You know I've ben whining about passive detection range until I read this

[Castout]

The link is here http://www.computerharpoon.com/wiki/main/index.php?title=Sonar_model

Let me quote a little, it's been stikied in the DW mod section. I thought this was worth sharing.

After reading this well it seems that DW is a better game than SC. . .in terms of passive detection range.:up:

And an unspeakable mod actually made some of the stuffs told in the article a reality such as the impossibility of detecting diesel boats.

So I say wow thank you Sonalysts.

Sonar in Real Life

Passive Sonar
Sea state and Target Noise always causes the biggest changes to sonar predictions. Target Noise and Target Speed were always calculated as one entry = Target Self Noise. Likewise, Receiver Self Noise, Receiver Speed, and Cavitation were grouped together as = Own Ship Noise. They were combined because the separate items are directly proportional to each other.
With newer nuclear submarines at speeds below 10-12 knots you're talking about detection ranges of less than a mile. Diesel submarines can become undetectable passively because they can shut down everything that makes noise, regardless of how modern they are. A modern diesel at a 2-3 knot patrol speed is probably not detectable beyond 1000 yards passively, less in high ambient noise environments. Obviously, a lot depends on ambient noise, propagation paths, layer depth, the sensitivity and location of the passive sonar receiver, proficiency of the submarine crew and operating mode, etc. In fact, in an inshore environment (shallow water, high ambient noise, high shipping density, high wreck density), attempting to track a diesel submarine passively is virtually impossible, and extremely difficult actively, and the US Navy relies primarily on non-acoustic methods for initial detection, i.e. a periscope search using ISAR radar being the most effective. MAD in a shallow water environment is handicapped also... wrecks, bottom topography, geologic features, etc., all contribute to false MAD contacts and high magnetic noise, reducing the detection range. For that reason, passive detection range for a diesel submarine in shallow water should be Zero.
Factors limiting active sonar performance in shallow water (the littoral environment) also play a major role... active sonar frequency and power affect bottom reverberation and absorption. Bottom compositions are rated on their ability to absorb and reflect sound energy. A muddy bottom will absorb a lot of energy, whereas a rocky, gravel bottom will reflect and scatter a lot of energy. Again, wrecks will give false contacts. A good diesel sub CO can avoid active detection by going dead in the water and pointing the bow or stern towards the sonar, reducing the target strength by as much as 80 per cent and not providing any Doppler return to the sonar. Or he can bottom, in which case his target echo is masked by the bottom reverb, and if he bottoms near a wreck you've got more problems.
The big point is that the environment pays a major role in the ranges observed. A Victor III in the Norwegian Sea (relatively quiet sea and deep) at 12 knots may be detected at several miles. The same submarine in the Med (relatively shallow and very noisy) may be detected at a 1000 yards. At flank speed (27 knots), the Victor III may be detected at 20 miles direct path, 25-40 miles bottom bounce, and possibly to 3 or more CZ's (convergence zones) at 30-33 miles, 60-66 miles and 90-99 miles in the Norwegian Sea, by ship based sensors and sonobouys, and for literally thousands of miles by SOSUS. What you see here is an overlap of ranges depending on transmission path, and that is entirely normal and expected. SOSUS exploits the deep sound channel, low frequency noise propagated for thousands of miles in a duct created by the effects of pressure and temperature at those depths.
This is just the tip of the iceberg, and my intent was to point out that you can't just assign hard and fast numbers. Under the right conditions a carrier may be detected acoustically well in excess of 140 miles, or may not be identified at all until it's in visual range. Assuming the carrier is detected at 140 miles, can the operator classify it as a carrier? Maybe, maybe not. If he is operating a sophisticated narrowband acoustic processor, possibly, assuming the carrier isn't using acoustic deception. If it is a broadband system (namely an active sonar being used in a passive mode), all he knows is something is making a lot of noise on a given bearing. That, combined with other intelligence may provide another piece of the puzzle, but you can't definitively classify a target with broadband sonar. A carrier launching and recovering aircraft is a different story. The noise of the catapults hitting the water brakes every 30 seconds or so is very distinctive, can be heard for long distances, and any submarine acoustic analyst has probably been trained to recognize that sound. A more comprehensive list of variables:

......
read from the link if you're interested

[SeaQueen]

Under the right conditions a carrier may be detected acoustically well in excess of 140 miles, or may not be identified at all until it's in visual range. Assuming the carrier is detected at 140 miles, can the operator classify it as a carrier? Maybe, maybe not.

This might be kinda geeky but a US carrier is quite distinct because it has more screws than any other ship. It's probably a bad example, but you're right in the sense that sonar ranges could be chosen at random and you might do as well as the one trying to nail it own to the smallest detail. So much depends on variables that might not be known at all, or if they are known it's only imprecisely.

[Blacklight]

Harpoon is definitely one of the the places to go for information like this. Heck, the tabletop miniatures game (more simulation than game) has a book of data annexes that pretty much read like a condensed set of Janes books about ships, aircraft, sensors, and weapons.

[Castout]

This might be kinda geeky but a US carrier is quite distinct because it has more screws than any other ship. It's probably a bad example, but you're right in the sense that sonar ranges could be chosen at random and you might do as well as the one trying to nail it own to the smallest detail. So much depends on variables that might not be known at all, or if they are known it's only imprecisely.

Judging from that article I'm surprised at how easy it is for us in DW to detect a submerged diesel boat.

The mod from Russia makes it right by making diesel very very quiet and hence very difficult to be detected passively.

[Hitman]

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions. I'd say that at least moving at 5 knots should be safe :stare:

[SeaQueen]

The mod from Russia makes it right by making diesel very very quiet and hence very difficult to be detected passively.

It depends on too many things to say one is any more right than the other.

