K-141, Project 949A. Kursk [АПЛ "Курск"] Oscar II Class

The loss of the Kursk is recent enough that it probably doesn't need to be retold here, but I will do so anyway, in remembrance of the men lost.

Kursk was an Oscar II class submarine, and the last submarine built in the Soviet era.  Construction began in 1990, and by the time she was completed and launched in 1994, the cold war had ended.

The Oscar II class were the largest attack submarines ever built, running about 500ft long, and 60 feet wide.  When viewed in cross-section, the inner hull of the Oscar II class was circular, while the outer hull was oval-shaped.  This oval-shaped outer hull gave the Oscar II ships the appearance of being fat.  Between the inner and outer hulls were missile tubes containing 24 anti-ship missiles, as well as air banks.

Below:  Oscar II submarines in port.  They look a little chubby compared to other subs.

Kursk in port.

Below:  The reason Oscar Class submarines look "fat".   Lots of anti-surface ship firepower.

 Profile of an Oscar II Class submarine

After the collapse of the Soviet Union, the sailors of the Northern Fleet were intermittently paid, and little money was available for repair and maintenance of the fleet.  Kursk only made a single patrol between her launching in 1994 and her loss in 2000.  With the lack of sea-time, it is probable that her crew was not well-trained, and certainly not proficient.  It's not clear whether a well-trained and proficient crew would have altered the outcome, however.

On August 12, 2000, Kursk was participating in the largest Russian Naval exercise in 9 years, following the collapse of the Soviet Union.  Three other submarines, the Russian flagship battlecruiser "Petr Velikiy" (Peter the Great) were participating, along with a flotilla of smaller vessels.

Kursk was preparing to fire a dummy torpedo at the battlecruiser Petr Velikiy, when an explosion occured.  The accepted theory is that the highly concentrated HTP (High-Test Peroxide) hydrogen peroxide which fueled the torpedo leaked out and reacted, causing the torpedo engine to detonate, starting a fire.

A similar explosion caused by an HTP-fuelled torpedo was responsible for the loss of HMS Sidon in 1955, after which the British Navy abandoned torpedoes propelled by peroxide.

This first explosion was recorded on the SOSUS network, and was estimated to have an explosive force of 220-550lb TNT.  A second, larger explosion measuring 6000-14000 lbs of TNT occured 135 seconds after the first explosion.  Kursk came to rest in just 350 feet of water.

Rescue offers were made immediately by US, British, and Norwegian teams, but these offers were rebuffed by the Russian Navy.  It was believed at the time that there were no survivors from the initial explosion.

I will turn the saddest part of this sinking over to Wikipedia:

Captain Lieutenant Dmitriy Kolesnikov, one of the survivors of the first explosion, survived in the ninth compartment in the turbine room at the stern of the boat after explosions destroyed compartments 1-5. Recovery workers found notes on his body. They showed 23 sailors (out of 118 aboard) had managed to enter compartment nine after the ship sank.

There has been much debate over how long the sailors might have survived. Some point out that many potassium superoxide chemical cartridges, used to absorb carbon dioxide and chemically release oxygen to enable survival, were found used when the craft was recovered, suggesting some of the crew survived for a significant time.

Kolesnikov's last note has a time of 15:15, indicating that he and the others in the aft compartment lived at least four hours after the explosion.   32 hours after the first explosion no sound was heard (i.e. hull tapping) to signal the Russian Submarine Rescue Vehicle Priz, when it attempted to mate with the aft escape trunk. 

The oxygen generator cartridges appear to have been the cause of death; a sailor appears to have accidentally brought a cartridge in contact with the sea water, causing a chemical reaction and a flash fire. The official investigation into the disaster showed some men appeared to have survived the fire by plunging under the water.  Fire marks on the walls indicate the water was at waist level in the lower area at this time.  However, the fire rapidly used up the remaining oxygen in the air, causing death by asphyxiation.

In July 2002, the investigation committee concluded that a technical malfunction on a single Type 65-76 "Kit" (Whale) torpedo caused the first explosion^, triggering a fire in the torpedo room which, two minutes later, caused 5-7 additional torpedo warheads to detonate.

The second explosion destroyed a large section of the submarine (at least 4 of the 9 compartments) killing up to 95 of the 118 crew members and causing the submarine to sink. Around 23 crew members survived the sinking and took refuge in the ninth compartment where they died due to carbon monoxide poisoning following a fire in that compartment (between 6 and 32 hours after the sinking).

Kursk was raised from the ocean floor in a difficult and expensive recovery project.  Her bow was an unrecoverable mess and was cut off, using carbide coated cables.  She was re-floated and returned to Russia, where her two reactors were decomissioned, and her side missiles were removed.  Those of her 118 crew that were recovered were buried with honors.

K-278 Komsomelets (Project 685 Плавник), Mike Class

K-278 was a unique and magnificent submarine.  Only one of this class of ship was built.  Because she was so unusual, construction took an unusually long 5 years.  Her construction began in April 1978, she was launched in May 1983, and commissioned on the last day of 1984.  The Soviet Navy rarely named their submarines, but this ship was special, and received the name of "Komsomelets" - which means "a member of the Young Communist League".

