The Kursk submarine disaster, the sinking of the Oscar-classsubmarine (Russian: Project 949A Антей) Kursk, took place during the first major Russian naval exercise in more than ten years, in the Barents Sea on 12 August 2000, killing all 118 personnel on board. Nearby ships registered the initial explosion and a second, much larger, explosion two minutes and fifteen seconds later, which was powerful enough to register on seismographs as far away as Alaska. The Russian Navy did not realise that the sub had sunk and did not halt the exercise or initiate a search for it for more than six hours. Because the sub's emergency rescue buoy had been intentionally disabled, it took more than 16 hours for them to locate the sunken boat.
Over four days, the Russian Navy used four different diving bells and submersibles to try to attach to the escape hatch without success. The navy's response was criticised as slow and inept. The government initially misled and manipulated the public and media about the timing of the accident, stating that communication had been established and that a rescue effort was under way, and refused help from other governments. On the fifth day, President Vladimir Putin authorised the navy to accept British and Norwegian offers of assistance. Seven days after the submarine went down, Norwegian divers finally opened a hatch to the escape trunk in the boat's ninth compartment, hoping to locate survivors, but found it flooded.
An official investigation after most of the wreck was raised along with analysis of pieces of debris concluded that the crew of Kursk was preparing to load a dummy 65–76 "Kit" torpedo when a faulty weld in the casing of the practice torpedo caused high-test peroxide (HTP) to leak, which caused the kerosene fuel to explode. The initial explosion blew off the internal torpedo tube cover and the external tube door, ignited a fire, destroyed the torpedo room, destroyed the bulkhead between the first and second compartments, severely damaged the control room, incapacitated or killed the control room crew, and caused the submarine to sink. The intense fire resulting from this explosion in turn triggered the detonation of between five and seven torpedo warheads after the submarine struck bottom. This second explosion was equivalent to between 2 and 3 tonnes (2.0 and 3.0 long tons; 2.2 and 3.3 short tons) of TNT. It collapsed the bulkheads between the first three compartments and all the decks, tore a large hole in the hull, destroyed compartments four and five, and killed everyone still alive who was forward of the nuclear reactor in the fifth compartment. An alternative explanation to the faulty weld offered by critics suggested that the crew was neither familiar with nor trained on firing HTP torpedoes and had unknowingly followed preparation and firing instructions intended for a very different type of torpedo. Combined with poor oversight and incomplete inspections, the sailors initiated a set of events that led to the explosion.
Following salvage operations, analysts concluded that 23 sailors in the sixth through ninth compartments had survived the two explosions. They took refuge in the small ninth compartment and survived more than six hours. When oxygen ran low, crew members attempted to replace a volatile potassium superoxidechemical oxygen cartridge when it contacted oily sea water that had seeped into the compartment. The resulting explosion killed several crew members and triggered a flash fire that consumed the remaining oxygen, suffocating the remaining survivors. All 118 personnel—111 crew members, five officers from 7th SSGN Division Headquarters, and two design engineers—aboard Kursk died. The investigation concluded the Russian Navy was completely unprepared to respond to the disaster. The following year, a Dutch team was contracted by the Russians to raise the hull. Employing newly developed lifting technologies, they recovered all but the bow of the vessel, including the remains of 115 sailors, who were buried in Russia. More than two years after the sinking, the Russian government completed a 133-volume, top-secret investigation of the disaster. The government released a four-page summary to the public that was published in Rossiyskaya Gazeta. It revealed "stunning breaches of discipline, shoddy, obsolete and poorly maintained equipment," and "negligence, incompetence, and mismanagement." The report said the rescue operation was unjustifiably delayed.
The boat had recently won a citation for its excellent performance and been recognised as having the best submarine crew in the Northern Fleet. Although it was an exercise, Kursk loaded a full complement of combat weapons. It was one of the few boats authorised to carry a combat load at all times. This included 18 SS-N-16 "Stallion" anti-ship missiles and 24 SS-N-19/P-700 Granit "Shipwreck" cruise missiles that were designed to defeat the best naval air defences.
Kursk was reputedly unsinkable. The submarine had a double hull with a 3.5-metre (11 ft) gap separating them, nine water-tight compartments, and was as long as two jumbo jets. The vessel had a mythical standing and it was claimed to be able to withstand a direct hit from a torpedo.
At 08:51 local time, Kursk requested permission to conduct a torpedo training launch and received the response "Dobro" ("Good"). After considerable delay, the submarine was set to fire two dummy torpedoes at the Kirov-classbattlecruiserPyotr Velikiy, the Northern Fleet's flagship. At 11:29 local time, the torpedo room crew loaded a practice Type 65 "Kit" torpedo, (Russian: tolstushka, or "fat girl", because of its size), without a warhead, into Kursk's number 4 torpedo tube on the starboard side. It was 10.7 metres (35 ft) long and weighed 5 tonnes (4.9 long tons; 5.5 short tons).
Initial seismic event detected
Norwegian Seismic Array seismic readings at three locations of the explosions on the submarine Kursk on 12 August 2000.
At 11:31:48, two minutes and 14 seconds after the first, a second event, measuring 4.2 on the Richter scale, or 250 times larger than the first, was registered on seismographs across northern Europe and was detected as far away as Alaska. The second explosion was equivalent to 2–3 tons of TNT.
The seismic data showed that the explosion occurred at the same depth as the sea bed. The seismic event, triangulated at 69°36′N37°34′E / 69°36′N37°34′E / 69.600; 37.567, showed that the boat had moved about 400 metres (1,300 ft) from the location of the initial explosion. It was enough time for the submarine to sink 108 metres (354 ft) and remain on the sea floor for a short while.