On the night of August 13, 2013, just before midnight, two explosions rocked the submarine and a huge ball of fire escaping from the conning tower hatch, the only hatch that is left open in harbour, lit the sky. Briefly thereafter the submarine sank. The 18 crew members who formed the duty watch were missing. The nature of the incident would immediately suggest that of the 18, only few who may have been in the aftermost compartments would have had any chance of survival. Normally, in harbour, nobody goes to the aft compartments except for periodic rounds. The nature of the incident, the loss of the submarine alongside and the tragic loss of lives of 18 ill-fated crew members makes it vital for the Navy to find the exact cause which triggered the accident.

It is very easy in such incidents to jump to conclusions and air some pet theories. Sabotage, problems with the modifications, hydrogen explosion or some handling accident that set off the chain of events are some of the pet theories floating—the most appealing being the sabotage theory because it makes this incident an open and shut case. Somebody did it and therefore we need only to find the culprit. The Board of Inquiry (BOI) should not get biased by these pet theories, but painstakingly analyse all evidence as possible under the circumstances. To find the truth is vital because the Navy needs to determine for itself not only the causes of this incident, but also put in place procedures and precautions that would ensure that such incidents never recur. The men also need to know 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 onboard any submarine.

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 onboard at about 0300 hours to prepare the submarine for sea. The full outfit of 18 weapons consists of a mixture of missiles, oxygen torpedoes and electric torpedoes with six stowed in the tubes and 12 on racks in the torpedo compartment. Normally weapons kept on the racks are not “armed”. This means that mechanisms and devices that are required to cause the high explosives (HE) in the warheads to explode are not placed, thus rendering them safe. If we take into consideration that only two explosions were heard, it would be apparent that the remaining 16 warheads each containing approximately 250 kg of HE did not explode. This inherent stability and safety of warhead design played a vital role in mitigating collateral damage. Of the two explosions heard, the first or the “trigger” could not have been a warhead explosion. Taking into consideration that heat and flame intensity would have been considerably higher after the second explosion and that 16 explosions were not heard, the second explosion also 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 and sustainers of the missile. Anyways what is important from a professional standpoint is that the apparently damaging explosions were caused only from the trigger source and the adjacent weapon. Warheads and fuel from other weapons do not appear to have contributed to and exacerbated the damage. It is hoped that the BoI will concentrate on these issues.

Normally an investigation will have recourse to various materials, log books, eyewitness accounts, and data from the various monitoring and data recording systems. In this incident, the flame travel 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 BoI will have to depend on advanced forensics to help it analyse the incident. Essentially this would entail chemical analysis of various materials to 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 BoI will need to take advice from experts in forensic chemical and accident investigation to chalk out and plan a course of action to collect samples before it is too late.

The damage control design basis of the submarines provide 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. This is when the submarine is trimmed for neutral buoyancy. The submarine puts on a diving trim by flooding various tanks at sea to avoid the tanks from having dirty water that obtains in harbour. Therefore, the submarine would have been 50-60 tonnes lighter than its normal diving trim. Despite this the submarine sank alongside. Nobody can provide a design basis that would allow floatation under conditions that existed on Sindhurakshak on that fateful night. What is worrying is that had the accident occurred any time later or at sea, the death toll would have been devastating and the submarine would have been lost.

The BoI has a tough task ahead. Tragically, the entire duty watch was lost in this unfortunate incident. The primary task is to identify the actual trigger and arrive at an explanation as to how the dangerous situation that obtained onboard the ill-fated submarine came into being. The missiles and torpedoes are supplied onboard after stringent examination by the Naval Armament Inspectorate throughout the preparation and despatch stages. The crew checks the weapon logbooks and the verifiable parameters before accepting and loading the weapons onboard. The tools required to check/handle or arm the weapons are kept under lock and key. The submarine was scheduled for an operational deployment. Therefore, crew proficiency must have been checked and found to be sufficient. Weapon safety checks and drills are an essential part of submarine workup. Therefore, with a stringent preparation procedure, multiagency inspection and acceptance and tried and tested SOPs on board. The answer to the question, of how these safeties were breached, is indeed difficult to arrive at. The status of salvaged weapons will probably be the first pointer. Thorough forensic analysis of the fore-ends will be the only reliable basis to build the evidence in this case. For any possibility that the board arrives, they have to explain how tough safety barriers were possibly breached.

After the Russian submarine Kursk was lost to a similar accident at sea, the Indian Navy made a lot of appropriate noises to earnestly pursue the long neglected submarine rescue capability. If the submarine was unfortunately lost at sea, the Navy would have had no moral force to explain why the Deep Sumbmergence Rescue Vehicle (DSRV) programme did not fructify even after 13 years. The Navy and the MoD need to explain this inexplicable inaction and procedural inertia.

Eighteen submariners lost their lives. Their families, the submarine arm, and the Navy need answers to ensure closure. The Chief of the Naval Staff said, “We will hope for the best and prepare for the worst.” It is high time that we equip ourselves to prepare for the worst but teach ourselves to ensure that we have the best.

The author is a veteran submariner who has held important positions such as Flag Officer, Submarines, Assistant Chief of the Naval Staff (Submarines), Inspector General, Nuclear Safety and finally the Flag Officer, Commanding-in-Chief, Southern Naval Command.