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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Radial image transfer by cylindrical, step-index optical waveguides

The theoretical extent of image transfer by perfect, cylindrical, step-index optical waveguides is examined. Azimuthal image structure is essentially removed by such waveguides, while substantial radial image structure is transmitted. The consequences of this behavior for optical-fiber image scramblers are discussed; such devices may be unsuitable for simple photometric applications but appear to be potentially useful in reducing zonal errors in slit spectroscopy.

Heacox, William D.↗
NASA NTRS1987

Interplanetary radial cosmic-ray gradients and their implication for a possible large modulation effect at the heliospheric boundary

It is proposed here that a large and time-variable part of the overall 11-year cosmic ray modulation in the heliosphere takes place near the heliosphere boundary itself. This conclusion is reached by examining interplanetary radial gradient measurements which show that out to 30-40 AU this gradient remains nearly independent of heliocentric distance throughout the solar cycle. Properties of the solar wind which suggest that the distance to the pressure balance boundary does not vary by more than + or - 25 percent over the solar cycle are also used in support of the proposal. The importance of the large modulation effect at the boundary could exceed that of interplanetary effects expected from present models.

Webber, W. R.↗
NASA NTRS1987

Radial velocities of late-type stars in the galactic center

The 2.0-2.4 micron spectra, with 120 km/s resolution, obtained for six late-type stars within 2 pc of the center of the Galaxy were used to derive spectral types and reddenings for these stars. The supergiant density in the Galactic center is lower than in previous determinations. The radial velocities of the Galactic center stars are measured to an uncertainty of 10 km/s using a cross-correlation technique. No correspondence is found between the stellar velocities and the Ne II velocities or other gas velocities observed along the same line of sight. No systematic rotation or ordered motion is seen in the stellar velocity distribution. The total mass distribution derived from the stellar velocity dispersion is compared to the stellar mass distribution derived from the 2 micron light and the total mass distribution derived from gas velocities.

Sellgren, K.↗
NASA NTRS1987

Evidence for periodic radial velocity variations in Arcturus

Evidence for periodic radial velocity variation in Arcturus based on Doppler accelerometer studies is reported. The most likely period and amplitude for these variations are 1.842 + or - 0.005 days and 160 + or - 10 m/s, respectively. Epoch-folding of 31 nights of Arcturus data taken between December 21, 1985 and March 31, 1986 reveals a sawtooth phase diagram. Two physical mechanisms as potential causes of this variation are briefly discussed.

Smith, P. H.↗
NASA NTRS1988

Static mechanical properties of 30 x 11.5 - 14.5, type 8 aircraft tires of bias-ply and radial-belted design

An investigation was conducted to determine the static mechanical properties of a 30 x 11.5 to 14.5, Type 8, bias-ply and radial-belted aircraft tire. The properties measured were the spring rate and damping characteristics of each tire from vertical- and lateral-loading hysteresis loops. Mass moment of inertia tests were also conducted. The results of the study are presented along with a discussion of the advantages and disadvantages of each type of tire.

Davis, Pamela A.↗
NASA NTRS1987

Nonvariability of the radial velocity of Eta Cassiopeiae A

Twenty-eight measurements of the radial velocity of the G0 V star Eta Cas A on 14 nights between December 11, 1986, and February 19, 1987 UT (inclusive) were made with an uncertainty per observation between + or - 10 and + or - 20 m/s. The velocity of the star never exceeded 30 m/s from the mean, even though the star was monitored on three occasions for three consecutive nights. The standard deviation of all 28 measurements is + or - 13.7 m/s.

Mcmillan, Robert S.↗
NASA NTRS1987

The composition and radial dependence of cometary ions in the coma of comet P/Halley

The heavy ion analyzer, RPA2-PICCA, on board the Giotto spacecraft detected an increase in the densities of cometary ions within a cometocentric distance of 150,000 km. The composition of cometary ions changed dramatically as the comet's nucleus was approached, but it was clearly dominated by the water group. The second and third most abundant ions identified were associated with the CO- or S-group and the CO2-group, respectively. Ions of larger atomic mass units were also present closer to the comet, and they possibly correspond to sulphur compounds and/or various hydrocarbons. Radial profiles of various groups of heavy ions and certain abundance ratios are presented. The peak density for all mass groups was detected at a cometocentric distance of about 11,000 km. A distinct boundary, where the ion velocity and temperature dropped significantly, was identified at about 27,000 km.

Korth, A.↗
NASA NTRS1987

The cause of two plasma-tail disconnection events in comet P/Haley during the ICE-Halley radial period

The causes of two plasma-tail disconnection events (DEs), which occurred in Halley's comet on March 20-22 and April 11-12, 1986, during the ICE-Halley radial period, are analyzed using the ICE magnetometer and electron plasma data. It is concluded that the DE of March 20-22 was most likely caused by an IMF polarity reversal. The DE of April 11-12 on the other hand, is attributed to either a compression region in the solar wind, an IMF polarity reversal, or a combination of the two. Assuming that the two DEs are due to frontside reconnection after an IMF reversal, it was estimated that the time period between the onset of reconnection and the final disconnection of the tail is between 0.1 and 0.6 day, suggesting that the average speed at which reconnection proceeds through the cometary magnetic field pile-up region is between 1 and 6 km/sec, or several tenths of the local Alfven speed.

Brosius, J. W.↗
NASA NTRS1987

Design and experimental evaluation of a high temperature radial turbine with a moveable sidewall nozzle

The uncooled, 2.27 kg/sec mass flow radial turbine designed to operate at 1477 K in the gas generator of an advanced, variable-capacity 683 kW turboshaft engine was configured with a cooled, movable sidewall nozzle capable of changing the stage flow capacity from 50 to 100 percent of maximum. Overall performance test data were obtained in a turbine test rig that duplicated engine Reynolds numbers; attention is given to the changing of flow capacity by moving the hub or shroud sidewall, vane sidewall leakage, vaneless space sidewall geometry, and nozzle-cooling injection. Data are presented in the form of turbine flow, efficiency, work parameter, and performance mappings.

