August 20, 2019: Russia has another naval disaster on its hands. Details have been slowly emerging, mainly because the submarine in question is a one-of-a-kind deep (6,000 meters) nuclear powered (AC-31 Losharik) vessel that can investigate items on the ocean floor. This would include American “taps” placed on Russian undersea cables or listening devices left on the bottom near Russian naval bases. Normally all information about Losharik is kept secret. But the extent of this accident has made it difficult to maintain the usual degree of secrecy.

The July 1st Losharik accident was caused by the lithium batteries overheating, causing a fire and then exploding. This killed fourteen of the 19 men abroad the submerged sub. The four surviving crew and one civilian specialist managed to surface the sub, shut down the nuclear reactor and get off onto the modified SSBN that serves as its mothership. Before the surviving crew left they were ordered to flood all compartments, to ensure that there was not another fire or explosion. The Defense Ministry says it will get the Losharik back in service but they are still studying the damage and getting estimates of how long repairs would take and how much it would cost. The cost may be more than Russian can afford right now, no matter how important Losharik is to Russian undersea operations.

There are still questions about the batteries the Losharik used. The sub was originally designed to use Ukrainian made silver-zinc batteries but since 2014 Ukrainian military imports have been less “available” and Losharik switched to Russian made lithium batteries, which behave differently than silver-zinc ones. Lithium batteries will catch fire and explode if they are short-circuited. How that happened on Losharik is still unknown, much less how to avoid it.

Losharik is a relatively new (entered service in 2004) and smaller (65 meters long) nuclear-powered sub whose full name is the AS-31 Losharik. This sub carries a crew of up to 25 and has a top speed (for emergencies only) of 72 kilometers an hour. Losharik can dive deeper than any other sub and is quite large for a deep-diving sub. That additional size makes the sub capable of finding and retrieving useful items that end up in very deep waters, as well as survey very deep sea bottoms for suitable sites for placing various electronic devices. The accident took place in shallow (300 meters) Russian territorial waters off the north coast. The AS-12 is stationed at a naval base on the Kola Peninsula it may have just been on a training mission.

The Losharik design was based on and surpassed an earlier (1960) American deep-diving submersible; NR-1. The American vessel could only go down 1,000 meters, but during decades of service (it was retired in 2008) it did a lot of valuable but largely classified work. Construction of Losharik began in the 1980s but was halted in the 1990s, like so much ship construction, because of budget cuts. Work was resumed by 2000 and completed in 2004. Since then Losharik appears to have been undergoing tests and modifications. Navy budgets are again under pressure and Russia may decide that they cannot afford to repair Losharik, not when there are so many other urgent submarine construction projects in danger.