Asteroid collision debris calculation

I wonder how to determine the directions, in which the collision debris is launched when 2 asteroids collide. I am aware of: m1*v1 + m2*v2 = m*v = m3*v3 + m4*v4 + m5*v5 + ... and this works just fine for the masses and valocity, however I find it difficult to determine the boundaries of the directions and under what circumstances shatter be produced or the asteroids will just "merge".

All info is appreciated :)

3. for some purposes, it could be useful to approximate the production of debris as proportional to the energy in the center of mass of the two colliding asteroids: $E_{\text{cm}}\propto n$ of fragments. Then assume a $n$-body decay, each with the same mass. Even in the case of $n\gtrsim 3$, you can only have a phase-space for these debris and some probability density functions for their production angles.
• Infinity... :) Consider for example the limit where the shatter debris are two very light-weight particles, other than the two original asteroids. Even further, suppose that these particles are photons! Their speeds are $c$ (ore close to..), while their total energies are fractions of the initial total energy: ${1\over 2}M{v_1}^2+{1\over 2}M{v_2}^2$. Dec 5 '13 at 12:14