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    Pump jet propulsion system in russian submarines

    PapaDragon
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    Post  PapaDragon on Fri Nov 02, 2018 8:37 pm

    slasher wrote:Not a very flattering assessment at all of the Project 885M.

    https://vpk-news.ru/articles/45818

    .........................................
    https://www.cna.org/CNA_files/PDF/IOP-2018-U-018268-Final.pdf?fbclid=IwAR2qPqYW2SJytdWyv6HFCOtXnoKWJC1zFdMs_vcAJWZAuijYP_o3BpxuZ4k


    This is that same BS article I posted a while back in my infinite curiosity and whole thing has been proven to be load of crap.


    This suggestion you refereed to is peak stupidity in itself:

    slasher wrote:........ He contends that way too much funding for the navy is being eaten up by a submarine project like this, and instead proper completion of R&D and testing should be carried out, thus slowing production and freeing up resources for surface ships and the naval aviation....


    So idea is to defund only component of Russian Navy that even remotely works in favor of decrepit, hopelessly obsolete and outclassed surface fleet and barely existing carrier aviation that could never be able to counter even a single 2nd tier western Navy let alone something like USN?

    I will say what I said before: if submarine fleet is not good enough then any investments in any kind of navy, surface one especially are nothing more than criminal negligence and treason.

    Operating surface navy under conditions described in that article is tantamount to mass murder of Russian naval personnel.
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    Post  Singular_Transform on Fri Nov 02, 2018 8:54 pm

    Arrow wrote:Simply Pump jet is quieter than a traditional screw. Therefore, everyone except Russians apply this to their SSN.

    Pump jet works only in a narrow range of depth.

    It increase the pressure of the water , and due to that it decreased the aviation.

    Problem is as the sub dive deeper the pressure increase, so the sub could be capable to go faster, but above the optimal design speed the pump jet assy is decrease the maximum speed, and (potentially ) even can increase the noise as well.

    And it means at the same time the maximum speed of a boat due to pumpjet is decreased.
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    Post  kumbor on Tue Nov 06, 2018 7:38 pm

    Singular_Transform wrote:
    Arrow wrote:Simply Pump jet is quieter than a traditional screw. Therefore, everyone except Russians apply this to their SSN.

    Pump jet works only in a narrow range of depth.

    It increase the pressure of the water , and due to that it decreased the aviation.

    Problem is as the sub dive deeper the pressure increase, so the sub could be capable to go faster, but above the optimal design speed the pump jet assy is decrease the maximum speed, and (potentially ) even can increase the noise as well.

    And it means at the same time the maximum speed of a boat due to pumpjet is decreased.

    And also, pump jet is less efficient when sailing at slow speed.
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    Post  Big_Gazza on Wed Nov 07, 2018 4:13 am

    Arrow wrote:Simply Pump jet is quieter than a traditional screw. Therefore, everyone except Russians apply this to their SSN.

    What simplistic empty-headed tosh...

    Its not a black and white engineering issue. Pump jets may be quieter at mid-high speeds (they are actually less efficient at low speeds), but they reduce the effective available power at high reactor settings. Russian philosophy seems to be that stealth is only useful until the first torpedo is fired. On contact with enemy SSN, the Ruskies probably consider stealth to be no longer useful and that raw kinetic performance, powerful active sonar, and effective counter-measures are the key to victory & survival. Once in combat, SSNs are not going to trade torpedo salvoes at low speed while trying to run silent. Active sonars will be switched on to maximise situational awareness of the enemy, and if it lights up your own boat like an underwater Motorhead concert, well so be it as long as it paints the bogey so he can't continue to hide. I think a pump jet is a disadvantage in this scenario for an SSN engaged in a high-energy knife fight.

    SSBNs are a different case as they need to maximise stealth to avoid detection over their full cruising speed ranges. The need to operate at high speed is limited to specific scenarios like attempting to flee from a hostile enemy SSN (rather than attempting to fight), but this is less important than stealth maximisation to optimize the chance of no-detection in the first place.

    The use of pump jets by USN/UK/French SSNs, and the lack of such on Yasens, is most likely to be a doctrinal issue, not technological.
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    Post  kumbor on Sat Dec 08, 2018 11:44 am

    Big_Gazza wrote:
    Arrow wrote:Simply Pump jet is quieter than a traditional screw. Therefore, everyone except Russians apply this to their SSN.

    What simplistic empty-headed tosh...  

    Its not a black and white engineering issue.  Pump jets may be quieter at mid-high speeds (they are actually less efficient at low speeds), but they reduce the effective available power at high reactor settings.  Russian philosophy seems to be that stealth is only useful until the first torpedo is fired.  On contact with enemy SSN, the Ruskies probably consider stealth to be no longer useful and that raw kinetic performance, powerful active sonar, and effective counter-measures are the key to victory & survival.  Once in combat, SSNs are not going to trade torpedo salvoes at low speed while trying to run silent.  Active sonars will be switched on to maximise situational awareness of the enemy, and if it lights up your own boat like an underwater Motorhead concert, well so be it as long as it paints the bogey so he can't continue to hide. I think a pump jet is a disadvantage in this scenario for an SSN engaged in a high-energy knife fight.

