The new French submarine is captioned above. Every navy is pushing for a quieter submarine because quiet is critical.

 

Russian Navy B-871 Alrosa (Kilo-class)

The Russian Navy is experimenting with pump jet/proulsor technology. In the photo, above, the Russian Navy B-871 Alrosa is the only Kilo-class sub that uses a pump jet propulsion system instead of a conventional propeller.

The US Navy has reached the limits of noise reduction with mechanical system propulsion. The current Virginia Class submarines use a propulsor or ‘pump jet’ instead of a traditional screw design. This type of design reduces the chances of cavitation to about zero and allows for quieter operation compared to traditional screw designs.

The planned Ohio Class Replacement Program for the next generation of ballistic missile submarines is expected to use a permanent magnetic motor. This technology was tried before by the US navy in 1960’s and 1970’s but proved to be troublesome at that time. The technology is now considered mature. This represents the limit of noise reduction with purely mechanical drive systems.

This technology is to be utilized in future Blocks of the Virginia class submarines to be built.

USS South Dakota

The recently launched USS South Dakota (SSN-790, a Block III Virginia Class) features an enhanced propulsor design which will be tested during the shakedown of the submarine. It is described as “an improved enhanced hybrid propulsor” developed by the US Navy and DARPA and is rumored to be a Hybrid Multi-Material Rotor.

If it is successful, it will be incorporated in future Virginia Class and Columbia Class submarines. It is promised to have a “significant return on investment”.

Further, Rear Admiral Micheal Jabaley (program officer for submarines US Navy) has stated:

“The field of biomimetics is very interesting to me when you look at nature in action and you think: ‘Boy, it would be great if we could design something that would take that leap forward and get us into a realm that would be acoustic-self unlike anything we’ve ever done before.”

Biomimetics or biomimcry is the imitation of the models, systems, and elements of nature.

16 COMMENTS

  1. Another leap with the Virginia class is the use of fly by wire, reducing electro-hydraulic noise, and IIRC the electrical power generated is DC and no longer 400CPS to avoid hum.

  2. Total landlubber here. Propellers are mature technology and able to handle ocean trash, seaweed, etc. Are these systems as robust? Subject to fouling? Mechanically efficient?

    I understand the need for quietness. Just wonder what the trade off is.

    Cost? Not a factor given what they equip.

    • Pump jet technology is several decades old. The original units such as those used by the Russians, are crude and heavy. USN has solved some of those problems. I had some interaction with pump jet tech for mini-subs with alternative energy sources. There really isn’t much of a trade off by eliminating a prop except that they cost more. They are safer from an acoustic signature perspective, they don’t foul, they aren’t prone to damage because they’re very much an enclosed system.

      You can travel much faster with a pump jet because you don’t need to worry about cavitation (big noise source) as the prop turns would increase. Even with extreme quieting tech, propellors reached the limit of their tech three decades ago or more.

      • “They are safer from an acoustic signature perspective, they don’t foul, they aren’t prone to damage because they’re very much an enclosed system.” Aren’t they trading the fouling aspect of the propeller with fouling of the intake ports providing water to the pump/s? With increasing revolutions creating cavitation with a prop, wouldn’t you get cavitation at the inlet ports also? Increased water (air)(electron) flow over a threshold will create cavitation, basically when you have any time of flow, there is some type of turbulence.

          • There are classified elements to pump jet/propulsar systems that I’m privy to, and I can’t get in the weeds too deeply on this. But as I noted above, the US Navy has moved through this tech and is at the apex in terms of where it can be taken.

            I refer you to the quote above, Further, Rear Admiral Micheal Jabaley (program officer for submarines US Navy) has stated:

            “The field of biomimetics is very interesting to me when you look at nature in action and you think: ‘Boy, it would be great if we could design something that would take that leap forward and get us into a realm that would be acoustic-self unlike anything we’ve ever done before.”

            Biomimemics would seem to be the next revolution in submarine design, beyond pump jets. I’m not aware of programs that are exploring those options for the 2050’s, but I’m sure that they exist.

    • @WSF – Yes, they’re very reliable and able to operate in shallower water.

      @LL – The first thing I thought when I saw the post title was “Engage the Caterpillar Drive!”, said in Sean Connery’s best Russian accent.

