In the Memory of the crew of the
nuclear powered submarine Kursk


Did a torpedo sink Kursk?

With speculation rife over the causes of the Kursk disaster, Richard Scott examines what could have happened if an explosion occurred in the torpedo room

Norwegian and UK divers last week confirmed that the Russian Oscar II-class (Antyey)(T949A) submarine Kursk (K141), stranded on the floor of the Barents Sea, was completely flooded, thus ending the faint hopes that some members of the submarine's crew might be found alive.

Seismologists in Norway recorded two explosions at the time the Kursk sank on 12 August. Video pictures of the submarine, lying in 100m of water, subsequently revealed extensive damage to an area of the submarine stretching from the bow back to the fin.

Plans are now being drawn up to salvage the stricken submarine and recover the remains of the 118 crew. This may yield new evidence on the cause of the loss of the Kursk, but for the time being speculation continues. Some Russian officials have continued to insist that a collision was responsible for the sudden and massive damage, with one senior officer from Russia's Northern Fleet blaming the disaster on a UK Royal Navy nuclear submarine.

However, one highly experienced torpedo engineer discounts the collision theory. "The amount of damage depicted in the press reports was extreme," he told Jane's Defence Weekly. "With the robustness of the hull design, for a collision to cause that much damage to the Kursk is very unlikely. The Project 949A 'Oscar II' boats have a tremendous amount of equipment and weapons outside the hull that would absorb a lot of energy before the inner (pressure) hull on the Russian boat would have been hit."

A conventional weapons incident - involving a torpedo fuel fire and detonation of one or more warheads - remains the most likely explanation.

"In a recent article in the Russian journal Military Parade, the director of Gidripribor, the Russian torpedo design bureau, commented on the fact the older generation torpedoes on Russian submarines had been replaced with modem [UGST] dual purpose, liquid mono-propellant fuelled, long-range torpedoes. In the past the Russians have also had hydrogen peroxide-fuelled torpedoes on their submarines, as well as torpedoes with high-pressure oxygen fuel and high-energy batteries.

"Each has its own problems and dangers, but years of experience with all the older systems might suggest that problems with the newer type might be the more likely."

If one accepts the veracity of the reports emanating from Russia, then the torpedoes on board

Kursk were indeed the newer UGST mono-propellant fuelled weapons. Press reports state that weapon-firing exercises were in progress and so weapons handling and loading proceeding firing would have been under way.

"Normally an exercise would involve torpedoes without warheads, but an operational submarine could have any number of warshots on board and in close proximity to the handling operation." According to this same source, preliminary analysis of available evidence suggests the following sequence of events that could have led to the loss of the Kursk.

"During the handling and firing operation, a torpedo fuel, leak develops and fuel is present in the torpedo room. If so, the sailors would start to respond to the leak. But before it is cleaned up a tool or other object either impacts the fuel or causes a spark.

"The fuel ignites and causes the fuel tank to deflagrate [first explosion detected by the Norwegians] the residual fuel bums for a period of time and results in a high order detonation of one or more torpedo warheads stored in the torpedo room [the second explosion].

"The submarine is designed to resist damage from the outside - not a detonation of one or several warheads inside the vessel. This would result in the first two compartments (including the control room) being destroyed instantly with total loss of life in those areas and buoyancy and the ballast tanks adjacent to the forward part of the ship.

"This submarine would sink very quickly. Emergency surface system would have been destroyed and may prevent the aft ballast tanks from being blown to provide some buoyancy and capability to surface."

The torpedo engineer also addressed the question of the composition of the mono-propellent fuel: "In the mono-propellant fuel the nitrate ester energetic ingredient can be very unstable and have a low flashpoint and impact resistance. Stabilisers are required to prevent that type of problem. For example the Western nations have been using OTTO II fuel in torpedoes for decades, quite safely and without incident.

"An incident resulting in ignition of this fuel is very unlikely, due to the stabiliser content added to the fuel during manufacture. It is quite difficult to light off OTTO fuel due to high Hash point (this also reduces energy content and is the trade off for safety and long term stability)."

So why could the torpedo leak fuel? There are a number of possible causes.

• The nitrate ester fuel needs special '0' rings that are not susceptible to deterioration when in contact with the fuel. If standard '0' rings were used, these would deteriorate over time and cause a leak when the torpedo was being moved.

• Inexperienced torpedo handling crew moving the torpedo might hit a piece of ship's structure (like a storage chock), drop it when removing a storage restraint, or drop a tool on to a weapon fuel tank causing the leak and a spark.

• Shore-based maintainers may have improperly assembled the torpedo. This may mean the seals were not installed correctly, causing a break in a tenuous seal when the torpedo was being moved in the weapons compartment or rammed into the tube.

The resultant fire, from whatever source, would bum for a time and once ignited would be very difficult to put out. A senior official told JDW: "The crew would try to put out the fire [but] fumes might overcome personnel in the torpedo room before they are able to put on breathing gear and extinguish the fire.

The Russian warhead explosive used in this case could not take the heat of a fully developed fire for more than a few minutes before it detonated.

A second, but less likely, cause of the fire is a solid rocket motor on a VA-111 Shkval super-cavitating torpedo. Explosive squibs generally utilised to initiate and light off a rocket motor are susceptible to static electricity.

"Normal handling of these motors requires a very specific set of actions and procedures to prevent initiation. If an inexperienced sailor made a mistake during torpedo loading the rocket motor could light off in the torpedo tube or room. It would likely take place at the moment when the torpedo is almost completely in the torpedo tube and the firing cables are being hooked up.

"A static discharge or a stray voltage in the firing cable results in rocket motor firing and the flame and exhaust would be back into the torpedo room.

"And would most certainly instantly kill all personnel in the area, if not the entire compartment, and initiate fires in other torpedoes and fuel, possible fuel tanks."

Until the submarine can be accessed without restriction, all causes and explanations remain speculative. As, and if, real data is made available the above explanations may by modified, reinforced or dismissed outright.

Richard Scott is JDW's Naval Editor

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