I'd assumed that only ships need to be checked for collisions against other objects. This makes things considerably simpler, and faster, than it would be otherwise - a little advantage to having immobile asteroids and debris.
As to question #1:
It's simple. That'll practically never come up. The reason for this is that AI would
automatically swerve to avoid coming within a certain distance of
any object, including other ships - if they smash into something, they're more or less screwed, and they wouldn't want that, would they? Even if, by some bizarre circumstance, they ended up inside each other, they would simply turn and move away, like putting two reversed magnets next to each other.
#2. You saw in the last update that mining and scanning works
just fine - keep in mind there weren't any collisions going on, and while there
was a single bizarre incident where a large mining ship got "stuck" in an asteroid as a "monument" (as Josh called it), that was it. Everything else functioned normally, and apart from that, the lack of collisions was practically unnoticeable.
And for #3:
Yeah. But, that won't come up, unless it's you. Stars and planets should
always be avoided by NPCs, no matter what. In fact, NPCs would probably avoid asteroids, too. Instances where they would actually
collide are likely to be few and far between. Instances where they go through a star? That's pretty much zero.
Collision handling is part detection, and part active avoidance. If you can get AI to recognize where an enemy ship is, it's much less likely that they'll collide. This would likely go on throughout the entire system all at once, unless Josh turns it off to save on frame rate.
Basically... if the ship collides in the first place, you're doing something wrong, or the ship was forced into it. Collision detection should be primarily for players, and weaponry. (weaponry is a bit harder to deal with, but not really - they're basically tiny spheres themselves.) (which reminds me, you forgot weapon fire.
)