Ivan Susanin-class patrol ship

Ivan Susanin class, also known by its Soviet designation Project 97P (97П), is a series of icebreaking patrol ships built for the Soviet Navy and Soviet Border Troops, and today operated by the Russian Navy and Coast Guard of the Border Service of the FSB.

, four Ivan Susanin-class patrol ships remain in service: Ivan Susanin with the Pacific Fleet and Ruslan with the Northern Fleet, both with their armaments removed, and Neva and Volga with the Border Service of the FSB.

Background
In the mid-1950s, the Soviet Union began developing a new diesel-electric icebreaker design based on the 1942-built steam-powered icebreaker Eisbär to meet the needs of both civilian and naval operators. Built in various configurations until the early 1980s, the Project 97 icebreakers and their derivatives became the largest and longest-running class of icebreakers and icebreaking vessels built in the world.

Project 97P (97П) was developed as a response to the renewed interest of the Soviet Navy and Soviet Border Troops on icebreaking patrol ships after United States Coast Guard and Canadian Coast Guard icebreakers began appearing more frequently near the country's northern maritime borders. New icebreaking patrol ships were needed because existing Soviet naval vessels could not operate in ice-covered waters and large icebreakers, in addition to being unarmed and operated by civilians, could not be distracted from their primary mission of escorting merchant ships. Central Design Bureau "Iceberg" selected the existing Project 97 as the design basis following positive operational experience and the difficulties associated with developing a new design.

Design
At 70 m long overall and with a beam of 18.1 m, Ivan Susanin-class patrol ships are slightly larger than the icebreakers on which they are based. Fully laden, the vessels draw 6.5 m of water and have a full load displacement of 3710 t. The hull, derived from an older Swedish-built icebreaker, features a round midship with a pronounced tumblehome and practically no flat bottom or sides; this makes the ships uncomfortable to the crew in heavy seas despite having two roll damping tanks. The enlarged deckhouse is built of aluminum-magnesium alloy to reduce weight and provides accommodation for a complement of 10 officers and 113 crew.

Ivan Susanin-class patrol ships share the same diesel-electric power plant with the other Project 97 variants. Their 1800 hp 10-cylinder 13D100 two-stroke opposed-piston main diesel engines are in fact reverse-engineered Fairbanks Morse 38 8-1/8 diesel engines manufactured by the Malyshev Factory in the Ukrainian Soviet Socialist Republic. The engines are coupled to double-armature DC generators (2 × 625 kWe) that provide power to 2400 hp DC propulsion motors driving two 3.5 m four-bladed fixed pitch propellers in the stern. While the patrol ships were not fitted with a third propeller in the bow like the icebreakers they were based on as it was seen prone to damage in Arctic ice conditions, they can still break up to 70 cm thick ice. In addition, the ships have five 6Ch2B/34 ship service diesel generators.

All Ivan Susanin-class patrol ships were initially armed with a twin 76 mm AK-726 deck gun and two 30 mm AK-630 close-in weapon systems, but the armament was later removed from the ships operated by the navy. Unlike the icebreakers, they are fitted with helideck over the aft deck for Kamov Ka-25 or Ka-27 helicopters.