DISINTEGRATION OF LARGE METEOROIDS IN EARTHS ATMOSPHERE - THEORETICAL-MODELS

Disintegration of large meteoroids, 1 m to 1 km in size, when affected by aerodynamic forces in flight is considered in this paper. Argument s are adduced that ablation is of secondary importance in comparison w ith mechanical processes of deformation and fragmentation. 2D hydrodyn amic simulations using the free-Lagrangian method and the Eulerian met hod with a volume-of-fluid front tracking procedure have been carried out. The cosmic body was treated as a fluid, with the equation of stat e of water, moving through gas of appropriate density. We find that di sintegration is more complex than simple models based on the estimate of lateral expansion due to differential ram pressure across a meteoro id make it. Rayleigh-Taylor instabilities strongly deform the body and it breaks up in the center. The outer radius of an originally spheric al or cylindrical body agrees with the analytic models of spreading. H owever, a body of accidentally aerodynamic shape does not have its cro ss section significantly enlarged.A sandbag model has been developed i n which a heavily dispersed meteoroid is represented as a conglomerati on of noncolliding particles moving through the atmosphere. The partic les transfer energy and impulse to the atmosphere and are enclosed by a single bow shock. Calculations show that a spherical swarm of partic les takes a conical form but lateral expansion agrees with the above-m entioned simple theoretical models. The approximate analytical approac h of a spreading fragmented impactor has got additional support: integ ration of the drag, ablation, and radiation equations produces results which are in a good agreement with light flashes registered by DoD sa tellites. (C) 1995 Academic Press, Inc.