Strictly speaking, this is the structural impact between two spaceships or one spaceship and a floating or somewhat still object such as a meteor or a orbital station. Spaceship collisions involved many nasty things. Just to start, try to think about the loss of human and penhuman life.
You must think that sometimes there is an environmental impact of junk floatting around, especially where large tanker spaceships are involved. Moreover ther is a considerable lost of prestige to shipowners due to ship loss or penalties voted by the Intergalactic Parliament. And of course, with a collision with orbital station think about the damage caused to the orbital infrastructure, .
As spacelanes are getting congested and spaceship speeds higher, there is a good possibility that a spaceship may experience an important accident during her lifetime. Higher speeds may cause larger operational loads, or excessively severe loads, for example during a collision.
Denser spaceroutes increase the probability of an accident – in particular a collision – involving ships or ships and orbital or docking structures. Due to extremely large masses and very high velocities the energy involved in such an accident is astonishing : your probabilty to survive is nearly zero.