CALCULATIONS OF SHAPE CHANGE AND FRAGMENTATION PARAMETERS USING VERY PRECISE BOLIDE DATA.
- Douglas O.
Using the theoretical formalism of ReVelle (2001d), we have analyzed 22 European (EN) and US Prairie Network fireballs (PN) with the most precise trajectory information available for shape change and fragmentation effects. For 14 bolides the shape change parameter, {mu}, was always > 0 and for the other 8 cases there were instances of {mu} < 0, but with large oscillations in its sign with height or time. When the shape change parameter, {mu}, was < 0, the fragmentation scale height was > 0 and in a few instances was briefly even smaller than the pressure scale height. This is the necessary condition in addition to the sufficient condition of {mu} < 0 for the onset of the catastrophic fragmentation process ('pancake' break-up). A histogram of all computed {mu} values indicates that an average value was <{mu} > {approx} 0.10, indicating that substantial shape change has taken place during entry for these bolides. This is fully consistent with the recent analyses of ReVelle and Ceplecha (2001g) of the changes in the shape-density coefficient, K, with time as well. Thus, the use of the {mu} = 2/3 (self-similar solution with no shape change) is not recommended for bolide modeling efforts. From our results we can conclude that most of the US DoD bolides can be successfully modeled using single-body theory without resorting to the 'pancake' catastrophic fragmentation model that was 'rediscovered' in the early 1990's by a number of workers. These researchers included Hills and Goda, Chyba, Thomas and Zahnle, etc. who specifically developed this break-up model for studying he impact into Jupiter of the huge Shoemaker Levy-9 comet.
- Research Organization:
- Los Alamos National Laboratory
- Sponsoring Organization:
- DOE
- OSTI ID:
- 975812
- Report Number(s):
- LA-UR-01-5653
- Country of Publication:
- United States
- Language:
- English
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