SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The arc protection subsystems that are implemented in the DSN high power transmitters are discussed. The status of present knowledge about waveguide arcs is reviewed in terms of a simple engineering model. A fairly general arc detection scheme is also discussed. Areas where further studies are needed are pointed out along with proposed approaches to the solutions of these problems.
The results of satellite, balloon-borne, and ground-based observations of auroral phenomena are discussed in terms of the morphology of auroral arcs and the behavior and characteristics of auroral electrons and ions. Further attention is given to auroral electric fields and field aligned currents, and to the development of models of auroral potential structures and energization of auroral particles. A simulation of space plasma phenomena is presented, along with numerical simulations of auroral potential structures and related phenomena, including the V-potential double layers and auroral arc deformations, and a simulation of auroral arcs. Plasma waves observed on auroral field lines and in laboratory conditions are reported, and theoretical studies of waves and turbulence in auroral plasmas are described.
On March 9, 1978, a sounding rocket launched from Poker Flat, Alaska, at 2200 LT, made a four-component measurement of a 0.5 Hz hydromagnetic wave as the payload crossed the poleward boundary of a quiet homogeneous auroral arc. An energy flux of about 10 to the -6th W/sq m was observed propagating upward with a left-handed polarization within the arc, and a flux 6 times greater was observed propagating downward with a right-handed polarization on the arc boundary. The waves were identified as shear mode Alfven waves. Various models for the source of the free energy are discussed with the conclusion that the most likely production mechanism was either the electromagnetic or electrostatic Kelvin-Helmholtz instability.
LEAF-Lite (Laser Enhanced Arc-Jet Facility) is a radiative laser heating facility that has been added to the 60 MW Interaction Heating Facility (IHF) convective plasma arc-jet located at NASA Ames Research Center. Together, these two systems can simulate both convective and radiative heating at heat fluxes reaching 551 W/cm2 by simultaneously combining a highest measured heat flux of 160 W/cm2 convective and 391 W/cm2 radiative heating on a 152-mm x 152-mm wedge model configuration. Adding radiant heating to an existing convective facility better simulates Earth atmospheric entry from hyperbolic lunarreturn speeds. The radiative heat is provided by multiple 50-kW CW IR lasers, which is nearly uniform across the illuminated surface with a total variation less than 6%, while the convective heat is provided by a high enthalpy plasma arc-jet. In a later phase, the facility will expand to test panel test articles of 432-mm x 432-mm and provide 100 W/cm2 of radiative heating in a plasma convective flow environment. The paper describes this new combined heating capability, its current testing conditions, and the unique application of the laser system with respect to the Orion test flight lunar orbits.
Arc jet chamber design for a magnetically spun direct current arc
Spectral energy distribution analyses for mercury- xenon arc, and carbon arc solar simulation tests on spacecraft
A data set used to normalize the detector response of the ARCS instrument see ARCS_256693.md in the data set for more details.
A data set used to normalize the detector response of the ARCS instrument see ARCS_58221.md in the data set for more details.
A data set used to normalize the detector response of the ARCS instrument. See ARCS_295641.md in the data set for more details.
Thermal analysis and study of arc-flow in anode regime of electric arc
Here, the present work investigates the effect of process parameters on the geometry of wire arc additive manufactured parts. The geometric accuracy of features produced with a weaving strategy is compared to what can be accomplished with a typical overlapping bead strategy. In this work, single-layer and multi-layer geometries were deposited under varying process and path parameters. The wavelength, amplitude, and torch speed of the weaving path were varied, while the power, wire feed speed, and contact tip to work distance remained constant. The geometric deposition efficiencies of several samples produced with a weave strategy are directly compared to samples generated with two parallel overlapping beads with torch speeds defined to match the deposition rate of the weave samples. Feature geometries were characterized using optical microscopy and laser scanning data. The results indicate that implementing a weave path strategy can improve the geometric accuracy of wire arc additive features, thus increasing the effective volumetric deposition rate of the process. It is shown that the most consistent improvements resulted from the combination of low wavelength and high amplitude, which correlate to wider and taller printed layers.
A data set used to normalize the detector response of the ARCS instrument. See ARCS_336659.md in the data set for more details.
The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.
The behavior was investigated of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 MW/sq m. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring-ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or microstructure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.
Arc heater evaluation for hypersonic wind tunnel heating
Large-scale additive manufacturing (AM) is of interest in the manufacturing industry to produce components of dimensions on the order of hundreds of millimeters to meters in scale. Wire-arc AM (WAAM) of Ti-6Al-4V (Ti64) is an attractive technique for large-scale AM in the aerospace industry, give the high strength-to-weight ratio of the material and high deposition rate of the process. However, due to the large scale, significant distortion and residual stresses are developed in the material during deposition and cooling, potentially leading to part failure. WAAM of a prototypical large-scale Ti64 machine tool component is studied in this work via finite element analysis (FEA). Element activation/deactivation technique is employed to simulate deposition and the resulting distortion and residual stress (RS) predictions are analyzed to evaluate the possibility of crack formation. Significant distortion (∼10 mm) and RS (>1300 MPa) is predicted, suggesting the formation of cracks and possible crack propagation into the build region. Incorporation of fillets significantly reduces RS concentration regions, thus reducing the possibility of part failure. Material deposition sequence also affects the RS pattern in the build.
Carbon-arc rod holder with front end of beryllium oxide, a high electrical resistor and good thermal conductor, prevents nonuniform burning of the positive carbon rod and corrosion of the rod holder.
US Army SECOR and optical tracking networks compared using Explorer 29 /GEOS 1/ long arc orbital solutions