K-8, Project 627 (проект 627)

November-Class submarine.  Source: Wikipedia

K-8 was a November-Class Soviet submarine.  The November class was the first class of Soviet nuclear attack submarines.  This class of submarines suffered from reliability problems related to the ships' steam generators.  The steam generators in these early nuclear ships frequently developed leaks. 

Leakage from a steam generator tube allows very radioactive primary coolant to exit the reactor coolant loop and enter the non-radioactive steam cycle loop.  This radioactivity, depending on the size and duration of the leak, can be hazardous to the crew.   With the November Class' dual reactor design, it would seem feasible to shut a damaged reactor down, reduce the primary system pressure, and limp home.

K-8 developed steam generator leaks on three separate occasions.  On one occasion however, the steam generator leak was so severe that one reactor experienced a Loss of Coolant Accident.  The crew struggled to make repairs and to refill the primary coolant loop in order to prevent a core meltdown due to decay heat.  Several of the crew received significant doses of radiation as well as radiation burns.

The end for K-8 came in a more mundane way however.  In April of 1970, while operating at a depth of 400ft, a short circuit caused a fire, which spread to two compartments via the ventilation system.  Both reactors were shutdown, and the captain ordered the ship abandoned.  Things must have been hellish inside. 

Fortunately, K-8 was part of a Soviet fleet exercise when the fire occurred, so help was nearby.  A surface vessel was dispatched to tow her back to port for repairs.

Disabled submarines are difficult to keep afloat (even next to a pier), and the reason is this:  Most of the ship is already submerged.  This is partly due to the thickness of the pressure hull, but also the ship is designed to be pretty close to neutral bouyancy.  When the main ballast tanks are full of air, a submarine will have positive bouyancy, but not a whole lot of it.

Submarines are not surface ships, so they are designed with round-bottom hulls.  This makes them wallow badly on the surface in heavy seas.  When a submarine pitches and rolls in the waves, air escapes from the main ballast tanks, which are vented at the bottom.  With each wave, a little main ballast tank air spills out, and a little bouyancy is lost. 

This air can be replaced by a couple of means.  The first is a massive low-pressure roots blower that takes air in from a large snorkel mast, and forces water out of the main ballast tanks.  This method only works if electrical power is available.  With both reactors out of service, it is unlikely that the storage battery of K-8 could have supplied the LP blower with electrical power for very long.

The other method for replacing air in the main ballast tanks involves briefly "puffing" them with very high pressure air from the ship's air banks.  I don't know the capacity of the high pressure air banks on this class of ship, but I do know the supply of air was not infinite.  In any case, without having electricity to run a high-pressure air compressor, these would eventually run out of pressure be unable to displace water out of the ballast tanks.

The abandon-ship order of the captain of K-8 was countermanded when the towing vessel arrived. 52 crewmembers, including the captain, re-boarded the ship for the tow back to port.   73 crewmembers were taken aboard the towing vessel.

The ships encountered rough weather.  After 80 hours of heroic but futile damage control, the K-8 flooded.  Sadly, even though ships were nearby, she took 52 men with her, who are now on eternal patrol with her.  

USS Scorpion (SSN-589) - Updated

Scorpion was a Skipjack-Class submarine.  The Skipjack class was the nuclear-powered attack submarine class previous to the Thresher/Permit class.  As such, they were not quite as deep-diving, although they did have a very sleek hull, which allowed for a high submerged speed.  Skipjack-class submarines held (classified) speed records while using somewhat noisy 5-bladed screws, but lost this high speed when the screws were eventually replaced with quieter 7-bladed screws.

USS Thresher (SSN-593)

The USS Thresher was the lead ship in a new, advanced class of US Submarines.  Her keel was laid in May of 1958 and she was launched in July 1960.

At the time of Thresher's launch, she was the deepest diving attack submarine in the world.  Until the arrival of Thresher, all submarines had bow-mounted (and most also had stern-mounted) torpedo tubes.  USS Thresher was the first to use angled, midship-mounted torpedo tubes.  This arrangement freed the bow for installation of an extremely high-sensitivity sonar array. 

The bow-mounted sonar consisted of a sphere covered with hydrophones, placed as far away as possible from the propulsion plant.  This new arrangement offered a huge improvement in sonar sensitivity, and Thresher had the ability to detect other submarines at far greater range than they could detect her.  The importance of detecting an enemy ship first cannot be overstated!!! 

In addition to the improvements in the sonar/torpedo tube arrangement, huge improvements had been made to silence the ship.  This was also the quietest nuclear submarine in the world.  For the first time ever, all rotating equipment in the ship was sound-isolated from the ship's hull.  The heavier equipment (propulsion turbines, turbine generators, primary coolant pumps, and reduction gears) were mounted to a subfloor that was suspended and accoustically isolated from the hull.  Smaller machinery and steam piping was mounted using sound-isolating snubbers. 

