Yeah the ships despawning is something I might rework after the jam :P the idea is that the ships each have their own hp tracker and can take damage from the bullets and will die if they get hit too many times... but in practice I'm not sure that this interaction adds much to the gameplay, especially since the player cannot shoot any projectiles of their own (...for now at least) and thus doesn't have much reason to think about enemy hp. They will one-shot every smaller ship they encounter.
...if I had more time, maybe I'd have also added a simple death animation for ships, so that you know they're getting destroyed and not just getting disappeared into the aether by a capricious piece of code spaghetti (...I mean, that is factually what's happening, but it's about presentation :P)