    SSBNs are a different case as they need to maximise stealth to avoid detection over their full cruising speed ranges.  The need to operate at high speed is limited to specific scenarios like attempting to flee from a hostile enemy SSN (rather than attempting to fight), but this is less important than stealth maximisation to optimize the chance of no-detection in the first place.

    The use of pump jets by USN/UK/French SSNs, and the lack of such on Yasens, is most likely to be a doctrinal issue, not technological.

    @Big gazza. I agree with you! While pump jet is quieter on mid/high speed, it is less efficient and makes sub less manoeuverable at low speed. The question is one of doctrine and not of technology, that`s true.
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    Post  GarryB on Sun Dec 09, 2018 2:59 am

    Regarding the pump jet stuff... Russia has a sub with a pump jet... a model of the Kilo class was fitted with a pumpjet and it was tested thoroughly... they have had plenty of time to learn all the features of such a propulsion system, and yet clearly they have not chosen to fit them to Yasen class subs.

    The reason might be as mundane as the areas where Yasen is expected to operate has lots of seaweed and old fishing nets that could easily jam up a pump jet and render it useless, or it might not be as wonderful as everyone claims and have some serious issues that make it not worth it.... you know... like a 100% focus on stealth for aircraft...
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    Post  kumbor on Sun Dec 09, 2018 10:02 am

    GarryB wrote:Regarding the pump jet stuff... Russia has a sub with a pump jet... a model of the Kilo class was fitted with a pumpjet and it was tested thoroughly... they have had plenty of time to learn all the features of such a propulsion system, and yet clearly they have not chosen to fit them to Yasen class subs.

    The reason might be as mundane as the areas where Yasen is expected to operate has lots of seaweed and old fishing nets that could easily jam up a pump jet and render it useless, or it might not be as wonderful as everyone claims and have some serious issues that make it not worth it.... you know... like a 100% focus on stealth for aircraft...

    If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?
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    Post  chinggis on Sun Dec 09, 2018 12:01 pm

    If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?[/quote]

    No, it is like any other classical propeller, if it is something clogged, propeller must be stopped and manually cleaned. Pump jet is similar to jet engine, you have a blades on rotor and a blades on stator, if you do not have this type arrangements you have a ducted propeller and that is other story. Only good thing with pump jet is higher speed and lover noise, actually it produce high frequency noise which is more muffled in water than low frequency noise produced by classical propeller. Explosion of 1kg TNT at Gibraltar strait, you can hear in entire west Mediterranean up to West coast of Greece because explosion produce low frequency noise and low frequency noise have a better propagation than high freq. noise.
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    Post  Big_Gazza on Sun Dec 09, 2018 11:33 pm

    GarryB wrote:Regarding the pump jet stuff... Russia has a sub with a pump jet... a model of the Kilo class was fitted with a pumpjet and it was tested thoroughly... they have had plenty of time to learn all the features of such a propulsion system, and yet clearly they have not chosen to fit them to Yasen class subs.

    The reason might be as mundane as the areas where Yasen is expected to operate has lots of seaweed and old fishing nets that could easily jam up a pump jet and render it useless, or it might not be as wonderful as everyone claims and have some serious issues that make it not worth it.... you know... like a 100% focus on stealth for aircraft...

    Furthermore, the 3x in-service Borei I and the new Borei II all have pumpjets... It's crystal clear that Russia has pump-jet tech in their pocket, and if they are not using it on Yasens then there is a good reason. That will not stop the usual Russophobe trolls and seppo flag-wavers from being stupid however, but thats OK. They should be allowed every opportunity to make fools of themselves Twisted Evil
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    Post  Big_Gazza on Sun Dec 09, 2018 11:37 pm

    kumbor wrote:If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?

    No chance. Suck in a fishing net, and you won't rid yourself of it by reversing prop rotation. By the time you know you have a problem the net will be well and truly ingested and entangled beyond hope. Divers in the water will be needed as a minimum, and that a bit of a problem on a combat mission Very Happy
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    Post  kumbor on Mon Dec 10, 2018 12:50 pm

    Big_Gazza wrote:
    kumbor wrote:If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?

    No chance.  Suck in a fishing net, and you won't rid yourself of it by reversing prop rotation.  By the time you know you have a problem the net will be well and truly ingested and entangled beyond hope.  Divers in the water will be needed as a minimum, and that a bit of a problem on a combat mission Very Happy

    Britts use pump jet for over 25 years. Are there any practice how to deal with clogging, if it occured, or if it was admitted!
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    Post  chinggis on Mon Dec 10, 2018 7:16 pm

    kumbor wrote:
    Big_Gazza wrote:
    kumbor wrote:If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?

