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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

An auroral arc in the late evening plasma flow reversal

The late evening plasma flow reversal over Alaska on January 27, 1980 and changes associated with an auroral arc are examined on the basis of radar observations and rocket measurements. In particular, attention is given to changes in the plasma flow patterns resulting from a small substorm and to several effects associated with the auroral arc, such as an inverted V electron energy spectrum and, on the equatorial edge, an intense burst of auroral hiss and a very thin sheet of field-aligned electrons. Details of the experimental payload and geophysical conditions of the launch are included.

Cahill, L. J., Jr.↗
NASA NTRS1986

Field-aligned electron precipitation at the edge of an arc

Measurements of field-aligned electrons at the edge of an arc are presented from a sounding rocket flight through a quiet afternoon auroral arc. High time resolution measurements show the evolution of the electron distribution function over the 2.3-km width of field-aligned precipitation. A nearly constant 1.2-eV perpendicular temperature was found for these field-aligned fluxes over a broad range of parallel energies (100 - 900 eV). The small perpendicular temperature indicates that the acceleration region is located at a low altitude. Two models of cold plasma convection into the edge of a V-shaped potential structure are examined and found to be consistent with both the observed fluxes and spatial width of the edge precipitation. Both models predict an average source plasma density less than 130/cu cm to account for the observed field-aligned fluxes and thus an acceleration region well above 1000 km.

Mcfadden, J. P.↗
NASA NTRS1986

1981N1 - A Neptune arc?

An object in the vicinity of Neptune detected in 1981 by simultaneous stellar occultation measurements at observatories near Tucson, Arizona, was interpreted as a new Neptune satellite. A reinterpretation suggests that it may have instead been a Neptune arc similar to one observed in 1984. The 1981 object, however, did not occult the star during simultaneous observations at Flagstaff, Arizona. This result constrains possible arc geometries.

Hubbard, W. B.↗
NASA NTRS1986

Occultation detection of a Neptunian ring-like arc

The apparent closest approach of the star SAO186001 to Neptune was observed photoelectrically on July 22, 1984 at Cerro Tololo Inter-American Observatory. A 32-percent signal drop, lasting about 1.2 s, was probably caused by a partially transparent arc of material at a distance of 67,000 km from Neptune. Neptune's arc(s) do not vary smoothly with azimuth, unlike the rings of other Jovian planets.

Hubbard, W. B.↗
NASA NTRS1987

Alternating-Polarity Arc Welding

Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

Schwinghamer, R. J.↗
NASA NTRS1987

Morphology of zirconia particles exposed to D.C. arc plasma jet

Zirconia particles were sprayed into water with an arc plasma gun in order to determine the effect of various gun operating parameters on their morphology. The collected particles were examined by XRD and SEM techniques. A correlation was established between the content of spherical (molten) particles and the operating parameters by visual inspection and regression analysis. It was determined that the composition of the arc gas and the power input were the predominant parameters that affected the melting of zirconia particles.

Zaplatynsky, Isidor↗
NASA NTRS1987

LEO high voltage solar array arcing response model

A series of mathematical models were developed that describe the electrical behavior of a large solar cell array floating electrically in the low Earth orbit (LEO) space plasma and struck by an arc at a point of negative bias. There are now three models in this series: ARCII, which is a fully analytical, linearized model; ARCIII, which is an extension of ARCIII that includes solar cell inductance as well as load reactance; Nonlinear ARC, which is a numerical model able to treat effects such as non-linearized, i.e., logarithmic solar cell I/V characteristics, conductance switching as a solar cell crosses plasma ground on a voltage excursion and non-ohmic plasma leakage current collection.