[SeaQueen]

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions.

This is not unrealistic. Contrary to a lot of people's beliefs, a kilo is NOT a super-submarine. Unless it's armed with cruise missiles, most diesel electric submarines are constrained simply by their kinematic ability to get in range of it's target. They can maneuver some, but they really aren't capable of chasing down a target like a nuke might. They have to wait for a target to come to them, and then make the correct decisions that will place them in a position to make an attack. If the target zigs at the wrong time, the attack is off and all the kilo can do is wait for another target to come along. This is why their second most important attribute is not just their silence, but that they're relatively inexpensive. In order to be effective you need a lot of them because it's unlikely the enemy would even encounter just a small number.

[Molon Labe]

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions. I'd say that at least moving at 5 knots should be safe :stare:

Um, you can get within attack range of skimmers at 5 knots without being detected passively... in LWAMI for sure, probably stock too, even in good acoustic conditions. The non-improved Kilo might get detected in LWAMI, but those are pretty old boats and 5 knots is on the fast end of "slow".

[Hitman]

This is not unrealistic. Contrary to a lot of people's beliefs, a kilo is NOT a super-submarine. Unless it's armed with cruise missiles, most diesel electric submarines are constrained simply by their kinematic ability to get in range of it's target. They can maneuver some, but they really aren't capable of chasing down a target like a nuke might. They have to wait for a target to come to them, and then make the correct decisions that will place them in a position to make an attack. If the target zigs at the wrong time, the attack is off and all the kilo can do is wait for another target to come alone. This is why their second most important attribute is not just their silence, but that they're relatively inexpensive. In order to be effective you need a lot of them because it's unlikely the enemy would even encounter just a small number.

I know, I know, and I apply those tactics. But I still think that a Kilo should be a bit more silent in LWAMI, I'm not pretending to be able to outmaneuvre targets or overtake them at speeds of 10+ knots, but I think that moving along at 4-5 knots should be safer than it is now. Of course, accoustic conditions can change things dramatically, but in general I have played also a lot with the 688i and I can hear Kilos moving at those 5 knots easier that I would think at first glance. Tests I have conducted with LWAMI seem to indicate however that with all stop and lying in the seabed, a 688 can go right over your conning tower and not hear you :hmm: , so it's probably a matter of rescaling a bit the curve of noise increasing with speed. But when you read those news telling how chinese diesel subs seem to get closer to exercising NATO task forces than they could first think, you have to wonder.....

Um, you can get within attack range of skimmers at 5 knots without being detected passively... in LWAMI for sure, probably stock too, even in good acoustic conditions. The non-improved Kilo might get detected in LWAMI, but those are pretty old boats and 5 knots is on the fast end of "slow".

That depends of what you consider a reasonable attack range. I have run several tests to determine the endurance of my torpedoes at different speeds, and the maximum distance I would ever try to attack a nuke is 5.5 NM (Around 10.000 metres). You can attack with the SSN-15 from greater distance, but for that you need a good solution (Specially the distance to target) and you obviously can hardly get that if you are limited to move that slow.

Being lucky and having an inspired day, I have been able to get as close as 6000 metres to an enemy submarine without being detected, but that's at a mere 2 knots.

Never mind.

EDITED TO ADD:

A good example of what I'm saying is a cold war scenario I did set up some time ago, using LWAMI 3.08. A Kilo 877 versus a 688 (Non improved) in the Barents Sea, representing the russian is out there watching for enemy submarines trying to track exiting boomers from Poljarny. I did set random start boxes and fixed a reasonable area to be able to hunt around. But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

[Molon Labe]

Well that's your problem right there--the Kilo is an ASUW weapon, and you're using it to hunt SSN's. Of course you're swimming upstream!

[PeriscopeDepth]

A US 688 should still have a massive sensor advantage over a Kilo. As ML said, the Kilo is an ASUW platform. It is not meant to hunt SSNs.

PD

[Castout]

EDITED TO ADD:

A good example of what I'm saying is a cold war scenario I did set up some time ago, using LWAMI 3.08. A Kilo 877 versus a 688 (Non improved) in the Barents Sea, representing the russian is out there watching for enemy submarines trying to track exiting boomers from Poljarny. I did set random start boxes and fixed a reasonable area to be able to hunt around. But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

I think RA should fix that(I'm not saying that LWAMI is bad). With All stop you will effectively disappear with the background noise. Playing with RA has made me to respect the value of diesel boats much much more. In fact now I HATE having to watch out for those diesel subs. Closing in even within 1 nm doesn't guarantee me of detecting them passively. At slow speds they are effectively quieter than even the Seawolf SSNs. So you can imagine their quietness.

Coordination with air platforms and or surface ASW are needed to hunt for SSK. So now I know why the British didn't find the Argentine's SSKs at all even with their carrier's ASW capability.

So when I play a scenario as a lone SSN having been assigned an area known to be patrolled by enemy diesels and I can't afford to reveal my position to enemy surface combatants in the area, I just pray that I'm not passing near them and rely on my high speed capability in the event that one launches a torp at me. I cannot possibly hope to detect any of them passively and in the event that I did that would mean they were already in the kill zone of my sub.

And when assigned to hunt for SSK in relatively shallow water I can forget finding them passively........I will glare with my active. Unless I'm willing to spend extended time to outtime the diesel boat's battery or if she's stopping, her supplies( but this is no modeled in game, I mean the supplies, because depleting batteries are modeled). Diesel boats are annoying little pric*s.....I HATE THEM.

which made me think that any diesel equipped with Shkval rocket torpedo would become a very lethal mobile mine.