    No chance.  Suck in a fishing net, and you won't rid yourself of it by reversing prop rotation.  By the time you know you have a problem the net will be well and truly ingested and entangled beyond hope.  Divers in the water will be needed as a minimum, and that a bit of a problem on a combat mission Very Happy

    Britts use pump jet for over 25 years. Are there any practice how to deal with clogging, if it occured, or if it was admitted!

    Ship is going into shipyard with floating dock, workers remove clogging material, put new paint on ship, repair what is not repaired last time and when everything is finished, ship sail away, workers got pay and all live in happiness Smile There is no other options because you need special tools and cranes and in many cases you do not have in on ship because it is big, heavy, cumbersome and you dont need it in 99% when ship is sailing.
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    Post  kumbor on Mon Dec 10, 2018 11:21 pm

    chinggis wrote:
    kumbor wrote:
    Big_Gazza wrote:
    kumbor wrote:If inflow to pump jet is constructed properly, with sufficient opening at the fore end, pump jet is easily cleaned by simply reversing pump jet! Otherwise, classical propeller must be stopped and divers sent to free the propeller of clogged objects. That`s what I think. May be i am wrong!?

    No chance.  Suck in a fishing net, and you won't rid yourself of it by reversing prop rotation.  By the time you know you have a problem the net will be well and truly ingested and entangled beyond hope.  Divers in the water will be needed as a minimum, and that a bit of a problem on a combat mission Very Happy

    Britts use pump jet for over 25 years. Are there any practice how to deal with clogging, if it occured, or if it was admitted!

    Ship is going into shipyard with floating dock, workers remove clogging material, put new paint on ship, repair what is not repaired last time and when everything is finished, ship sail away, workers got pay and all live in happiness Smile There is no other options because you need special tools and cranes and in many cases you do not have in on ship because it is big, heavy, cumbersome and you dont need it in 99% when ship is sailing.  

    I am starting from similarity in comparison with low power commercial waterjets / pump jets. American PBRs in Vietnam (with Jacuzzi waterjets), as well as many modern yachts with similar propulsion, if waterjet got clogged with seaweed, simply reversed their waterjets, and in vast majority of cases the propulsion gets free of undesirable objects. Such practice was widespread in ex yugoslav navy also, with class 620 LCUs, powered by two MTU 8V331TC of 900hp each and two Castoldi waterjets! I`ve heard about such practice from their commanding officers, professional military mariners.

    I know that big submarine and surface ship waterjets are different and more complex in many ways, but the principles should be similar, I think. Reversing cannot always help, but in some situations can help.
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    Post  GarryB on Tue Dec 11, 2018 6:10 am

    I would think an inlet guard on a pump jet would make more sense to prevent the problem in the first place... design it so that when reversed the propulsion system blows air back out of the inlet and blows away all the problem material...

    But as BigGazza said... they have them on their Borei SSBNs and not on their SSNs... think that might be a clue that they don't want them on their attack subs...
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    Post  kumbor on Tue Dec 11, 2018 11:32 am

    GarryB wrote:I would think an inlet guard on a pump jet would make more sense to prevent the problem in the first place... design it so that when reversed the propulsion system blows air back out of the inlet and blows away all the problem material...

    But as BigGazza said... they have them on their Borei SSBNs and not on their SSNs... think that might be a clue that they don't want them on their attack subs...

    Waterjets / pumpjets works in the water, so "the system blows WATER back when reversed!
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    Post  GarryB on Wed Dec 12, 2018 5:18 am


    I know that big submarine and surface ship waterjets are different and more complex in many ways, but the principles should be similar, I think. Reversing cannot always help, but in some situations can help.

    Can we also categorically state they have pump jet propulsion systems on the Borei SSBNs and one of the Kilo class SSKs... the latter was for testing, which was tested thoroughly, so the issue is clearly not that they don't know how to make them or can't afford the technology...

    Their reasons might be as simple as when operating in northern waters there is a chance of water freezing inside the pump jet and jamming the whole propulsion system, or hiding for long periods amongst ice fields is a problem for pump jets as you need an external propeller to chomp up ice so the sub can move in places western subs might have problems with.

    I mean we see that British ships have problems operating in warm water because they need colder water to cool their engines with... you really don't know these things for sure until you test them... and the Russians clearly tested them.
















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    Post  kumbor on Wed Dec 12, 2018 8:05 am

    GarryB wrote:

    I know that big submarine and surface ship waterjets are different and more complex in many ways, but the principles should be similar, I think. Reversing cannot always help, but in some situations can help.

