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  • Weitere Quellen  (17)
  • NASA Technical Reports  (17)
  • 1970-1974  (17)
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  • Weitere Quellen  (17)
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  • NASA Technical Reports  (17)
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  • 1970-1974  (17)
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  • 1
    Publikationsdatum: 2006-03-12
    Beschreibung: The theory of Backus and Gilbert gives a technique for solving the general linear inverse problem. Observational error and lack of data are shown to reduce the reliability of the solution in different ways: the former introduces statistical uncertainties in the model, while the latter smooths out the detail. Precision can be improved by sacrificing resolving power, and vice versa, so that some compromise may be made between the two in choosing the best model. Nonlinear inverse problems can be brought into the domain of the theory by linearizing about a typical solution. The inverse problem of electrical conductivity in the mantle is used to illustrate the Backus-Gilbert technique; an example of the tradeoff diagram is given.
    Schlagwort(e): ELECTRONICS
    Materialart: NASA. Ames Res. Center Math. of Profile Inversion; 8 p
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2016-06-07
    Beschreibung: The earth resources activity is comprised of two basic programs as follows: advanced applications flight experiments, and microwave remote sensing. The two programs are in various stages of implementation, extending from experimental investigations within both the AAFE program and the microwave remote sensing program, to multidisciplinary studies and planning. The purpose of this paper is simply to identify the main thrust of the Langley Research Center activity in earth resources.
    Schlagwort(e): GEOPHYSICS
    Materialart: 4th Ann. Earth Resources Program Rev., Vol. 1; 12 p
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2019-06-27
    Beschreibung: Comparative lubrication tests were run with OH-58A helicopter tail rotor drive shaft bearings. The tests were run in an outdoor environment with ambient temperatures ranging from 10 to 75 F. Dust was periodically applied to the bearings to simulate field conditions. The cause of bearing failure was associated with dust penetration. Rotor shaft failure was found to be caused by the shaft rotating in the standard rubber collar due to seizure of the bearings. Bearings with a positive rubbing seal having a MIL-G-81322 grease produced lives greater than with bearings having labyrinth seals and a mineral oil paste lubricant. An elongated collar prevented failure of the rotor shaft during bearing seizure. In a limited test, installation of tail boom shrouds over the bearings which excluded dust and water resulted in bearing lives in excess of 1800 hours or 1200 hours greater than the current 600 hours TBO, regardless of the lubricant-bearing combination used.
    Schlagwort(e): MACHINE ELEMENTS AND PROCESSES
    Materialart: NASA-TM-X-68118 , E-7054
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: The radiation effects on typical science instruments according to the Jupiter trapped radiation design restraint model are described, and specific aspects of the model where an improved understanding would be beneficial are suggested. The spacecraft design used is the TOPS 12L configuration. Ionization and displacement damage are considered, and damage criteria are placed on the most sensitive components. Possible protective measures are mentioned: selecting components as radiation resistant as possible, using a difference in desired and undesired signal shapes for electronic shielding, orienting and locating the component on the spacecraft for better shielding, and adding passive shields to protect specific components. Available options are listed in decreasing order of attractiveness: attempt to lower the design restraints without compromising the success of the missions, trade off experiment objectives for increased reliability, alter the trajectory, and remove sensitive instruments from the payload.
    Schlagwort(e): PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
    Materialart: Proc. of the Jupiter Radiation Belt Workshop; p 159-177
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-06-27
    Beschreibung: Four groups of 12.7 millimeter diameter vacuum-degassed AISI 52100 balls were tested, each at a maximum Hertz stress in the range of 4.5 times 10 to 9th power to 6.0 times 10 to 9th power N/m2. Tests were run in the five-ball fatigue tester at a contact angle of 30 deg and a shaft speed of 10,000 rpm. The 10 percent fatigue lives at the four stress levels indicated that fatigue life is inversely proportional to maximum Hertz stress raised to the power of 12. This result agrees with a survey of the literature which suggests that a stress-life exponent of approximately 12 is typical of vacuum-processed bearing steels rather than the exponent of 9 which has been generally accepted by the bearing industry.
    Schlagwort(e): MACHINE ELEMENTS AND PROCESSES
    Materialart: NASA-TN-D-6745 , E-6768
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2019-06-27
    Beschreibung: AISI 52100, a high carbon chromium steel, has the longest fatigue life of eight bearing materials tested. Fatigue lives of the other materials ranged from 7 to 78 percent of the fatigue life of AISI 52100 at a temperature of 340 K (150 F).
    Schlagwort(e): MATERIALS
    Materialart: LEW-11592
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2019-06-27
    Beschreibung: A mechanical prestress cycle suitable to induce compressive stress beneath the surface of the inner race of radially loaded 207-size bearings was determined. Compressive residual stress in excess 0.69 x 10 to the 9th power N/sq m (100,000 psi), as measured by X-ray diffraction, were induced at the depth of maximum shearing stress. The prestress cycle consisted of running the bearings for 25 hours at 2750 rpm at a radial load which produced a maximum Hertz stress of 3.3 x 10 to the 9th power N/sq m (480,000 psi) at the contact of the inner race and the heaviest loaded ball. Bearings subjected to this prestress cycle and subsequently fatigue tested gave a 10 percent fatigue life greater than twice that of a group of baseline bearings.
    Schlagwort(e): MACHINE ELEMENTS AND PROCESSES
    Materialart: NASA-TN-D-6995 , E-6922
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: The extent of the radiation effects problem is delineated, along with the status of protective designs for 15 representative science instruments. Designs for protecting science instruments from radiation damage is discussed for the various instruments to be employed in the Grand Tour type missions. A literature search effort was undertaken to collect science instrument components damage/interference effects data on the various sensitive components such as Si detectors, vidicon tubes, etc. A small experimental effort is underway to provide verification of the radiation effects predictions.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Washington Proc. of the Natl. Symp. on Nat. and Manmade Radiation in Space; p 729-734
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2019-06-27
    Beschreibung: Test design parameters for accelerated dose rate radiation effects tests for spacecraft parts and subsystems used in long term mission (years) are detailed. A facility for use in long term accelerated and unaccelerated testing is described.
    Schlagwort(e): FACILITIES, RESEARCH, AND SUPPORT
    Materialart: NASA, Washington Proc. of the Natl. Symp. on Nat. and Manmade Radiation in Space; p 570-576
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 2019-07-13
    Beschreibung: A spectrophotometer for monitoring the solar EUV in three broad wavelength bands is described. The kind of data obtained, along with sources of error, are presented. The content of the tape library which contains the data is outlined. The scientific results are discussed. These include the following: solar flares in the EUV, solar eclipse observations in the EUV, SFD's and relationship to solar flares, and the application of satellite sunrise and sunset data for the study of model upper atmospheres for the earth.
    Schlagwort(e): SPACE RADIATION
    Materialart: NASA-CR-130159
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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