Mathematical models of the entry trajectory for various types of meteo
rs have frequently been applied in an effort to determine the nature o
f the Tunguska object. This approach has been used to support both a s
tony asteroid and a cometary object as the most probable cause of the
event. An accurate trajectory model must include an evaluation of both
the mechanical fragmentation and the aerothermal ablation and must co
uple these two processes. Inaccuracies in the calculated ablation rate
can lead to substantial errors in the predicted terminal altitude of
a given entry body; this is particularly true for relatively weak, icy
objects such as comets. The present study uses an analytical approxim
ation of the mechanical fragmentation and radial spreading of the boli
de and examines aerothermal ablation in some detail, including an eval
uation of radiative cooling of the shock layer gases and the effect of
radiation blockage by ablation products coming off the meteor's surfa
ce. Such calculations can be performed only in an approximate manner s
ince the properties of high temperature gases are not Well established
at the extreme pressures and temperatures involved. It is found that
the sudden release of energy approximately 8 km above the surface whic
h was associated with the Tunguska event could have been produced by t
he disruption of either a comet or an asteroid, although a cometary or
igin would have required a very steep atmospheric entry angle. Therefo
re, although an asteroidal origin seems more likely, it is concluded t
hat a trajectory analysis of this type cannot be: used at the present
time to exclude either type of object with absolute certainty. (C) 199
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