    Can we also categorically state they have pump jet propulsion systems on the Borei SSBNs and one of the Kilo class SSKs... the latter was for testing, which was tested thoroughly, so the issue is clearly not that they don't know how to make them or can't afford the technology...

    Their reasons might be as simple as when operating in northern waters there is a chance of water freezing inside the pump jet and jamming the whole propulsion system, or hiding for long periods amongst ice fields is a problem for pump jets as you need an external propeller to chomp up ice so the sub can move in places western subs might have problems with.

    I mean we see that British ships have problems operating in warm water because they need colder water to cool their engines with... you really don't know these things for sure until you test them... and the Russians clearly tested them.
















    Their reasons might be as simple as when operating in northern waters there is a chance of water freezing inside the pump jet and jamming the whole propulsion system, or hiding for long periods amongst ice fields is a problem for pump jets as you need an external propeller to chomp up ice so the sub can move in places western subs might have problems with.

    Sorry, but i think that subs are not projected, neither constructed to lay still in the water. If water freezes within pump jet than a whole sub would be stuck in pack ice and made useless. i have never heard of such case in the history of submarines.
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    Post  GarryB on Wed Dec 12, 2018 8:37 am

    The Akula class (NATO codename Typhoon) was designed to hide under thin areas of arctic sheet ice and surface through that ice to launch its missiles... I would expect newer designs would at least use the ice to hide around... and SSBNs mission is not to constantly move around all the time... its mission is to remain hidden but able to receive instructions when needed... if it hides on one side of an iceberg then at least it is protected from one side...

    When the Germans were designing tanks they had the brilliant idea of overlapping the wheels as that spreads the weight and reduces gaps between the wheels where enemy penetrator rounds could go through to penetrate the hull side.

    In practise mud and snow and ice got in between the wheels during driving during the day and overnight it all froze solid and the vehicle could not move at all in the morning.

    Something might sound like a clever solution, but you need to test it to see if it is all good or if there are any problems with the new technology.

    They adopted it for the Borei class SSBN which suggests it is useful for the places they operate and they way they operate... the fact that the new SSKs and SSNs and SSGNs don't have pumpjet systems suggests there are some serious issues for certain tactics and methods of use or perhaps locations that make a normal propeller more suitable.
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    Post  kumbor on Wed Dec 12, 2018 9:28 am

    GarryB wrote:The Akula class (NATO codename Typhoon) was designed to hide under thin areas of arctic sheet ice and surface through that ice to launch its missiles... I would expect newer designs would at least use the ice to hide around... and SSBNs mission is not to constantly move around all the time... its mission is to remain hidden but able to receive instructions when needed... if it hides on one side of an iceberg then at least it is protected from one side...

    When the Germans were designing tanks they had the brilliant idea of overlapping the wheels as that spreads the weight and reduces gaps between the wheels where enemy penetrator rounds could go through to penetrate the hull side.

    In practise mud and snow and ice got in between the wheels during driving during the day and overnight it all froze solid and the vehicle could not move at all in the morning.

    Something might sound like a clever solution, but you need to test it to see if it is all good or if there are any problems with the new technology.

    They adopted it for the Borei class SSBN which suggests it is useful for the places they operate and they way they operate... the fact that the new SSKs and SSNs and SSGNs don't have pumpjet systems suggests there are some serious issues for certain tactics and methods of use or perhaps locations that make a normal propeller more suitable.

    I agree. pr.941 Akula SSBNs were specially projected to surface even through 2m ice. Borei pr.955 is much smaller, with less capability to surface through pack ice, but places with difficult ice situation are a common operation area for russian subs in general!
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    Post  GarryB on Wed Dec 12, 2018 9:51 am

    They had special instruments to find the thin areas of ice... I think they called them Polyanas or something for the Akula to surface and break through... perhaps now they have special explosives to shatter the ice above the smaller lighter subs so they can surface and still fire their missiles.

    I seem to remember images of deltas sitting on the surface in a solid ice field with their high missile structure on the subs giving them good clearance for a launch... though to be fair they might just have been drawings by US intelligence... it was 30 years ago...
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    Post  kumbor on Wed Dec 12, 2018 5:14 pm

    GarryB wrote:They had special instruments to find the thin areas of ice... I think they called them Polyanas or something for the Akula to surface and break through... perhaps now they have special explosives to shatter the ice above the smaller lighter subs so they can surface and still fire their missiles.

    I seem to remember images of deltas sitting on the surface in a solid ice field with their high missile structure on the subs giving them good clearance for a launch... though to be fair they might just have been drawings by US intelligence... it was 30 years ago...

    I think that explosive charges are not used or rarely used to break ice, though old straight running torpedoes can be used for that purpose. Ice free sea "lakes" are polynyas - полыня, accented on the last syllable. Special "ice sonars" are also used. All russian subs in service can launch missiles submerged down to 50m depth at least. Missile itself can break some ice thickness also.

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