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  • Other Sources  (3)
  • 1980-1984  (3)
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  • 1
    facet.materialart.
    Unknown
    Calculational investigation of impact cratering dynamics - Material motions during the crater growth period (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The considered investigation was conducted in connection with studies which are to provide a better understanding of the detailed dynamics of impact cratering processes. Such an understanding is vital for a comprehension of planetary surfaces. The investigation is the continuation of a study of impact dynamics in a uniform, nongeologic material at impact velocities achievable in laboratory-scale experiments conducted by Thomsen et al. (1979). A calculation of a 6 km/sec impact of a 0.3 g spherical 2024 aluminum projectile into low strength (50 kPa) homogeneous plasticene clay has been continued from 18 microseconds to past 600 microseconds. The cratering flow field, defined as the material flow field in the target beyond the transient cavity but well behind the outgoing shock wave, has been analyzed in detail to see how applicable the Maxwell Z-Model, developed from analysis of near-surface explosion cratering calculations, is to impact cratering
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 17, 1980 - Mar 21, 1980; Houston, TX
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Initial energy partitioning and some excavation stage phenomenology in laboratory-scale cratering calculations in clay (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: One impact and two explosive cratering calculations have been analyzed with emphasis on the early excavation stage. The early excavation stage is here defined as that part of the excavation stage that occurs after energy partitioning is 90% complete, but before the cratering flow field can be well described by Z-type flow fields with values of Z uniformly greater than two. Impact generated flow fields seem to have a much longer early excavation stage than explosion generated flow fields, due possibly to the slower momentum transfer versus energy transfer rate between projectile and target. During this time when the projectile retains a significant portion of its original momentum, Z values less than two are observed in the impact generated flow field. Z values less than two are not observed at any time in the explosion generated flow fields.
    Keywords: GEOSCIENCES (GENERAL)
    Type: Lunar and Planetary Science Conference; Mar 16, 1981 - Mar 20, 1981; Houston, TX
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Z-model analysis of impact cratering - An overview (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Maxwell Z-Model has been applied to two continuum mechanics computer calculations: (1) a laboratory-scale impact of an aluminum projectile into plasticene clay, and (2) a planetary-scale impact of an iron meteor into gabbroic anorthosite. The material flow in the cratering flow field may be well approximated by incompressible flow for most of the excavation stage of crater growth. The center of the flow field is located beneath, not at, the surface. Soon after energy partitioning is complete, Z can assume values less than 2.0 associated with the initial directedness of the projectile's momentum. The Z-Model parameters are time dependent during a significant portion of the crater growth time, and Z increases steadily with time from about 2.0 or slightly less at the beginning of the excavation stage to level off at values in the neighborhood of about 3.0 before the excavation stage is half-over.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Multi-ring basins: Formation and evolution; Nov 10, 1980 - Nov 12, 1980; Houston, TX
    Format: text
    Location Call Number Expected Availability
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    NASA TECHNICAL REPORTS
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