      The “Permanent Magnet” motors are very similar to the “Brushless AC” motors that run most power tools these days, and my little Radio Controlled race cars. Subs used to use big DC motors because they had huge batteries to power them when submerged, and big Diesels to spin generators to power the motor and recharge the batteries. But big DC motors have big brush assemblies that need maintenance and have definite lifetimes. With the advent of modern electronic speed controls, AC Induction Motors were able to be used, eliminating the maintenance headaches that come with brushes. The next big advance was to replace the “Squirrel Cage” rotor, which gets magnetized by the rotating field generated by the windings in the housing (Stator), with a permanently magnetized rotor. This increased the torque, and allowed the windings in the stator to be much more optimized to take advantage of further advances in the electronic speed control.

      These boats should be REEEEEEALLY quiet!

      • They’re like a hole in the water, DRJIM, even at speed, even at depth. And they are becoming increasingly lethal. There are things that I think are happening, which I won’t discuss on a blog or on-line or on the phone, but maybe in person, which are even more exotic, and I’m not referring to biomimemics. More practical here and now sorts of things that increase lethality.

        When hypersonic missiles come on-line in this decade, the new Virginia Class boats with their high capacity for launch and the new SSGNs arrive in the fleet, the capacity for more whiz-bang things will be expanded.

        The future is submarines. Surface ships are targets. There is the practical value of a surface navy, but it will ALWAYS need to be protected by SSN’s.

      • DrJim
        AC vs DC is something I have a slight familiarity from railroad locomotives. WWII USA subs had Fairbank-Morse diesels originally developed for locomotives.

        There are many opinions on which is best for diesel-electrics. Since I’ve reached the limit of my knowledge, I’ll quit there. I believe you were once involved with them.

        • Yes, when I worked for McGraw-Edison I used to go to the Conrail Freight Classification Yard Repair Depot in Enola, PA to help install and test a solid-state conversion we sold them for their electric locomotives. All the freight ran “Under The Wire”, like an old streetcar, and the locomotives were 100% electric. The overhead wire had 12.5kV, 25Hz AC, and since the traction motors in the locos were DC, a rectifier was required. The original rectifiers provided by GE were a type of “Thyratron”, and had a (somewhat) limited life. PRR and Conrail bought every last one GE had in stock when GE quit making them. Our solid-state replacement needed much less maintenance, and had almost unlimited life. The traction motors (Series-Connected DC motors) could be rebuilt indefinitely as they’re just a big DC motor, very common at the time in industry where variable speed was required. I was told the Diesel Electric propulsion system in the Sea Launch Launch Platform used the motors, controls, shafting, and propeller from some type of “submarine”, and I had fun talking a bit with the LP’s Engineer about the DC motors and drives.

          Big DC motors are interesting beasts, and I did a lot of work with them, as well as AC induction motors, and all the different types of speed controls used with them.

  3. Every decade submarines get quieter and deadlier. They are the only technology that poses a real threat to US Navy carrier groups. Even the small coastal boats used by countries like Sweden
    are capable of taking down any capital ship and are almost undetectable while doing so. If we ever learn to instrument effectively to detect gravitational changes from moving masses we will be able to track subs as easily underwater as we track planes in the air. But that’s a big if. Till that or some other means of tracking large masses in water becomes available submarines will be pose major headaches for war planners.

  4. Tom Kratman, in his ‘Carrera’ series, postulated the production of submarines made mostly of non-metallic materials (evolution of large diameter plastic pipes) as coastal defense subs. Would not be surprised if this was a real thing that is already out there, just needs a real high-tech base to do.

    And I’ve heard that the Japanese subs are rather annoyingly quiet and hard to pick up. Something the Chi-Coms need to remember, as the Japanese do have a long history of being rather innovative with subs.

    • I have practical experience, having been aboard a modern Japanese submarine, and won’t comment on how quiet they are or are not. I think that modern Japan struggles with getting back into the game militarily such that they are no longer a ‘self defense force’ – define that in any way that you’d like.

      The Chinese openly taunt the Japanese and threaten their territory, and that doesn’t go down well. They’re building their own F-35’s now, and are painfully aware of their proximity to China.

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