Torpedoes: At the time of sailing the Kursk was carrying 24 torpedoes, two with dummy warheads, the remainder with conventional explosives, and all stored within № 1 compartment. Analysis of the acoustic data from the cruiser Pyotr Veliky suggested that around seven torpedo rounds were destroyed as a series of explosions in rapid succession. The survey of the second debris field revealed a number of torpedo components but these, collectively, did not account for the remaining 15 or so armed rounds.
These missing rounds could have been hidden within the hull, particularly in the mangled wreckage of what remained of the bow compartment and some could have been thrown into the wreckage of the second compartment (which was subsequently shown to be the case when the internals of the wreck was dried out and inspected at Rosljakovo). Some or all of the rounds could have burnt during the explosions, some might have fragmented, and others might remain intact and hidden under the submarine hull.
Such was the uncertainty surrounding the presence, state and stability of these missing torpedo rounds that an explosion from this source had to be considered a credible fault condition at any time during the lift operations. Factors in mitigation were:
i) the dispersion of the remaining torpedoes and fragments of torpedoes, made a sympathetic detonation less likely;
ii) detonation would be unconfined and not directed through the hull towards the reactor compartment (compared to the original explosion that was initially confined by the pressure hull);
iii) the design basis capability of the reactor plant to withstand shock remained available (to an undeclared amount); and
iv) any fragment revealed during silt clearance etc., be removed by the RF, using remotely operated equipment to at least 70m from the submarine — torpedoes and fragments within the cut zone would also be removed.
v) the silt clearing equipment was unlikely to cause detonation of a torpedo or explosive fragment.
The NCG nominated a fault condition whereby the equivalent of two torpedo rounds (~450kg TNT in total) simultaneously detonated during the bow separation operation or the lifting operation. The NCG sought assurance, with explanations, from the RF of each reactor’s capability to withstand such an explosion. In addition, an analysis of the effect of the explosion gave the strength requirements of the hull plating of the attending barges and the length limitation for smaller vessels attending the barges, a requirement that these be larger that the sea surface bulk cavitation and gas bubble diameters that would put smaller vessels at risk of sinking. Also, the analysis provided the minimum lashing requirements for the heavy equipment operating on the barge decks, particularly the two 60t crawler cranes working on the Giant 4 lifting barge, in account that these could topple into the sea and descend onto the Kursk in the reactor compartment area or onto the cruise missile silos.
Missiles: At the time of loss, the Kursk was armed with 23 SS-N-19 GRANIT cruise missiles with conventional explosives. These missiles were located in forward slanting silo tubes, 12 either side of the submarine, the first being just behind № 1 compartment and within 3m of the cut line that was to isolate the bow wreckage, and the last two missiles being some 30m ahead of the reactor compartment.
Relevant features of the SS-N-19 missiles are:
i) the propellant fuel is kerosene, with a small (7kg TNT equivalent) powder charge for ejection from the silo to the turbojet firing altitude above the sea surface;
ii) the launching ‘trigger’ or arming and firing system (AFS) comprised five independent degrees of protection or latches;
iii) each missile was held within shock mountings within the silo, which itself had the same material characteristics and strength as the submarine pressure hull; and
iv) the missile could be launched only after the silo cap had been opened, which required hydraulic actuation that was no longer available.
Unlike a torpedo round explosion, which was considered to be credible and tolerable, full detonation of a single 760kg missile warhead could not be tolerated at any stage of the lift, conveyance from the wreck site and transfer to the floating dock because this would have imperiled all of those personnel manning the salvage vessels and had the potential to result in a release of radioactivity to the marine environment and hence to the M-S personnel. Thus, it was absolutely essential to determine the most unstable condition for the missile systems and the main fill and ejection charges and if any of the five AFS latches had been enabled by the foundering explosions and the subsequent M-S recovery operations.
This was determined by a series of trials in which fully assembled missiles were subject to a range of conditions simulating the impulse and vibration environments. Particular regard was given to the vibration spectra that was to be generated by the M-S cutting technique deployed to sever the bow section, since there was a possibility that a sympathetic vibration could not only result in the release of the cap of the first starboard side missile silo which had been damaged during the original explosion, but it could also override one of the acceleration/deceleration sensitive latches of the weapon firing system.