Russian Submarine Kursk Explosion - The Explosion

The Explosion

On the morning of 12 August 2000, as part of a naval exercise, Kursk was to fire two dummy torpedoes at Kirov-class battlecruiser Pyotr Velikiy, the flagship of the Northern Fleet. At 11:29 local time (07:29:50 UTC), a 65-76 "Kit" torpedo was loaded into Kursk's number 4 torpedo tube. Due to a leaking weld in the torpedo's fuel system, high test peroxide, a form of highly concentrated hydrogen peroxide used as an oxidiser for the torpedo's engine, escaped into the torpedo casing where it catalytically decomposed on the metals and oxides present there, yielding steam and oxygen. The resulting overpressure ruptured the kerosene fuel tank, causing an explosion that registered as a weak seismic signature on detectors hundreds of kilometers away. A similar incident was responsible for the loss of HMS Sidon in 1955.

Recovered remains of the torpedo later allowed the first explosion to be pinpointed to the middle part of the torpedo. According to maintenance records the dummy torpedoes, manufactured in the 1990s, had never had their welds checked; such checks were considered unnecessary as the torpedoes did not carry warheads.

The explosive reaction of 1.5 tons of concentrated hydrogen peroxide and 500 kg of kerosene blew off the external torpedo tube cover and the internal tube door. (The torpedo tube cover was later found on the seabed and its position relative to the rest of the submarine served as evidence of this version of events.) The tube door, which should have been capable of withstanding such an explosion, was not properly closed; the electrical connectors between the torpedoes and the tube doors were unreliable and often required repeated reclosing of the door before a contact was established, so it is likely that at the moment of explosion the door was not fully closed. The blast entered the front compartment, probably killing all seven men there. The bulkhead should have arrested the blast wave, but it was penetrated by a light air conditioning channel which allowed passage of the blast wave, fire and toxic smoke into the second and perhaps third and fourth compartments, injuring or disorienting the 36 men in the command post located in the second compartment and preventing the initiation of an emergency ballast tank blow to resurface the submarine. Additionally, an automatic emergency buoy, designed to release itself on detection of conditions such as fire or rapid pressure changes and intended to help rescuers locate the stricken vessel, did not deploy. The previous summer, in a Mediterranean mission, fears that the buoy might accidentally deploy and reveal a submarine's position to the U.S. fleet had led to it being disabled.

Two minutes and fifteen seconds after the initial eruption, a much larger explosion ripped through the submarine. Seismic data from stations across Northern Europe show that the explosion occurred at the same depth as the sea bed, suggesting that the submarine's collision with the sea floor, combined with rising temperatures due to the initial explosion, had caused other torpedoes to explode. The second explosion was equivalent to 2-3 tons of TNT, or about 5-7 torpedo warheads, and measured 4.2 on the Richter scale. Acoustic data from Pyotr Velikiy indicated an explosion of about 7 torpedo warheads in rapid succession.

The second explosion ripped a 2-square-metre (22 sq ft) hole in the hull of the craft, which was designed to withstand depths of 1,000 metres (3,300 ft), and also ripped open the third and fourth compartments. Water poured into these compartments at 90,000 litres (3,200 cu ft) per second killing all those in the compartments, including five officers from 7th SSGN Division Headquarters. The fifth compartment contained the ship's two nuclear reactors, encased in 13 centimetres (5.1 in) of steel and resiliently mounted to absorb shocks in excess of 50g. The bulkheads of the fifth compartment withstood the explosion, allowing the two reactors to shut down automatically and preventing nuclear meltdown or contamination.

Later forensic examination of two of the reactor control room casualties showed extensive skeletal injuries which indicated that they had sustained shocks of just over 50g during the explosions. These shocks would have temporarily disoriented the operators and possibly other sailors further aft.

"It's dark here to write, but I'll try by feel. It seems like there are no chances, 10-20%. Let's hope that at least someone will read this. Here's the list of personnel from the other sections, who are now in the ninth and will attempt to get out. Regards to everybody, no need to be desperate. Kolesnikov."

Twenty-three men working in the sixth through ninth compartments survived the two blasts. They gathered in the ninth compartment, which contained the secondary escape hatch (the primary hatch having been in the destroyed second compartment). Captain-lieutenant Dmitri Kolesnikov (one of three surviving officers of that rank) appears to have taken charge, writing down the names of those who were in the ninth compartment. The air pressure in the compartment following the secondary explosions was still normal surface pressure and so it would be possible, at least from a physiological point of view, to don survival suits and use the hatch to escape one man at a time, swimming up through 100 metres (330 ft) of Arctic water to await help at the surface.

It is not known if the escape hatch was workable from the inside; opinions differ about how badly it was damaged. However, the men would likely have rejected risking the escape hatch even if it were operable. They may have preferred instead to take their chances waiting for a submarine rescue ship to clamp itself onto the hatch. It is not known with certainty how long the remaining men survived in the compartment. As the nuclear reactors had automatically shut down, emergency power would soon have run out, plunging the crew into complete blackness and falling temperatures. Kolesnikov wrote two further messages, much less tidily.

There has been much debate over how long the sailors survived. Russian sources say that they would have died very quickly. The Dutch recovery team report a widely believed two to three hour survival time in the least affected sternmost compartment. In normal operation, water leaks into a stationary Oscar-II craft around the propeller shafts, and at 100 metres (330 ft) depth it would have been impossible to prevent. Others point out that many superoxide chemical cartridges, used to absorb carbon dioxide and provide oxygen in an emergency, were found to have been used when the craft was recovered, suggesting survival for several days. The cartridges seem to have been the final cause of death: a cartridge appears to have come in contact with oily sea water, causing a chemical reaction and flash fire. The official investigation into the disaster showed that some men survived this fire by plunging under water (fire marks on bulkheads indicate the water was at waist level at the time) but the fire would have rapidly used up any remaining oxygen in the air, causing death by asphyxiation.