On a side note, the Soviet Navy gets credit for envisioning and building the first submarine to carry an ICBM, the Zulu Class submarine. The Zulu was a conventional diesel-electric submarine that was modified with an extended sail to carry a single nuclear-tipped long-range missile. It was also the first submarine to test launch a ballistic missile.
The Zulu class was followed by a series of specifically designed (diesel powered) Golf Class units, which were eventually accompanied by the nuclear-powered Hotel Class. Both of these classes had three vertical launch tubes incorporated in the sail of each submarine.
The missiles initially fielded by these submarines could only be launched with the ship on the surface, but these were soon followed by missiles that could be launched with the ship submerged. The Soviet submarine K-19 (about which the movie was made) was a first-generation nuclear powered ballistic missile Hotel Class submarine.
The US, meanwhile, had much bigger plans for submarines and ballistic missiles. George Washington class ships were literally a Skipjack Class attack submarine, split in half, with a sixteen-tube missile compartment welded into the ship just behind the sail. George Washington class subs carried 16 Polaris ICBMs, each with a yield of 600 kilotons and a range of 2500 miles. That's some serious nation-damaging capability for a single ship...
Yankee Class submarines were the Soviet result of duplicating the enormous firepower carried by US "George Washington" Class submarines (thus the code name "Yankee"). The missile compartment is the elevated section right behind the sail, at the center of the ship. These ships even came equipped with sail-mounted forward planes (aka "fairwater planes"), which all US nuclear submarines had at that time. To my knowledge these were the only Soviet subs that had fairwater planes.
In October of 1986, K-219 was on patrol to the southeast of Bermuda, operating within a box that kept her missiles within range of the intended US targets. On October 3, seawater was discovered to be leaking into missile tube #6. This is the missile tube in the third row behind the sail on the left (port) side of the ship.
The crew began draining seawater from the missile tube, but the seawater had already reacted with residual liquid fuel from the missile. The water draining from the missile tube soon became steam, and then nitric acid vapor began blowing out the vent. The weapons officer declared an emergency, and the captain brought the ship to a safer depth (150ft), and ordered all compartments sealed.
The weapons officer attempted to release the pressure inside tube #6 by opening the missile launch door atop the ship. Before he could do that, an explosion occurred in the missile tube. Two sailors were killed in the explosion and a third died later from toxic gas inhalation. The hull of the submarine was breached in the missile compartment, and it began flooding. The ship descended uncontrollably to a depth of 980ft before the descent was stopped. The ship returned to periscope depth once control was re-established.
The fact that the ship's hull was breached is evidence of the power of the explosion. Submarine hulls are made of high yield steel several inches thick.
K-219 surfaced, with 25 men trapped aft of the missile compartment in the engine room. One of the reactors had shut down during the emergency, but the other had not. The second reactor compartment developed a fire, and the reactor controls could not shut it down. One enlisted man volunteered to enter the reactor compartment and shut the reactor down manually. He did so, but the fire had increased air pressure in the reactor compartment. This pressure was too high for the crew to re-open the reactor compartment hatch. The sailor died of asphyxiation inside the reactor compartment.
The initial casualties had been dealt with, but the ship was badly damaged. She was adrift, without main propulsion, and was drawing down the main storage battery. The order was given to surface and send out an emergency call for help. A tow ship arrived. Due to leaks of toxic gas into several compartments, the capain ordered his crew topside, and then eventually onto the towing ship.
Towing the disabled submarine was unsuccessful, and eventually the stricken ship sunk on Oct 6. (see the bottom of this post for reasons why disabled submarines don't stay afloat). It went to the bottom, carrying a full load of nuclear missiles, in 18,000 feet of water. No men were lost in the sinking.
Below: K-219, following the explosion and depth excursion. Note the damaged outer skin, missing missile tube door, and hull damage. Fairwater planes are nearly straight up and down following the flooding emergency - these are normally aligned with the ship's hull.
Below, a color image of K-219, with brownish-red fumes issuing from the damaged missile tube. Based on the color, I would guess this to be a combination of nitric acid vapor and nitrous oxides.
Afterwards the Soviet Navy attempted to blame the loss of K-219 on a collision with a US Submarine, and in fact US submarines were operating in the area. However both the US Navy and the captain and crew of K-219 deny that a collision occurred. Years earlier, K-219 had experienced a similar mishap in a different missile tube. That missile tube had been so badly damaged that it was removed from service and welded shut. Invoking a collision was not necessary to explain this disaster.
Point of interest: Two years later, in 1988, a Russian deep-sea exploration vessel sent submersibles down to view the wreckage of K-219. She was found upright, but broken in half behind the sail. Several of the missile tube hatches had been forced open, and the missiles inside them were gone.