[SeaQueen]

But no matter how slow I moved, the 688 always shot at me first, without me even having been able to hear it! The first notice I have, is a TIW report. Yeah, it's a 877, but moving around at 4 knots it should be more silent, I think, specially for a non-improved 688 (Which has not the improved towed array of the 688i IIRC).

I would expect that sort of behavior. The Kilo is really not intended as an ASW platform. It has an ASW capability which is to say that it can shoot back, but that's very different from saying, "my platform of choice for ASW is a kilo." Really, they designed the kilo for sitting off the coast of Norway, Petropavlosk, and the Baltic Sea in order to deter amphibious assault. Hunting subs was for nukes and other platforms.

[Castout]

I would expect that sort of behavior. The Kilo is really not intended as an ASW platform. It has an ASW capability which is to say that it can shoot back, but that's very different from saying, "my platform of choice for ASW is a kilo." Really, they designed the kilo for sitting off the coast of Norway, Petropavlosk, and the Baltic Sea in order to deter amphibious assault. Hunting subs was for nukes and other platforms.

Yes Seaqueen but he was not emphasizing on killing the 688 but rather his own Kilo poor acoustic performance. He expected the Kilo to be more silent. And that the 688 to be noisier than him crawling at 4 knots which is a logical expectation imo.

[Molon Labe]

I would expect that sort of behavior. The Kilo is really not intended as an ASW platform. It has an ASW capability which is to say that it can shoot back, but that's very different from saying, "my platform of choice for ASW is a kilo." Really, they designed the kilo for sitting off the coast of Norway, Petropavlosk, and the Baltic Sea in order to deter amphibious assault. Hunting subs was for nukes and other platforms.
Yes Seaqueen but he was not emphasizing on killing the 688 but rather his own Kilo poor acoustic performance. He expected the Kilo to be more silent. And that the 688 to be noisier than him crawling at 4 knots which is a logical expectation imo.
And the Kilo is, in fact, quieter than the 688 at 4 knots in LWAMI (by about 2.5 points). :roll: The Kilo still gets detected first because it has a POS sonar.

[Castout]

And the Kilo is, in fact, quieter than the 688 at 4 knots in LWAMI (by about 2.5 points). :roll: The Kilo still gets detected first because it has a POS sonar.

Thank you for clarifying that. Nice to know the little stuffs like that.

[Molon Labe]

And the Kilo is, in fact, quieter than the 688 at 4 knots in LWAMI (by about 2.5 points). :roll: The Kilo still gets detected first because it has a POS sonar.
Thank you for clarifying that. Nice to know the little stuffs like that.
http://icanhascheezburger.files.wordpress.com/2008/02/nbc_the_more_you_know.jpg (http://home.insightbb.com/%7Enotenoughsand/Updated%20PSL%203.08.xls)

(click it!)

EDIT: what? where'd it go? There should be a pic linked to this: http://home.insightbb.com/%7Enotenoughsand/Updated%20PSL%203.08.xls It shows up in the preview...

[Hitman]

Yes Molon is right, and I must clarify something: I expect the Kilo to be quieter than the 688, and I know it is, but of course another very different matter is the quality of their sensors: The Kilo sensors are poor and the 688 sensors are good (Though there are even better ones in the game in the 688i and Seawolf). That has a big influence in the results, because if your Kilo is quieter than the 688 but he still will hear you from farther away than you hear him (Even if he's louder) the results are obviously the same.

But my point is that I not just did not hear the enemy before I get a TIW report, but also when switching to "show truth" I find him at a distance where I would have never thought he should have been able to hear me :stare:

So I was essentially saying that it should be a bit more quieter. Even if the Kilo was not designed as an ASW platform (Seaqueen is of course right) I think that it should be able to play that role correctly as long as he isn't expected to move at more than 5 knots. But being detected at slower speeds earlier than you can hear a nuke.....seems somehow not correct to me. Of course another nuke is the proper tool for ASW, and then you will have different tactics, including high speed legs on the other side of the layer to get a better solution asap, but I still think that a Kilo in a coastal environment of poor sound transmission (Not in open sea) should be able to move silently enough to have a nuke in his detection and weapons range before being detected.

In open sea it's a different game, but in the North Sea, coast of Norway and the Barents Sea, the Kilo should work better IMHO. That's the environment it was designed for, after all.

[Frame57]

Yeah, I'm normally a Kilo player and its current level of noise in LWAMI/Stock forces you to go too slow or even stop completely in ambush style. But given the poor range of Kilo weapons and detection ranges, this renders you harmless in too many ocasions.

This is not unrealistic. Contrary to a lot of people's beliefs, a kilo is NOT a super-submarine. Unless it's armed with cruise missiles, most diesel electric submarines are constrained simply by their kinematic ability to get in range of it's target. They can maneuver some, but they really aren't capable of chasing down a target like a nuke might. They have to wait for a target to come to them, and then make the correct decisions that will place them in a position to make an attack. If the target zigs at the wrong time, the attack is off and all the kilo can do is wait for another target to come along. This is why their second most important attribute is not just their silence, but that they're relatively inexpensive. In order to be effective you need a lot of them because it's unlikely the enemy would even encounter just a small number.Yep! I used to wonder why we would transit to/from our OP area at 12 knots. The reason was if we steamed faster we would be far too noisy and could be detected easily. Kilos are in the same predicament, they have to get to where they are going and they are not going to do that on their battery at 2 knots. IMO they make for a good coastal patrol boat but nothing more...

[Molon Labe]

...but I still think that a Kilo in a coastal environment of poor sound transmission (Not in open sea) should be able to move silently enough to have a nuke in his detection and weapons range before being detected.

