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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Magnetic moments and angular momenta of stars and planets

Using published data on magnetic fields, radii, masses, and rotation, we have compiled a data set of magnetic moments mu and angular momenta L for stars and planets. In our subsample of hotter stars (classes A, B, and O), there are 171 objects. In the subsample of cooler stars (classes F, G, K, and M), there are 54 objects. We include 33 white dwarfs, of which 19 are in cataclysmic variables. The pulsar subsample contains 32 pulsars in binaries and 429 isolated pulsars. Som subsamples exhibit significant empirical correlations between log mu and log L. For the hot and cool stars, the correlations are positive. However, the hot-star correlation is significantly shallower than for the cool stars. In the solar system subsample, the correlation has essentially the same slope as for the cool stars, although the magnetic moments are two to three orders of magnitude smaller for the solar system objects at a given L value. For isolated white dwarfs, the correlations are weak or absent. Pulsars and white dwarfs in close binaries show strong negative correlations: the results are quantitatively consistent with magnetically enforced synchronism with the orbital period. When we consider the centers of gravity of the different subsamples of objects, a significant positive correlation appears between log mu and log L.

Arge, C. N.↗
NASA NTRS1974

An experiment in manipulator control with proximity sensors

Optical proximity sensors were used in a feedback loop to automatically position a manipulator hand for grasping. The experiment was a simplified one, involving two dimensional motion only. Two proximity sensors were mounted on the hand, and control signals derived from their outputs were used to drive the hand vertically and horizontally. The sensors employ a pulsed gallium arsenide light-emitting diode together with a silicon detector. They indicate, without contact, the approximate distance between the manipulator hand and object in the range from 5 to 12 cm. Positioning within approximately + or - 5 mm was observed. Extension of the technique to general three-dimensional control is briefly discussed.

Johnston, A. R.↗
NASA NTRS1993

The role of visual context in manual target localization

During space flight and immediately after return to the 1-g environment of earth, astronauts experience perceptual and sensory-motor disturbances. These changes result from adaptation of the astronaut to the microgravity environment of space. During space flight, sensory information from the eyes, limbs, and vestibular organs is reinterpreted by the central nervous system in order to produce appropriate body movements in the microgravity. This adaptation takes several days to develop. Upon return to earth, the changes in the sensory-motor system are no longer appropriate to a 1-g environment. Over several days, the astronaut must re-adapt to the terrestrial environment. Alterations in sensory-motor function may affect eye-head-hand coordination and, thus, the crewmember's ability to manually locate objects in extrapersonal space. Previous reports have demonstrated that crewmembers have difficulty in estimating joint and limb position and in pointing to memorized target positions on orbit and immediately postflight. The ability to point at or reach toward an object or perform other manual tasks is essential for safe Shuttle operation and may be compromised particularly during re-entry and landing sequences and during possible emergency egress from the Shuttle. An understanding of eye-head-hand coordination and the changes produced during space flight is necessary to develop effective countermeasures. This summer's project formed part of the study of the sensory cues use in the manual localization of objects.

Barry, Susan R.↗
DOE OSTI2025

A tri-level distribution locational marginal price-based demand response framework

Here, in this paper, we propose a tri-level, nested, two-stage price-based demand response (PBDR) framework that considers distribution locational marginal price (DLMP) as DR enabler between load-serving entities (LSE), demand response providers (DRPs), and customers in the day-ahead distribution market. It enables LSE and customer interactions by using multiple DRPs, positioned in-between, and independently optimizes their objectives. The problem is formulated using linear power flow with approximated power losses and its application in DLMP as DR pricing. The tri-level problem is solved using a nested reformulation & decomposition (R&D) method and tested on the real Indian-108 bus distribution system under various dynamic pricings. Further, the temporal–spatial variations in DLMPs are assessed using fairness criteria. Numerical analyses demonstrate that DLMP applications can effectively improve economic efficiency, and transparency in DR programs valuation with a favorable fairness margin. The results show that DLMP as DR pricing signal induces (0-2) % variation in DLMP for DR participation up to 10 %. Further, it gives over 90 % fairness over temporal–spatial variation for all the customers.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1972

ATS C-2 satellite VLBI experiment

A proposal is presented to conduct a satellite VLBI experiment using the ATS C-2 spacecraft. The main objectives of the experiment are: (1) precision spacecraft position determination with the VLBI technique and comparison of the L-band interferometric technique with the L-band R and R technique from the viewpoint of operational simplicity and precision, (2) comparison of the single differential Doppler and the wideband VLBI technique for such uses as tracking, geodesy, etc., (3) derivation of real time ionospheric corrections and phase scintillation effects utilizing simultaneous two-frequency (L- and C-band) tracking of the spacecraft in both time delay and Doppler interferometry, (4) development of techniques for precise time dissemination, particularly to marine users, through wideband time-delay interferometry, (5) development of techniques to use synchronous satellites as stable platforms in space in the area of marine geodesy, (6) station location and calibration, and (7) aid to L-band navigation experiments which utilize precise spacecraft position and time in deriving the user's position.

Ramasastry, J.↗
NASA NTRS1972

Search for optical circular polarization in quasars and Seyfert nuclei.

