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  • 1
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    Coupling of pulsed 0.35‐μm laser radiation to titanium alloys (1982)
    American Institute of Physics
    Details
    Publication Date: 1982-08-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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    PAPER CURRENT
  • 2
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    Laser-induced breakdown in nitrogen and the rare gases at 0.53 and 0.357μm (1987)
    Institute of Physics
    Details
    Publication Date: 1987-10-14
    Print ISSN: 0022-3727
    Electronic ISSN: 1361-6463
    Topics: Physics
    Published by Institute of Physics
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    PAPER CURRENT
  • 3
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    Ionisation path formation in gases using a laser with retractable focus (1979)
    Institute of Physics
    Details
    Publication Date: 1979-01-01
    Print ISSN: 0022-3727
    Electronic ISSN: 1361-6463
    Topics: Physics
    Published by Institute of Physics
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    PAPER CURRENT
  • 4
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    Laser driven launch vehicles for continuous access to space (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The availability of megawatt laser systems in the next century will make laser launch systems from ground to orbit feasible and useful. Systems studies indicate launch capabilities of 1 ton payload per gigawatt laser power. Recent research in ground to orbit laser propulsion has emphasized laser supported detonation wave thrusters driven by repetitively pulsed infrared lasers. In this propulsion concept each laser repetition cycle consists of two pulses. A lower energy first pulse is used to vaporize a small amount of solid propellant and then after a brief expansion period, a second and higher energy laser pulse is used to drive a detonation wave through the expanded vapor. The results are reported of numerical studies comparing the detonation wave properties of various candidate propellants, and the simulation of thruster performance under realistic conditions. Experimental measurements designed to test the theoretical predictions are also presented. Measurements are discussed of radiance and opacity in absorption waves, and mass loss and momentum transfer. These data are interpreted in terms of specific impulse and energy conversion efficiency.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: NASA. Lewis Research Center, Vision-21: Space Travel for the Next Millennium; p 193-201
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Significant reduction in arc frequency biased solar cells: Observations, diagnostics, and mitigation technique(s) (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A variety of experiments were performed which identify key factors contributing to the arcing of negatively biased high voltage solar cells. These efforts have led to reduction of greater than a factor of 100 in the arc frequency of a single cell following proper remediation procedures. Experiments naturally lead to and focussed on the adhesive/encapsulant that is used to bond the protective cover slip to the solar cell. An image-intensified charge coupled device (CCD) camera system recorded UV emission from arc events which occurred exclusively along the interfacial edge between the cover slip and the solar cell. Microscopic inspection of this interfacial region showed a bead of encapsulant along this entire edge. Elimination of this encapsulant bead reduced the arc frequency by two orders of magnitude. Water contamination was also identified as a key contributor which enhances arcing of the encapsulant bead along the solar cell edge. Spectrally resolved measurements of the observable UV light shows a feature assignable to OH(A-X) electronic emission, which is common for water contaminated discharges. Experiments in which the solar cell temperature was raised to 85 C showed a reduced arcing frequency, suggesting desorption of H2O. Exposing the solar cell to water vapor was shown to increase the arcing frequency. Clean dry gases such as O2, N2, and Ar show no enhancement of the arcing rate. Elimination of the exposed encapsulant eliminates any measurable sensitivity to H2O vapor.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Space Photovoltaic Research and Technology Conference; 10 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Arcing of negatively biased solar cells in a plasma environment. I - Experimental observations (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A variety of experiments have been performed which identify key factors contributing to the arcing of negatively biased high voltage solar cells operating in a low earth orbit plasma environment. These efforts have led to a reduction of greater than a factor of 100 in the arc frequency of a single cells following proper remeditation procedures. Experiments naturally led to and focused on the adhesive/encapsulating that is used to bond the protective cover slip to the solar cell. An image-intensified CCD camera system recorded UV emission from arc events which occurred exclusively along the interfacial edge between the cover slip and the solar cell. Microscopic inspection of this interfacial region showed a bead of encapsulant along this entire edge. Elimination of this encapsulant bead reduced the arc frequency by two orders of magnitude.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 92-2990
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Solar cell arcing: The role of outgassing and contamination (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The effect of outgassing, venting, and thruster firing events on spacecraft system performance has been a long standing issue. Recent laboratory measurements on negatively biased high voltage solar cells at Physical Sciences Inc. (PSI) suggest that some currently designed and certainly future space power systems must address/re-evaluate this issue. Our observations show that exposing these cells to moderate levels (10 exp -3 torr-min) of H2O vapor enhances the arcing frequency, while heating to 85 C to remove water vapor significantly reduces the arc frequency. The interaction of the adhesive used to attach the cover glass to the solar cell with ambient water vapor is the key factor in determining arcing rates. Elimination of adhesive exposed to the environmental plasma reduces the arc frequency more than two orders of magnitude, and eliminates any sensitivity to H2O exposure. The adhesive may also become a source of spacecraft contamination. Macroscopic amounts were observed to blow off some arc events, and (we assume) electrostatically precipitate at other negatively biased locations. Data, analysis, and potential impact for future space platforms are discussed.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Johnson Space Center, 5th Annual Workshop on Space Operations Applications and Research (SOAR 1991), Volume 2; p 669
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Arcing of negatively biased solar cells in low earth orbit (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A set of experiments is described in which the arcing of negatively biased solar cells is examined and characterized in terms of the primary factors that cause such behavior. The experiments are conducted in an ultrahigh vacuum chamber, and an image-intensified CCD camera is employed to monitor UV emission from arc events at the interfacial edge between the cover slip and the solar cell. A bead of encapsulant along the interfacial edge is noted which can be removed to reduce arc frequency, and water contamination is found to further enhance arcing. Frequency of arcing is found to vary indirectly with temperature and directly with exposure to H2O, but no other significant correlations are noted. The sensitivity to H2O vapor is eliminated by simply removing the adhesive/encapsulant, and the corresponding arc-rate performance is low.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 92-0578
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Optical mixing in a magnetoactive plasma (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Homogeneous plasma electrostatic oscillations excitation by electromagnetic waves nonlinear interaction in magnetic field, deriving expression for density perturbation
    Keywords: PHYSICS, PLASMA
    Type: ; UGREVUE(
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Arcing in space structures in low Earth orbit (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This report describes results of an experimental and theoretical program to investigate arcing of structures containing dielectric and conducting materials when they are biased negatively with respect to a plasma. An argon ion source generated Ar(+) ions of directed energy 20 to 40 eV and density approximately 10(exp 7) cm(exp -3) that impinged upon samples containing a dielectric material on top of a negatively biased Kovar plate. Arcing events were studied for bias voltages between -300 and -1000V with respect to the ion beam. The samples were Dow Corning 93-500 adhesive on Kovar, fused silica cover slips bonded on Kovar, and silicon solar cells mounted on Kovar. Measurements of discharge current, Kovar plate voltage, and radiation from the arc versus time were carried out. Microsecond duration exposure images and optical spectra in the 0.24 to 0.40 micron band were also acquired during arcing events. Arcing events were found to be associated with exposed adhesive and means were found to eliminate arcing altogether. The charging of a silica cover plate and the fields around the plate were calculated using a particle-in-cell code. Models were developed to explain the ignition of the arc and the physical processes occurring during the discharge.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-194223 , NAS 1.26:194223 , PSI-2123/TR-1153
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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