Ship noise reduction techniques - why surface ship can’t be made as quiet as submarine?.

[DWG]

Sonar can detect a submarine of course, but the point is that a submarine can detect surface fleet from much greater distance than when it can be detected

So? That's been true for decades, didn't stop the Allies winning the Battle of the Atlantic or billions being poured into Cold War ASW.

The submarine may manage to get off the first shot if it carries missiles, but it's not going to swamp a CVBGs defences with a handful of SSMs, it'd have a hard enough job swamping the defences of a modern ASW frigate. If it wants to engage with torpedoes it has to venture into the territory where it becomes significantly easier to detect and counter. And that's been the situation for decades.

 

[Ronny]

So? That's been true for decades, didn't stop the Allies winning the Battle of the Atlantic or billions being poured into Cold War ASW.

WW II submarine aren’t nearly as dangerous to surface ship as their modern counterparts. They move much slower, use short range weapon adn have to surface very often. U-boat torpedo can swim about 8 km whereas battleship cannon can fire as far as 40 km. Nowadays, a submarine can attack as far as surface ship.

The submarine may manage to get off the first shot if it carries missiles, but it's not going to swamp a CVBGs defences with a handful of SSMs, it'd have a hard enough job swamping the defences of a modern ASW frigate.

A yasen-M can carry 32 Zircon, that is 32 hypersonic targets, intercepting all of them with 100 % accuracy is questionable at best

If it wants to engage with torpedoes it has to venture into the territory where it becomes significantly easier to detect and counter. And that's been the situation for decades.

Not neccessary, poseidon torpedo effectively has infinite range thanks to the nuclear engine

 

[Nicknick]

Just because wikipedia does not offer a clear distinction does not mean there is one. A pumpjet is typically defined as a ducted propulsor with a decelerating duct. A pumpjet typically has a large diameter, low RPM, short duct in relation to its diameter, has fixed components except for the rotor, and is always an axial flow design. It is much more akin to a traditional propeller than a pump. That the name contains the word "pump" is unfortunate and probably contributes to the confusion.

A waterjet has a small diameter, high RPM, a long duct, may have moving nozzles or thrust reversers, and may have an axial, centrifugal, or mixed flow design. It is much more akin to a pump than a traditional propeller. Both pumpjets and waterjets are examples of turbomachinery propulsors, but the difference is stark if you compare images of waterjets to the pumpjet photos posted above. One can really not confuse the two; they are very different.

As I wrote before ["Pump jets of surface ships have little in common with pump jets in submarine..."] technically, they are indeed very different. Wikipedia might not be the most reliable source for technical definitions, but combined with google it is at least a good source on how are things called like (right or wrong) and both show no clear distinction between waterjets and pump jets.

The examples of pump jets for surface ships right here in this threads are "waterjets" and not "pumpjets" by your definition.

 

[Vepr157]

The examples of pump jets for surface ships right here in this threads are "waterjets" and not "pumpjets" by your definition.

I have no idea how you came to that conclusion. I explained the differences between waterjets and pumpjets and posted several photos and a technical paper on surface ship pumpjets. They are different and used for different purposes.

It is a mistake to rely on Wikipedia or Google as the ultimate source of technical terminology. In any case, this is a matter of semantics and not worth discussing further.

 

[Scott Kenny]

I know Surface ship can be detected by radar and other means, however, given that submarine is the biggest threat to surface ship, it would make a lot of sense to make them more quiet

The primary offensive sensor for a submarine attacking surface ships is the Periscope, not sonar.

A yasen-M can carry 32 Zircon, that is 32 hypersonic targets, intercepting all of them with 100 % accuracy is questionable at best

A single Burke can intercept that volley. It'll empty the VLS of SAMs, but it'd be stopped.

 

[Ronny]

The primary offensive sensor for a submarine attacking surface ships is the Periscope, not sonar.

As far as I know, submarine can rely on passive sonar and motion analysis to geolocate enemy ship, pretty much only WW II u-boat need periscope to complete an engagement. Russia submarine for example are designed to launch their Ashm while completely submerged

A single Burke can intercept that volley. It'll empty the VLS of SAMs, but it'd be stopped.

I find that questionable at best, Arleigh Burke barely has about 2 interceptors per target


The Ukraine war has shown us that interception rate of supersonic and hypersonic targest are much lower than 50%

 

[Nicknick]

I have no idea how you came to that conclusion. I explained the differences between waterjets and pumpjets and posted several photos and a technical paper on surface ship pumpjets. They are different and used for different purposes.

