The Navy has much at stake in a thorough investigation of the INS Sindhurakshak incident as officers and sailors need to be assured that the fault lines have been found and rectified

Just before midnight on August 13, two explosions rocked the INS Sindhurakshak and a huge ball of fire escaping from the conning tower hatch, the only hatch that is left open in the harbour, lit the night sky. Briefly thereafter, the submarine sank alongside. The 18 crew members who formed the duty watch were missing. Since the flame came out of the conning tower hatch nobody in these areas would have survived. There might have been a possibility of survivors had any of the sailors been in the aftermost compartments, but normally, in harbour nobody goes to the aft compartments except on periodic rounds. The nature of the incident, the loss of the submarine and the tragic loss of lives of those 18 ill-fated crew members makes it vital for the Navy to find the exact cause of the accident.

It is very easy in such incidents to jump to conclusions and air pet theories. Sabotage, problems with the modifications, hydrogen explosion or a handling accident that set off the chain of events are some of the theories being floated — the most tempting of these being the sabotage theory because that makes the incident an open-and-shut case. We should not fall for or be distracted by pet theories. To find the truth, the Navy needs to determine for itself not only the cause of this incident but also put in place procedures and precautions that would ensure such incidents never recur. Sailors and naval officers also must be assured that we can determine the fault lines and set them right so that they have the confidence to continue to work in the potentially dangerous environment that exists on board any submarines.

From available information, the submarine was being prepared for an operational deployment and was expected to sail early in the morning. The entire crew was scheduled to arrive on board at about 0300 hrs to prepare the submarine for sea. The full outfit of 18 weapons in this type of submarine consists of a mixture of missiles, oxygen torpedoes and electric torpedoes. Of these, six are stowed in the tubes and 12 on racks in the torpedo compartment. Normally, weapons kept on the racks are not “armed.” This means mechanisms and devices that are required to detonate the high explosives in the warheads are not placed in them, thus rendering them safe.

Taking into consideration that only two explosions were heard, that would mean the remaining 16 warheads, each containing approximately 250 kg of HE, did not explode. This indicates that the inherent stability and safety of the warhead’s design played a vital role in mitigating collateral damage.

Initial assessment

Going by where the flame came out, the explosion originated in the torpedo room, and not from the tubes. Of the two explosions, the first one, or the “trigger,” could not have been a warhead explosion (which, given the design, could have happened only had there been a tremendous shock to the unarmed weapons). Considering that heat and flame intensity would have been much higher after a second explosion, and that it did not cause a further 16 explosions, the second too could not have been a warhead explosion. Therefore, prima facie the trigger explosion appears to be from the weapon fuel — i.e. either oxygen from the torpedo or the booster of the missile. Anyhow what is important is that apparently damaging explosions were caused just from the trigger source and the adjacent weapon. Other weapons do not appear to have contributed to the damage. The Board of Inquiry, I am sure, will concentrate on these issues.

Normally an investigation would have recourse to various materials, log books and eyewitness accounts. In this incident, the spread of the flame from the forward compartments to the control would have incinerated everything. Reconstructing the events that led to the accident would be difficult, to say the least. Therefore the board will have to depend on advanced forensics to help it analyse the incident. Essentially this would entail chemical analysis of various materials to see if we can determine the nature of fuel that caused the burn. A lot of valuable evidence will lie in the debris of the fore ends. Much of this will be diluted by the sea water and most of it will be lost in the pumping out that will have to be done to bring the submarine to the surface. The Board of Inquiry will need to take advice from experts in forensic chemical and accident investigation to chalk out a course of action to collect samples before it is too late.

Damage control

The damage control design basis of the submarines provides for survival and maintenance of sufficient reserve of buoyancy when the pressure hull is breached and one compartment is fully flooded and two adjacent ballast tanks are destroyed. When this happens, the submarine is trimmed for neutral buoyancy. The submarine puts on a diving trim by flooding various tanks only when at sea, so as to avoid having to flood the tanks with the dirty water in the harbour. Therefore, Sindhurakshak would have been 100 tonnes lighter than its normal diving trim. Despite this the submarine sank alongside. Nobody can provide a design basis that would allow flotation under conditions that existed on the Sindhurakshak on that fateful night.

What is worrying is that had the accident occurred when the submarine was out at sea, the death toll would have been devastating and there would have been no chance of salvaging any part of it. The Navy does not have any submarine rescue capability. The Deep Submergence Rescue Vehicle programme has not borne results even 13 years after the Kursk incident. There was much hot air after the Russian disaster but we still do not have the capability.

The Chief of Naval Staff said we should hope for the best and prepare for the worst. It is high time that we equip ourselves for the worst and also teach ourselves to ensure that we have the best.

(The writer, who retired as Flag officer Commanding-in-Chief of the Southern Naval Command, was a submariner who served on Foxtrot and Shishumar-class submarines. He was Flag Officer Submarines and ACNS (Subs) before becoming Inspector General, Nuclear Safety in the Navy.)

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