Russia Completes Hybrid Submarine


Russia’s Sevmash shipyard at the Arctic city of Severodvinsk has completed a hybrid submarine powered by a diesel-electric plant and a small nuclear reactor. Designated B-90 and named Sarov, the submarine was completed on 17 December.

The submarine is known as Project 20120 in Russian design terminology. She apparently employs the small nuclear reactor — known to some engineers as a “teakettle” — to keep a charge on the battery, providing essentially unlimited underwater endurance on relatively quiet electric propulsion. In effect, this is an Air-Indpendent Propulsion (AIP) system.

The “teakettle” concept is not new. The Soviet Navy deployed a Project 651 (NATO Juliett) cruise missile submarine (SSG) in 1986-1991 with a similar diesel-electric/nuclear plant. That craft had a pressurized-water reactor with a single-loop configuration coupled with a turbogenerator. The Soviet report stated that the sea trials “demonstrated the workability of the system, but revealed quite a few deficiencies. Those were later corrected.”

However, no follow-on efforts were undertaken at that time. (The Soviets built 16 diesel-electric Juliett SSGs from 1963 to 1968.)

The B-90 was designed by the Rubin design bureau in St. Petersburg. Construction was begun at the Krasnoe Sormovo shipyard in Nizhnii Novgorod (formerly Gor’kiy), and the submarine was then transported through the inland waterways to the Sevmash yard for completion.

There is no available information on the size of the B-90 program. In the past the Soviet Union was an early leader in AIP-type submarines. As early as 1938 the Soviets began development on a “single-drive” submarine that could operate diesel engines while submerged and surfaced. After World War II the Soviets built the Project 617 (Whale), an AIP submarine based on German technology. She was followed by 23 coastal submarines of Project A615 (Quebec), which were torpedo and gun-armed combat craft. Other AIP experiments followed.

Today several navies are operating AIP submarines, with the U.S. Navy having “borrowed” the Swedish AIP submarine Gotland in 2005-2007 to serve as an anti-submarine target for U.S. carrier task forces. The Gotland, according to Swedish officers, could not be located by U.S. naval forces in exercises until the submarine “wanted to be found.”

The Soviet B-90 may be a follow-on submarine to the Kilo-class diesel-electric submarines that have been transferred in large numbers to other navies, including China and India. The B-90, especially when operating in coastal or littoral waters, could pose a significant threat to Western maritime interests.

Norman Polmar

  • Jerome Mrozak

    So the sub contains a small reactor. I understand that reactors need cooling, and that the resulting gurgle is what makes them so noisy. That is a bit different than a diesel AIP. I suppose that the reactor would be smaller in capacity, perhaps as capable as a Skate-sized ship. But that ought to be large enough to be noisy. Or am I missing something here?

  • DC2 Jennings

    That is a fairly brilliant design, but I would not call it air independent. If that were the case then there would be no need for the diesel engine. I would imagine the nuclear reactor can keep the batteries charged for a longer period of time, but the batteries will still drain. Sonar, motors, etc. take a lot of juice.

  • Engage

    I don’t follow. Why is a hybrid diesel/nuke an advantage? Are diesels that much quieter? If so how has the US sub force been so successful?
    Someone please break it down Sesame Street style for me.

  • C

    the diesel part of the powerplant isn’t so quiet (one of the big reasons the superpowers went nuclear) but the electric part certainly is. like a locomotive, the motor is actually a direct-drive electric and the diesel (or nuke) plant just makes the electricity.
    i agree with the other posters that it’s confusing why they would do a hybrid instead of all nuke.

