While the Navy concentrated its efforts on Wednesday on salvaging the submerged INS Sindhurakshak and ascertaining the fate of the 18 personnel on board,the inquiry that has been ordered into the incident will follow several strands of investigation to establish what caused the twin explosions.
The most probable cause that will be looked at is a triggering-off of a component of one of the armaments on board the submarine which was fully loaded for a routine mission,set to start early on Wednesday morning. The vessel was carrying torpedoes,a new class of Klub anti-ship and land attack missiles as well as mines.
It is believed that armaments had been loaded recently prior to the explosion. Sources said the presence of a senior officer on board the vessel the second-in-command of the Sindhurakshak,Lt Commander Nikhilesh Pal indicated that an important task had emerged. Also on board was anti-submarine warfare officer Vinay Ramakrishnan,whose task is to ensure the preparedness and safety of the torpedo systems of the vessel.
While it is less likely that the primary explosion was triggered by a warhead explosion,investigators will probe the possibility of leakage of the fuel system of either the torpedoes or the Klub class missiles on board.
At least two fatal submarine accidents have taken place due to faulty torpedoes caused by leaks of the fuel system the Russian Kursk that went down with 118 sailors in 2000 and the British Sidon that suffered an explosion in 1955. It was still not clear by Wednesday night whether the second-in-command and the anti-submarine officer had been called on board to deal with an emerging situation.
The third officer on board was Arun Kumar Sahu,a communications officer. Sources said that as per the usual pattern,a submarine docked at night in peacetime is manned by a skeleton crew with just one officer on board.
Investigators will probe whether the primary explosion caused by propellent or oxidiser leak could have triggered off a warhead that led to the second,bigger explosion that was witnessed by many and has even been caught on camera from a distance.
Source said the initial theory that the Navy deemed probable was that the primary explosion which took place in the bow of the vessel was caused by the leakage of hydrogen gas that is sometimes generated when the massive battery clusters that power the submarine underwater are being charged.
While hydrogen is constantly pumped out when the battery clusters are being charged,if there are problems in ventilation and the percentage of gas in air crosses four per cent,it becomes highly volatile. However,by evening,Navy Chief Admiral D K Joshi discounted this possibility,saying the battery charging cycle had last taken place three days ago and nothing abnormal was found. Given that the battery was not being charged,the leak of hydrogen gas as the cause of explosion seems unlikely.