polar cap deposits of Mars, while erosion exposes these layers on the equator-facing slopes of layered terrain. The stripping of layers occurs in areas of strong and multidirectional wind, forming striped terrain. Also noted is the production of steep scarps with crescentic planform by local wind scour, in frequent association with dune fields positioned immediately downwind. Unconformities, which are common within layered deposits in areas of complex topography at the north pole, indicate that deposition episodes of 5-10 layers alternate with the slight erosion of pole-facing trough walls. It is suggested that poles may migrate poleward, replacing the relief increase by depositional infilling when they near the poles.

Howard, A. D.↗
NASA NTRS1982

Lunar anorthosite 60025, the petrogenesis of lunar anorthosites, and the composition of the moon

The mineral chemistry of the lunar anorthosite 60025 is investigated, and a model for the differentiation of the moon is proposed based on these findings. Among other results, it is concluded that 60025 is a mixture of pieces from a related sequence of anorthosites, and that this sequence was generated by near-perfect accumulate growth during strong fractional crystallization. The parent liquid of the most primitive anorthosite was saturated with olivine, plagioclase, pigeonite, and chromite, and evolved to one saturated with plagioclase, pigeonite, high-Ca clinopyroxene, and ilmenite. The steep slope of anorthosites on an Mg (mafics) vs. Ab (plagioclase) diagram is a result of the very low alkali content of the magma and of the original magma ocean. The bulk moon had low Al2O3, a sub-chondritic Ca/Al ratio, and REE abundances and patterns which were probably close to chondritic. In addition, mare basalt sources were found to be too magnesian and some contain too much high Ca clinopyroxene to be directly or simply complementary to a floated anorthosite crust.

Ryder, G.↗