Metz, Roger N.↗
NASA NTRS1987

Self-clamping arc light reflector for welding torch

This invention is directed to a coaxial extending metal mirror reflector attached to the electrode housing or gas cup on a welding torch. An electric welding torch with an internal viewing system for robotic welding is provded with an annular arc light reflector to reflect light from the arc back onto the workpiece. The reflector has a vertical split or gap in its surrounding wall to permit the adjacent wall ends forming the split to be sprung open slightly to permit the reflector to be removed or slipped onto the torch housing or gas cup. The upper opening of the reflector is slightly smaller than the torch housing or gas cup and therefore, when placed on the torch housing or gas cup has that springiness to cause it to clamp tightly on the housing or gas cup. The split or gap also serves to permit the feed of weld wire through to the weld area,

Gordon, Stephen S.↗
NASA NTRS1987

The identification of excited species in arc jet flow

Spectrographic work done at the Atmospheric Reentry Material and Structures Facility (arc jet) located at the Johnson Space Center has led to the identification of several excited molecular and atomic states. The excited molecular states identified are: first positive nitrogen system, second positive nitrogen system, the first negative nitrogen system, the gamma system for nitric oxide, and the 306.4 nm system of OH. Excited atoms identified were nitrogen, oxygen, hydrogen, silicon, copper, sodium, barium, potassium, and calcium. The latter five are considered contaminants. Excited molecular states of oxygen were not seen, suggesting full dissociation of oxygen molecules to oxygen atoms within the arc column and nozzle. Further, evidence exists that O(-) may be present since a background continuum is seen, and because of the existence of positive species (first negative system of N2(+)). Interpretation of spectrographic plates was enhanced by the use of a microdensitometer, and by the application of a second order least squares routine which determined wavelength as a function of plate location. Results of this work will ultimately improve models used in the calculation of heat transfer rates to the space shuttle and the aerobraking orbit transfer vehicles.

Willey, Ronald J.↗
NASA NTRS1986

The 7 and 25 June 1985 Neptune occultations - Constraints on the putative Neptune 'arc'

Data were obtained on stellar occultations by Neptune on June 7 and 25, 1985 in an attempt to validate previous data which supported the presence of a ring-like 'arc' near the planet. The data were taken with an IR photometer at the South African Astronomical Observatory using continuous measurements at 2.2 microns. One dip was observed in the light curve of an occulted binary star. The dip was similar to a previously observed dip and, because no dip was seen for the companion star, indicated a discontinuous structure. Two estimates, around 62,600 and 63,760 km, are made for the equatorial radius of the potential arc structure, which may be discontinuous on a scale of a few thousand kilometers.

Covault, C. E.↗
NASA NTRS1986

A possible SAR arc energization source - Precipitating electrons

Coincident measurements by ground-based photometers and satellite-borne electron sensors have shown the association of precipitating electrons and Stable Auroral Red Arcs at midlatitudes. Modeling of these events has suggested that, within the constraints imposed by uncertainties of the electron energy spectrum, the electron influx carries sufficient energy to establish ionospheric temperatures required to power the arcs.

Slater, D. W.↗
NASA NTRS1988

Tool Removes Arc-Light Reflectors

New tool makes installation, adjustment, and removal of self-clamping arc-light reflectors on welding torches easy and simple. Consists of two arms reaching around from back of torch. Lip on each arm hooks into slot of arc-light reflector clamp. When handles squeezed together, slot spreads enabling easy installation, adjustment, or removal of reflector without disassembly of welding apparatus.

Gordon, Stephen S.↗
NASA NTRS1988

Preventing Arc Welding From Damaging Electronics

Shielding technique developed to protect sensitive electronic equipment from damage due to electromagnetic disturbances produced by arc welding. Established acceptable alternative in instances in which electronic equipment cannot be removed prior to arc welding. Guidelines established for open, unshielded welds. Procedure applicable to robotics or computer-aided manufacturing.

Sargent, Noel↗
NASA NTRS1988

Redundant Grounding Circuit For Arc Welding

Arc burns at loose ground connections prevented. Protective grounding scheme for arc-welding power supply includes four ground leads to workpiece and circuit that automatically turns off welding current if one or two ground leads becomes disconnected. Prevents burns and inadvertent welding occuring where full welding current passes through single loose ground contact.

