K-219 was a Project 667A Navaga-class ballistic missile submarine (NATO reporting name Yankee I) of the Soviet Navy. It carried 16 R-27U liquid-fuel missiles powered by UDMH with nitrogen tetroxide (NTO), and equipped with either 32 or 48 nuclear warheads. K-219 was involved in what has become one of the most controversial submarine incidents during the Cold War on Friday 3 October 1986. The 15-year-old vessel, which was on an otherwise routine Cold War nuclear deterrence patrol in the North Atlantic northeast of Bermuda, suffered an explosion and fire in a missile tube. While underway a submerged seal in a missile hatch cover failed, allowing high-pressure seawater to enter the missile tube and owing to the pressure differential rupture the missile fuel tanks, allowing missile's liquid fuel to mix and ultimately combust. Though there was no official announcement, the Soviet Union claimed the leak was caused by a collision with the submarine . Although Augusta was operating within the area, both the United States Navy and the commander of K-219, Captain Second Rank Igor Britanov, deny that a collision took place. The incident was novelized in the book Hostile Waters, which reconstructed the incident from descriptions by the survivors, ships' logs, the official investigations, and participants both ashore and afloat from the Soviet and the American sides. Explosion Shortly after 0530 Moscow time, seawater leaking into silo six of K-219 reacted with missile fuel, producing chlorine and nitrogen dioxide gases and sufficient heat to explosively decompose additional fuming nitric acid to produce more nitrogen dioxide gas. K-219 weapons officer Alexander Petrachkov attempted to deal with this by disengaging the hatch cover and venting the missile tube to the sea. Shortly after 0532, an explosion occurred in the silo. K-219 had previously experienced a similar event; one of her missile tubes was already disabled and welded shut, having been permanently sealed after an explosion caused by reaction between seawater leaking into the silo and missile fuel residue. An article in Undersea warfare by Captain First Rank, Igor Kurdin, Russian Navy – K-219s previous XO (executive officer) – and Lieutenant Commander Wayne Grasdock, USN described the explosion occurrence as follows: Two sailors were killed outright in the explosion, and a third died soon afterward from toxic gas poisoning. Through a breach in the hull, the vessel immediately started taking on sea water, quickly sinking from its original depth of to eventually reach