In open sea it's a different game, but in the North Sea, coast of Norway and the Barents Sea, the Kilo should work better IMHO. That's the environment it was designed for, after all.
You mean to tell me you couldn't get within 5nm undetected in littoral-simulating acoustic conditions? The earlier 5nm result sounds consistent with surface ducting; you should be able to knock a lot off that with a bottom limited SSP and a soft bottom. Also, don't forget that bad acoustics conditions don't just effect the nuke's sonar, it effects the Kilos sonar too, so it's still getting counterdetected first even in poor conditions.

EDIT: Just ran a test to be sure, detection range for a TB-23 vs. unimproved Kilo @4kts in the above conditions is 2.7nm.


Even if the Kilo was not designed as an ASW platform (Seaqueen is of course right) I think that it should be able to play that role correctly as long as he isn't expected to move at more than 5 knots. But being detected at slower speeds earlier than you can hear a nuke.....seems somehow not correct to me. Back when PSLs were being set I was making this same argument to LW and Ami, and I lost. Their position, which makes a lot of sense, was that the older Kilo is, well, old. Very old. So it just doesn't have the quieting that the Kilo Improved has, and does NOT represent the new generation of D-E subs that are considered undetectable but rather a generation of subs that is somewhat obsolete. As such, the old Kilo needs to operate in the littorals of DW to be invisible. Although I lost this fight, looking back I think they were right.

[Castout]

but also when switching to "show truth" I find him at a distance where I would have never thought he should have been able to hear me :stare:


That my friend is a thing that I agree with you. The 688 should not be able to detect a well handled SSKs so easily. Try RA.
But of course everybody has got their own estimates on how far out a well handled SSK could begin to be detected. . .

In that regard, the RA has a substantially much lower estimates than the LWAMI and stock.


But to defend LWAMI estimates or RA estimates we need hard data which is of course not available to public so this point is not worth debating over. Just throw your opinion and let it be because there is now way to truly defend it. Neither LWAMI or RA estimates.

Only people with RL experience aboard the Kilo or US Los Angeles class have any clue to what we have been discussing here and they are not going to speak up for sure because of their oath of secrecy. So unless you claim to have served aboard a Los Angeles class submarine that had detected a Kilo or aboard a Kilo that had detected a Los Angeles class submarine it is pointless to debate this over.

[Bubblehead Nuke]

Yep! I used to wonder why we would transit to/from our OP area at 12 knots. The reason was if we steamed faster we would be far too noisy and could be detected easily.

It was not that you are more noisy, it is that you lose sensor sensitivity. You did not want to blunder into someone because you could not hear them. If you got too close you give them a chance to hear you.

[Castout]

Yep! I used to wonder why we would transit to/from our OP area at 12 knots. The reason was if we steamed faster we would be far too noisy and could be detected easily.
It was not that you are more noisy, it is that you lose sensor sensitivity. You did not want to blunder into someone because you could not hear them. If you got too close you give them a chance to hear you.

Both reasons that you and Frame put are reasonable imo. So both are probable.

[Pillar]

Even with certain mods installed, I find the Kilo Improved shows up on the waterfall from quite a distance, at least 5nmi, even when they are stationary or drifting at 1 Kt. Is that realistic? What's making the noise? Sea floor was ~300ft.

PS - It's the sphere usually that grabs the signal, but the TA also picks it up somewhat less well and usually without good tonals.

[Castout]

Pillar I belive you must be using AT not RA installed. AT is LWAMI with more playables and new 3D models.

In RA I don't think you can detect diesel sub passively unless you're very very lucky and that advantage is already lost once you realized that you've detected a diesel.

[Hitman]

Humm that doesn't sound correct, I did a test long ago and a Kilo stopped and lying in the seabed was not heard by a Los Angeles even if at a few hundreds of yards :hmm: As it should be, BTW, because a stopped diesel-electric theoretically does not generate any noise.

[To be]

If electric subs were this amazing, why hasn't the US, France, the UK, Russia, invested in diesel electric or AIP subs as their front line SSes (as opposed to SSNs). Clearly if you can't be detected at all that makes up for any transit time problems. The reason they haven't is because: Diesel-electric subs are marginally quieter than nukes, even at low speed, they are slower, incapable of acting as much more than a smart mobile mine, and limited in range and engagement ability. There is one big advantage of non-nuclear propuslion, its cheap.

[Hitman]

That's not the only reason. The US is a nation that projects its force far away, they want to be able to wage war far from their frontiers -that has worked well in the past- and a diesel is obviously too short ranged and dependant from supply to do that.

We are talking here about the Kilos, but think about the modern european projects, the U-214 is a marvel, much quieter than a nuke, with huge firepower and good solutions for Germany and many nations that don't need anything else than coastal defence.

[Pillar]

Passive sonar ain't the only sonar...

[Pillar]

Reinstalled fresh, patched 1.04, installed a mod (Not AT or LWAMI).. result: Kilo on waterfall ~8nm, Kilo doing 1kt straight towards me. My platform was SSN Seawolf.

I can't figure out how to get the Kilo to sit at 0 knots.

Anyone want to send me a test scenario that they have working on their end? m o i ety12 at hotmail, add the com ignore the spaces.

[Dr.Sid]

Also state sea state, bottom type and SSP type.
Bottom type affects signal strength (rock best, mud worst), sea state affects noise.
For these test I suggest bottom limited SSP.

[Kazuaki Shimazaki II]

If electric subs were this amazing, why hasn't the US, France, the UK, Russia, invested in diesel electric or AIP subs as their front line SSes (as opposed to SSNs). Clearly if you can't be detected at all that makes up for any transit time problems. The reason they haven't is because: Diesel-electric subs are marginally quieter than nukes, even at low speed, they are slower, incapable of acting as much more than a smart mobile mine, and limited in range and engagement ability. There is one big advantage of non-nuclear propuslion, its cheap.

