system
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human
[Star Wars] How do you quantify the durability of Star Wars spaceships?

I've recently noticed a pretty big inconsistency when it comes to the durability of star ships in the Star Wars franchise. See, there have been many, many times when these ships have crash landed on planets and survived relatively intact. This is all well and good until you realize that they would need to be withstanding several kilotons of force to survive such an impact, when only moments before they had likely been shot down by a laser or missile that obviously does not pack that kind of punch. So, what gives? How durable are these ships?
gpt
Really depends on the size, outfitting, construction and type of ship. 

Stuff like TIEs are paper flimsy, they have no shields and little to no armor-rock collisions or heavy man portable weaponry can be take one out in one hit. More advanced TIEs (like the TIE Advanced or Defender or First Order TIEs) have both shielding and slightly heavier armor. The Advanced can survive being struck by another TIE without destroying the ship, but first order TIEs are still weak to collision damage. 

Something like an X-Wing or B-Wing packs beefier shields, more armor and is a bit more survivable. A T-65 X-Wing can survive a crash landing into a swamp without much damage (likely with shields up) but a T-70 can be disabled and destroyed with heavy arms fire. 

Going up a class or two is when you get the tankier ships. We’ve seen ships like the Millennium Falcon and the Ghost take on damage that would obliterate smaller ships. The Falcon is presumably still eventually flight worthy after a crash landing, and can take a fair amount of small arms fire without much issue (but things like E-WEB blasters do seem to pose a threat). Hits that would likely destroy a TIE (such as losing the radar dish in RotJ) are survivable, and we can see in VII that it can handle a rough takeoff and crash landing without much issue now-the upgrades Han made to the Falcon seem to have helped a ton. 

At the higher scale we have capital ships, which are much much much stronger. Invisible Hand is able to still function to an extent with half a ship, and even manages a survivable atmospheric landing. A Star Destroyer can shrug off the impact of a Hammerhead corvette(?) colliding into it even with shields down, but of course can’t survive a collision with another destroyer. Other ISDs are shown to be able to shrug off the impact of a few asteroids near Hoth, but one is taken out by a large enough impact. The Executor is even more resistant. Although the kamikaze A-Wing took out the primary bridge when shields were down, the rest of the ship was fine-it was just very close to a large body, and the time it took to get the backup bridge up and running wasn’t enough to stop it from colliding with the Death Star. And at the extreme edge, you have the First Order Mega Class Star Destroyer. Although it was split in half by another capital ship accelerating at light speed, a large portion of the ship was still partially functional. 

TL;DR, bigger ships more likely to have better armor and shielding.