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    Nuclear power in Russian ships

    GarryB
    GarryB

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    Post  GarryB on Thu Jul 09, 2020 1:38 pm

    With electric drive you could use a small nuclear power generator whose primary role might just be keeping the batteries topped up and to boost speed.

    You could have multiple nuclear power plants throughout the ship... it does not need to be centralised, and would be better for battle damage resistance if they were widely separated.

    Being able to hold station precisely and to manouver in tight quarters is useful for any sized ship, but more so large ships.

    US and Norwegian experience with civilian ships suggests that even at night collisions are an issue... being able to rapidly stop and move sideways would be invaluable... and being able to manouver precisely means you could sail in to places other ships couldn't follow you...

    It has close to 200 MW shaft power, means with a podded full electric propulsion it would nee 2000-3000 tons of electrical motors.

    I doubt they have motors of that weight, but more importantly have never tried to make electric motors for ships of that size and weight.

    Actually making ships that size and weight will mean work will be done to reduce weight and size and improve performance.

    You sound like PD saying EM cats are a waste of time and money, yet the reasons for making catapults using EM instead of steam are pretty clear, and the technology and materials needed to make them efficient would also be very valuable in an all electric drive ship propulsion system.

    If they can get them working well it has enormous growth potential and enormous performance potential that will make ships safer and faster and much more manouverable even if it just has two podded electric motors at the front that can angle down to lift the hull in high forward speeds with the rear props fixed like traditional props for forward propulsion and high speed...
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    mnztr

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    Post  mnztr on Thu Jul 09, 2020 10:03 pm

    Singular_Transform wrote:
    mnztr wrote:Ships need eletricity anyway, and more and more of it. I am not sure what a COGOG gearbox weighs but it can't be light. Also with an effcient electric drive you can carry less fuel.

    Let check the Ford carrier example.

    It has close to 200 MW shaft power, means with a podded full electric propulsion it would nee 2000-3000 tons of electrical motors.

    It could increase the ship weight by 2-3%, and what savings are on the other side ?


    And the Ford actually has 200 MW generating capacity, because the high RPM generators weight so small it doesn't affect the ship weight  by measurable ways.

    The Ford has about 260K hp but AZIpods are super efficient, just 60MW with 3 Azipods can move this behemoth at 25Knots:

    https://en.wikipedia.org/wiki/Harmony_of_the_Seas
    Singular_Transform
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    Post  Singular_Transform on Fri Jul 10, 2020 1:05 am

    mnztr wrote:[

    The Ford has about 260K hp but AZIpods are super efficient, just 60MW with 3 Azipods can move this behemoth at 25Knots:

    https://en.wikipedia.org/wiki/Harmony_of_the_Seas


    The ABB marketing department can't be this good : )


    The power requied to move the ship and the speed has cubic relationship, menas the 3.5 times bigger engines on the Nimitz can move the ship 53% faster than this crusie ship.


    So, twice as big speed require eight times bigger engine.


    The azipod has same efficiency advantage, but that is around 5% or maybe less.

    Double the turbine size require less weight than the 5% performance gain due to azipods.

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    mnztr

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    Post  mnztr on Fri Jul 10, 2020 6:12 am

    Its not as simple as that, the cruise ship is also probably narrower and has a shallower draft. However, azipods put the props in clean water outside of hull effect, and their location is completely independant of the turbines/diesels. I don't really see how this can be "marketing" the ship has done it in sea trials, so it can either do it or not. Also as I said, as Azipods are located subsurface, they are fully displaced and have a reduced requirement of bouyancy from the hull vs systems that are in the engine room. Also they take up very little space. In either case I am sure commercial ship builders are purchasing them for good reasons. If you have a HUGE containership, they use direct drive with massive diesels, no gearbox at all. That is also super efficient .
    Singular_Transform
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    Post  Singular_Transform on Sat Jul 11, 2020 9:39 am

    mnztr wrote:Its not as simple as that, the cruise ship is also probably narrower and has a shallower draft. However, azipods put the props in clean water outside of hull effect, and their location is completely independant of the turbines/diesels. I don't really see how this can be "marketing" the ship has done it in sea trials, so it can either do it or not. Also as I said, as Azipods are located subsurface, they are fully displaced and have a reduced requirement of bouyancy from the hull vs systems that are in the engine room. Also they take up very little space. In either case I am sure commercial ship builders are purchasing them for good reasons. If you have a HUGE containership, they use direct drive with massive diesels, no gearbox at all. That is also super efficient .

    1. I have no clue about the shape of the ship, and it is realy doesn't matter - the basic equation given, that govern the speed-power relationship
    2. For a small ship it can be, but with bigger ships the pod can't be portrude out of the ship, or the ship navigation capability will be severly restricted
    3. You say that the ABB Azipod would float on the water ? the whole cross section of it is metal, copper and iron. And actually how the cost and capability relationships could be affected by this ? If same part of the ship self boyant then it doesn't cost money ?
    4. Yes ,because ship operators like the faster docking and the savings on tug fees. But it has no deal with capability of naval ships.

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