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  • 1
    Publication Date: 2005-11-30
    Description: Exposure of the volatile condensable material (VCM) from Silastic 140 RTV adhesive sealant to 147. 0-nm radiation, simulating the space radiation environment in synchronous earth orbits, induces absorption of visible light by the VCM. This results in an increase in the absorptance of coated optical elements, such as solar cell cover glasses and second-surface mirrors for thermal control. A contaminant thickness of 0.1 micron or more could result in a change in solar absorptance of the second-surface mirrors from 0.06 to approximately 0.16 in a period of about 1.5 years in space. Calculations indicated that the VCM thickness would have to be less than approximately 0.005 micron to keep the change in solar absorptance 0.01 for a 3-year mission.
    Keywords: MATERIALS, NONMETALLIC
    Type: NASA. Goddard Space Flight Center Space Simulation; p 173-177
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  • 2
    Publication Date: 2013-08-31
    Description: UltraFlex is the generic term for a solar array system which delivers on-orbit power in the 400 to 6,000 watt per wing sizes with end-of-life specific power performance ranging to 150 watts-per-kilogram. Such performance is accomplished with off-the-shelf solar cells and state-of the-art materials and processes. Much of the recent work in photovoltaics is centered on advanced solar cell development. Successful as such work has been, no integrated solar array system has emerged which meets NASA's stated goals of 'increasing the end-of-life performance of space solar cells and arrays while minimizing their mass and cost.' This issue is addressed; namely, is there an array design that satisfies the usual requirements for space-rated hardware and that is inherently reliable, inexpensive, easily manufactured and simple, which can be used with both advanced cells currently in development and with inexpensive silicon cells? The answer is yes. The UltraFlex array described incorporates use of a blanket substrate which is thermally compatible with silicon and other materials typical of advanced multi-junction devices. The blanket materials are intrinsically insensitive to atomic oxygen degradation, are space rated, and are compatible with standard cell bonding processes. The deployment mechanism is simple and reliable and the structure is inherently stiff (high natural frequency). Mechanical vibration modes are also readily damped. The basic design is presented as well as supporting analysis and development tests.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center, Proceedings of the 12th Space Photovoltaic Research and Technology Conference (SPRAT 12); p 177-187
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  • 3
    Publication Date: 2013-08-31
    Description: The development of a mechanism for instrumentation and solar-array deployment is discussed. One part of the technology consists of a smart motor which can operate in either an analog mode to provide high speed and torque, or in the stepper mode to provide accurate positioning. The second technology consists of a coilable lattice mast which is deployed and rotated about its axis with a common drive system. A review of the design and function of the system is presented. Structural and thermal test data are included.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA, Marshall Space Flight Center, The 23rd Aerospace Mechanisms Symposium; p 77-100
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  • 4
    Publication Date: 2013-08-31
    Description: Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-Lyndon B. Johnson Space Center, The 21st Aerospace Mechanisms Symposium; p 329-343
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  • 5
    Publication Date: 2018-06-08
    Description: Radio telescopes at eight sites in Astralia and one in South Africa operate as a VLBI array during several periods each year.
    Keywords: Communications and Radar
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  • 6
    Publication Date: 2018-06-08
    Description: X2000 is a technology program at the Jet Propulsion Laboratory to develop enabling technologies for future flight missions at affordable cost.
    Type: IEEE Aerospace Conference; Big Sky, MT; United States
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  • 7
    Publication Date: 2018-06-08
    Description: A sub-parsec scale radio counterjet has been detected in the nucleus of the closest radio galaxy, Centarus A (NGC 5128), with VLBI imaging at 2.3 and 8.4 GHz.
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  • 8
    Publication Date: 2019-06-28
    Description: The key characteristics of an intelligent advisory system is explored. A central feature is that human-machine cooperation should be based on a metaphor of human-to-human cooperation. ALLY, a computer-based operator's associate which is based on a preliminary theory of human-to-human cooperation, is discussed. ALLY assists the operator in carrying out the supervisory control functions for a simulated NASA ground control system. Experimental evaluation of ALLY indicates that operators using ALLY performed at least as well as they did when using a human associate and in some cases even better.
    Keywords: CYBERNETICS
    Type: NASA, Lyndon B. Johnson Space Center, Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90); p 499-506
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  • 9
    Publication Date: 2019-06-28
    Description: The performance of an alumina-supported Pt catalyst system used to maintain the gas purity in an electron-beam-sustained (636) isotope CO2 laser amplifier has been tested. The system characteristics using the two-zone, parallel flow reactor were determined for both continuous- and end-of-day reactor operation using on-line mass spectrometric sampling. The laser amplifier was run with an energy loading of typically 110 J-l/atm and an electron-beam current of 4 mA/sq cm. With these conditions and a pulse repetition frequency of 10 Hz for up to 10,000 shots, increases on the order of 100 ppm O2 were observed with the purifier on and 150 ppm with it off. The 1/e time recovery time was found to be approximately 75 minutes.
    Keywords: LASERS AND MASERS
    Type: NASA, Langley Research Center, Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers; p 379-382
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  • 10
    Publication Date: 2016-06-07
    Description: In response to the premature failure of Rb lamps used in Rb atomic clocks onboard NAVSTAR GPS satellites experimental and theoretical investigations into their failure mechanism were initiated. The primary goal of these studies is the development of an accelerated life test for future GPS lamps. The primary failure mechanism was identified as consumption of the lamp's Rb charge via direct interaction between Rb and the lamp's glass surface. The most effective parameters to accelerate the interaction between the Rb and the glass are felt to be RF excitation power and lamp temperature. Differential scanning calorimetry is used to monitor the consumption of Rb within a lamp as a function of operation time. This technique yielded base line Rb consumption data for GPS lamps operating under normal conditions.
    Keywords: LASERS AND MASERS
    Type: NASA. Goddard Space Flight Center Proc. of the 13th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 767-788
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