We report and discuss the results from a series of catastrophic disrup
tion experiments involving 21-cm spherical targets of alumina cement.
These experiments were performed in the open air using a contact charg
e technique to simulate an impact at similar to 6 km/s, typical of col
lision velocities between asteroids in the main belt. The 1992 experim
ents reported here, the most recent in an extensive experimental progr
am initiated by Giuseppe Martelli before his death in 1994, follow dir
ectly from those described in I. Giblin et al. (1994a, Icarus 110, 203
-224), with a number of improvements to our instrumentation and analys
is. By using two high-speed cameras at a mutual angle of 60 degrees we
have made possible a three-dimensional analysis of fragment velocitie
s alongside the standard size, shape, ejection angle and rotation rate
measurements which can easily be made from appropriately oriented sin
gle film records. In this paper we report on the results of the 1992 e
xperiments, together with various unpublished data from 1989. We make
a comparison between these sets of data and between our data and those
of other researchers in this field. Also, we compare our results to t
hose of the most recent semi-empirical model (SEM) of P, Paolicchi et
al. (1996, Icarus 121, 126-157) and to appropriate data concerning rea
l asteroids, focusing on the dynamical families, which are believed to
be remnants from the catastrophic disruption of precursor asteroids.
A secondary purpose of this paper is to document our experiences and t
echniques in the implementation and analysis of these experiments. We
find considerable variation in the slope of the fragment size distribu
tion, even between closely similar experiments. Fragments are found to
be slightly flatter and/or more elongated than those from some previo
us work, but in agreement with the previous study mentioned above. Fra
gment velocities are generally between 4 and 20 m/s with a few fast fr
agments observed up to 35 m/s. Only a weak correlation is found in eit
her linear or angular velocity versus mass. We also test for the exist
ence of a possible ''radiant point'' from which fragment velocities ap
proximately originate and find that although it serves as a useful com
ponent in a model of the break-up, the location of such a point is not
constant in our experiments. (C) 1998 Academic Press