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Author Topic: NSSN Virginia-class - current status and future  (Read 70217 times)

Offline Aeroengineer1

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Re: NSSN Virginia-class - current status and future
« Reply #30 on: July 28, 2009, 03:44:16 pm »
I wonder what the possibility would be that it would be mistaken for an "Akula" class on the surface?

I very much doubt that there was any concern of a mistaken identification in combat -- modern subs do not fight on the surface, period. 

The objection that it looks too much like a Soviet design was likely more one of perception -- that it would give the appearance that the US Navy was having to copy a Soviet design concept.  Given that the Soviets sometimes did have an edge in aerodynamics and hydrodynamics, there might be a kernel of truth in that, but the USN would take great pains to avoid making that admission.




This statement is not quite correct as hydrodynamics are directly related to acoustic of the boat.  while it may be true that some of their boats did have lower hull drag, (though a more thorough analysis would be needed to validate this claim), the strong vortexes that develop off of the faired in sail have caused it being delayed in its introduction on the boat.  It was originally slated for introduction in the block II boats (or the current boat that is being produced along with the revised bow), but it has been found that it greatly increases its acoustic signature.  There have been a few open source papers describing the basic research that has been done on the topic to test it out, and the sail shown on the LSV2 in one of the previous posts is one of those.  This sail was not the most ideal in the form of drag, but offered a faired in storage area for uuv's to be stored in the aft portion of the sail and not in the hull. 

As for the Russian boats being more hydrodynamic, see that the current generation of Russian boats are mimicking the styling of us boats with long untapered portions in the center section.  The "ideal" teardrop shape is about 6-8:1 length over diameter for drag purposes.  There is a very sharp drop in drag up to about 5:1 then a very flat section in the curve up to about 9:1 and then a very gentle rise after that (ie almost a straight line).  So for a given boat shape the Russians had to make their outer hull even bigger to support a cylindrical pressure hull, where as with the US boat there was only a single hull built to the maximum outer diameter, and hence more space efficient.  US boats though tended to have less reserve buoyancy than Russian boats. 

Adam

Offline Abraham Gubler

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Re: NSSN Virginia-class - current status and future
« Reply #31 on: July 28, 2009, 07:24:22 pm »
So for a given boat shape the Russians had to make their outer hull even bigger to support a cylindrical pressure hull, where as with the US boat there was only a single hull built to the maximum outer diameter, and hence more space efficient.  US boats though tended to have less reserve buoyancy than Russian boats.

Soviet submarines had significantly more reserve buoyancy than US and western boats because they were designed to be "unsinkable". Unsinkable being the term used to describe a boat being able to recover to the surface with one compartment fully flooded. Considering how many times Soviet submarines had major onboard accidents this was probably a good idea... Of course because western boats were much safer and not having the same degree of accidents it didn't make the Soviet boats 'better' overall.

The Soviets used double hulls because this not only made it easier to provide plenty of buoyancy tanks but also easier to build the pressure hulls as they didn't need to be hydrodynamically shaped on their outside. This was part of the experience brought to the Soviet Union from Germany after WW2 (Type XXI). Of course building a double hulled submarine has major drawbacks in acoustic silencing. The outer hull needs to be heavily 'tuned' if it isn't going to act as an acoustic resonator.

Much of the Soviet submarine experience is finding ways around inherent system fails. Of course with the exception of the Project 705 (NATO: ALFA) the most revolutionary submarine since the Type XXI.
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Online flateric

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Re: NSSN Virginia-class - current status and future
« Reply #32 on: July 28, 2009, 11:24:10 pm »
Unsinkable being the term used to describe a boat being able to recover to the surface with one compartment fully flooded.

even up to three in case of Typhoon class
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stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline Aeroengineer1

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Re: NSSN Virginia-class - current status and future
« Reply #33 on: July 29, 2009, 03:17:09 pm »
Sadly though, as was seen with the Kursk, there is not too much to defend against a torpedo that is well placed.  Avoidance is the best method to be able to come back to the top.  (And no I am not saying that it was torped by another boat, just their hot load that went off).

Adam

Offline F-14D

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Re: NSSN Virginia-class - current status and future
« Reply #34 on: July 29, 2009, 07:29:00 pm »
Sadly though, as was seen with the Kursk, there is not too much to defend against a torpedo that is well placed.  Avoidance is the best method to be able to come back to the top.  (And no I am not saying that it was torped by another boat, just their hot load that went off).