Rogo, Casimir↗
NASA NTRS1987

Static mechanical properties of 30 x 11.5-14.5, type VII, aircraft tires of bias-ply and radial-belted design

An investigation was conducted to determine the static mechanical characteristics of 30 x 115-14.5 bias-ply and radial aircraft tires. The tires were subjected to vertical and lateral loads and mass moment of inertia tests were conducted. Static load deflection curves, spring rates, hysteresis losses, and inertia data are presented along with a discussion of the advantages and disadvantages of one tire over the other.

Davis, Pamela A.↗
NASA NTRS1988

Analyses of hydrodynamic radial forces on centrifugal pump impellers

An experimental and theoretical study of the hydrodynamic interactions occurring between a centrifugal pump impeller and a volute is presented. The theoretical analysis provides a quasi-one-dimensional treatment of the flow in the volute, and it is extended to include the hydrodynamic force perturbations caused by the impeller whirling eccentrically in the volute. It is noted that these perturbations are often destabilizing. The theoretical models were found to accurately predict the radial forces caused by the flow through the impeller. The pressure acting on the front shroud of the impeller is shown to have a significant effect on the destabilizing hydrodyamic forces.

Adkins, D. R.↗
NASA NTRS1988

Eigenfunctions of the magnetospheric radial-diffusion operator

The applicability of eigenfunction methods to the theory of magnetospheric radial diffusion is investigated analytically, with a focus on the operator (Lambda) for radiation-belt and ring-current particles. It is shown that the eigenfunctions of Lambda can be expressed in terms of a linear combination of ordinary Bessel functions of the first and second kinds, and that the solution for the drift-averaged phase-space density can be expressed as the sum of a quasi-static solution and a time-dependent superposition of the eigenfunctions of Lambda. Results for illustrative and practical sample problems are presented in extensive tables and graphs and discussed in detail.

Schulz, Michael↗
NASA NTRS1987

Spacelab experiments on convection in a rotating spherical shell with radial gravity

Data from the geophysical fluid flow cell experiment on Spacelab 3 revealed the diverse forms of fluid motion that can occur in geometrically simple models of global convection with rotation and radial gravity. The following types of convection were observed: midlatitude waves interacting with the low-latitude columnar convection rolls or 'banana cells', spiral waves' near the poles when latitudinal heating gradients are present on the bounding surfaces, and 'triangular waves' coupling midlatitude and equatorial disturbances under similar differential heating. It is believed that concepts based on the Taylor-Proudman theorem have a central role in many flows realized in the rapidly rotating experiments when H is approximately 0; however, the resulting banana cells are subject to secondary instabilities that produce intricate time dependence and eventually turbulent flows in which only hints of the simpler patterns are recognizable.

Toomre, Juri↗
NASA NTRS1988

A radial-velocity survey of the Hyades

Photoelectric radial-velocity measurements, obtained with external error as small as 0.1 km/s using the 200-inch Hale telescope at Palomar Observatory during the period 1971-1986, are reported for over 400 candidate members (with V magnitude between 6 and 14) of the Hyades cluster. The history of Hyades observations is recalled; the Palomar instrumentation and observing program are described; the data-reduction and standardization procedures are discussed in detail; and the data are presented in extensive tables and graphs. About 200 of the stars are classified as cluster members, including 60 spectroscopic binaries.

Griffin, R. F.↗
NASA NTRS1988

On correcting radial orbit errors for altimetric satellites using crossover analysis

A method is proposed for correcting radial orbit error in measurements of sea surface height using a satellite altimeter. Traditionally, the orbit error is modeled in terms of a Fourier series with the Fourier coefficients determined by minimizing the residual crossover difference in a least-squares sense. In this method an a priori constraint must be imposed to obtain a unique solution. It is shown that by using singular value decomposition, no such constraint is needed. This proposed method leaves the geographically dependent errors unchanged and makes only those corrections warranted by the information contained in crossover differences. Thus, the resultant ocean topography is free from any undue distortion which might be incurred by an a priori constraint. It is suggested that the method is useful for application to high-accuracy altimetric mission, because the orbit error can be reduced without compromising the accuracy of the measured mean ocean topography.

Fu, Lee-Lueng↗
NASA NTRS1989

Radial deformation of the earth by oceanic tidal loading

A high-degree spherical harmonic series is used to compute the radial deformation of the Earth by oceanic tidal loading. By exploiting fast numerical transforms, this approach is found to be much more efficient, but no less accurate, than the traditional Green's function approach. The method is used to derive an atlas of load tide maps for 10 constitutents of the NSWC ocean tide model.

Ray, R. D.↗
NASA NTRS1988

Radial velocity studies and absolute parameters of contact binaries. I - AB Andromedae

New radial velocity curves have been obtained for the contact binary AB And, using the cross-correlation technique. A mass ratio of 0.479 is determined, which is revised to 0.491 when the velocities are corrected for proximity effects using a light curve model. These values differ by less than ten percent from the photometric mass ratio. An analysis of the symmetric B and V light curves reported by Rigterink in 1973 using the spectroscopic mass ratio yields a consistent set of light and velocity curve elements. These also produce a reasonably good fit to the infrared J and K light curves reported by Jameson and Akinci in 1979. Absolute elements are determined, and these indicate that both components have a main-sequence internal structure. These absolute parameters, together with the Galactic kinematics, suggest an age for the system similar to or greater than that of the Sun.

Hrivnak, Bruce J.↗