  • ohwilleke

    One suspects that the virtues of a diesel-nuclear hybrid may include:
    (1) Longer periods submerged between refuelings than a diesel (for which a week might apply). The additional submerged time that would be secured by an all nuclear design may be useless because the need to reprovision requires periodic surfacing anyway.
    (2) Nuclear fuel has much higher energy density than than diesel reducing fuel requirements and hence also reducing total submarine size.
    (3) A teakettle, because it is smaller than other nuclear reactors, is probably quieter than the threshold that existing ASW technologies targeted at nuclear submarines were designed to detect. It also probably requires less shielding since the radioactive source is smaller.
    (4) Nuclear submarines are more expensive to build than diesel-electrics; reducing the size of the nuclear fuel plant probably reduces cost.
    (5) There are many potential commercial and military applications for very small nuclear reactors, particularly in places like Siberia with small isolated communities that have to fly in all of their fuel, and isolated military bases. Similar commercial nuclear power plant applications are being considered for use in Alaskan villages. This program allows Russian military R&D money to be used to develop the technology with human test subjects who can’t opt out because they are military personnel.
    Also in response to another Engage, a full fledged AIP (which this doesn’t sound like it is, it sounds like this is a traditional air driven diesel that surfaces to recharge the batteries), or battery drive alone, should be significantly quieter than a nuclear submarine.
    Why then has the U.S. submarine force been a success? Mostly because it has no opposition. Very few countries have blue sea navies (where U.S. nuclear submarines mostly operate) of any consequence. Fewer have decent ASW resourced and the subtle differences between nuclear subs and AIP or battery driven subs is very slight unless the opposition has good ASW. Also, none of those countries with good ASW has found it politically expident to target U.S. submarines.
    Likewise, the U.S. has not, to my knowledge, every fired a shot in anger from a U.S. nuclear attack submarine. One reason that U.S. attack submarines haven’t been tested is that in the kinds of naval engagements that come up between the kind of major naval wars, like taking potshots at pirates, a surface ship is preferred because it leaves no doubt about who is responsible. A submarine strike attributed to the wrong country could spawn diplomatic mayhem.
    The U.S. Navy and I as one of the many people whose tax dollars help fund it would like to think that if we had to knock on wood that the U.S. attack submarine force would perform admirably, but it has never been tested in an actual conflict.

  • Joe

    Sure are glad we scrapped all those obsolete S-3’s.

  • joe

    Some of the missles fired at Afghanistan in 1998 were from a sub. At least that is the story as I heard it.

  • Asterix

    The Americans did this with the Tullibee (SSN-597) in 1958. No idea if we were the first or not.
    The short-term tactical advantage of a nuke plant over AIP / batteries / the “teakettle” is explosively fast submerged speed and acceleration. A non-nuke boat is functionally an underwater mine, practically stationary. Either B-90’s plant is very low output, and thus limited in submerged speed, or it is as big as a regular reactor plant, and just as noisy. According to most sources (for instance, the main source of noise for Russian boats is the drivetrain, not the reactor, anyway. An American nuclear sub at low speed is just as quiet as a boat on batteries; you don’t get much quieter than utter silence.
    As far as size of the plant goes, either this thing has a lot of bulky shielding, or it fries the crew. Russian naval history points towards frying the crew.
    American nuclear attack submarines have fired Tomahawks in both Iraq wars, among other conflicts; see . The US government, when launching Tomahawks, uses subs as much as possible; this keeps them looking useful for political reasons until Chinese saber-rattling becomes convincing. To my knowledge the only warshot torpedoes fired in anger from a nuke were by the British during the Falklands war.