Russia is building an AIP sub for itself IIRC - the Saint Petersburg. It just isn't building anything very fast due to budget issues. The UK also wanted diesels until it was diesels or nukes.

As for the US, there is this phobia that if they make workable diesels, that's all they will get in the future, especially if the costs of subs skyrockets like they do...

[Bubblehead Nuke]

Humm that doesn't sound correct, I did a test long ago and a Kilo stopped and lying in the seabed was not heard by a Los Angeles even if at a few hundreds of yards :hmm: As it should be, BTW, because a stopped diesel-electric theoretically does not generate any noise.

It will not have any propulsive noise, however that does not mean it is silent.

Unless they are using direct DC powered gear (and that would be difficult), you are going to have the DC-AC Motor generators running that are providing power to the AC buses. You will have HVAC equipment running in order to maintain the proper temp in the boat. You will also have other ancillery gear running that is required to operate and fight with the boat and maintain habitability. All it takes is ONE piece of equipment to soundshort and you are royally screwed. That is where the 50/60hz tonals come from. The AC bus and the equipment that it runs.

It is these CONSTANT equipment noises that will give you away. Yes, you can raft and sound isolate most of this gear, but you have to remember: a diesel boat is SMALL and that limits what you can do. The more mass that a electric powertrain has to move, the shorter its legs. Thus they will scrimp and cut corners in that all important weight/effectiveness consideration. You also have to bring on FUEL. This is a LOT of mass that has to be considered into this equation. Thus as you can see there are a LOT more variables here than I think you realize. I could give some good real world examples and such, but I hope the point has been made.

With a nuke boat you have unlimited fuel. You do not have to worry about your underwater endurance. You can include the more comprehensive rafting and sound isolation considerations. You are not worried about the size of your boat because you have a LOT more power that will not run out on you. You then have OTHER considerations but the biggest one is solved and manageable.

A diesel boat is quiet. But it is not as quiet as you would believe.

Also, there is something BAD about being DEAD quiet. If you can isolate a line of bearing that is LOWER than background noise and is MOVING. Um.. guess what, you have found something that is trying to hide. That was becoming a problem when I got out. The sonar gear was getting so good you could do just this and they actually had to make sure that you did not get TOO quiet as a large moving object that is occluding background noise and moving at 8 knots can be a bad thing.

[Pillar]

Hehe, wow.

I changed the test from rocky to sand and surface duct to bottom limited... now I pick up a 1kt kilo from about 2.5nm on the sphere. Better, but still... that's a long way!

I'd love to hear more about equipment noises BN. Those real world examples you alluded to would be welcome. Interesting stuff.

Can't a Kilo just shut down everything and go dead in the water if it wants to? You'd only need to do it for a short time, to let the baddies pass by. I guess I'd really like to see the diesel electric boats be able to just disappear entirely from passive sonar when they hit zero knots.

[Bubblehead Nuke]

The US Navy uses nuke boats because they are FAST and have essentially unlimited endurance. They are supposed to take the war to the OTHER guy in short order. They also have to provide ASW defense for a surface action force. They will sprint ahead and sanitize an area that they are going to pass through. This means they need high speed and endurance.

With intel/spec ops, it is the ability to loiter for long periods of time without having anything other than a mast or 2 above the surface. You do not have to charge batteries. You do not have to LEAVE the area TO charge the batteries. You can sit right on someone doorstep and listen/watch and they will never know you are there. In the event you are counterdetected, you can clear datum QUICKLY, evade the search, and them come right back.

In wartime, it is not area denial that the USN is interested in. As someone said earlier, a diesel boat is effectively a smart minefield. Yes, it is mobile, but there are severe restrictions that are applied to it. The latest generation of AIP is changing this some, but it moves it from a local to a regional area. It does not make it GLOBAL.

Yes they are more expensive, but they have a MUCH broader mission that you can possibly know unless you served on one.

[Pillar]

That is where the 50/60hz tonals come from. The AC bus and the equipment that it runs.

The tonals I pick up are 1050 and 1500 roughly, and on the sphere. The TA doesn't hear a much of anything with "sand" and "bottom limited"...

What equipment do those tones represent? What am I hearing?

[Bubblehead Nuke]

Can't a Kilo just shut down everything and go dead in the water if it wants to? You'd only need to do it for a short time, to let the baddies pass by. I guess I'd really like to see the diesel electric boats be able to just disappear entirely from passive sonar when they hit zero knots.

Nope, not really. Sounds good on paper but in reality you do NOT turn off vital gear (sonar & fire control systems, steering and diving hydraulics, DC-AC converters, atmopshere control, etc etc etc) unless you REALLY REALLY have to. It might not come back on. :o

As I said, there is a LOT more going on here than you might think. EVERY submarine has what we called 'hotel' loads. These are things that NEVER get turned off (unless for maintenance and then under VERY controlled conditions). They are what we termed 'vital'. Some of these items REQUIRE you to return to port if they went down as the safety of the boat could be jeopardized. Granted, in wartime we had diffrent rules, but I hope that lends the level of importance of these systems.

[Pillar]

Yeah I see what you mean. I'm curious what specifically might be giving out those tones.

[Bubblehead Nuke]

That is where the 50/60hz tonals come from. The AC bus and the equipment that it runs.

The tonals I pick up are 1050 and 1500 roughly, and on the sphere. The TA doesn't hear a much of anything with "sand" and "bottom limited"...

What equipment do those tones represent? What am I hearing?

Boats have either 50hz electrical gear or 60hz electric gear. This is just like the AC that is in your house. North American and some other places use electricity that is running at 60hz. Russia, Europe and others run at 50hz. There are different voltages as well, but they do not matter for this discussion.

For the MOST part, you end up using the same frequency on your sub that you use at home. That is so you can sync up to shore power (hey, you didn't think we run the plant ALL the time did you) and power the boat from regular electricity.

