A torpedo will actually hit a corvette, you just have to time fire either from directly in front, or directly behind. And, firing from behind, you gotta make sure you took out that bloody turret, or your torpedo will only serve to kill the turret real good (though, if you're just goofing around, putting a torp into that turret can be quite satisfying; the little bitch).
Or, you can use an HS missile to eliminate that turret. Then there's a nice blind spot where the other turrets can't get you. When I'm not in a hurry, I like to slide up behind the corvette and play "peekaboo" with the other turrets, gunning them to pieces as soon as I see them.