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  • 1
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    Experimental investigation of crater growth dynamics (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This work is a continuation of an ongoing program whose objective is to perform experiments and to develop scaling relationships for large-body impacts onto planetary surfaces. The centrifuge technique is used to provide experimental data for actual target materials of interest. With both power and gas guns mounted on the rotor arm, it is possible to match various dimensionless similarity parameters, which have been shown to govern the behavior of large-scale impacts. The development of the centrifuge technique has been poineered by the present investigators and is documented by numerous publications, the most recent of which are listed below. Understanding the dependence of crater size upon gravity has been shown to be key to the complete determination of the dynamic and kinematic behavior of crater formation as well as ejecta phenomena. Three unique time regimes in the formation of an impact crater have been identified.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-176392 , NAS 1.26:176392
    Format: application/pdf
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  • 2
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    Centrifuge Impact Cratering Experiments (1985)
    In:  CASI
    Details
    Publication Date: 2014-10-08
    Description: The kinematics of crater growth, impact induced target flow fields and the generation of impact melt were determined. The feasibility of using scaling relationships for impact melt and crater dimensions to determine impactor size and velocity was studied. It is concluded that a coupling parameter determines both the quantity of melt and the crater dimensions for impact velocities greater than 10km/s. As a result impactor radius, a, or velocity, U cannot be determined individually, but only as a product in the form of a coupling parameter, delta U micron. The melt volume and crater volume scaling relations were applied to Brent crater. The transport of melt and the validity of the melt volume scaling relations are examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 167-169
    Format: text
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  • 3
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    Crater ejecta scaling laws - Fundamental forms based on dimensional analysis (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Self-consistent scaling laws are developed for meteoroid impact crater ejecta. Attention is given to the ejection velocity of material as a function of the impact point, the volume of ejecta with a threshold velocity, and the thickness of ejecta deposit in terms of the distance from the impact. Use is made of recently developed equations for energy and momentum coupling in cratering events. Consideration is given to scaling of laboratory trials up to real-world events and formulations are developed for calculating the ejection velocities and ejecta blanket profiles in the gravity and strength regimes of crater formation. It is concluded that, in the gravity regime, the thickness of an ejecta blanket is the same in all directions if the thickness and range are expressed in terms of the crater radius. In the strength regime, however, the ejecta velocities are independent of crater size, thereby allowing for asymmetric ejecta blankets. Controlled experiments are recommended for the gravity/strength transition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 88; Mar. 10
    Format: text
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  • 4
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    On the scaling of crater dimensions. II - Impact processes (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Holsapple and Schmidt (1980) previously addressed the problem of the scaling of explosive cratering. Their analysis included results which show under which conditions the scaling can be bounded between quarter-root and cube-root rules. The present investigation is an extension of the earlier analysis and approaches the case of impact cratering. More restrictive bounds are found for impact cratering than for the explosive case. These stronger results come from considering the role of the impactor momentum as an independent variable for impact cratering. Attention is given to impact cratering variables, general scaling rules, the bounds on scaling rules, a generalization to more variables, and previous scaling rules and results.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 87; Mar. 10
    Format: text
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  • 5
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    Meteor Crater: Energy of formation - Implications of centrifuge scaling (1980)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Recent work on explosive cratering has demonstrated the utility of performing subscale experiments on a geotechnic centrifuge to develop scaling rules for very large energy events. The present investigation is concerned with an extension of this technique to impact cratering. Experiments have been performed using a projectile gun mounted directly on the centrifuge rotor to launch projectiles into a suitable soil container undergoing centripetal accelerations in excess of 500 G. The pump tube of a two-stage light-gas gun was used to attain impact velocities of approximately 2 km/sec. The results of the experiments indicate that the energy of formation of any large impact crater depends upon the impact velocity. This dependence, shown for the case of Meteor Crater, is consistent with analogous results for the specific energy dependence of explosives and is expected to persist to impact velocities in excess of 25 km/sec.
    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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  • 6
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    Point source solutions and coupling parameters in cratering mechanics (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The use of a point source of an impactor energy and momentum to replace the effects of the impactor is examined. The general framework and notation of the impact cratering problems are described; it is determined that the cratering phenomena are governed by Froude, Cauchy, and Reynolds numbers. The coupling parameter concept is defined mathematically as the measure that governs limit point source solutions. Examples of cases where coupling parameters are used are presented. The relationships of the coupling parameter concept with steady flow and the Z-model of cratering of Maxwell (1973, 1977) are studied. Crater size, ejecta distributions, growth histories, time of formation, melt volume, and shock decay for various scale factors for impact cratering mechanics are calculated, and the applicability of the coupling parameter to the study of cratering mechanics is revealed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 6350-637
    Format: text
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