On July 1, a secretive Russian AC-31 (Project 10831) nuclear-powered submersible suffered a deadly onboard fire and explosion while operating underwater in the Barents Sea, close to the entrance to the Kola Bay (the Murmansk Fjord).
Fourteen members of the AC-31 crew—including all senior officers aboard—perished in the fire. Four crew members and a civilian survived. To date, officials have not disclosed the nature of the doomed vessel’s last mission or details regarding the construction of the AC-31 itself (see EDM, July 8). Authorities only revealed that the AC-31 is an unarmed naval “scientific vessel” and was exploring the sea bottom. This secretive submersible is unofficially known in the Russian navy as the “Losharik”—derived from the name of a children’s cartoon horse made out of interconnected balls—because the pressure hull of the AC-31 is apparently a chain of connected titanium alloy spheres that contain the nuclear reactor, crew quarters and equipment. These titanium spheres can withstand massive water pressure, thus allowing the Losharik to reportedly dive as deep as six kilometers. According to Kremlin spokesperson Dmitri Peskov all details concerning the submersible and its possible missions are a state secret, “but the President [Vladimir Putin] has been fully briefed” (Interfax, July 3).
The ice-free-year-round Kola Bay is a 57-kilometer-long fjord of the Barents Sea that cuts into the northern part of the Kola Peninsula. Along its banks are Murmansk (the world’s largest city and commercial port north of the Arctic Circle), Severomorsk (the main base of the Northern Fleet), and a number of other Russian military facilities and shipyards.
The Losharik is equipped with underwater mechanical hands/manipulators and floodlights, making it able to scan the seafloor and gather “samples.” Apparently, the Losharik was modeled on the United States’ unique nuclear-powered deep submergence vessel NR-1, built in 1969 and retired in 2008. The NR-1 conducted numerous classified missions involving the recovery of objects from the deep sea bottom. It was used to retrieve sensitive objects lost by the US military (jet, missile and ship debris) before the Soviets/Russians could reach them as well as to pick up equally sensitive objects the Soviets/Russians themselves lost at the bottom of the sea. The Losharik was designed to be like the NR-1 but superior, made of expensive titanium capable of descending 6 km (the NR-1 could barely make it 1 km down) and with a larger crew capacity of up to 24 men. The Losharik is carried to mission zones attached to a mother nuclear-powered submarine, thus providing comfort and concealment; whereas, the small NR-1 was towed by a surface mother ship, with the crew forced to endure sea sickness on the way. The construction of the Losharik began during the Cold War, in the 1980s, was abandoned in the 1990s due to cost concerns, but resumed after Putin came to power. By 2004, the Losharik had entered service (Lenta.ru, July 2; RBC, July 9).
All Losharik missions remain classified (as are the NR-1 missions), but they apparently were successful, since its entire crew was promoted to the rank of senior captain and was highly decorated (Gazeta.ru, July 3). The nuclear-powered Losharik can stay underwater searching the seafloor for as long as the crew can endure and its food supply holds out. The relatively large crew allows for running round-the-clock shifts focused on the mission at hand. The Barents Sea, at the entrance to the Murmansk Fjord, is only 200–300 meters deep—not really a typical Losharik mission zone. But just before meeting disaster, its onboard crew may have been searching for intelligence-gathering equipment potentially planted by the US military on the seafloor to monitor activities in the North Sea. Or maybe, the Russian navy itself had lost something during exercises. Another possibility is that this was a mission to test some new equipment, which may explain the presence of a defense industry civilian specialist onboard (RBC, July 9).
Defense Minister Sergei Shoigu told Putin the fatal fire happened in the electric battery compartment of the submersible (Kremlin.ru, July 4). Nuclear-powered submarines use rechargeable batteries as backups—mostly traditional lead-acid ones that were used by submariners for more than a century. But the Losharik apparently has a more modern lithium-ion battery, like ones ubiquitous in mobile phones. Lead-acid batteries can produce hydrogen gas during recharging, which is a known fire/explosion hazard on submarines. Lithium-ion batteries, meanwhile, are more powerful, smaller, more reliable and considered safer than lead-acid; nonetheless, they also are known to catch fire and explode when short-circuited. Such an explosion apparently occurred on July 1, as the Losharik was docking with its mother ship, the BC-136 Orenburg, a modified Project 667BDR (Delta-3) nuclear strategic submarine. A series of explosions reportedly ravaged the Losharik’s bow, killing the 14 men inside. The crew members in the main command post of the submersible sealed the bow compartments, completed the docking procedure, switched off the nuclear reactor and abandoned the Losharik by boarding the Orenburg. The mother ship’s crew, apparently fearful the explosions and fire could spread and sink them, too, flooded the entire pressure hull of the Losharik with sea water and returned to base with the submersible and its dead crew inside the flooded hull. The surviving though injured crew (apparently four sailors and a civilian) were taken to a hospital but eventually released. A special commission is investigating what happened (Fontanka, July 9).
Shuigu told Putin, “The nuclear reactor of the submersible is intact, and this gives us hope to restore the entire ship soon” (Kremlin.ru, July 4). The Losharik is unique, and plenty of missions await it. For one thing, the Losharik can reportedly sabotage the United States’ SOSUS seabed sound surveillance system in the Atlantic Ocean, which would allow Russian submarines to break out of Severomorsk into the open Atlantic undetected (RBC, July 9). Moreover, a US RQ-4 Global Hawk drone was shot down by the Iranians in the Strait of Hormuz in June 2019. The Iranians gathered some floating debris, but there is surely a treasure trove left scattered on the seabed. And in April 2019, a Japanese US-made F-35A stealth jet crashed in the Pacific. Again, some floating debris was recovered, but more valuable technology could still be found underneath (Interfax, April 15). The Losharik tragedy came at the worst time for Russia, and Shoigu seemed nervous when reporting the bad news to Putin, anxious to stress that the disaster can be mitigated soon.