THE DANGERS OF THE DEEP

By

Vijai S. Chaudhari[1]

Just before midnight, on August 13-14 this year, the Indian Navy’s submarine INS Sindhurakshak suffered two internal explosions.  The submarine sank shortly afterwards and 18 members of the crew lost their lives.  Efforts are on to raise the submarine.  The cause of the explosions is being investigated but conclusive answers may only be known after the submarine is brought to the surface.  The disaster has also drawn attention to the risks inherent to submarine operations, a fact that has been underscored from time to time by other similar tragedies.  The Kursk, that sank after an explosion 13 years ago almost to the day, is relevant because of the lessons learnt from the disaster.

            The Kursk was an Oscar-II class nuclear-powered cruise missile submarine of the Russian Navy's Northern Fleet.  It was named after a city where, in 1943, Russian and German forces fought the largest tank battle in military history.  Building of the Kursk began in 1990 and she was commissioned in December 1994. Being 154 metres in length and four decks (stories) high, she was the largest attack submarine ever built. The outer hull, made of special stainless steel, 8.5 millimetres thick, had good resistance to corrosion and a weak magnetic signature to help evade detection. The inner pressure hull was made of 50.8 millimetres thick steel.  Experts believe that this combination of two extremely strong hulls could withstand a small nuclear explosion.

In August 2000, the Russian Navy organised its largest training exercise since the collapse of the Soviet Union, nine years earlier.   Four attack submarines, the fleet's flagship Pyotr Velikiy (Peter the Great) and numerous smaller ships were taking part.  During the exercise, Kursk was to fire dummy torpedoes at Pyotr Velikiy.   Instead of explosive warheads, these practice torpedoes had instruments for recording the practice firing.  On August 12, 2000, at 11:28 AM there was an explosion while the crew was preparing for the practice firing.  The explosion produced a blast equal to 100–250 kilograms of TNT and registered as a Richter 2.2 earthquake at a monitoring station in the vicinity.  A second explosion followed, 135 seconds later, registering 3.5 to 4.4 on the Richter scale.  This was the equivalent of 3 to 7 tons of TNT.  The submarine sank to the relatively shallow seabed and came to rest at 108 metres, about 135 kilometres from Severomorsk.

Though assistance offered by British and Norwegian teams, Russia declined their help. All 118 sailors and officers aboard Kursk ultimately perished. The Russian Admiralty at first suggested that most of the crew had died within minutes of the explosion.  Subsequent findings disproved this theory.

Once the Kursk sank, attention turned to rescuing any surviving members of the crew. The submarine was divided into nine sections separated by strong bulkheads and heavy watertight hatches.  The Captain, Lieutenant Commander Dmitriy Kolesnikov, survived the explosions and took refuge in Compartment 9 in the rearmost portion of the submarine because the explosions had destroyed the forward compartments.  Recovery workers found notes on his body showing that 23 members of the crew were with him.

When the bodies of the crew were recovered, there was much debate over how long the survivors in Compartment 9 remained alive.  The preliminary conclusion was that they died very quickly because water leaks into stationary Oscar-II class of submarines through the propeller shafts.   Subsequently, it emerged that chemical cartridges, used to absorb carbon dioxide and to generate oxygen were found to have been used.  This suggests that some of the crew could have survived for several days.   Captain Kolesnikov's last note shows the time as 3:15 PM.  This is clear evidence that he was alive at least four hours after the explosion.  With hopes of rescue rapidly fading, the final note only recorded a terse observation:

"It seems that there are no chances. Maybe 10 or 20 percent,"

Ironically, the chemical cartridges that provided the survivors with oxygen may have become the cause of their death.  It appears that a sailor accidentally dropped a cartridge in the sea water seeping into Compartment 9.  This caused a chemical reaction that turned into a flash fire. The Captain was probably killed by the explosion of the chemical cartridge.  The official investigation concluded that some sailors may have survived even this fire by taking shelter under water.  However, the brave survivors were then confronted with insurmountable odds.  The fire consumed the remaining oxygen in the air, converting it into deadly Carbon Monoxide.  Experts estimated that the last of the 118 member crew died six to eight hours after the explosion.

            The government commission that investigated the Kursk disaster considered nineteen possible causes before identifying a torpedo explosion as the most likely cause.  The High-Test Peroxide (HTP) fuel used in the torpedoes was introduced by the German Navy during the Second World War.  HTP is a concentrated solution of hydrogen peroxide, 85 to 98 percent pure. The remainder is mostly water.  When HTP comes in contact with a catalyst, it rapidly changes into a high-temperature mixture of steam and oxygen.   This makes it a suitable fuel for rockets, torpedoes and high-performance engines.  HTP can also be mixed with other chemicals to form Otto fuel, named after its inventor Dr Otto Reitlinger.  It is a distinct-smelling, reddish-orange, oily liquid that does not need oxygen to burn and release energy.  Otto fuel is ideal for use under water.  Although the fuel can be made to explode, this requires extreme conditions. The fuel is able to provide far more energy than advanced electric batteries used in other torpedoes, providing exceptional range and speed.

            After the Second World War, HTP technology fell into the hands of the victorious Allies.  The British Navy experimented with HTP the high-speed submarines, Explorer and Excalibur, between 1958 and 1969.  The Navy halted experiments with HTP as a torpedo fuel after a peroxide fire resulted in the loss of the submarine HMS Sidon in 1956.  However, air-dropped torpedoes using Otto fuel, basically a mixture of HTP and kerosene, remained in use up to 1989.  The US Navy also gave up on Otto fuel because of safety concerns.  The Type 53-57 was the first Russian HTP torpedo (53 refers to the diameter of the torpedo tube in centimetres and the 57 to the year in which it was introduced). Caught up in the competition of  the Cold War, Russia developed  a larger HTP torpedo, for firing from 65 centimetre torpedo tubes.

