The Air Independent Propulsion System is supposed to be insanely quiet.. Saw something a number of years ago that Norway has a sub(probably more now) that uses this system.. The sub and its crew were being rented by the USN for attack sub exercises..
Nope its the swedes that were rented by the usn. Our subs dont have AIP yet, but the next class we get will. Basicly the AIP system is about as quiet as running on battery depending on what kind of AIP system is used. There are two kinds of AIP systems and you can find both on wikipedia. They both have their strenghts. The french (soon), swedes, germans, israelis (soon) koreans and spanish (soon) and a few others have them now. The russians are also making a version of the Kilo class with an AIP system both for domestic and export use, but i dont think they are operational yet.
