Russia's Unusual Mother Submarine For Spy Missions On The Sea Floor

CLICK to enlarge. Original artwork

BS-64: Russia's Unusual Mother Submarine For Spy Missions On The Sea Floor

Flag Russia Central to the Russian Navy's seabed warfare capabilities are its ginormous 'mother submarines'. Created by cutting a missile submarine in half and inserting a special compartment in place of the missile tubes, they are among the largest submarines on the planet. And their mission is essentially as a spy submarine.

BS-64 Podmoskovye (Подмосковье; ‘Moscow Oblast’) is a Project 667BDRM DELTA-IV class SSBNs which have been cut-and-shut in this way. She was originally launched as K-64, in 1982. In the 2000s work started to rebuild her as a 'special missions' submarine. The model for this was already established in the Russian Navy with both YANKEE and DELTA-III boats having been modified before. But BS-64 was to be bigger, making her long enough to accommodate the now-famous Losharik mini submarine.

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Losharik (or the older PALTUS class) is carried in a recess under the keel. A hatch on her back connects to a docking collar to the submarine. The basic modus operandi is that the mother submarine (more properly 'Host Submarine') carries Losharik to where the mission is. Losharik then detaches and goes down to the sea floor to do whatever it came there for. The mother submarine waits to assist in an emergency and to carry Losharik home.
BS-64 submarine
OSINT image of BS-64 operating off Kildin in the Arctic, August 2021

Despite their nuclear propulsion, the mini-submarines do not have the speed or endurance to operate without the mother submarine. In the case of BS-64 she appears to retain her torpedo tubes so se can also offer protection to the operation.

The Missions

This arrangement allows covert operations in ways that surface vessels (i.e. Yantar) cannot. It also allows operations under ice. The types of missions anticipated include:

Design of BS-64

BS-64 retains the forward and aft compartments of the DELTA-IV design. This includes the sonar and torpedo tubes in the bow, making her more or less as combat capable as an SSN.

The differences are in the middle. The two missile compartments are replaced by a new hull section. This is longer to allow the 70 meter long Losharik to be docked underneath. Although unconfirmed, I expect that the new hull section is of a smaller diameter to allow the sail of Losharik to be accommodated.

There is also a main hatch on the back of the submarine. This can accommodate a cradle for a deep-diving submarine. In practice this has been the smaller Pr. 18270 Bester DSRV. This may be an alternative to the Losharik, or potentially act as a rescue vehicle in an emergency. However it was not being carried when Losharik suffered a serious fire on July 1 2019.

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One interesting possibility is the the trunk connecting BS-64 to Losharik might also be connected directly to the main hatch above. The two appear to be aligned although this cannot be confirmed. This would open the possibility of transfers between the two smaller submarines without entering the mother submarine directly. We can also speculate that this area has hyperbaric chambers for decompression and other support facilities.

BS-64 is also equipped wit the Klavesin-29-2M (aka harpsichord) deep-diving autonomous underwater vehicle. This is carried in a hangar on the back bind the sail.

Aditional Covert Shores Articles on BS-64

2016: BS-64 Podmoskovye - New Russian Special Mission spy-sub
2019: Russian 'Special Mission' submarine BS-64 carries payloads on back

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