INS Sindhurakshak, which caught fire after a massive explosion at the Mumbai Naval Dockyard late on Tuesday night, is a Sindhughosh class submarine and was commissioned into the Indian Navy on December 24, 1997. INS Sindhurakshak has Pennant No. S 63 (used to distinguish between ships with the same or similar names with the S standing for submarine) and all Sindhughosh class submarines belong to the Kilo class diesel-electric submarines and are designated 877EKM.
There are 10 Sindhughosh class submarines with the Navy and INS Sindhurakshak is one of the latest. All Sindhughosh class submarines were built under a contract between Rosvooruzhenie and the Indian Defence Ministry. The submarines have displacement with full load of 2,300 tons while the dived displacement is 3,100 tons.
The maximum diving depth is 300 meters, top speed of 18 knots, and the submarines of this class are able to operate solo for 45 days with a crew of 53. The total complement of personnel is 68 including seven officers. The submarine is 73 meter long with a beam of 10 meter.
INS Sindhurakshak is a diesel-electric submarine and underwent $80 million upgrade in Russia June 2010 with sea trials starting in October 2012. The submarine has in-built electronic warfare systems, control systems and integrated weapon control system. The submarine carries new Russian missile system Club-S with 200-km cruise missile range.
There was a fire in 2010 on the submarine which was caused due to a defective battery in which one person was killed.
The torpedoes in the submarine are fuelled by oxygen, which is a volatile element. Next to the torpedo room is the battery compartment where hydrogen is present and if oxygen mixes with hydrogen, then it causes explosion.
Navy officials say the front section of the submarine has been twisted, bent and crumpled due to the explosion with water entering the forward compartment. Only the submarine's tail is visible.