  • Ezio Bonsignore

    At least based on the news as reported, something doesn’t add up. Please consider:
    – In modern diesel/electric subs (unlike their WW2 ancestors) the diesel engine is ONLY intended to generate electricity for the electric motor + reloading the batteries. That is, the diesel is never connected to the power shaft and rather acts as a source of energy. The boat is always powered by the electric motor, this being fed electricity by the diesel + generator when on the surface or snorkeling and by the batteries when submerged.
    – AIP systems (Stirling, fuel cells or Mesma turbine) are a way to extend underwater range (but at very low speeds!) by reloading the batteries without having to come to the surface or snorkel depth. In practical terms, what happens is, the boat can move at very slow speed (some 4-5 knots) for very long periods with minimal or no drain on the batteries, which thus remain fully laden should a burst to max. underwater speed be required.
    – In the standard configuration of nuclear power plants, the reactor acts basically as a boiler, producing steam which powers geared turbines acting on the shat through reduction gears. It is my understanding that the reduction gears are by far the most significant source of noise in a nuclear submarines.
    – For the above reason, it is sometime preferred (e.g. the French Navy) to rather use the turbines to power a generator, which then feeds electric energy to an electric propulsion motor. This of course takes more space and weight and entails not insignificant energy losses, but it is easier to silence.
    – Based on the news, the Russian system looks like a contraption whereby a small reactor + turbine + generator would be used in the same vein as AIPs, i.e. to keep the batteries loaded while moving underwater at slow speed.
    – Point is, this makes no sense in either technological or operational sense. Such a mini- nuclear power plant is certainly more complex and probably even more costly to design than a “full-size” one. The Russians did use a different type of similarly complicated hybrid power plant (nuclear + stem) on the “Kirov” class cruisers, but this was because they could not develop a suitably powerful reactor.
    – If there is a logic, this is purely commercial. The international market for conventional subs is increasingly dominated by AIP-equipped designs, which the Russians currently cannot offer. It is thus possible that they are trying and recovering their lost commercial positions by offering a “semi-nuclear” boat.

  • Tom

    Actually what you are seeing is part of a revolution in the design and fielding of small nuclear reactors. Over the next ten years or so a large renaissance in nuclear power will occur as the engineering community has finally found a way to build very safe, very small and extremely inexpensive nuclear reactors. Toshiba recently gave a small Alaskan town a stand alone system that is only 20 feet long and six feet wide.

  • jas

    “U.S. attack submarine force would perform admirably, but it has never been tested in an actual conflict.”
    . . . that you know of.
    There are a number of Mk48’s “missing” from U.S. inventories during cold war.
    A full accounting of what these fish were used for won’t be public knowledge for years/decades to come. It might be interesting for some here to look at the Soviet sub inventory for “missing” boats. More than a couple have disappeared never to be seen again.

  • Mark Toth

    The real story continues to be the USN and the shipbuilders selling large subs relying on high tech toys verses the “many small” with right-sized high tech paths taken by several other European and allied navies.
    Now with 688, Seawolf and Virginia we shall have too few of boats too large and expensive, while foreign boats like the GFR’s U-212 look mighty fine for small crew complimmmment, good tech, some legs though slow at a more affordable price.
    The HMAS Collins class bares watching as one forward looking program. (Unlike the Canadians buying RN wrecks.)
    About 10-20 small boats should be a target build to compliment the 50 or so big nuc attack boats that get built. These would be driven by one or more combination of Sterling engine, Diesel-Electric, or a small nuc (80-100 MW) plant in a 20-25 ft diam hull with crew target of 24-50 men and 3-5 Officers in mixed bag of SSK and SSKN add-ons. These would serve as both local and far coastal patrol or small island hopper. This would be meant to compliment the open-ocean Virginia sports cars and Ohio underwater boomer hotels as these would provide the killer patrol capability lost when the tall sail & twin-screwed boats were decom’d.
    Poor Definition
    “Hybrid Desiel-Electric / Nuc boat” is a definition without merit. All boats with the Nuc plant have battery and diesel. All have an electric motor as emergency propulsion (somewhere) with use of battery and diesel for supply of power to get a few knots closer to home. Tulibee and Lipscomb used motors for propulsion verses steam propulsion turbine drive with reduction gears. Any pumps the larger, the more, and the faster running with reduction gears make the most noise. The Skates, Halibut and Tulibee had smaller plants with less and smaller motors.
    While I don’t know how sister Skate did in an underwater drag race with Tulibee in the small pond, but our slower transit in the big pond was noticeble when the LA showed up but still not too arduous. Besides it gave us move time to drill and we loved (gag) our drills. Our only claim to boast was that we could out race the round hulls on surface coming into port from stress limits on their single shaft.

  • John Sidles

    The “missing link” that several have commented upon is this: these reactors use direct thermoelectric conversion of nuclear heat into electric power.
    Thus there is no “diesel” and no “turbo” element.
    Rather, it’s 200kW of power for station-keeping, plus lithium-ion batteries for tactical “sprints”.
    Cheap. Quiet. Simple.
    There’s nothing classified here … any US boat store will sell you the thermoelectric converters.