Hydrogen peroxide works best as a fuel only when concentrated to about 70% or more.  This is a turning point for safety as well as efficiency.   The concentrated fuel changes entirely into heated gas, without leaving behind any water or other liquids.  The higher the concentration, the hotter the resulting gas. This very hot mixture of steam and oxygen generates maximum power but also increases the risk of dangerous explosions.  The commission investigating the Kursk accident found that the tragedy started with the explosion of the oxidizer compartment of the 65 centimetre torpedo. The report stated that the explosion could only have occurred inside the torpedo as it was impossible to explode the device from outside. There may have been a production defect, or something could have gone wrong during the practice firing.   Maurice Stradling examined the similarities between the sinking of the Kursk and the Sidon submarines.  Having read the secret papers from the Board of Inquiry into the Sidon disaster, he believes the cause of the accident to be a broken HTP pipe that sprayed the inside of the torpedo with superheated water, pure oxygen and hydrogen peroxide under pressure. At this point a completely uncontrolled reaction occurred, bursting the submarine hull open.  In the Kursk, explosion of the practice torpedo set off a massive secondary explosion in the adjacent weapons sending the submarine to the bottom of the sea.

When the Kursk tragedy occurred in the month of August, it strengthened notion of the August Curse.  Many journalists and scholars have noted that, beginning in 1991, the most tragic events in Russia tend to take place in August.  These include many deadly accidents, terrorist attacks and two major wars.  There has been a lot of speculation in the Russian media about the reasons behind this strange coincidence.  It could be that many people take vacations in August, leaving critical services undermanned, making it easier for terrorists and criminals to exploit the situation.  Supernatural explanations for the August curse also abound. Astrologist Yelena Kuznetsova believes that the positions of Saturn and Uranus in Russia's horoscope are responsible for the troubles in August.  Others have blamed the usually hot weather in August for the disasters.  The role of the August Curse in the Kursk tragedy will perhaps never be fully explained.

Catastrophic submarine accidents in peacetime may be infrequent but are by no means impossible. Besides accidents in conventional submarines, eight nuclear submarines have been lost due to accidents: two from the United States Navy, four from the Soviet Navy, and two from the Russian Navy. In three of these accidents there were no survivors: two from the United States Navy and one from the Russian Navy. All sank as a result of accident with the exception of K-278.  She was scuttled in the Kara Sea, after a fire in the engine room, because repair was impossible and decommissioning too expensive.

Modern submarines have extensive provisions for safety and damage control.  Thus there is always the possibility that a sunken submarine will have survivors trapped inside.  For survivors escaping from a stranded submarine, the two greatest dangers are pressure and temperature.  Exposure to extreme cold can quickly prove fatal but is less of a problem in a tropical climate.  Water pressure is an ever present danger.  Modern submarines typically have a maximum operating depth of 300 to about 1000 metres.  Even at 300 metres, the water pressure is 30 times the atmospheric pressure or about 30 kilograms per square centimetre.  This amounts to roughly 500 tons of pressure acting on the entire surface of the human body.  Under such extreme pressures the body tends to accumulate gases.  If the ascent to the surface is too fast, the gases form bubbles in the bloodstream.  Decompression sickness can cause symptoms such as severe pain in the joints, seizures and even paralysis.

The possibility of survivors after a submarine accident makes it important to have rescue capabilities.   The traditional method of escape was for the crew of the distressed submarine to leave the submarine and to reach the surface without assistance.  Advances in technology made aided ascent possible with an escape apparatus.  However, there are dangers in both methods of escape. The chances of suffering from decompression illness remain high and in most cases there is no protection against the elements when the submariner reaches the surface. This was clearly brought out when the British submarine, HMS Truculent, collided and sank in 1950. All 72 crew members made it to the surface, but only 15 survived while the rest were lost at sea.

After the Second World War, new methods were developed to increase the chances of survival. Most modern navies use two methods to rescue the crew of a disabled submarine.  The first is a tethered chamber that is lowered to the disabled submarine and then raised with the survivors.  This requires the rescue vessel to be positioned very accurately above the submarine in distress.  The second and more effective option is to use a Deep Submergence Rescue Vehicle or DSRV.  As the DSRV can propel itself under water, it only has to be lowered in the vicinity of the sunken submarine.  It can then manoeuvre on its own to carry out the rescue.  Modern DSRVs can be transported by heavy transport aircraft and then operate form a suitable craft of opportunity.

The Indian Navy acquired a submarine rescue capability when it acquired the INS Nistar in 1971.  The ship could rescue the crew of a disabled submarine using a rescue bell.  This made it possible to carry out a ‘dry rescue’, greatly reducing the risk of decompression sickness as the survivors did not have to enter the water.  Nistar was decommissioned in 1989  and a similar facility now exists on board the diving support vessel INS Nireekshak.  The Shishumar class submarines of the Indian Navy have a unique rescue sphere.  In an emergency, the entire crew of the submarine can enter the rescue sphere and float to the surface without external assistance.  However, the DSRV is a more flexible and capable option for all the other submarines in the fleet.  After more than a decade of bureaucratic procrastination the Ministry of Defence has finally initiated the process for purchasing a modern submarine rescue system.  The Request for Information was issued on August 06, 2013, a week before the Sindhurakshak sank.  Hopefully, the tragedy will speed up the glacial pace at which such purchases normally proceed.

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[*] The author is a former Rear Admiral of the Indian Navy and currently Additional Director at the Centre for Joint Warfare Studies, New Delhi.  Views are personal.