Chondrules are millimeter-sized silicate spherules ubiquitous in primitive meteorites , but whose origin remains mysterious .
One of the main proposed mechanisms for producing them is melting of solids in shock waves in the gaseous protoplanetary disk .
However , evidence is mounting that chondrule-forming regions were enriched in solids well above solar abundances .
Given the high velocities involved in shock models destructive collisions would be expected between differently sized grains after passage of the shock front as a result of differential drag .
We investigate the probability and outcome of collisions of particles behind a 1D shock using analytic methods as well as a full integration of the coupled mass , momentum , energy and radiation equations .
Destruction of protochondrules seems unavoidable for solid/gas ratios \epsilon \gtrsim 0.1 , and possibly even for solar abundances because of “ sandblasting ” by finer dust .
A flow with \epsilon \gtrsim 10 requires much smaller shock velocities ( \sim 2 vs 8 km s ^ { -1 } ) in order to achieve chondrule-melting temperatures , and radiation trapping allows slow cooling of the shocked fragments .
Initial destruction would still be extensive ; although re-assembly of mm-sized particles would naturally occur by grain sticking afterward , the compositional heterogeneity of chondrules may be difficult to reproduce .
We finally note that solids passing through small-scale bow shocks around few-km-sized planetesimals might experience partial melting and yet escape fragmentation .