79 research outputs found

    Cooling Technology for Large Space Telescopes

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    NASA's New Millennium Program funded an effort to develop a system cooling technology, which is applicable to all future infrared, sub-millimeter and millimeter cryogenic space telescopes. In particular, this technology is necessary for the proposed large space telescope Single Aperture Far-Infrared Telescope (SAFIR) mission. This technology will also enhance the performance and lower the risk and cost for other cryogenic missions. The new paradigm for cooling to low temperatures will involve passive cooling using lightweight deployable membranes that serve both as sunshields and V-groove radiators, in combination with active cooling using mechanical coolers operating down to 4 K. The Cooling Technology for Large Space Telescopes (LST) mission planned to develop and demonstrate a multi-layered sunshield, which is actively cooled by a multi-stage mechanical cryocooler, and further the models and analyses critical to scaling to future missions. The outer four layers of the sunshield cool passively by radiation, while the innermost layer is actively cooled to enable the sunshield to decrease the incident solar irradiance by a factor of more than one million. The cryocooler cools the inner layer of the sunshield to 20 K, and provides cooling to 6 K at a telescope mounting plate. The technology readiness level (TRL) of 7 will be achieved by the active cooling technology following the technology validation flight in Low Earth Orbit. In accordance with the New Millennium charter, tests and modeling are tightly integrated to advance the technology and the flight design for "ST-class" missions. Commercial off-the-shelf engineering analysis products are used to develop validated modeling capabilities to allow the techniques and results from LST to apply to a wide variety of future missions. The LST mission plans to "rewrite the book" on cryo-thermal testing and modeling techniques, and validate modeling techniques to scale to future space telescopes such as SAFIR

    Vision 2020: A View of Our Energy Future

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    The Morning Address was given by The Honorable George Allen. “The Regulatory Framework: Where Are We Headed?” session by Eric Finkbeiner, Senior Adviser for Policy, Office of Governor Robert McDonnell; David Christian, Chief Executive Officer, Dominion Generation; and Professor Joel Eisen, University of Richmond School of Law. Professor Noah Sachs, University of Richmond School of Law, served as moderator. “The Future of Coal” session by John Lain, Partner at McGuireWoods LLP; Cale Jaffe, Senior Attorney with the Southern Environmental Law Center; and W. Thomas Hudson, President of W. Thomas Hudson and Associates, Inc. and of the Virginia Coal Association. Stephen E. Taylor, Allen Chair Editor for the University of Richmond Law Review, served as moderator. “Nuclear Power: Is There a ‘Renaissance’?” session by Donald Irwin, Hunton & Williams; Christopher Paine, Director of Nuclear Program, Natural Resources Defense Council (invited); and Michael H. Montgomery, Vice President of Fuel Development, Lightbridge Corporation. Tricia Dunlap, Robert R. Merhige, Jr. Fellow at the University of Richmond School of Law, served as moderator. “Emerging Issues in Energy Policy” session by Mark Rosen, Deputy General Counsel, CNA Corporation; Jefferson Reynolds, Water Policy Director with the Virginia Department of Environmental Quality; Kruskaia Sierra-Escalante, Senior Counsel for the International Finance Corporation; and Edward Lowe, General Manager for Renewable Energy Market Development, GE Energy. Andrea W. Wortzel, Counsel with Hunton & Williams and Vice Chair of the Environmental Law Section of the Virginia State Bar, served as moderator. The Closing Address was given by The Honorable Carol M. Browner, Assistant to the President for Energy and Climate Change and Former Administrator of the Environmental Protection Agency (invited)

    Basic Atomic Physics

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    Contains reports on five research projects.National Science Foundation Grant PHY 89-19381U.S. Navy - Office of Naval Research Grant N00014-90-J-1322Joint Services Electronics Program Contract DAAL03-89-C-0001National Science Foundation Grant PHY 86-05893U.S. Army Research Office Contract DAAL03-89-K-0082U.S. Navy - Office of Naval Research Grant N00014-89-J-1207U.S. Navy - Office of Naval Research Grant N00014-90-J-164

