[2] Although K-278 was commissioned in the Soviet Navy to evaluate the technology for the fourth-generation of Russian nuclear submarines, she was capable of combat maneuvering and deployment.

During her third operational patrol in the Arctic Ocean in 1989, a serious fire in the aft compartments led to her sinking in the Barents Sea off the coast of Norway.

[5] The pressure hull was composed of seven compartments with the second and third protected by stronger forward and aft bulkheads creating a "safety zone" in case of an emergency.

An escape capsule was fitted in the fin above these compartments to enable the crew to abandon ship in the event of an underwater emergency.

Initial Western intelligence estimates of K-278's speed were based on the assumption that the boat was powered by a pair of liquid metal cooled reactors.

In October 1988, K-278 became one of the few Soviet submarines to be given a name: Komsomolets (Комсомолец, meaning "a member of the Komsomol"), and her commanding officer, Captain 1st rank Yuriy Zelenskiy was honoured for diving to 1,020 metres (3,350 ft).

On 7 April 1989, while under the command of Captain 1st Rank Evgeny Vanin and running submerged at a depth of 335 metres (1,099 ft) about 180 kilometres (100 nmi) southwest of Bear Island (Norway),[7] a fire broke out in an engineering compartment[3] due to a short circuit,[8] and even though watertight doors were shut, the resulting fire spread through bulkhead cable penetrations.

At 15:15,[9] several hours after surfacing, the boat sank in 1,680 metres (5,510 ft) of water, about 250 kilometres (135 nmi) SSW off Bear Island.

[11] Of the 69 crewmen, 27 survived the incident and 42 died: nine during the accident and the subsequent sinking, 30 in the water of hypothermia or injuries, and three aboard the rescue boat.

Under pressure from Norway, the Soviet Union used deep sea submersibles operated from the oceanographic research ship Keldysh to search for K-278.

On 24 June 1995, Keldysh set out again from Saint Petersburg to the Komsomolets to seal the hull fractures in Compartment 1 and cover the nuclear warheads, and declared success at the end of a subsequent expedition in July 1996.