It is a mistake to rely on Wikipedia or Google as the ultimate source of technical terminology. In any case, this is a matter of semantics and not worth discussing further.

take a look on No. 17, according to your definition, this is a waterjet and not a pumpjet, but even here it is called a pump jet.

The water outlets are semi submerged on the photo, but this is typical for waterjets, when the vessel is driving, the water level at the rear is lower and the exit will be above the waterline

 

[Scott Kenny]

As far as I know, submarine can rely on passive sonar and motion analysis to geolocate enemy ship, pretty much only WW II u-boat need periscope to complete an engagement. Russia submarine for example are designed to launch their Ashm while completely submerged

You still use the periscope for fine tuning the target ship's course and speed predictions.

And for making sure there's no MPA in the area to see when you launch.

And to verify that the missile booster separates.

 

[Vepr157]

take a look on No. 17, according to your definition, this is a waterjet and not a pumpjet, but even here it is called a pump jet.

Yes, that's a waterjet. And I posted some photos of pumpjets. I don't understand your point.

 

[Scott Kenny]

You still use the periscope for fine tuning the target ship's course and speed predictions.

And for making sure there's no MPA in the area to see when you launch.

And to verify that the missile booster separates.

And for making sure that the surface contact you're tracking is what you think it is.

 

[Nicknick]

Yes, that's a waterjet. And I posted some photos of pumpjets. I don't understand your point.

It started with me writing not to confuse xxx-jets for surface vessels with xxx-jets for submarines. Both are a part of this thread and the fundamantel differences have not been noted.

 

[DWG]

Not neccessary, poseidon torpedo effectively has infinite range thanks to the nuclear engine

Seriously? Poseidon? It can't be carried by a sub short of building the sub around it and those four subs won't be venturing out of the Arctic redoubts. It's reported to have a carrier attack mode, but that pretty much presumes the carrier comes to it, because you don't send SSBNs out hunting. I suspect the carrier attack mode is similar to that of the Shkval - fire it straight down the threat vector and hope using a nuclear weapon solves the targeting issues.

Poseidon's problem is it can sneak up on a sitting target such as a city, but to track a mobile target such as a CVBG it needs to be moving faster than the target is, so can't use low noise mode. And how does it find the target in the first place? It doesn't have the large sonar arrays of an SSN or SSBN, so either it's used against close targets, or it relies on external guidance. At attack speed (54kts) even the Russians assume a detection radius of 43km. And its warhead legitimises the use of an NDB for self-defence.

 

[DWG]

The Ukraine war has shown us that interception rate of supersonic and hypersonic targest are much lower than 50%

That's in an area with heavy ongoing jamming, and with raids of up to 100+ missiles + drones, so not necessarily pertinent to war at sea. It's also shown us that Russian land attack missiles have trouble hitting the broad side of a city with any precision. What suggests that they would do better against a moving target at sea requiring a more complex sensor solution?

What's sauce for the goose is sauce for the gander.

ETA: A lot of the engagements in the Ukraine will have been against crossing targets, missiles passing miles off and never closing. For a CVBG, or any other naval task group, while the missiles targeting ships other than the firing vessel are still technically crossing targets, they're all incoming into the formation, giving a better engagement geometry.

 

[DWG]

A yasen-M can carry 32 Zircon, that is 32 hypersonic targets, intercepting all of them with 100 % accuracy is questionable at best

Currently there are three or four Yasen-M operational, but the first Tsirkon capable boat will be Perm, which isn't due to commission until later this year. Based on previous Russian usage, it's likely to carry a mix of weapons - land attack Klubs, land attack Tsirkons, ASW Klubs if that's an option, plus several nuclear armed weapons that will be retained for strategic use. AShM Tsirkons will likely be the largest element of the loadout, but they won't be the sole element.

 

[Dilandu]

A single Burke can intercept that volley. It'll empty the VLS of SAMs, but it'd be stopped.

You are clearly too optimistic.

 

[Dilandu]

And its warhead legitimises the use of an NDB for self-defence.

Problem is, that USN did not have nuclear depth charges anymore.

 

[DWG]

Problem is, that USN did not have nuclear depth charges anymore.