When you get a freqency on sonar, you are picking up a piece of equipment. Sometimes what you are hearing is a harmonic of the base frequency of this equipment. This can be usefull in telling you what nationality the contact may be. If you are getting harmonics of a 50hz then you can pretty much rule out an american contact. (sonar guys, can you lend a hand here? It has been awile since I had to think of this part of the boat. Quals were a LONG time ago)

Now, as to what may be MAKING that noise?? Well, that is classified WAY up there. Each contact class has its OWN set of distinct tonals. If you get a good enough cut on the contact, you can tell WHO and WHAT it is. You can tell this down to a specific ship I believe.

One of my assigned duties was Sound Silencing. I had to make sound cuts of EVERY STINKIN PIECE of mechanical gear on the boat and work to minimize this problem. Let me tell you, that job took a LOT of patience and had a lot of stress. Think about it. I was responsible DIRECTLY for the overall quietness of the equipment and thus the BOAT. If I messed up, my shipmates lives were at stake.

Want to know pride? I was on a 3rd flight VLS boat and we took out a 688i in a TOPTORP competition. On paper, there were supposed to be WAY quieter than us. We flat creamed them. I got an admirals letter of commodation for the work I did. The hard work paid off.

[Castout]

Speaking of diesel lately I've been reading 'submarines in Indonesia' in which it in part tells about the whiskey class diesel sub.

In every domestic (up to a period I assume) naval ASW exercise the whiskey and the newer type 209 of the Indonesian Navy for that matter have never been able to be detected by surface combat forces. These diesel subs were very very quiet.
The results of these exercises were photographs of the surface combatant hulls.

One Whiskey even came close to a British carrier passing near Indonesian waters during the 60s I think. It surfaced when it was well within torpedo range after taking photographs of the carrier to say Bon Voyage! :D

[Castout]

Can't a Kilo just shut down everything and go dead in the water if it wants to? You'd only need to do it for a short time, to let the baddies pass by. I guess I'd really like to see the diesel electric boats be able to just disappear entirely from passive sonar when they hit zero knots.
Well you should be able to just set speed to 0 knots or all stop and you'll effectively disappear with the background sea noise. Or at least that's what I've been told.

2.5nm yea that seems quite far off. I believe I've detected a 4 knots diesel at lesser range than that. Are you sure you got it right? The diesels are supposed to be almost undetectable passively in RA more so in shallow noisy waters than in deep quiet waters.

[Pillar]

Amazing :) I'm curious about how you guys bagged the 688, if more detail can be spared without breaking your vows to the country.

Is there a list somewhere that describes in very general terms what different kinds of equipment on both nuclear and conventional boats produce what range of tones?

Castout - The stories of the USN vs Gotland also come to mind too. Is there a way to get the AI to stop dead? Problem is I can't test the noise output of the Kilo when I'm controlling it. :)

[Castout]

Castout - The stories of the USN vs Gotland also come to mind too. Is there a way to get the AI to stop dead? Problem is I can't test the noise output of the Kilo when I'm controlling it. :)
I think even AI diesel subs are made to disappear at all stop. If you open the database, all diesel subs are made to have a passive noise level of 50 making them at 0 knots to be effectively undetectable passively. The noise of the diesel subs will be added as the screws rotate. The faster you move the more noise it emits.

Edit: I did one simple test and it seems that AI couldn't stop. And yea at 2 knots at 100 yards range the AI was detectable in the STA mode as a very thin line. while on 500 yards a 4 knots Kilo(not improved) was only detectable in the sphere ITA mode. I didn't check the towed array though. Mind you I did't check for maximum detectable range.

[Hitman]

Many thanks for your comments Bubblehead Nuke, I knew you still had to run something even if at dead stop, but I didn't think it was so much and so noisy. Also, the point of something effectively obscuring background noise is something that I hadn't thought of! We live to learn... :up:

It's these things I love from subsim.com, you discuss and theorize with friends, suddenly a real submariner pops up and shares a piece of his knowledge, wow....I love subsim.com :up: :up:

[Frame57]

Humm that doesn't sound correct, I did a test long ago and a Kilo stopped and lying in the seabed was not heard by a Los Angeles even if at a few hundreds of yards :hmm: As it should be, BTW, because a stopped diesel-electric theoretically does not generate any noise.

It will not have any propulsive noise, however that does not mean it is silent.

Unless they are using direct DC powered gear (and that would be difficult), you are going to have the DC-AC Motor generators running that are providing power to the AC buses. You will have HVAC equipment running in order to maintain the proper temp in the boat. You will also have other ancillery gear running that is required to operate and fight with the boat and maintain habitability. All it takes is ONE piece of equipment to soundshort and you are royally screwed. That is where the 50/60hz tonals come from. The AC bus and the equipment that it runs.

It is these CONSTANT equipment noises that will give you away. Yes, you can raft and sound isolate most of this gear, but you have to remember: a diesel boat is SMALL and that limits what you can do. The more mass that a electric powertrain has to move, the shorter its legs. Thus they will scrimp and cut corners in that all important weight/effectiveness consideration. You also have to bring on FUEL. This is a LOT of mass that has to be considered into this equation. Thus as you can see there are a LOT more variables here than I think you realize. I could give some good real world examples and such, but I hope the point has been made.

With a nuke boat you have unlimited fuel. You do not have to worry about your underwater endurance. You can include the more comprehensive rafting and sound isolation considerations. You are not worried about the size of your boat because you have a LOT more power that will not run out on you. You then have OTHER considerations but the biggest one is solved and manageable.

A diesel boat is quiet. But it is not as quiet as you would believe.

