Wednesday, 14 August 2013

Inside the INS Sindhurakshak : Three scenarios of doom (Updated to four)

UPDATE: Additional information in this post, via Business Standard:

I managed to find the internal layout of a Russian Kilo-class submarine off the internet. It took me a while to clean up the image and label the neccessary components, but here it is. (Original image courtesy - fair use for educational purposes)

To the security-conscious : Internal layout schematics of the Russian Kilo class and several warships of various navies are available on the internet. How accurate these schematics are is a matter of question. I will take this particular image as accurate for the sake of finding out how far any sailors trapped in INS Sindhurakshak are from the batteries and torpedo units, and I assume it's accurate enough. The Kilo is an old boat and there is nothing at all in the way of secrets to spill.

(Click on image to enlarge)

The Project 877, known to NATO as the 'Kilo' class and the Indian Navy as the 'Sindhughosh' class, has been around since the early 1980s. It's 72.6 (some sources say 72.9 meters) long and 9.9 meters wide and approximately as tall since the submarine's hull is circular. The displacement (weight) of the vessel varies in various sources. There are two major possible culprits for the Sindhurakshak accident - Hydrogen Peroxide torpeodes (like the ones that destroyed Kursk) and a possible hydrogen leak from the batteries. I've coloured the torpedoes red and the batteries yellow.

1. Scenario one: A repeat of the Kursk accident. A torpedo leaking hydrogen peroxide that came into contact with rust or corrosion in the torpedo room. A Kilo-class submarine carries a total of 18 torpedoes in the torpedo room, and some of the news sources I see claim that the submarine had a full load of torpedoes. Of course, I have no way to know how true this is - but even a single torpedo carries several hundred kilograms of explosive.

Whether anything up front leaked hydrogen peroxide or not is an open question in the absence of testimony from the sailors on board. There was apparently enough warning for several sailors to jump off the submarine and run for their lives. A peroxide leak falling onto rust would cause high temperatures and a release of oxygen, igniting the kerosene fuel of the torpedoes if in close proximity. A fire started in such a manner would have sent any crew in the vicinity fleeing, and it would take a couple of minutes for the torpedo warheads to cook off and produce the giant fireball seen in video footage.

A torpedo explosion would completely obliterate compartment 1 and compartment 2, as well as the submarine's sonar dome and torpedo tubes. Compartment 3 is not likely to survive either, and compartment 4's bulkhead is only 15 meters from the explosion. Compartment 5 and 6 have their bulkheads 24 and 31.5 meters from compartment 1's bulkhead and are shielded by the heavy diesel generator and other machinery in Compartment 4. It's in these two compartments that the 18 sailors would have to run into and shut themselves in if they were likely to survive. Russian submarines have extensive watertight compartmentalization unlike their American equivalents, and in the event of a torpedo explosion it's still likely that compartments 5 and 6 are safe. There are air flasks above compartment 5, so the crew can still breathe.

There's a real problem with the torpedo scenario - in Kursk, the fire and explosion happened in the closed confines of a poorly-secured, rusty torpedo tube, not inside the torpedo room itself. It's possible to have a repeat accident within the torpedo room, but this is pure conjecture.

2. Scenario two: Hydrogen fire from the forward batteries causing the torpedo fire. I didn't know about the torpedo room batteries when I made my last post. In this case it's not a leaky torpedo starting the fire, but the batteries up front leaking hydrogen and causing the fire. The extent to which the burning hydrogen would have spread prior to the explosion of the torpedoes and the huge fireball is not determinable without a clear understanding of air circulation within the submarine. I can't say whether or not the hydrogen fire would have been worse than a torpedo catching fire either. But the crew should be safe in compartments 5 and 6.

UPDATE: In Business Standard, Vice Admiral (Retired) A.K. Singh has pointed out this very issue with the location of the torpedo compartment above the batteries. This particular submarine had ventilation worries too.  So there's definitely one expert favoring Scenario Two : a hydrogen fire from the front batteries setting off the torpedoes.

3. Scenario three : Hydrogen fire in the rear batteries spreading and causing the torpedo fire. This is the worst scenario of the three, because the rear batteries are located in compartment 3, housing the crew. That means the fire was effectively centralized in the submarine and free to spread to the diesel generator room to the aft, or to the command spaces in front. The torpedo compartment isn't adjacent to this bank of batteries, so the fire from this would have to be especially bad to reach and set off the torpedoes in the front.

This scenario also places the men trapped behind in even greater peril. A fire powerful enough to set off torpedoes two full compartments forward would have used a lot of the air in the submarine already. The likelihood of crew injuries from fire and smoke is magnified. Compartments 5 and 6 are closer to the blaze, making it less likely that they were properly secured before the torpedoes went off.

Hopefully, scenario three is not the scenario that will manifest itself.

4. Scenario four (Information from 15 Aug 20:41 IST) -
Based on this NDTV news report and a later Times of India report. A preliminary inquiry suggests that the 3M-14E land attack cruise missiles (aka the 'Klub-S') on board were not being loaded into the submarine properly and that these may have been to blame. Apparently these had been just integrated into the submarine. The land-attack missile has the 450 kilogram warhead mentioned by VAdm(Ret.) A.K. Singh.

The 3M-14E uses a combination of a rocket first stage and a turbojet 'sustainer' engine. The turbojet engine should not be any great danger if it uses standard aviation kerosene, which is not volatile by its very nature (You can toss a lighted match into aviation kerosene and it'll be put out). I've looked in the public domain but haven't been able to find out what solid propellant this missile uses and whether or not it's highly sensitive in nature. Normally the missile's propellant is capped off to prevent it from being exposed to the air, as well as to prevent the crew from coming in contact with the often-toxic chemicals. If a Klub indeed caused the explosion, it would appear to be a fairly bad violation of operational procedures. Then again, this is a preliminary report, and there's a lot of information that I can't find out about the missile.

If I were to risk a little wild speculation, a loaded missile may have been dropped onto a 53-65 torpedo, and leaking turbojet fuel from the missile and leaking High Test Peroxide from the torpedo could have caused a flash fire and explosion. This would be a real stretch, but it seems to me a little more feasible based on what little I've read about missiles and torpedoes. (And assuming that the Klub's propellants are not very volatile, something I am not certain of).

UPDATE 1 (Aug 14): Another very intriguing news article comes up. A Mumbai fire bridgade officer managed to stop the fire from spreading to INS Sindhuratna, which was moored alongside. For how long had Sindhurakshak been burning like that? A sustained fire suggests diesel fuel - so this sub was fully fueled and was charging her batteries to head to sea when the big bang happened, it looks.

If this article is accurate, it raises the question of what the Navy officers aboard Sindhurakshak and Sindhuratna were doing when the second sub was in danger. What exactly was going on there? Exactly how long did it take for the fire engines to arrive? How long did it take for Sindhuratna to get underway? Too many questions, no clear answers yet. The quality of the reporting itself is suspect - which adds to the question of what happened.

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