Named Belgorod, the Russian navy’s newest vessel can dive to 1,700ft, and has been design to carry and deploy nuclear-powered torpedo drones.
The submarine – which is the world’s longest – was launched last week at the Sevmash shipyard on the White Sea, while President Vladimir Putin watched the ceremony via satellite.
Known officially as Project 09852, it will act as a mothership to other underwater vessels.
Apart from its ability to launch Poseidon nuclear torpedo drones, Belgorod will also be able to carry a Losharik class mini-sub which will be attached to the bottom of its hull.
The 230-foot-long Losharik mini subs – which are also nuclear powered – are equipped with multi-directional robotic arms that allow them to manipulate subsea cables and access other seafloor infrastructure down to 1,000m.
Western observers have noticed that, unlike other Oscar II-class vessels, Belgorod has a large bulge at its stern with several hatches, and its starboard-side rudder skeg appears to have arrangements for towing.
The modifications may mean that Belgorod is equipped with a spool and deployment system for covert cable laying.
Western analysts believe Belgorod will carry six of the 80-foot-long Poseidon drone torpedoes, which will have a range of 6,000 miles, a top speed of 55 knots, and a nuclear payload capacity of 100 megatons.
Belgorod’s nuclear reactor will be tested this year – before its sea trials begin in 2020.