Also, there is something BAD about being DEAD quiet. If you can isolate a line of bearing that is LOWER than background noise and is MOVING. Um.. guess what, you have found something that is trying to hide. That was becoming a problem when I got out. The sonar gear was getting so good you could do just this and they actually had to make sure that you did not get TOO quiet as a large moving object that is occluding background noise and moving at 8 knots can be a bad thing.yep, excellent points. How about coolant pumps? How noisy do you think they were? Lets say circa 1980's?

[Bubblehead Nuke]

yep, excellent points. How about coolant pumps? How noisy do you think they were? Lets say circa 1980's?

You know I can not get into that area of discussion, even in a roundabout way.

Strictly FORBIDDEN to even go into this area.

I can not even give you a rough list of the the constant running things that were NOT propulsion related. That stuff was on of those uber kill before reading type lists.

Way too much info for a sim.

WAY too much for general disclosure.

[Pillar]

Either it is classified or not. Who is asking and for what reason has nothing to do with it.

[jmr]

The Complete Idiot's Guide to Submarines (http://books.google.com/books?id=W0_BL3_ImDIC&dq=the+complete+idiots+guide+to+submarines&pg=PP1&ots=jnOxlh5vOO&source=bn&sig=8JlCq6IRzplPXTZyK3x4nBf3YXk&hl=en&sa=X&oi=book_result&resnum=7&ct=result) is an awesome source of info for these kinds of discussions but sadly the book is no longer in print and copies of it on Amazon range from $450 ~ $800! You should be able to check out a copy through an inter library loan.


With regards to reactor coolant pumps, the author says the pumps are car-sized and are quiet in slow speed but loud as freight trains in fast speed.

[Castout]

The Complete Idiot's Guide to Submarines (http://books.google.com/books?id=W0_BL3_ImDIC&dq=the+complete+idiots+guide+to+submarines&pg=PP1&ots=jnOxlh5vOO&source=bn&sig=8JlCq6IRzplPXTZyK3x4nBf3YXk&hl=en&sa=X&oi=book_result&resnum=7&ct=result) is an awesome source of info for these kinds of discussions but sadly the book is no longer in print and copies of it on Amazon range from $450 ~ $800! You should be able to check out a copy through an inter library loan.


With regards to reactor coolant pumps, the author says the pumps are car-sized and are quiet in slow speed but loud as freight trains in fast speed.
Hmm only an idiot would want to buy a book that costs $800.00 that clearly stated that it's intended for idiots.

First the book mocks your intelligence then you confirm it by buying the book at $800.00? :rotfl:I'll pass.

[bishop]

Hmm only an idiot would want to buy a book that costs $800.00 that clearly stated that it's intended for idiots.

First the book mocks your intelligence then you confirm it by buying the book at $800.00? :rotfl:I'll pass.

Those prices are crazy (hmmmm... my copy is in really good condition, lol)

The title aside (and I bought it when it was in print for $18.95US), it's written by Micheal DeMercurio and is an excellent read, definitely recommended for anyone interested in modern subs. Lots of interesting details you won't find in other books about nukes.

[Bubblehead Nuke]

The Complete Idiot's Guide to Submarines (http://books.google.com/books?id=W0_BL3_ImDIC&dq=the+complete+idiots+guide+to+submarines&pg=PP1&ots=jnOxlh5vOO&source=bn&sig=8JlCq6IRzplPXTZyK3x4nBf3YXk&hl=en&sa=X&oi=book_result&resnum=7&ct=result) is an awesome source of info for these kinds of discussions but sadly the book is no longer in print and copies of it on Amazon range from $450 ~ $800! You should be able to check out a copy through an inter library loan.


With regards to reactor coolant pumps, the author says the pumps are car-sized and are quiet in slow speed but loud as freight trains in fast speed.

I would say more of a refrigerator in size.

As for the noise, I would say that is a little bit of an fudging on their part. They are a little quieter than that.

That book, from the parts that I have read, is a LOT more then an idiots giude. I'll bet it NEVER sees a printing again. It should have been classified NOFORN at the very least.

[Kazuaki Shimazaki II]

Hmm only an idiot would want to buy a book that costs $800.00 that clearly stated that it's intended for idiots.

First the book mocks your intelligence then you confirm it by buying the book at $800.00? :rotfl:I'll pass.

I'm feeling very lucky that I bought that book while it was still priced reasonably (read, at least less than US$100, a LOT less).

Anyway, IMO the book says a lot about American submariner(s), and for at least some of it, I hope for the US Navy's sake that "submariner" will be without the "s". For example, the sheer percentage dedicated to the reactor can't help but bring up memories of "Rickoverized" criticisms - the priorities of the average American sub officer...

As for his anecdote about their sub careening past a Russian submarine due to a gross operator error. He knows that there is little chance of the Soviet sub not hearing him, but when it doesn't immediately try and ram, he actually concludes that they somehow didn't. Apparently, this "Dmitri" was dumb.

I don't know, but based on the information provided, I can't help but think of this alternate scenario on the Soviet Vcitor:

BCh-7 officer: Comrade Commander, I have a target. American submarine, coming out of our shadow zone.

Commander: Damned American acoustic advantage! Did you get a print of him?

Bch-7 officer: Yes, Comrade, we have him on tape. Thanks to him we have a beautiful noiseprint of an American Sturgeon class submarine through its acceleration and deceleration cycle.

BCh-1: Comrade Commander, I have plotted an evasive course.

Commander: Watch officer, Execute the Evasive Drill.

Deputy Division Commander: Negative. Stay on your original course and speed. Remember, young Sergei, the American submariner is blessed with good hydroacoustic equipment and even better measures for reducing their physical acoustical field. However, they, not being good Marxist-Leninists, are cursed with their capitalist, subjectivist thought pattern. Therefore, if we stay our original course, the Americans will probably chew out whoever made that error, BUT they will think that they were undetected and continue to track us at their typical, dangerously close ranges, right in the supposed safety of our shadow zone of acoustical illumination. This gives us an excellent solution regarding the Target's Elements of Motion.