I suspect you could just use a B61 in laydown mode, with the appropriate delay to get it to depth, or rapidly adapt it for that.

 

[Dilandu]

I suspect you could just use a B61 in laydown mode

You probably could, but jet plane is a rather poor delivery platform in terms of accuracy & reaction time. Something like JDAM kit probably could solve accuracy problem. And helicopter probably would not be able to escape the blast.

 

[Ronny]

Seriously? Poseidon? It can't be carried by a sub short of building the sub around it and those four subs won't be venturing out of the Arctic redoubts. It's reported to have a carrier attack mode, but that pretty much presumes the carrier comes to it, because you don't send SSBNs out hunting. I suspect the carrier attack mode is similar to that of the Shkval - fire it straight down the threat vector and hope using a nuclear weapon solves the targeting issues.

Poseidon's problem is it can sneak up on a sitting target such as a city, but to track a mobile target such as a CVBG it needs to be moving faster than the target is, so can't use low noise mode. And how does it find the target in the first place? It doesn't have the large sonar arrays of an SSN or SSBN, so either it's used against close targets, or it relies on external guidance. At attack speed (54kts) even the Russians assume a detection radius of 43km.

These submarines that carry Poseidon doesn’t seem to carry any ballistic missile so it seem incorrect to call them SSBNs



I don’t think Poseidon has any resemblant to Shkval either. Shkval is a supercavalting torpedo with extremely short range and originally no terminal guidance system. Poseidon on the otherhand, should have pretty much conventional guidance of a torpedo but just infinite range. Given the diameter of Poseidon, it should have much bigger sonar array compared to the average torpedo. If the average LWT like Mark 54 is sensitive enough to track and find a submarine, I have little doubt that Poseidon can find the CBG. With practically infinite range, Poseidon can get into position just like a submarine would

And its warhead legitimises the use of an NDB for self-defence.

Yeah but USN has no more nuclear depth charge, and even if they still do, the radius that NDB can affect a modern submarine is not very wide, something like 100-200 meters radius, so you still need to pin point the submarine location, which is not easy

 

[Scott Kenny]

I suspect you could just use a B61 in laydown mode, with the appropriate delay to get it to depth, or rapidly adapt it for that.

Eh, maybe?

I don't know if the B61 has a depth pressure sensor. And I doubt it can take a Quickstrike or Quicksink fuze.

 

[Scott Kenny]

These submarines that carry Poseidon doesn’t seem to carry any ballistic missile so it seem incorrect to call them SSBNs

A 100MT warhead makes them very strategic in use, not even a tactical nuke.

Even if it isn't a "ballistic" missile.

I don’t think Poseidon has any resemblant to Shkval either. Shkval is a supercavalting torpedo with extremely short range and originally no terminal guidance system. Poseidon on the otherhand, should have pretty much conventional guidance of a torpedo but just infinite range. Given the diameter of Poseidon, it should have much bigger sonar array compared to the average torpedo. If the average LWT like Mark 54 is sensitive enough to track and find a submarine, I have little doubt that Poseidon can find the CBG. With practically infinite range, Poseidon can get into position just like a submarine would

The Poseidon will not be able to hear anything on passive sonar while over 20 knots due to flow noise. It'd have to be active pinging for the whole search time.

Operationally, both Poseidon and Shkval are lobbed in the general direction of the target, relying on the nuke warhead for damage.

 

[Scott Kenny]

You are clearly too optimistic.

That's only assuming a Pk of about 0.5.

 

[DWG]

Eh, maybe?

I don't know if the B61 has a depth pressure sensor. And I doubt it can take a Quickstrike or Quicksink fuze.

Just work out the sink rate and set a delay.

 

[Ronny]

A 100MT warhead makes them very strategic in use, not even a tactical nuke.

Even if it isn't a "ballistic" missile.

Initial report of 100 MT warhead on Poseidon seem questionable at best, beside, I don’t think they can’t put conventional warhead on it if they wanted to, similar to what they did to Oreshnik

The Poseidon will not be able to hear anything on passive sonar while over 20 knots due to flow noise. It'd have to be active pinging for the whole search time.

Do you have some source or data on this?. Common torpedo like Spearfish or Mark48 seem to be able to go pretty fast but active sonar is not compulsory. But even if we assume it need to use active sonar, it not like USN has any hard kill against torpedo either. The only thing they can do is trying to out run a torpedo with infinite range, decoy it might not be useful if it is wake homing

Operationally, both Poseidon and Shkval are lobbed in the general direction of the target, relying on the nuke warhead for damage.

