It is shown that during the motion of two initially gravitationally bound spherical shells , consisting of point particles moving along ballistic trajectories , one of the shell may be expelled to infinity at subrelativistic speed v _ { exp } \leq 0.25 c .
The problem is solved in Newtonian gravity .
Motion of two intersecting shells in the case when they do not runaway shows a chaotic behaviour .
We hope that this toy and oversimplyfied model can give nevertheless a qualitative idea on the nature of the mechanism of matter outbursts from the dense stellar clusters