Kappa 5 is the SHU that you need to disable, it is always the last one in the group of five. The other SHUs can be a pain in this mission and are more dangerous that the T/Is so destroy the other ones on the way in if you can. Assign Kappa 5 to memory position two (SHIFT-F5) and the rescue SHU to memory position two (SHIFT-F6), this will allow to you keep an eye on them both during the procedings. After you have disabled Kappa 5 take out the T/Is as quickly as you can and keep one eye on the rescue SHU as they go after it as well. If a T/I slips past you launch a torpedo at it as if even one make it through to the rescue SHU it is dead! Try and keep yourself between the rescue SHU & the T/Is, this will give it a better chance.