"Killer" subs are designed to "kill" other subs. They're distinguished from nuclear missile subs, and from subs used mainly for scouting and transport.
> "Killer" subs are designed to "kill" other subs. They're distinguished from nuclear missile subs
Isn't that what I said?
> and from subs used mainly for scouting and transport
For actual navies (as opposed to for example drug smugglers) scouting and transport (which is super-niche) is done by hunter killer submarines - they aren't a separate thing.
Perhaps one designed for tapping into undersea cables, stealthy deployment of Special Operations teams in hostile waters, and such? (Yes, if of any size, such a sub would probably have some torpedoes or other lethal weapons. But for military naming purposes, a few "hopefully it'll never actually need this thing..." weapons hardly qualify as it as a "killer".)
AIP isn't quieter than a batter powered submarine, it's quieter than a nuclear powered submarine.
Unless you're doing ridiculously long research dives (in which case batteries don't suffice), or you care about noise on the surface (where you would use a traditional air burning diesel engine to recharge) it doesn't seem like this brings any advantages.