A search for optical circular polarization has been made in six quasars, the nuclei of three Seyfert galaxies, BL Lac, and OJ 287. No positive effect was found in any of these objects, several of which have been reported to show circular polarization at radio wavelengths. It thus appears that optical circular polarization in quasars, if there is any, is not as strong as at radio wavelengths, and in the best-measured objects it is definitely less than 0.2%.

Landstreet, J. D.↗
NASA NTRS1977

Tracking and Data System Support for the Mariner Venus/Mercury 1973 Project

The Tracking and Data System, which provided outstanding support to the Mariner Venus/Mercury 1973 project during the period from January 1970 through March 1975 are chronologically described. In the Tracking and Data System organizations, plans, processes, and technical configurations, which were developed and employed to facilitate achievement of mission objectives, are described. In the Deep Space Network position of the tracking and data system, a number of special actions were taken to greatly increase the scientific data return and to assist the project in coping with in-flight problems. The benefits of such actions were high; however, there was also a significant increase in risk as a function of the experimental equipment and procedures required.

Davis, E. K.↗
NASA NTRS1976

Ion drive - A step toward 'Star Trek'

The design of a solar-powered electric propulsion system is seen as the first step in the ultimate development of an ion drive system which might incorporate many features of a spacecraft propulsion system described in a science fiction novel written by Anderson (1970). The considered ion propulsion systems would make it possible to augment significantly the operational capabilities of space transportation systems utilizing the Shuttle orbiter in combination with a solid-propellant interim upper stage. The use of the ion drive in a number of applications is discussed, giving attention to the resulting enhancement of national space capabilities, the role of the ion drive in the space transportation system, the development and the operation of a manned space station, satellite positioning and service, the elimination of space debris objects, the study of Halley's comet, interplanetary or lunar shuttle services, and space missions involving the outer planets.

Atkins, K. L.↗
NASA NTRS1981

Recent developments in space-borne zodiacal light photometry

The zodiacal light experiment to be flown aboard the International Solar Polar Mission in 1985 is presented. Overall objectives of the Zodiacal Light/Background Starlight Experiment include the study of the brightness, polarization, and color of the diffuse sky brightness and the determination of the spatial distributions and physical properties of the interplanetary dust as a function of spacecraft position in and out of the ecliptic. To meet these objectives, a multicolor sky-scanning photopolarimeter will be carried on the NASA spacecraft which will provide optimized stray light suppression and a capability for changing the viewing cone angle based on the use of a stepping device. Brightness and polarization measurements will be made for 11 center wavelengths in the UV and visible with 5.6 deg circular and 1.0 sq deg rectangular fields of view.

Schwehm, G. H.↗
NASA NTRS1984

Vertical-Control Subsystem for Automatic Coal Mining

Guidance and control system automatically positions cutting drums of double-ended longwall shearer so they follow coal seam. System determines location of upper interface between coal and shale and continuously adjusts cutting-drum positions, upward or downward, to track undulating interface. Objective to keep cutting edges as close as practicable to interface and thus extract as much coal as possible from seam.

Griffiths, W. R.↗
NASA NTRS1986

Orbit determination for the Mariner Mark II Comet Rendezvous/Asteroid Flyby mission - The orbiting phase

The Comet Rendezvous/Asteroid Flyby (CRAF) mission is the first of the Mariner Mark II mission set, designed to explore the outer solar system. Major objectives of orbit determination will be determine the positions and masses of the comet and asteroid and the relative position of the spacecraft, which is important to accurate pointing of the scan platform on which the narrow angle camera and scientific instruments are positioned. Position prediction is also important, since continuous commuication with the spacecraft will not be possible. The small gravitational attractions and poorly known ephemerides of the comet and asteroid, and the small, slow spacecraft orbit about the comet, pose significant new problems for orbit determination. Results of simulations studying the effectiveness of key data types, the accuracies of estimates, and prediction capabilities, are presented.

Weeks, C. J.↗
NASA NTRS1986

Spectral evolution of young stellar objects

An evolutionary sequence, from protostars to pre-main-sequence stars, is suggested for the classification of young stellar objects. This sequence is derived by comparing the predictions of the theoretical models of Adams and Shu with the morphological classification scheme of Lada and Wilking. We first define the spectral index in the near- and mid-infrared, n is identical to d log(nu F sub nu)/d log nu, and then interpret the class of sources with negative spectral indices as protostars. The inferred mass infall rates for these objects are generally consistent with the measured gas temperatures of approx. 35 K in Ophiuchus, and of approx. 10 K in Taurus. Fitting the data requires us to adopt cloud rotation rates in Ophiuchus which are typically an order of magnitude greater than in Taurus, and we speculate on the mechanistic origin for this difference. Next, we consider a subclass of T Tauri stars with near- and mid-infrared excesses and positive or zero spectral indices. We find that the objects with the steeper indices can be understood as the post-infall products from the collapse of rotating cloud cores, where the infrared excesses arise from the simple reprocessing of visible stellar photons in optically thick but spatially thin disks. The sources with flatter spectra may require massive accretion disks. Given the existence of protostars and naked star/disk systems, there is a natural interpretation of another subclass of T Tauri stars, those with two peaks in their emergent spectral energy distributions. These are readily explained as intermediate cases in which dust envelopes still surround the stars and disks. Finally, we find that the theory can be extended to explain the spectral energy distribution of FU Orionis, a famous outburst source. Our model suggests that FU Orionis has a disk, but it offers no discrimination between the competing ideas that the outburst took place on the star or in the disk.