  • wolfie

    In regards to what was said about WWII boats by a poster,about the diesel being directly tied to the screws. This is not correct regarding U.S. boats. These boats were true diesel electric drive.

  • windsailor

    The issue here, as I see it, is not particularly that the Russians built a hybrid sub,but, more importantly, that they are back in the armaments business again. After allowing their nuclear sub fleet to rot at the dock, they are equipping themselves again. This also means that they will ,most likely, be marketing to third world wanna-bee countries.

  • navblk4

    Does anybody know if the Rubin Design Bureau in St. Petersburg, is named after T. Rubin the Hungarian whom received a US Medal of Honor?

  • Byron Skinner

    Good Evening Folks,
    I believe that the German Submarine Technology as used the U-212 is not AIP but whichis being developed in Sweden among other countries but Hydrogen Fuel and battery technology. Two completely different types of propulsion.
    Byron Skinner

  • Just A Reader

    I find it amazing that Russia could build or design anything using their own technology and design. I know nothing about subs but I have watched for years how they have copied all out aircraft up to and including the Space Shuttle. Why should their boat building be any different?

  • Edd the talking mule

    2 busy working in the t-shirt factory 2 comment! besides, you don’t wont 2 see or smell me with my head out of myass!!
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  • John F

    Strategy Page (a blog) had a recent article which talked about a Russian AIP submarine, but it had the electrical source being an ethanol/oxygen fuel cell, not nuclear. My recollection is that the article was not about Russian work, per se, but about Indian development work being undertaken with Russian cooperation. As I recall, the submerged time was around two weeks.

  • stephen russell

    Cant the US reengineer our subs with same power system as Russians
    Save on Next Gen subs alone.
    Who will
    Nice- diesel & nuclear power.
    Imagine this in Hitlers U Boats in WW2.
    Very doable
    & cut our Sub Dev in 1/3rd time alone.
    Same prefab BUT Faster Dev & Seatime vs Nuclear test time.
    Must have for the Navy Sub Force.

  • Ezio Bonsignore

    There is no discussion that the ideal power plant for submarines is a nuclear reactor, provided that the boat is large enough to accommodate one. Conventional (i.e. diesel/electric) subs still exist in part due to specific operational requirements for small and exceedingly silent boats operating in coastal waters, in part because of cost reasons, but overwhelmingly because of the political implications of nuclear-powered warships. That is, virtually all navies that operate diesel/electric submarines do so simply because they are prevented from building or acquiring nuclear boats due to international or/and domestic political considerations.
    Given this, the Russian hybrid/nuclear proposal makes no technological or commercial sense. If a country can afford (politically and financially) to procure a nuclear-powered submarine, it would want the “true thing”, not a contraption which effectively combines the shortcomings of both nuclear and conventional power plants with none of their advantages.

  • freya

    how do kilo class submarines compare to the australian collins class sub?

  • kevin

    IT sounds like something Canada worked on the 1980″s a small nuclear reactor using heat to create a Rankine cycle power supply for higher underwater endurance for a conventional submarine.
    A modified version has been proposed to improve the performance of the Victoria class thus turning our”ex .uk. junk. into proper sskn’s.
    Even in the ufortunate condition we recieved them comentatators have compared the subs to trafalgar class without the kettle. so even putting back a small teakettle would improve there performance

  • kevin

    IT sounds like something Canada worked on the 1980″s a small nuclear reactor using heat to create a Rankine cycle power supply for higher underwater endurance for a conventional submarine.
    A modified version has been proposed to improve the performance of the Victoria class thus turning our”ex .uk. junk. into proper sskn’s.
    Even in the ufortunate condition we recieved them comentatators have compared the subs to trafalgar class without the kettle. so even putting back a small teakettle would improve there performance

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  • shantanu chatterjee

    umm pardon my ignorance but exactly why do u need the diesel if u have small nuclear reactor/nuclear battery to charge the electric battery infact why do u need the battery at all can’t the nuclear device deliver electricity to the turbines directly or is the battery an emegency power reserve for tactical burst speed etc?

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