I think the different between them is like the different between B-61 and Trident-II

 

[DWG]

You probably could, but jet plane is a rather poor delivery platform in terms of accuracy & reaction time. Something like JDAM kit probably could solve accuracy problem. And helicopter probably would not be able to escape the blast.

Helicopters carried NDBs throughout the Cold War.

 

[Dilandu]

Helicopters carried NDBs throughout the Cold War.

And it was considered bad enough idea that USN developed a DASH drone specifically so it could be sacrificed.

 

[DWG]

I don’t think Poseidon has any resemblant to Shkval either. Shkval is a supercavalting torpedo with extremely short range and originally no terminal guidance system. Poseidon on the otherhand, should have pretty much conventional guidance of a torpedo but just infinite range. Given the diameter of Poseidon, it should have much bigger sonar array compared to the average torpedo.

Do we have any evidence Poseidon has any guidance system beyond inertial?

 

[DWG]

And it was considered bad enough idea that USN developed a DASH drone specifically so it could be sacrificed.

And then ditched DASH. As I said, helicopters were tasked with NDB delivery throughout the Cold War.

 

[Scott Kenny]

Initial report of 100 MT warhead on Poseidon seem questionable at best, beside, I don’t think they can’t put conventional warhead on it if they wanted to, similar to what they did to Oreshnik

I gotta admit, I'm wondering how they make a nuclear warhead work at all without shielding the everliving hell out of it. Without some major neutron shielding, that warhead is going to be eating a whole lot of neutrons from an operating reactor.

Do you have some source or data on this?. Common torpedo like Spearfish or Mark48 seem to be able to go pretty fast but active sonar is not compulsory. But even if we assume it need to use active sonar, it not like USN has any hard kill against torpedo either. The only thing they can do is trying to out run a torpedo with infinite range, decoy it might not be useful if it is wake homing

I was a USN submariner, qualified in Subs on USS Georgia (SSBN-729)(Gold) and USS Kentucky (SSBN-737)(Gold)

Flow noise sets in at about 20 knots on all subs. Spearfish and Mk48 are wire-guided, usually, and usually go active when they lose the wire. Only a snapshot, the emergency response to a torpedo in the water, would cut the wire immediately.

 

[Ronny]

I was a USN submariner, qualified in Subs on USS Georgia (SSBN-729)(Gold) and USS Kentucky (SSBN-737)(Gold)

Flow noise sets in at about 20 knots on all subs. Spearfish and Mk48 are wire-guided, usually, and usually go active when they lose the wire. Only a snapshot, the emergency response to a torpedo in the water, would cut the wire immediately.

May be it can loiter at slower speed to get into position? Or lay dorman waiting for its prey like CAPTOR mine

 

[Dilandu]

I gotta admit, I'm wondering how they make a nuclear warhead work at all without shielding the everliving hell out of it. Without some major neutron shielding, that warhead is going to be eating a whole lot of neutrons from an operating reactor.

Erm... first of all, why do you assume it's a problem? Boomer submarine have nuclear reactors even close to warheads (at least relatively).

Secondly, I fail to see why a shield bulkhead - or simply a ballasat tank - can't be installed inbetween. Water is quite good in neutron absorbtion.

Thirdly, as far as I know, modern boosted-fission cores are immune to neutron poisoning; even the incomplete assembly would still be "hot" enough to activate fusion inside, and the fusion would "afterburn" the fission fuel around.

 

[Scott Kenny]

Erm... first of all, why do you assume it's a problem? Boomer submarine have nuclear reactors even close to warheads (at least relatively).

Boomers also have human-habitable-levels of radiation shielding between their reactor and the missile compartment, at least in the USN. I would hope that the Russians would as well, since training submariners is not easy.

My total dose from one patrol was negative. Well, below background, technically, since the background count assumes you're on the surface and not under a couple hundred feet of seawater to stop extra cosmic rays etc.

Secondly, I fail to see why a shield bulkhead - or simply a ballasat tank - can't be installed inbetween. Water is quite good in neutron absorbtion.

The closer the warhead is to the reactor, the greater portion of the radiation emission sphere gets absorbed by the warhead.