    Globally, functional traits are weak predictors of juvenile tree growth, and we do not know why

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    1. Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates. 2. If community-level relationships between traits and growth have general predictive value, then similar relationships should also be observed in analyses that integrate across taxa, biogeographic regions and environments. Such global consistency would imply that traits could serve as valuable proxies for the complex suite of factors that determine growth rate, and, therefore, could underpin a new generation of robust dynamic vegetation models. Alternatively, growth rates may depend more strongly on the local environment or growth–trait relationships may vary along environmental gradients. 3. We tested these alternative hypotheses using data on 27 352 juvenile trees, representing 278 species from 27 sites on all forested continents, and extensive functional trait data, 38% of which were obtained at the same sites at which growth was assessed. Data on potential evapotranspiration (PET), which summarizes the joint ecological effects of temperature and precipitation, were obtained from a global data base. 4. We estimated size-standardized relative height growth rates (SGR) for all species, then related them to functional traits and PET using mixed-effect models for the fastest growing species and for all species together. 5. Both the mean and 95th percentile SGR were more strongly associated with functional traits than with PET. PET was unrelated to SGR at the global scale. SGR increased with increasing SLA and decreased with increasing wood density and seed mass, but these traits explained only 3.1% of the variation in SGR. SGR–trait relationships were consistently weak across families and biogeographic zones, and over a range of tree statures. Thus, the most widely studied functional traits in plant ecology were poor predictors of tree growth over large scales. 6. Synthesis. We conclude that these functional traits alone may be unsuitable for predicting growth of trees over broad scales. Determining the functional traits that predict vital rates under specific environmental conditions may generate more insight than a monolithic global relationship can offer

    Basic Atomic Physics

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    Contains reports on five research projects.Joint Services Electronics Program Contract DAAL03-89-C-0001National Science Foundation Grant PHY 87-06560National Science Foundation Contract PHY 86-05893U.S. Army Research Office Contract DAAL03-89-K-0082U.S. Navy - Office of Naval Research Contract N00014-89-J-1207U.S. Navy - Office of Naval Research Contract N00014-83-K-069

    Basic Atomic Physics

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    Contains reports on four research projects.Joint Services Electronics Program Contract DAAL03-92-C-0001National Science Foundation Grant PHY 89-19381U.S. Navy - Office of Naval Research Grant N00014-90-J-1322National Science Foundation Grant PHY 89-21769U.S. Army - Office of Scientific Research Contract DAAL03-89-K-0082U.S. Navy - Office of Naval Research Grant N00014-89-J-1207U.S. Navy - Office of Naval Research Grant N00014-90-J-164

    Basic Atomic Physics

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    Contains reports on seven research projects.National Science Foundation (Grant PHY 87-06560)Joint Services Electronics Program (Contract DAAL03-86-K-0001)Joint Services Electronics Program (Contract DAAL03-89-C-0002)National Science Foundation (Grant PHY 86-05893)U.S. Navy - Office of Naval Research (Contract N00014-83-K-0695)U.S. Navy - Office of Naval Research (Contract N00014-89-J-1207

    Basic Atomic Physics

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    Contains reports on five research projects.National Science Foundation Grant PHY 89-19381U.S. Navy - Office of Naval Research Contract N00014-90-J-1322Joint Services Electronics Program Contract DAAL03-89-C-0001Joint Services Electronics Program Contract DAAL03-92-C-0001U.S. Army Research Office Contract DAAL03-89-K-0082U.S. Navy - Office of Naval Research Grant N00014-89-J-1207U.S. Navy - Office of Naval Research Grant N00014-90-J-1642National Science Foundation Grant PHY 86-05893National Science Foundation Grant PHY 89-2176
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