Adams, F. C.↗
NASA NTRS1987

Monovision techniques for telerobots

The primary task of the vision sensor in a telerobotic system is to provide information about the position of the system's effector relative to objects of interest in its environment. The subtasks required to perform the primary task include image segmentation, object recognition, and object location and orientation in some coordinate system. The accomplishment of the vision task requires the appropriate processing tools and the system methodology to effectively apply the tools to the subtasks. This paper describes the functional structure of the telerobotic vision system used in the Langley Research Center's (LaRC) Intelligent Systems Research Laboratory (ISRL) and discusses two monovision techniques for accomplishing the vision subtasks.

Goode, Plesent W.↗
NASA NTRS1988

Position And Force Control For Multiple-Arm Robots

Number of arms increased without introducing undue complexity. Strategy and computer architecture developed for simultaneous control of positions of number of robot arms manipulating same object and of forces and torques that arms exert on object. Scheme enables coordinated manipulation of object, causing it to move along assigned trajectory and be subjected to assigned internal forces and torques.

Hayati, Samad A.↗
NASA NTRS1987

Monovision techniques for telerobots

The primary task of the vision sensor in a telerobotic system is to provide information about the position of the system's effector relative to objects of interest in its environment. The subtasks required to perform the primary task include image segmentation, object recognition, and object location and orientation in some coordinate system. The accomplishment of the vision task requires the appropriate processing tools and the system methodology to effectively apply the tools to the subtasks. The functional structure of the telerobotic vision system used in the Langley Research Center's Intelligent Systems Research Laboratory is discussed as well as two monovision techniques for accomplishing the vision subtasks.

Goode, P. W.↗
NASA NTRS1990

Mass loss from red giant stars. II - Carbon stars

A millimeter-wave survey has been made of bright relatively unobscured, carbon stars, chosen on the basis of their optical properties. Out of 26 program objects, (J = 2-1)CO emission is detected from 15. Most of these had not been previously detected. There are many differences among the observed objects, but one rather interesting trend emerges: a positive correlation, at moderate IR excesses, between the IR dust emission and the expansion velocity of the dense wind. A similar, positive correlation with the mass-loss rate implies that stars with larger mass fluxes also accelerate them to larger velocities. At high-IR excesses, both correlations break down, and the momentum rate may be limited by the momentum rate of the stellar radiation. All these effects could be ascribed to differences in the gas-to-dust ratio, assuming that radiation pressure initiates and accelerates the wind.

Wannier, P. G.↗
NASA NTRS1993

Detection of an ultraviolet and visible counterpart of the NGC 6624 X-ray burster

We have detected, in images taken with the HST FOC, the UV and optical counterpart of the X-ray source 4U 1820-30 in the globular cluster NGC 6624. Astrometric measurements place this object 2 sigma from the X-ray position of 4U 1820-30. The source dominates a far-UV FOC image and has the same flux at 1400 A as was seen through the large IUE aperture by Rich et al. (1993). It has a B magnitude of 18.7 but is not detected in V. It is 0.66 arcsec from the center of NGC 6624, a fact that may change the interpretation of the P-average of the 11 minute binary orbit. The flux drops between 1400 and 4300 A at a rate that is nearly as steep as that of a Rayleigh-Jeans curve. The flux is far too large to come from the neutron star directly but could accord with radiation from a heated accretion disk and/or the heated side of the companion star.

King, I. R.↗
NASA NTRS1993

Drop dynamics in space and interference with acoustic field (M-15)

The objective of the experiment is to study contactless positioning of liquid drops, excitation of capillary waves on the surface of acoustically levitated liquid drops, and deformation of liquid drops by means of acoustic radiation pressure. Contactless positioning technologies are very important in space materials processing because the melt is processed without contacting the wall of a crucible which can easily contaminate the melt specifically for high melting temperatures and chemically reactive materials. Among the contactless positioning technologies, an acoustic technology is especially important for materials unsusceptible to electromagnetic fields such as glasses and ceramics. The shape of a levitated liquid drop in the weightless condition is determined by its surface tension and the internal and external pressure distribution. If the surface temperature is constant and there exist neither internal nor external pressure perturbations, the levitated liquid drop forms a shape of perfect sphere. If temperature gradients on the surface and internal or external pressure perturbations exist, the liquid drop forms various modes of shapes with proper vibrations. A rotating liquid drop was specifically studied not only as a classical problem of theoretical mechanics to describe the shapes of the planets of the solar system, as well as their arrangement, but it is also more a contemporary problem of modern non-linear mechanics. In the experiment, we are expecting to observe various shapes of a liquid drop such as cocoon, tri-lobed, tetropod, multi-lobed, and doughnut.

Yamanaka, Tatsuo↗