Adam

In the case of the Kursk, the fact that it went off inside the pressure hull is particularly significant.  Outside the hull would change the dynamic somewhat.  Whatever else you might say for or against their designs, the Soviets built strong boats.  Remember, a Yankee had an SLBM cook off in one of the tubes (no nuclear detonation, of course), yet the sub still managed to surface and stay afloat for three days.  I believe it was even traveling under its own power for awhile until it finally went under (after the crew was saved).  No comparable US sub would have done as well (of course, since we don't use liquid fuel, we wouldn't have a missile  cook off in the first place). 

On a related note, the Seawolf class has eight 660 mm torpedo tubes, instead of the 533mm that had been standard for decades before and returned to for the Virginias.  Although the USN says they are that big for "stealth reasons, to allow the torpedoes to swim out, that wasn't the only reasons for the big tubes.  Back when Seawolf was being designed there was a real concern that the upcoming Soviet subs it was expected to face over its life would be so strong that a near detonation, or maybe even a direct glancing hit might not be enough to cripple one of them.  Design work began  for a larger diameter, more powerful torpedo that would be carried by Seawolf.  That project was terminated, either for cost reasons or further intelligence that indicated the existing torpedo size would be powerful enough after all.  The Seawolf design, though, was too far along to make that kind of a substantial change, so they just pressed on with the bigger tubes.  After all, they did permit a stealthy swim-out launch.   

Offline Austin

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Re: NSSN Virginia-class - current status and future
« Reply #35 on: July 29, 2009, 10:07:34 pm »
Is there any  US Congress or other reports from publication , which shows how Seawolf/Virgina stacks up against Akula-2 specially the Gepard.

Way back in early and mid 90's there were reports from US congress and USN which concluded that Akula-2 has surpassed Improved LA in quietening ... nothing much after that.

Offline sferrin

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Re: NSSN Virginia-class - current status and future
« Reply #36 on: July 30, 2009, 05:29:26 am »
Sadly though, as was seen with the Kursk, there is not too much to defend against a torpedo that is well placed.  Avoidance is the best method to be able to come back to the top.  (And no I am not saying that it was torped by another boat, just their hot load that went off).

Adam

In the case of the Kursk, the fact that it went off inside the pressure hull is particularly significant.  Outside the hull would change the dynamic somewhat.  Whatever else you might say for or against their designs, the Soviets built strong boats.  Remember, a Yankee had an SLBM cook off in one of the tubes (no nuclear detonation, of course), yet the sub still managed to surface and stay afloat for three days.  I believe it was even traveling under its own power for awhile until it finally went under (after the crew was saved).  No comparable US sub would have done as well (of course, since we don't use liquid fuel, we wouldn't have a missile  cook off in the first place). 

On a related note, the Seawolf class has eight 660 mm torpedo tubes, instead of the 533mm that had been standard for decades before and returned to for the Virginias.  Although the USN says they are that big for "stealth reasons, to allow the torpedoes to swim out, that wasn't the only reasons for the big tubes.  Back when Seawolf was being designed there was a real concern that the upcoming Soviet subs it was expected to face over its life would be so strong that a near detonation, or maybe even a direct glancing hit might not be enough to cripple one of them.  Design work began  for a larger diameter, more powerful torpedo that would be carried by Seawolf.  That project was terminated, either for cost reasons or further intelligence that indicated the existing torpedo size would be powerful enough after all.  The Seawolf design, though, was too far along to make that kind of a substantial change, so they just pressed on with the bigger tubes.  After all, they did permit a stealthy swim-out launch.   


See also "micro nukes" for the same reason.  The idea of fitting torpedos with 0.020 - 0.050 kt nukes (20 -50 tons) warheads was kicked around.
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Offline F-14D

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Re: NSSN Virginia-class - current status and future
« Reply #37 on: July 30, 2009, 10:36:14 am »
Is there any  US Congress or other reports from publication , which shows how Seawolf/Virgina stacks up against Akula-2 specially the Gepard.

Way back in early and mid 90's there were reports from US congress and USN which concluded that Akula-2 has surpassed Improved LA in quietening ... nothing much after that.

