Russian submarine K-84 Ekaterinburg

K-84 Ekaterinburg (К-84 Екатеринбург) is a Project 667BDRM Delfin class (NATO reporting name: Delta IV) nuclear-powered ballistic missile submarine. The submarine was laid down on 17 February 1982 at the Russian Northern Machine-Building Enterprise (Sevmash). She was commissioned into the Soviet Navy on 30 December 1985. After the collapse of the Soviet Union, the submarine continued to serve in the Russian Navy. Initially known only by her hull number, in February 1999 she was renamed after the city of Yekaterinburg.

Construction
Construction of the nuclear submarine Ekaterinburg (K-84) began at the Northern Machinebuilding Enterprise (Sevmash) in Severodvinsk on 17 February 1982, before being commissioned into the Soviet Navy on 30 December 1985. She was the second of the seven-boat Project 667BDRM Delfin class, which was developed at the Rubin Design Bureau in September 1975. A ballistic missile submarine, she was designed primarily to carry up to 16 R-29RM Shtil (NATO designation: SS-N-23 Skiff) SLBM for use against military and industrial facilities in the case of a nuclear war. Each Shtil missile carries ten 100 kt multiple independently targeted reentry vehicles, and has a circular error probable of 500 m. She is also equipped with RPK-7 Veter (NATO designation: SS-N-16 Stallion) anti-ship missiles for use against large surface vessels, and self-defense torpedoes.

Operational history
After commissioning, Ekaterinburg was deployed to the base at Olenya Bay, and during the second half of 1986 underwent acoustic trials. In August 1989, Ekaterinburg conducted a failed launch of all its missile under Operation Behemoth. Four months later, in December 1989, she was the first submarine to attempt to launch all her missiles while underwater; the first launch was successful, though the second was not. In 1993, she was transferred to the base at Sayda-Guba. On 3 December 1996, Ekaterinburg entered the Zvezdochka shipyard in Severodvinsk for an overhaul, though work did not begin until March 1998. She re-entered service in 2003, based in Yagelnaya Bay. She test-fired R-29RMU Sineva missiles in December 2003 and June 2004, and during Northern Fleet exercises in August 2005 fired missiles at the Kamchatka range. Also in 2005, Ekaterinburg was awarded the Navy Commander's Prize for her missile launches. In 2006, she successfully fired missiles at the Chizha Range from the North Pole. On 20 May 2011, the boat fired the first R-29RMU2 Liner SLBM, aimed at the Kura Test Range.

Fire incident and near nuclear catastrophe
On 29 December 2011 around 1220 UTC, Ekaterinburg caught fire while in drydock in Murmansk, and after several hours of firefighting efforts, she was partially sunk in an effort to control the fire. Initial statements from Russian authorities indicate there were no injuries or radiation leakage, and that the vessel was not carrying any weapons as she was drydocked for repairs. The fire apparently began when sparks from welding being done on the boat's hull ignited wooden scaffolding around the ship, then spread to the flammable rubber coating covering the hull. Russian President Dmitry Medvedev ordered the repair of the submarine and a thorough investigation of the incident on 30 December 2011. The boat's hydro acoustic system was disabled in the fire. Some sources speculate that the submarines pressure hull suffered possible structural damage due to the intense heat, the temperature inside the torpedo room allegedly rose to 60-70°C.

A commission will study the damage to the submarine and determine whether it is economical to repair it. A Zvezdochka shipyard spokesperson said that the repairs will take more than a year.

On January 12, 2012 ITAR-TASS reported that the repair of the submarine will take three to four years. The repair will be combined with a scheduled refit that was to start in 2013. As it will be some months before the submarine can be transferred to the shipyard due to winter sea ice, the repairs will begin in May–June, 2012, so the submarine is not expected to return to service before 2015.

On February 14, 2012, Vlast reported that the submarine had been carrying 16 R-29RM Shtil (NATO designation SS-N-23 Skiff) SLBMs, armed with four nuclear warheads in each missile, at the time of the fire, though officials had said at the time of the fire that no nuclear weapons were on board, as they had been unloaded before the fire broke out. According to Vlast, the presence of nuclear weapons on the burning vessel would have meant that "Russia, for a day, was on the brink of the biggest catastrophe since the time of Chernobyl."

Viktor Litovkin, editor-in-chief of Nezavisimoye Voyennoye Obozreniye, seriously doubted that a nuclear submarine could undergo maintenance with missiles and torpedoes on board because an off-duty submarine cannot have any weapons on board due to the Russian-American Prague agreement on nuclear arms. Litovkin explains that “when such a submarine is in dock, all missile pits are opened so that the Americans could check from surveillance satellites that there are no missiles in them... Moscow and Washington notify each other when nuclear missile carriers are going off duty for maintenance and Russia does the same surveillance of American subs."

During 1985 to 1989, US submarines did not have to remove their ballastic missiles (with nuclear warheads) to enter what was known as a floating drydock. This would seem agree with the possibility of the Russian sub having its nuclear weapons on board at the time. The reference to some US/Russian agreement may not have covered floating drydocks or Subs lifted out of the water on these for short duration repairs.