Burley, Richard K.↗
NASA NTRS1987

Examination of the physical processes associated with the keyhole region of variable polarity plasma arc welds in aluminum alloy 2219

The morphology and properties of the Variable Polarity Plasma Arc (VPPA) weld composite zone are intimately related to the physical processes associated with the keyhole. This study examined the effects of oxide, halide, and sulfate additions to the weld plate on the keyhole and the weld pool. Changes in both the arc plasma character and the bead morphology were correlated to the chemical environment of the weld. Pool behavior was observed by adding flow markers to actual VPPA welds. A low temperature analog to the welding process was developed. The results of the study indicate that oxygen, even at low partial pressures, can disrupt the stable keyhole and weld pool. The results also indicate that the Marangoni surface tension driven flows dominate the weld pool over the range of welding currents studied.

Walsh, Daniel W.↗
NASA NTRS1987

Numerical arc segmentation algorithm for a radio conference-NASARC (version 2.0) technical manual

The information contained in the NASARC (Version 2.0) Technical Manual (NASA TM-100160) and NASARC (Version 2.0) User's Manual (NASA TM-100161) relates to the state of NASARC software development through October 16, 1987. The Technical Manual describes the Numerical Arc Segmentation Algorithm for a Radio Conference (NASARC) concept and the algorithms used to implement the concept. The User's Manual provides information on computer system considerations, installation instructions, description of input files, and program operating instructions. Significant revisions have been incorporated in the Version 2.0 software. These revisions have enhanced the modeling capabilities of the NASARC procedure while greatly reducing the computer run time and memory requirements. Array dimensions within the software have been structured to fit within the currently available 6-megabyte memory capacity of the International Frequency Registration Board (IFRB) computer facility. A piecewise approach to predetermined arc generation in NASARC (Version 2.0) allows worldwide scenarios to be accommodated within these memory constraints while at the same time effecting an overall reduction in computer run time.

Whyte, Wayne A., Jr.↗
NASA NTRS1987

Numerical Arc Segmentation Algorithm for a Radio Conference-NASARC, Version 2.0: User's Manual

The information contained in the NASARC (Version 2.0) Technical Manual (NASA TM-100160) and the NASARC (Version 2.0) User's Manual (NASA TM-100161) relates to the state of the Numerical Arc Segmentation Algorithm for a Radio Conference (NASARC) software development through October 16, 1987. The technical manual describes the NASARC concept and the algorithms which are used to implement it. The User's Manual provides information on computer system considerations, installation instructions, description of input files, and program operation instructions. Significant revisions have been incorporated in the Version 2.0 software over prior versions. These revisions have enhanced the modeling capabilities of the NASARC procedure while greatly reducing the computer run time and memory requirements. Array dimensions within the software have been structured to fit into the currently available 6-megabyte memory capacity of the International Frequency Registration Board (IFRB) computer facility. A piecewise approach to predetermined arc generation in NASARC (Version 2.0) allows worldwide scenarios to be accommodated within these memory constraints while at the same time reducing computer run time.

Whyte, Wayne A., Jr.↗
NASA NTRS1987

G0.18-0.04 - Interaction of thermal and nonthermal radio structures in the arc near the galactic center

Using a high-resolution radio-continuum image made at a frequency of 4.8 GHz, the radio source G0.18-0.04 located at the intersection of the galactic center Arc with the galactic plane is discussed. In this direction, the radio Arc is composed of a set of linear, nonthermal filamentary structures superimposed on a narrow, sickle-shaped, thermal feature which crosses them. The radio image suggests a physical interaction between the thermal and nonthermal structures. It is argued that the magnetic field is dynamically important and that its strength is estimated to be very large (0.001 G). Furthermore, it is suggested that the ionization of G0.18-0.04 is caused by collisional ionization rather than ultraviolet photons from massive stars. The discussion presents possible ways in which some of the energy of the relativistc particles or the magnetic field in the nonthermal filaments might be extracted to ionize ambient gas in the galactic plane.

Yusef-Zadeh, Farhad↗