What would happen if two spaceships with Alcubierre warp bubbles were colliding? Would the space bubble collapse? Would they reject or push each other? Would they survive it without problems?
This question is well above my metaphorical pay grade, but I would assume they would throw each other MASSIVELY off course if they were approaching each other at a sharp angle.
If they were traveling perpendicular to one another and passed close enough, I assume whichever one hit the expanded space behind the other first would break the speed of light barrier, meaning it would either grow infinitely dense or it would instantly and infinitely break down into pure energy.
If they were traveling parallel to one another, no idea.
I imagine if a 'faster' alcubierre enabled craft (as in their bubble of real-space was being flung across the universe at a faster relative speed) ran into the back of another ships alcubierre 'wake' then the compressed section of time-space from the first craft would collide into the distended section of time-space of the second craft. As the space is compressed and distended at the same time it would end up a sort of zero-sum equation. Once the rear of your alcubierre bubble is collapsed then the forefront would also be unable to hold as far as I understand it. (as a double effect of compressed and distended space-time around a bubble of normal space-time is how you are propelled at FTL speeds)
If however they were to crash on a perpendicular course then the compressed 'front' of your craft may not stay as the most compressed section. If the side of your alcubierre bubble is the most compressed section briefly then your path may be altered, possibly to disastrous effect.
but hey, what does a cat know about theoretical FTL devices?