The Typhoon class submarines are the largest undersea vessels ever built
The Typhoon class (Project 941 Akula) boats are the largest undersea vessels ever built, and are based on a double hull design that comprises two separate pressure hulls joined by a single outer covering to give increased protection against ASW weapons.
The class was built specifically for operations with the Soviet Northern Fleet in the Arctic ice pack. The reinforced sail, advanced stern fin with horizontal hydroplane fitted aft of the screws and retractable bow hydroplanes allow the submarine to break easily through spots of thin ice within the Arctic ice shelf.
The first unit was laid down in 1977 at Severodvinsk and commissioned in 1980, achieving operational status in 1981. To arm the Typhoon, design of a fifth-generation SLBM, the R-39 Taifun (SS-N-20 Sturgeon), began in 1973. Six vessels were constructed between 1981-89, entering service to form part of the 1st Flotilla of Atomic Submarines, within the Western Theatre of the Northern Fleet, and based at Nyerpicha. Construction of a seventh vessel was not completed.
The R-39 allowed the submarine to fire the weapon from within the Arctic Circle and still hit a target anywhere within the continental US. The Typhoons, were originally to be retrofitted with the improved R-39M (SS-N-28) missiles.
_wN vessels were decommissioned in 1997, and in 2002 only two remained in service although it has been reported that three of the class will remain active in order to test the R-39M or the new_BTlava SLBM, contravening the Co-operative Threat Reduction Program. The Typhoon class will be
eventually replaced with the Borei class submarines