Thresher was also the first ship to carry the SUBROC missile. The SUBROC was a Stand-off weapon system for attacking enemy ships at greater distances than a torpedo could reach.  The SUBROC was a SUBmarine ROCket that carried a W55 nuclear warhead with a yield of 250 kilotons TNT. It was propelled by a solid fuel rocket motor that would ignite following ejection from a torpedo tube. The SUBROC would then angle up, clear the ocean surface, fly a certain distance, then release the warhead. The warhead would enter the water and detonate at a depth that was programmed prior to launch.

In short, the ship was revolutionary.  She was quiet, fast, deep-diving, had the keenest hearing on the planet, and could shoot a nuclear-tipped rocket out her torpedo tubes.  

Then on April 9, 1963 she sank with all hands.  She took 129 men along with her.  Seven days after being lost, Thresher was stricken from the ship's registry. 

As the lead ship of a new class of submarines, this new class of ship had been called the Thresher (593 class).  After striking Thresher from the registry, the class was renamed after the second ship in the class, the USS Permit class (594 class).



What happened:
Thresher had performed operational testing of all her systems, particularly the weapons and sonar systems for two years. In July 1962 she entered shipyard to inspect equipment conditions, make repairs and correct deficiencies noted during the operational testing.   She un-docked on April 8.

On April 9, Thresher got underway from Portsmouth Naval Shipyard in Maine, for the purpose of conducting a dive to test depth.  Diving to test depth is always done immediately following any major overhaul or repair, so that the sea-worthiness of the ship can be tested.

Thresher rendezvoused with a submarine rescue vessel named Skylark, and then conducted a slow descent in 100ft increments, while circling Skylark in order to maintain communications.  As Thresher neared test depth, Skylark received a message over the underwater telephone stating "...minor difficulties, have positive up-angle, attempting to blow".  Lastly there was a final garbled message that included the number "900".  When Skylark received no further communication, surface observers gradually came to realize that Thresher had sunk.

Thresher had gone down in 8400ft of water, and it was difficult to gather evidence or get photographs to determine what had caused the loss of the ship.  A court of inquiry was convened, and a picture of events began to unfold.

In this class of ship, the major heat loads were cooled by seawater-supplied heat exchangers.  A/C Units, Generators, oil coolers - everything was supplied by high-pressure seawater piping.  At the time, most of the joints in these seawater pipes were silver-soldered, rather than welded.  Many of the silver-soldered joints were faulty, and there was no process in place for quality control.

It is conjectured that one of the larger silver-soldered joints sheared off near test depth, filling the ship from *both* ends of the damaged seawater pipe.  This in itself would not have sunk the ship, but several other things likely compounded the problem.  The seawater would have blasted in and created a mist as it struck other surfaces.  This saltwater mist probably created enough electrical grounds and disturbances to trip (or scram) the reactor. 

A shutdown reactor also should not have caused the ship to be lost.  Enough heat remains in the primary coolant to generate propulsion steam for several minutes.  However, the procedures in place at that time called for the main steam stop valves to be shut whenever the reactor scrammed (to conserve heat in the primary coolant).  This action eliminated the option of driving the ship toward the surface using the propulsion turbines, just as Thresher was taking on additional weight due to flooding.

The captain ordered an emergency main ballast tank blow.  An emergency blow releases extremely high pressure air from large air tanks into the main ballast tanks.  The air displaces water out the bottom of the ballast tanks and makes the ship more bouyant.   The emergency blow also should have saved the ship, but it did not. 

Previous classes of submarines did not dive this deep, and therefore did not require air at such high pressure to blow their main ballast tanks while at maximum depth.  No previous submarine had needed to dehydrate compressed air, and this class of ship did not have compressed air dryers either.

The air in the high pressure air banks was moist air.  It is believed that during the emergency main ballast tank blow, as the air pressure dropped, ice formed in the piping and blocked further air flow, preventing a full blow of the ballast tanks.

The Thresher is believed to have made some progress toward reaching the surface, before flooding overcame the bouyancy created by the partial ballast tank blow.

Loss of the Thresher came as a huge shock to the Navy, and to the Submarine Service.  As a result of the investigation, the SUBSAFE program was initiated.  This was a QA/QC program to ensure all parts of the ship subject to seawater pressure were of the highest quality, and pedigreed with a paper trail, from smelting to installation.

Other improvements included remotely-operated hydraulic shutoff valves for all seawater systems that didn't rely on electrical power, air dryers and larger diameter piping for the compressed air systems, and procedural changes that allowed crews to use residual primary coolant heat for emergency steam propulsion.  Not much point protecting the reactor, if the ship will be lost in the process...

Later classes of submarines (engineered from the ground up with SUBSAFE) in would use seawater-freshwater heat exchangers for everything except the main propulsion condensers.  This other cooling system circulated low pressure fresh water to machinery that required cooling, and so minimized the amount of high-pressure seawater piping within the ship.

Those are the engineering improvements that we are able to take away from this tragedy. 

Thresher was lost at sea and never decommissioned.  Both she and her crew, as well as a number of civilian shipyard workers, remain on Eternal Patrol.