Originally posted 9th Sept 2014.
Sarov Class submarine demystified
The Project 20120 Sarov Class (Б-90 "Саров") submarine is critical to Russia’s development of the new 'Poseidon' Intercontinental Nuclear-Powered Nuclear-Armed Autonomous Torpedo (NATO: KANYON, aka Status-6 and Skif) weapon. She is home ported in near the Zvezdochka shipyard in Severodvinsk and rarely puts to sea. Her mission is to test the Poseidon vehicle.

Original artwork of Sarov with Poseidon torpedo - CLICK IMAGE FOR HIGH-RESOLUTION.

*Official Russian Ministry of Defense footage seemingly taken aboard Sarov during a launch test of Poseidon, and released 20th Feb 2019. The mode of launch and markings on the object are broadly consistant with the image of the weapon painted for testing but differences are apparent (right-most image).

Construction of this submarine started in the final years of the Cold War but like so many other projects she was halted when the Soviet Union imploded. Somehow surviving the scrap merchants, the hull was mothballed and eventually restarted in the mid-2000s. Christened B-90 Sarov (Russian: Б-90 "Саров"), the boat was eventually launched in 2007 and commissioned into the Russian Fleet in 2008.

It was immediately clear that she was special, and there was at the time a lot of speculation and the euphemistic descriptions given to special submarines only added to the aura of mystery. The excitement is largely because she bears no real resemblance to the boat that was originally planned. As laid down, she was a Project 877 KILO Class diesel-electric attack submarine (SSK), but as finished she is a Project 20120 nuclear-electric sub. That propulsion arrangement is one of the things that makes her so unique and interesting, there isn't even designation for it.
Sarov in dry dock
Sarov in dry dock
The above photographs clearly show the overhanging nose and bow door. Note the lack of torpedo tubes.

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One of the first misinformations on the internet is her size. Because she was based on a KILO Class submarine hull her length is generally quoted as 72m (236ft) long and 9.9m (32ft) wide. In fact she is nearer to 98m (322ft) long. This is immediately apparent from satellite imagery and from photographs of her tied up alongside a KILO Class boat. The extra length fits with the addition of the nuclear reactor section immediately aft of the sail. The sail itself is also much larger than on the KILO and now contains an escape capsule section like on recent Russian nuclear submarines.
Sarov in dry dock
A good size comparrison with the KILO Class SSK (lower), also at Severodvinsk.

Sarov in dry dock
Sarov in dry dock

Sarov in dry dock
Overall dimensions shown in dry dock at Severodvinsk, Sept. 2009

Sarov in dry dock
If the SAROV is based on the KILO,then the inner hull is deeply buried.

The main curiosity is the forward section, which has a pronounced overbite just below the waterline. The receding chin seems to follow the same profile as the KILO class, with the upper section being an extension. There is no provision for torpedo tubes but the protruding nose features a large square cut hanger door where the torpedo tubes would ordinarily be. Along the waterline are large sponsons which seem to contain small diameter (~1.5m) pressure hulls. They appear to be double-hulled like the rest of the boat and have crew access hatches at the aft end. One possibility is that these contain compensation tanks for the heavy test payload.

Behind the hangar doors there this room for multiple large diameter torpedo tubes or one KANYON nuclear propelled torpedo. The KANYON is much larger than regular torpedoes at 24m length and 1.5m diameter.
Sarov seen loading a test weapon, 16th Oct 2009.

The ‘knife’ stern is reminiscent of the old TANGO Class SSKs and earlier boats which owe their linage straight back to the German Type-XXI of WW2. She appears to have a single screw like the KILO and more modern boats. The aft casing runs all the way to the stern, running along above the rudder with the steering mechanism in the casing. This is old-fashioned and seemingly a backwards step from the KILO, looking very much like a late-1950s boat. There are no rear firing torpedo tubes so this arrangement is hard to explain when all other modern boats of her size have the classic pointed tail with the screw behind the control surfaces. Possibly the enlarged stern allows for additional trim and ballast tanks to balance the bow.

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