Seawolf is much quieter than an LA class boat, and Virginia, although not carrying as much armament and not being as fast (although reportedly the Virginias have turned out to be significantly faster than expected), at least match the Seawolf in quietness.  Of greater significance that the absolutely highest level of quietness is their tactical or "quiet" sped.  That's the highest speed at which they can operate and still be below the level of detectability by competitive subs.  For most subs, that's something around 3-5 knots.  On these two classes, the open literature suggests it's above 20 knots. 

That's amazing, but remember, these boats cost a lot of money!

Offline Austin

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Re: NSSN Virginia-class - current status and future
« Reply #38 on: July 30, 2009, 11:13:14 am »
I remember reading in Janes that the Akula-2 has high tactical quite speed and their sonars are operational up to 25 knots like Seawolf.

Is there any documented information or any thing from US congress where a Seawolf or Virginia managed to track an Akula-2 ?

Offline F-14D

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Re: NSSN Virginia-class - current status and future
« Reply #39 on: July 30, 2009, 02:09:05 pm »
I remember reading in Janes that the Akula-2 has high tactical quite speed and their sonars are operational up to 25 knots like Seawolf.

Is there any documented information or any thing from US congress where a Seawolf or Virginia managed to track an Akula-2 ?


The question, of course, is where Jane's s getting its information from these days.  Back in the '90s and early 2000s, there were a number of charges flying around that because of staff cutbacks, some of its information was coming from companies' marketing depts.  

Keep in mind also that Akula II was designed a long time ago and they've only got a handful.  I understand that in addition to its own SSNs, India is paying for completion of two Akula IIs that were never finished due to lack of money, which they will then operate in a lease/buy arrangement.  

Regarding who has tracked who, that information is so highly classified by both sides that it'll be a long time, if ever, that we learn about that.  Almost anything from the US Congress is going to be shaded for political reasons by whoever wants to be in front of the TV cameras that day, so one would need to verify with other sources.  
« Last Edit: August 02, 2009, 10:14:09 pm by F-14D »

Offline Austin

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Re: NSSN Virginia-class - current status and future
« Reply #40 on: July 31, 2009, 09:52:11 am »
The Akula submarine has been constantly modified , as per its chief designer no two Akula were similar and these were constantly updated as new boats were launched , taking into account the technology which was available.

The Gepard was classified as Akula-3 and was a 3 plus Gen type ,approaching close to the characteristic of 4th gen sub as per its designer.

Both the Akula and Oscar will start getting upgrade from 2010 , and we should see further improvement in quietening which is a common practice observed during major upgrade.


Offline F-14D

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Re: NSSN Virginia-class - current status and future
« Reply #41 on: August 02, 2009, 10:22:14 pm »
The Akula submarine has been constantly modified , as per its chief designer no two Akula were similar and these were constantly updated as new boats were launched , taking into account the technology which was available.

The Gepard was classified as Akula-3 and was a 3 plus Gen type ,approaching close to the characteristic of 4th gen sub as per its designer.

Both the Akula and Oscar will start getting upgrade from 2010 , and we should see further improvement in quietening which is a common practice observed during major upgrade.



Keep in mind that Akula class was designed in the 1980s.  Gepard herself sat on the ways for years after 1991 because there was no money to finish her.  Although her larger sail and smaller, streamlined towed array may indicate some modifications, since she was already building there are certain things you simply can't do at such a late state.  Except for the ones funded by India, I wonder if there will be any more Type 971s beyond Nerpa.  I would think more effort would go into Graney and her sisters (assuming the money is really there to build one SSN per year). 

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Re: NSSN Virginia-class - current status and future
« Reply #42 on: August 03, 2009, 12:32:25 am »
Gents, topic is for "NSSN Virginia-class - current status and future"
If you are to discuss future of Russian submarine force, feel free to start a new thread
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stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline F-14D

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Re: NSSN Virginia-class - current status and future
« Reply #43 on: August 03, 2009, 10:53:35 am »
Gents, topic is for "NSSN Virginia-class - current status and future"
If you are to discuss future of Russian submarine force, feel free to start a new thread

Touche


Offline Grey Havoc

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Re: NSSN Virginia-class - current status and future
« Reply #44 on: January 19, 2013, 12:05:51 pm »
A 1997 NDU Core Course Essay called "THE SUBMARINE FORCE: UTILITY IN THE FUTURE NMS?"

May give some insight into USN thinking of the period regarding the NSSN.
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