/m-aintenance

Nanomachines.

Depends on the specific franchise, really.

In BattleTech, there are steady manufacturers of weapons (even model-specific ones) as well as parts for 'Mechs, and it gets even easier once you enter the OmniMech era where everything is standardized. Barring that, battlefield salvage is the name of the game, where it's assumed that as long as a specific weapon or part has not taken a crit or has its internal structure completely destroyed, it's perfectly fine (thus why it's sometimes referred to as BalloonTech, because there's somehow a shitload of empty space inside those things due to critical checks). If you blow off a limb, you can salvage the parts on it (the specific manuals have checks for various types and differing manufacturers), and if you blow up the head and nothing else (happens far more often than one would think, especially if you're on the receiving end), the rest of the 'Mech is free game once you replace the head.

As for Gundam, it's one of those things that's glossed over depending on the specific series. In 00 you see high-end weapons being destroyed and limbs being chopped off, yet they have no problem replacing them outside of "We just got supplies from stopping at a base or meeting with a supply ship!", but in G-Tekketsu it's somewhat more nuanced with them salvaging the mobile suits they defeat and even commandeering and using them themselves in numerous cases (the first Ryusei-Go, Rebake, etc.). And then there's X where the destroyed Satellite Cannon means that they have to downgrade it to the X-Divider permanently.

>>15038064
>Do they just have a ton of extra limbs already manufactured? Or do they mine asteroids and make the limbs on board ship?
It's both of those actually. When Kai gets the Guncannon's arm blown off they mention fabricating a new arm in the machine shop.

File: Russian aircraft carrier Admiral Kuznetsov in the English Channel off Dover on Oct 21st 2016.jpg (365KB, 2048x1909px) Image search: [Google]

365KB, 2048x1909px

Same way they do with fighter jets in real life, anon.

At air bases, you just have a constantly updating "Parts-on-Order" list that you get new engines and such from when need be.

On Carriers, you bring as much extra-shit as you can and when you start running out you either turn-tail and run for port or you start making do with fewer and fewer machines at 100% readiness.

>>15038077
good pilots don't get hit.