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  • 1
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    Rare earth doped yttrium aluminum garnet (YAG) selective emitters (2001)
    Elsevier
    Details
    Publication Date: 2001-10-01
    Print ISSN: 0261-3069
    Electronic ISSN: 1873-4197
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Rare earth doped high temperature ceramic selective emitters (1999)
    Elsevier
    Details
    Publication Date: 1999-10-01
    Print ISSN: 0955-2219
    Electronic ISSN: 1873-619X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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    PAPER CURRENT
  • 3
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    Development of the Packed Bed Reactor ISS Flight Experiment (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Packed bed reactors are compact, require minimum power and maintenance to operate, and are highly reliable. These features make this technology a leading candidate as a potential unit operation in support of long duration human space exploration. On earth, this type of reactor accounts for approximately 80% of all the reactors used in the chemical process industry today. Development of this technology for space exploration is truly crosscutting with many other potential applications (e.g., in-situ chemical processing of planetary materials and transport of nutrients through soil). NASA is developing an ISS experiment to address this technology with particular focus on water reclamation and air revitalization. Earlier research and development efforts funded by NASA have resulted in two hydrodynamic models which require validation with appropriate instrumentation in an extended microgravity environment. The first model developed by Motil et al., (2003) is based on a modified Ergun equation. This model was demonstrated at moderate gas and liquid flow rates, but extension to the lower flow rates expected in many advanced life support systems must be validated. The other model, developed by Guo et al., (2004) is based on Darcy s (1856) law for two-phase flow. This model has been validated for a narrow range of flow parameters indirectly (without full instrumentation) and included test points where the flow was not fully developed. The flight experiment presented will be designed with removable test sections to test the hydrodynamic models. The experiment will provide flexibility to test additional beds with different types of packing in the future. One initial test bed is based on the VRA (Volatile Removal Assembly), a packed bed reactor currently on ISS whose behavior in micro-gravity is not fully understood. Improving the performance of this system through an accurate model will increase our ability to purify water in the space environment.
    Keywords: Man/System Technology and Life Support
    Type: E-18159 , 50th AIAA Aerospace Sciences Meeting; Jan 09, 2012; Nashville, TN; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Process of making thin film 2H .alpha.-sic by laser ablation (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Thin films of 2H .alpha.-silicon carbide are produced by pulsed laser ablation.
    Keywords: Solid-State Physics
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Progress in the Development of Metamorphic Multi-Junction III-V Space-Solar Cells at Essential Research Incorporated (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Theoretical calculations have shown that highest efficiency III-V multi-junction solar cells require alloy structures that cannot be grown on a lattice-matched substrate. Ever since the first demonstration of high efficiency metamorphic single junction 1.1 eV and 1.2 eV InGaAs solar cells by Essential Research Incorporated (ERI), interest has grown in the development of multi-junction cells of this type using graded buffer layer technology. ERI is currently developing a dual-junction 1.6 eV InGaP/1.1 eV InGaAs tandem cell (projected practical air-mass zero (AM0), one-sun efficiency of 28%, and 100-sun efficiency of 37.5%) under a Ballistic Missile Defense Command (BMDO) SBIR Phase II program. A second ongoing research effort at ERI involves the development of a 2.1 eV AlGaInP/1.6 eV InGaAsP/1.2 eV InGaAs triple-junction concentrator tandem cell (projected practical AM0 efficiency of 36.5% under 100 suns) under a SBIR Phase II program funded by the Air Force. We are in the process of optimizing the dual-junction cell performance. In case of the triple-junction cell, we have developed the bottom and the middle cell, and are in the process of developing the layer structures needed for the top cell. A progress report is presented in this paper.
    Keywords: Spacecraft Propulsion and Power
    Type: 17th Space Photovoltaic Research and Technology Conference; 8-13; NASA/CP-2002-211831
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Strategies for Radiation Hardness Testing of Power Semiconductor Devices (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Plans on the drawing board for future space missions call for much larger power systems than have been flown in the past. These systems would employ much higher voltages and currents to enable more powerful electric propulsion engines and other improvements on what will also be much larger spacecraft. Long term human outposts on the moon and planets would also require high voltage, high current and long life power sources. Only hundreds of watts are produced and controlled on a typical robotic exploration spacecraft today. Megawatt systems are required for tomorrow. Semiconductor devices used to control and convert electrical energy in large space power systems will be exposed to electromagnetic and particle radiation of many types, depending on the trajectory and duration of the mission and on the power source. It is necessary to understand the often very different effects of the radiations on the control and conversion systems. Power semiconductor test strategies that we have developed and employed will be presented, along with selected results. The early results that we have obtained in testing large power semiconductor devices give a good indication of the degradation in electrical performance that can be expected in response to a given dose. We are also able to highlight differences in radiation hardness that may be device or material specific.
    Keywords: Solid-State Physics
    Type: NASA/CR-2005-213807 , Paper 1021 , E-15164 , American Nuclear Society Annual Meeting; Jun 05, 2005 - Jun 09, 2005; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K.
    Keywords: Solid-State Physics
    Type: NASA/TM-1999-208835 , E-11446 , NAS 1.15:208835 , Nov 29, 1998 - Dec 04, 1998; Boston, MA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Selective Emitter Pumped Rare Earth Laser (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A selective emitter pumped rare earth laser provides an additional type of laser for use in many laser applications. Rare earth doped lasers exist which are pumped with flashtubes or laser diodes. The invention uses a rare earth emitter to transform thermal energy input to a spectral band matching the absorption band of a rare earth in the laser in order to produce lasing.
    Keywords: Lasers and Masers
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Rare Earth Doped High Temperature Ceramic Selective Emitters (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study develops a spectral emittance model for films of rare earth containing materials. Although there are several possible rare earth doped high temperature materials, this study was confined to rare earth aluminum garnets. Good agreement between experimental and theoretical spectral emittances was found for erbium, thulium and erbium-holmium aluminum garnets. Spectral emittances of these films are sensitive to temperature differences across the film. Emitter efficiency is also a sensitive function of temperature. For thulium aluminum garnet the efficiency is 0.38 at 1700 K but only 0.19 at 1262 K.
    Keywords: Solid-State Physics
    Type: NASA/TM-1999-208491 , E-11275 , NAS 1.15:208491
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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