According to the available data, the Russian nuclear-powered Oscar-II class cruise missile submarine Kursk experienced malfunction and hit the seabed at the depth of 100 meters on Saturday, August 12. The position of the submarine is 69’40 N, 37’35 E, just outside the cost of the Kola Peninsula east of Murmansk.
The Operation Centre of the Northern Fleet failed to establish a scheduled contact with the submarine the same day. The position of the submarine was located in the evening of August 12. A team of surface vessels was dispatched to the area of the accident. Reinforcement consisting of rescue vessels was reportedly sent to the area in the evening on August 13. The same day, the Northern Fleet finalised the military exercise that started on August 9-10 and involved around 30 submarines and surface vessels, as well as aviation.
Thus, the information about the accident was kept secret for at least two days and was made public only on Monday, August 14, by the press centre of the Russian Navy.
Since Monday, the Russian Navy has provided the media with various versions of what happened to the nuclear-powered submarine Kursk (Oscar II-class). Analysing the information from the official channels, three definite facts can be established: the submarine is lying at the seabed around 100 meters deep, the bow part of the submarine and the superstructure (bridge) are damaged, a sound resembling an explosion was detected by American Navy vessels patrolling the area at the time of the accident.
The expert team of the Bellona Foundation suggests the following two scenarios:
The Oscar II-class submarine was off the coast of the Kola Peninsula at a depth of about 40 meters. That is the regular diving depth for a submarine in waters around 100 meters deep, to avoid collisions with surface vessels while at the same time keeping a safe distance from the seabed. The submarine was about to surface to take contact with headquarters as planned.
Two different events may have triggered the accident:
- The pilot shifted the controls to manual. The moment of shifting to manual operation is crucial, when a single mistake may lead to severe consequences. The mistake was made, the submarine was steered down. Once the submarine hit the ground damaging the bow part, the high-pressurised air tanks exploded destroying the superstructure. This would have happened in a matter of seconds.
- Suddenly a tank containing high-pressurised air, located in the bow part of the submarine, explodes. It has happened in the past that high-pressurised tanks explode due to the penetration into the system of oil from the compressor that builds up the air pressure. Another possibility is a fraction in the high-pressured air tank that eventually led to explosion. Both reasons are the result of the lack of proper maintenance.
Neither the human error nor the technical malfunction mentioned above would be unexpected, given the current economical situation in the Russian Navy.
The Oscar II-class has two hulls; the ballast tanks and the high-pressurised air tanks are placed between them.
The explosion damages the ballast tanks located adjacent to the pressurised air tank. It is powerful enough to damage the superstructure. The captain of the submarine decides to surface. The crew starts the process of pushing the water out of the ballast tanks to execute an emergency surfacing operation. While the crew succeeds in emptying the ballast tanks in the rear part of the boat, the damage to the bow part does not allow to empty one of the ballast tanks there. At that time, the submarine moves at a regular speed of 5-6 knots. With the rear tanks emptied, the submarine bows 5-6 degrees down. In 20-25 seconds the submarine hits the seabed, damaging the bow section.
Once the submarine hits the ground, the automated system shuts down the two reactor installations. The system could react on various disturbances caused by meeting the ground.
The captain of the submarine cannot restart the reactors since the systems for taking seawater for cooling down the main condensation device in the nuclear installation are located at the bottom of the submarine and could be contaminated with sand from the seabed.
When the reactors are shut down in an emergency manner, the nuclear installation requires additional cooling. As is clear from the reports, the submarine has no electricity sources onboard: the reactors are shut down, while the batteries are not even capable of providing light. This means that there are no ways to provide the water circulation in the reactor installation to cool it down. Russian third-generation submarines are equipped, however, with a system called “battery-free cooling system” or “natural water circulation system.” The system functions in a way that the water continues circulating in the reactor installation without electricity supply.
The exercise the Kursk participated in started on Wednesday or Thursday last week and continued until Sunday (for Kursk most probably until Saturday). If the submarine entered the training session directly from being idle in a base, its reactors would not have warmed up significantly by Saturday, when the submarine went down.
Given that the natural water circulation system operates without malfunction, there is no danger of pressure growing in the nuclear installation of the vessel, resulting in an explosion.
During the past two days, a number of theories evolved with regards to the cause of the accident: (1) malfunction during launch of a torpedo; (2) torpedo explosion in the torpedo tube; and, finally, (3) collision with another submarine.
- The malfunction during a torpedo launch resulting in water penetrating through the inner torpedo hatch is unlikely to ground a submarine with around 17,000 ton displacement when submerged. It neither explains the damage to the superstructure nor the sound of an explosion.
- A torpedo explosion in the torpedo tube is a highly unlikely scenario, if at all possible. The reference to earlier explosions of missiles in the shafts are attributed to the fact that the earlier generations were using combustible liquid fuel (torpedoes do not use fuel at all; they are pushed out by pressure).
- The collision with another submarine is a most unlikely scenario as well, because the other vessel would have suffered severe damage and most probably would have been grounded nearby.
Russia operates 11 Oscar-II class submarines. Oscar-II is the most advance submarine the Russian Navy operates. Kursk was commissioned in 1994 and put into operation in 1995. The submarine’s dimensions are 154 x 18,2 x 9 meters. Full complement consists of 135 men. The crew onboard Kursk was reportedly 107-115 men. The submarine is capable of carrying nuclear cruise missiles, torpedoes and mines.