Foraging Slime
Skeletron Prime
Whoa there budy, slow down. there are multiple issues in your plan. the first and foremost, no, there are no "air vents." i mean think about it, YOUR IN ING SPACE! But really, the ship has no air vents. also, there is no "Main frame." the closest three things to that are, the main computer, bridge, and warp core.*Lands on the roof of the ship like thor in avengers assemble except with a blizzard instead of lightning and thinks upon how to get inside, then decides upon air vents because it's always air vents, navigates the way to the mainframe, drops down behind the guards and says hello there*
But the second you land on the hull, the external sencors pick you up and the bridge crew is alerted to your presence. (do note, your on a ship that measures over 3600 feet in length.)