It's the shadow shield concept.

The SSBN doesn't need to give full shielding out to the edges of the reactor compartment, because that area is going out into the ocean, not into the crew. Just needs full shielding on the forward and aft reactor compartment bulkheads.

Thirdly, as far as I know, modern boosted-fission cores are immune to neutron poisoning; even the incomplete assembly would still be "hot" enough to activate fusion inside, and the fusion would "afterburn" the fission fuel around.

I'm not willing to buy that for long term radiation exposure. Instantaneous neutron flux, sure. Sustained, over the course of an hour? Doubtful.

I'm assuming a nice big fission-fusion-fission device to get to 100MT, full Tsar Bomba style.

What happens when U238 (in the outer tamper) catches a neutron from your running reactor? It turns into U239 that then pretty much instantly decays into Np239 (~20 minute half-life), which then decays into Pu239 (~2 day half-life).
Np239 doesn't seem to be fissionable, or at least I'm not finding anything online saying what the fission fragments are.
Now, Pu239 can spit out an alpha particle (helium atom) and turn into U235. Nicely fissionable when you smack it with a neutron, does not prevent full kaboom, but it will be a little lower energy (~2% or so) than a Pu-boom.
Or Pu239 catches a neutron and turns into Pu240. Pu240 is a nasty contaminant in nuclear weapons, it has so many natural fissions that it's very likely to cause a fizzle or predetonation (small partial boom, not full yield). Anything over 7% Pu240 won't go boom the way you want it it.
Pu239 that caught a neutron and fissions typically turns into Xenon and Zirconium, and those are highly highly-radioactive isotopes that decay further.

The concern (from the designer's POV) is that the Pu240 will cause a fizzle of under a kiloton.

 

[Dilandu]

Boomers also have human-habitable-levels of radiation shielding between their reactor and the missile compartment, at least in the USN. I would hope that the Russians would as well, since training submariners is not easy.

And? Why do you assume that drone could not be designed accordingly?

The closer the warhead is to the reactor, the greater portion of the radiation emission sphere gets absorbed by the warhead.

And? Why do you assume that warhead is close to reactor at all?

Seriously, with all respect, but you are inventing problem out of some rather strange assumption which boil down to "maybe they didn't do the obvious"

 

[Scott Kenny]

And? Why do you assume that drone could not be designed accordingly?

Because that amount of shielding is bulky and heavy. I'm talking 3+m of fuel oil and about that much more water outside the reactor compartment, plus however much shielding there is inside the RC.

And? Why do you assume that warhead is close to reactor at all?

Because the cutaway shows the reactor roughly amidships, with the warhead fairly close to it. It's more efficient to put all the guidance package at the very nose, then the warhead, then reactor (including shielding forward), then turbine, reduction gears, etc...

And "safe for human habitation" from a running reactor of pretty much any power level at all means ~6+m of pure shielding...

 

[Dilandu]

Because that amount of shielding is bulky and heavy. I'm talking 3+m of fuel oil and about that much more water outside the reactor compartment, plus however much shielding there is inside the RC.

And? We are talking about rather large drone, after all. There are plenty of things that could be placed between reactor and warhead - ballast tanks, for example.

Because the cutaway shows the reactor roughly amidships, with the warhead fairly close to it. It's more efficient to put all the guidance package at the very nose, then the warhead, then reactor (including shielding forward), then turbine, reduction gears, etc...

Seriously?) You automatically assume that this schematic cutaway accurately represent the real thing? Please.

 

[Scott Kenny]

And? We are talking about rather large drone, after all. There are plenty of things that could be placed between reactor and warhead - ballast tanks, for example.

Ballast tank which then causes the drone to weight more and go slower.

but freaking 6m of water ballast is better than however-many tons a lead&etc shield would be in terms of buoyancy.

Seriously?) You automatically assume that this schematic cutaway accurately represent the real thing? Please.

It was laid out in a logical setup, so that you don't have to run wires past the nuclear warhead to the guidance package.

Hell, it was laid out roughly in the same manner as a USN Mk48... Nose section, Warhead section, Centerbody, (turbine and reduction gears), and afterbody. For the Mk48, the turbine and reduction gears would be replaced with the Fuel tank. Navy Women Can F* Anything.


Look, I know Russian engineers ARE NOT STUPID. So I am wondering how they fixed that problem, because they often use a different method than the west does.