The RPK-2 Viyuga (, meaning blizzard), also designated 81R, and identified by NATO as Starfish and the United States Department of Defense as SS-N-15, is a Russian submarine-launched, nuclear-armed anti-submarine missile system, launched exclusively through 533mm torpedo tubes. The RPK-2 uses a 82R torpedo or 90R nuclear depth charge in the 533 mm version, and a 83R torpedo carrying or 86R nuclear depth charge in 650 mm version.