Wednesday, 14 August 2013

INS Sindhurakshak - Critical look at the Hindustan Times report

(Linked above)

"What exactly lead to the blast?" The Hindustan Times asks. A perfectly good question. In line with the three scenarios of doom that I've put together with what little information I have, I'm going ahead and taking a good look at this report.

First off, it seems like the reporter here has been talking to quite a good source. I can't imagine most people who are not Naval experts/fans/nerds describing the vessel as a "classic" diesel-electric submarine. The epithet is true - diesel-electric submarines have been around for over a century now, and the Sindhurakshak is indeed a descendant of the same submarines that caused terror on the high seas during World War One. Their batteries do need to store a lot of energy to move a 3000-ton vessel around for hours.

That being said, there are some details here that call for further explanation. Quoted below-

 There are usually two battery rooms on a submarine. Forward battery room is placed beneath the officer’s quarters and aft battery room is beneath control room.
I'm placing the image I used in the three scenarios of doom post below this one.  (Click to enlarge)

Looking through the labels on the original image, there is indeed an 'accommodation' between the forward battery bank and the torpedo storage area above it (The "1" is right on it, in fact). Whether this is a crew accommodation or officer's quarter isn't evident from the sources I have. However, the aft battery room in the diagram that I have (labeled in Russian) is under another crew's quarters, not the sub's control spaces. What the HT reporter has either not mentioned or not been told is that the forward batteries are separated from the torpedo storage by just one deck. Hydrogen, the lightest of all gases, would go up and collect in the torpedo room through ventilation ducts (and there's the issue of blowers not working, which I'll come to). It just needs a spark for hydrogen leaking from the forward batteries to blow up in or near the torpedoes - with catastrophic results.

I am in no position to comment on the hydrogen build-up rate, concentration or mixture. The article states that the blowers used to suck hydrogen out of the battery compartments were not working. The one-crore-rupee-questions here are : why were the blowers not working, and where do the blowers usually vent their hydrogen gas?

A submarine recharges its batteries and replenishes its air on the surface - so presumably the blowers would be working and blowing the hydrogen out of the submarine with the waste air during the normal course of a battery recharge. Why was that not being followed? Was it merely an oversight caused by the submarine being at the dock, or had something else broken down? Was the submarine being charged by an external diesel generator rather than its own engine at the time?

Now comes the haunting part of the report -

Two separate explosions happened almost simultaneously, one after the other on the aft side of the shift, which is adjacent to the ship’s torpedo department.
The first explosion was comparatively small, and could have triggered the second explosion.
This brings to mind Kursk, almost 13 years ago. Nevertheless, I'll take this apart slowly. 

By "aft side of the shift", he really should mean "aft side of the ship". This is confusing. Looking at the diagram, it's quite clear that the torpedo compartment is forwards in the bow, or the front end of the shift. The aft, or rear end of the ship is occupied by the diesel generator, electromotors, steering and auxiliary mechanisms. The reporter seems to have jumbled the layout of the submarine quite badly, or perhaps his source messed up (An older generation of submarines- such as the majority of World War Two submarines and the Project 645 'Foxtrot' do have an aft torpedo compartment, but this submarine very plainly does not).

However, if the report is right and the fire and explosion happened somewhere close to the aft end of the submarine, it supports the rear bank of batteries exploding in an unusually violent manner, violent enough to rupture the submarine's hull. This is as strange as it is horrific - how much hydrogen could have built up to cause such a volcanic explosion? 

The odd thing is that the two separate explosions are said to have happened nearly simultaneously - and the first one is said to be much smaller - which is quite hard to reconcile with the explosion happening aft and blowing a hole in the submarine's hull.

"The first explosion was relatively small and could have triggered the second explosion" - this is, in a nutshell, what happened to Kursk on August 12, 2000. A hydrogen peroxide torpedo exploded and knocked out the submarine's command spaces. The resultant fire set off multiple torpedo and missile warheads, causing Kursk to explode. An explosion of hydrogen gas or a faulty torpedo in the bow torpedo room seems quite likely to have caused the first explosion in a confined space. That, in turn, could easily have set off a few torpedo or missile warheads and in turn caused the second, larger explosion. Much like Kursk, the second blast would have turned the front of the submarine into a mangled wreck.

Probably the key to understanding the blast is whether the second explosion happened instantly after the first, or if there was a delay of a few minutes as the fire from the first explosion cooked off the warheads. The rocket motors of any Klub missiles on board would also be a 'wildcard' if on board- their propellants, if ignited, would start a blaze that could not be starved of oxygen.

"What exactly lead to the Sindhurakshak blast" does not do a good enough job of explaining the disaster on all these points. Nevertheless, for a highly trained crew to be caught unawares and left without time to prepare speaks of a sudden, horrific disaster on board, and that such a disaster should happen does not bode well at all.

No comments:

Post a Comment