There are certain parts of your ship that can be blown off such as the wings or fins. Everything else has no effect, I've flown back to base with 1% health before. I did notice a destroyable value on the engines once, hmm I wonder...

I think parts stop falling off when your ship explodes Other than that I don't know.

Ya, My Engine and my Shield got totaled at one point and I still had a sheilds and engines until I docked.. then they werent there and I couldnt boost and I didnt have shields when i lfited off.. weird...

I've had a time where my ship was totally flaming and smoking, with the hull down to practically nothing as I docked with a station. I'm sure if I had taken just a bit longer it would have exploded. The repair cost once inside was huge, but I had the cash

I also remember flying a Hammerhead and one time had both wings shot off - it really looks weird with them gone.

I was in a Rhino got up, and it had basically everything attached to it get blowed up. Which was especially impressive since it doesn't even have wings.

Not too sure about your engine being destroyed but I know your thruster is a targetable item. This is that little black circular thingy that boosts you up to 200 m/s. But for your engines... I usually shot those when attacking NPC ships and they don't seem to blow off.

Shields engines etc prolly have a damage value assigned for radiation damage etc in the game.

After taking radiation damage my shield system always needs to be repaired.
<shrug>

the most horrifying nightmare was in my defender, went there with a full cargo of nanobots and shield batteries, and being confident cuz i did it before in one try, i didn't bother upgrading shields. . . 1024 i think, well, along with that i decked it out with lvl 6 guns. . . (or the max) medium fire rate, and a full pod of torps, and javelin missile. i went, in, came back out, many of u might have read this, but i have to repeat. . .after the trauma . . .well, i came back out wingless, both stocks of shield batteries and nanobots totally flat out, and down to two useless guns (drails, dunno why i kept them) and the torp. surprisingly, my booster still stuck. with that, and a burning a$$, i went in after the rheinland gunboats, and did them farewell, but so did my sheilds and the voice 'hull breach-imminent' was blaring. . . the repair cost was amazing, considering how much i used to buy the ship itself. . . some several thousands. . . lucky i stocked a bit...

presently, my world is upside down, so if u do not mind, u'll have to tok to my a$$