Sierra Class Submarine - Russia:
The Sierra I class (Project 945) nuclear submarine was the Soviet Union's successor class to the partly successful Project 705 Lira (Alfa) class submarine. The Sierra class has a light and strong titanium pressure hull which enables the class to dive to greater depths, reduce the level of radiated noise and increase resistance to torpedo attacks. It is powered by a single OK-650 pressurized water reactor. Sierra I and its successor Sierra II classes submarines are designed by Lazurit Central Design Bureau.
The Sierra II class (Project 945A) nuclear submarine was a successor to the Sierra I with improved quieting and sonar. The Sierra II was specifically developed for search and destroy missions against US nuclear submarines. It has a smaller turning circle than any other modern submarine, with speeds and diving depth greater than its American counterparts.
The Sierra II class has a considerably larger sail which is 5 m (16.4 ft) longer than the Sierra I type. The sail also has a curious flat, square leading edge. The masts are offset on the starboard side to make way for two escape pods in the sail. The starboard side also has a 10-point environment sensor fitted at right angles to the front end of the sail. Also, the Sierra II type has a much larger pod on its after fin. The pod houses the Skat 3 passive very low frequency towed array. More details