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  • LUNAR AND PLANETARY EXPLORATION  (6)
  • Fluid Mechanics and Thermodynamics; Numerical Analysis  (1)
  • Nonmetallic Materials  (1)
  • 1
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    Degradation of Coflon in Methanol at Temperatures Around 140 C (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An unexpected and significant physico-chemical degradation of Coflon PVDF specimens was observed at the end of 1994 during routine scheduled exposure exercises on strained material. The intent was to age various samples, including some strained in a 4-point bend configuration, in methanol at 140 C and subsequently submit the aged samples to various tests including dynamic fatigue and fracture toughness. However, the samples deteriorated to such an extent that such testing was not possible: only when conditions were made less severe was it found possible to perform such testing. The purpose of the current report is to describe the nature of the PVDF deterioration observed during a number of tests performed to examine this phenomenon. This report also records, as Appendix 1, some SEM/X-ray microanalysis data on Coflon samples exposed to a methanol/amine mixture, and to other amine or H2S-aged samples.
    Keywords: Nonmetallic Materials
    Type: NASA/CR-95-207623 , NAS 1.26:207623 , CAPP/M.6
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    NASA TECHNICAL REPORTS
  • 2
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    Cosmic ray exposure ages of features and events at the Apollo landing sites (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Cosmic-ray exposure ages of lunar samples have been used to date surface features related to impact cratering and downslope movement of material. Only when multiple samples related to a feature have the same rare-gas exposure age or when a single sample has the same Kr-81 -Kr and track-exposure age can a feature be considered as reliably dated. Based on these criteria, there are only five well-dated lunar features: Cone Crater (Apollo 14), 26 m.y,; North Ray Crater (Apollo 16), 50 m.y.; South Ray Crater (Apollo 16), 2 m.y.; the emplacement of the Station 6 boulders (Apollo 17), 22 m.y.; and the emplacement of the Station 7 boulder (Apollo 17), 28 m.y. Other features are tentatively dated or have limits set on their ages: Bench Crater (Apollo 12), upper limit of 99 m.y.; Baby Ray Crater (Apollo 16), upper limit of 2 m.y.; Shorty Crater (Apollo 17), approximately 30 m.y.; Camelot Crater (Apollo 17) upper limit of 140 m.y.; the emplacement of the Station 2 boulder 1 (Apollo 17), 45 to 55 m.y.; and the slide which generated the light mantle (Apollo 17), lower limit of 50 m.y.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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    NASA TECHNICAL REPORTS
  • 3
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    Horizontal transport of the regolith, modification of features, and erosion rates on the lunar surface (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Impact-ejecta systematics are developed for the smaller cratering events which, with cumulative crater populations observed in young mare regions and on Copernicus ejecta fields, yield rates and a range distribution for the horizontal transport of material by impact processes. The deposition rate for material originating more than 1 m away is found to be about 8 mm per million years. Material from 10 km away accumulates at a rate of about 0.08 mm per million years, providing a steady influx of foreign material. From the degradation of boulder tracks, a rate of 5 plus or minus 3 cm per million years is computed for the filling of shallow lunar depressions on slopes. Mass wastage and downslope movement of bedrock outcroppings on Hadley Rille seem to be proceeding at a rate of about 8 mm per million years. The Camelot profile is suggestive of a secondary impact feature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 4
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    The Effect of Resistance on Rocket Injector Acoustics (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Combustion instability, where unsteady heat release couples with acoustic modes, has long been an area of concern in liquid rocket engines. Accurate modeling of the acoustic normal modes of the combustion chamber is important to understanding and preventing combustion instability. This study evaluates the effect of injector resistance on the mode shapes and complex eigen-frequencies of an injector/combustion chamber system by defining a high Mach-flow form of the convective wave equation (see Eq. 1) in COMSOL Multiphysics' Coefficient Form PDE Mathematics Module.
    Keywords: Fluid Mechanics and Thermodynamics; Numerical Analysis
    Type: M15-4797 , COMSOL Conference 2015; Oct 07, 2015 - Oct 09, 2015; Boston, MA; United States
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  • 5
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    Cosmic-ray exposure history at Taurus-Littrow (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 6
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    The regolith history of 14307 (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Noble gas and trace element analyses of matrix and a clast from breccia 14307 are reported. This sample was exposed to a large neutron fluence, as seen by an elevated Sm-150/Sm-149 ratio and by noble gases, particularly Xe-136 from neutron fission of U-235. Strong constraints on the exposure history result from combined consideration of Sm-150, Xe-136, and spallation noble gases. Both clast and matrix were irradiated for about 1 AE under substantial shielding beginning at least 2 AE ago, probably more than 3 AE ago. The manifestations of soil exposure seen in the matrix - solar wind gases, glass formation, etc. - thus must have been acquired in an ancient epoch. The matrix has had a longer exposure to cosmic rays than the clast, presumably during its prebrecciation history as a soil. Brecciation probably occurred more than 1 AE ago, perhaps more than 3 AE ago, but at least 0.4 AE after the formation of the matrix constituents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 7
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    The excess fission xenon problem in lunar samples (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper presents noble-gas (neon, krypton, and xenon) data obtained in stepwise heating of five lunar breccias: 14063, 14082, 15205, 15405, and 15445. These data are discussed in terms of spallation gas content, cosmic-ray exposure ages, and content of fission xenon. None of these samples is rich in solar-wind gases, and none contains more fission xenon than would be expected for in situ fission of U-238 and Pu-244. The essential features of the excess-fission-xenon phenomenon seen in several Apollo 14 samples are reviewed, as are models which might account for this phenomenon and criteria by which these models may be evaluated. The lack of excess fission xenon in 14063 and 14082 eliminates models relying on microscale xenon redistribution. A model is proposed in which the excess fission xenon originates in local material and percolates through and is adsorbed on regolith material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 15, 1976 - Mar 19, 1976; Houston, TX
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  • 8
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    Exposure histories of Bench Crater rocks (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A description is presented of the results of mass spectrometric analyses of the noble gases krypton and xenon, in eight Apollo 12 basaltic rocks. The significance of the results is evaluated. It is concluded that the Bench Crater rocks are not what they appear to be in their field relationships. They are not fragments ejected from bedrock by the Bench impact. Most, if not all, have had a previous history of regolith residence prior to the Bench impact. In retrospect, sampling of fresh ejecta from lunar craters during the Apollo missions turned out to be surprisingly difficult. Sampling was successful for Cone and North Ray craters where large boulders were available, but fresh South Ray ejecta was surprisingly elusive. The reported investigation shows that fresh ejecta was not obtained from Bench, and moreover, that the concept of 'radial sampling', in which the rocks sampled from a crater rim are supposed to represent the deepest material excavated, fails very badly for Bench.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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