How does the collision physics work?

[SomethingOrAnother]

Hello all! I need some help understanding the specifics of how KSP renders and calculates the collisions between parts and vessels. 

Long story short, I've been attempting to test build some "space missiles" in a primarily stock game that me and a friend will eventually be save sharing in. The exact purpose of this testing is to make some missiles that can do damage to other ships in orbit. The trouble I've come to, however, is that nothing seems to be working, hardly at all, let alone reliably. 

I started with classic Macey Dean style LV-1 Ants attached to Oscar tanks, but those never did anything. I've since slowly upped the size and speed of my projectiles, but to no avail. My most successful design was just a straight RT-5 Flea, but even those had a close to 70% failure rate. I've noticed some of my projectiles just phase through the target, which I suspect is to the game not rendering the physics fast enough and the missile passing through too quickly. But even when they hit and things explode, there's never anything done to the target vessel. It seems like using parts that have a higher Impact Tolerance than the target parts is also useless, as those just explode harmlessly as well. 

Here's the actual question: How do the collision physics work? Does Impact Tolerance or anything else have a major impact on how the game calculates and renders the breaking of parts? 

Is there something that I'm missing here? I feel like every other time I play this game I could rip space stations apart with an accidental burst of RCS in the wrong direction, but the moment I sling 2T projectiles at 250m/s, the kraken just blocks my shots. 

[king of nowhere]

all this is very strange, because in my experience stuff explodes easily. I keep having problems with my huge launchers because spent boosters touch theh rocket and stuff explode.

Even when I activate indestructibility from cheats, stuff still explode if hit hard enough.

[SkyFall2489]

If you're looking for tips on space missiles:

1. Macey's missiles are no good anymore. we've moved on to much more advanced missiles and armor since that ancient time

2. You want a part with a high impact tolerance making first contact so it explodes stuff before it gets exploded

3. a good impact speed is around 300-400 m/s (source: digging through the naval battle club thread) - lower and less damage, more and they phase through

4. high mass projectiles work well, so they can punch through multiple layers

5. missiles are no longer the KSP combat meta - I've found that fireworks are much better against most ships, except heavily armored ones. plus they are often easier to aim. They can be often deflected, but will do lots of damage to other parts.

 

As for collision physics in general, they are kinda wonky. Firework shells at 100 m/s are deflected by making history structural tubes with impact tolerances of 14 m/s.

Impact tolerance only deals with impacts, however- there are some breaking tolerance things that also affect how parts that are connected break apart during stress. I don't know much about that. But once some connection snaps, the rest of the rocket is likely gonna blow.