While a concrete opinion on the probable cause of the incident remains to be ascertained, suspicion heavily rests on the Klub-S (3M-14E) cruise missile that the submarine was redesigned to fire.
“Something might have gone wrong when the missiles were being loaded into the torpedo tubes in the front part of the submarine. It could be either with the missile’s rocket motor or the warhead. Chances of the former are likely,” said a former submariner, who retired in 2005 as a Rear Admiral.
A potent missile, the Klub is unconventionally launched horizontally through the torpedo tubes and then turns vertical to exit the water where a secondary motor takes over.
There were also unconfirmed reports about hydrogen exhausts from the battery — during recharging —causing the blast but seemed less possible after Chief Admiral D.K. Joshi earlier clarified that they had been charged around a week ago.
Interestingly, according to sources, the batteries over some of the Sindhugosh class submarines were replaced a few years ago. “We replaced them with German-designed and Indian-built main batteries which also improved the cooling. I am, however, not sure whether the replacement had taken place on the Sindhurakshak,” said a Navy source.
The lead boat of the class, INS Sindhugosh (S-55) was berthed right beside the Sindhurakshak during the blast but was saved after fire-fighters from the Mumbai fire brigade sprayed a “wall” of water jet between the two boats to prevent the fire from spreading.
The Sindhurakshak was commissioned on December 24, 1997 and sent for overhauling and modernisation in Russia in March 2010.