How you adjudicate multiple torpedoes depends on how you choose to fire them.
Typically, firing multiple torps would be a Multifire attack.
However, if a character were willing to accept the Multiple Action Penalty, he could fire each one individually. It might look like a rapid burst of torpedo fire, but in game terms it's a bunch of separate actions. (In short, it's a "special effect," in HERO System terms ).
Does that answer your question? If not, post a follow-up and I'll see if I can clarify.