Commander: I understand, Senior Chief. (turns) BCh-3 will set up two TEST torpedoes for firing into the shadow zone of acoustical illumination. Adjust their initial courses so they cover our baffles from 1-4000 yards. That should be enough to cover the likely zone the American will be.

Zampolit: And that's why Communism will prevail.

DDO: That's good, Commander. Keep learning little lessons like this up the rest of this patrol and when we get back I'll recommend you for Independent Command. Then I'll be in your hair a bit less.

[Frame57]

yep, excellent points. How about coolant pumps? How noisy do you think they were? Lets say circa 1980's?

You know I can not get into that area of discussion, even in a roundabout way.

Strictly FORBIDDEN to even go into this area.

I can not even give you a rough list of the the constant running things that were NOT propulsion related. That stuff was on of those uber kill before reading type lists.

Way too much info for a sim.

WAY too much for general disclosure.The 637's are razor blades now, so I am not sure that matters. But I do recall the russkies having very noisy coolant pumps.

[Bubblehead Nuke]

The 637's are razor blades now, so I am not sure that matters. But I do recall the russkies having very noisy coolant pumps.

While the 637's are razor blades a lot of things still carried overs into the more modern plants. Thus we do need to be careful. Even the old Nautilus info is still classified. I am more familiar with the 688 & 726 class of submarines. Particularly the engineering plants. The S8G plant design has a HEAVY influence on the newer boats.

However, the russian gear?? Yeah, they could be noisy, especially the early stuff. Older sonar guys used to complain that it messed thier ears up if they listened too long.

They had some fundemental design and operational philosophies that did not lend themselves to quiet plant operations. I am not saying they made junk. Far from it. They build some TOUGH stuff. It is that they have a different mission with different objectives.

[AirHippo]

Probably a futile question, but has anyone ever come across material discussing Russian/Soviet torpedo sonar sets? The UGST, being the latest in their arsenal, should (I had fondly hoped) be fairly good, but certainly in my games (playing with LWAMI and the 1.04 patch), it's nothing short of pathetic - just a moment ago no less than four UGSTs managed to miss a 688, even one which can have been no more than a thousand yards off the target (which was doing 35 knots) and was, supposedly, in passive mode went for an active decoy! 'course, I am assuming here that SCS modelled a difference in torpedo performance vis-a-vis detection and tracking between different torpedoes.

Come to think of it, any material on Russian sonar full stop wouldn't be bad. Even if it's in Russian.

[Molon Labe]

Probably a futile question, but has anyone ever come across material discussing Russian/Soviet torpedo sonar sets? The UGST, being the latest in their arsenal, should (I had fondly hoped) be fairly good, but certainly in my games (playing with LWAMI and the 1.04 patch), it's nothing short of pathetic - just a moment ago no less than four UGSTs managed to miss a 688, even one which can have been no more than a thousand yards off the target (which was doing 35 knots) and was, supposedly, in passive mode went for an active decoy! 'course, I am assuming here that SCS modelled a difference in torpedo performance vis-a-vis detection and tracking between different torpedoes.

Come to think of it, any material on Russian sonar full stop wouldn't be bad. Even if it's in Russian.

Torps in passive mode as a general rule will not work against submarines in LWAMI, this is not a UGST thing.

[goldorak]

That book, from the parts that I have read, is a LOT more then an idiots giude. I'll bet it NEVER sees a printing again. It should have been classified NOFORN at the very least.

This is a sign of our times,
it doesn't matter if it will be in print or not, with the internet you can be assured a :arrgh!: copy is somewhere awaiting to be downloaded. :rotfl:

[jmr]

I contacted the author at his website (http://www.ussdevilfish.com/index01.htm) and specifically asked him if the Navy had the book pulled from shelves and he replied that the publisher only printed a small number of copies on it's first and only run. I recall seeing it on the shelves at Border's years ago but thought nothing of it. Now I'm kicking myself for not picking up a few copies :damn:

[Bubblehead Nuke]

That book, from the parts that I have read, is a LOT more then an idiots giude. I'll bet it NEVER sees a printing again. It should have been classified NOFORN at the very least.

This is a sign of our times,
it doesn't matter if it will be in print or not, with the internet you can be assured a :arrgh!: copy is somewhere awaiting to be downloaded. :rotfl:

As much as I HATE to admit it, but I have looked for a downloadable version of it. There are none to be found. I would HAPPILY pay the author for his work if I could find it.

[Frame57]

The 637's are razor blades now, so I am not sure that matters. But I do recall the russkies having very noisy coolant pumps.

While the 637's are razor blades a lot of things still carried overs into the more modern plants. Thus we do need to be careful. Even the old Nautilus info is still classified. I am more familiar with the 688 & 726 class of submarines. Particularly the engineering plants. The S8G plant design has a HEAVY influence on the newer boats.

However, the russian gear?? Yeah, they could be noisy, especially the early stuff. Older sonar guys used to complain that it messed thier ears up if they listened too long.

They had some fundemental design and operational philosophies that did not lend themselves to quiet plant operations. I am not saying they made junk. Far from it. They build some TOUGH stuff. It is that they have a different mission with different objectives.That is what i recall too. It was our means of picking of Soviet Boomers, not so much the screw noise but the coolant pumps and other equipment that they did not have sound mounted and the noise transferred to the hull nicely.

[AirHippo]

Torps in passive mode as a general rule will not work against submarines in LWAMI, this is not a UGST thing.

Oh, right. I did wonder. Well anyway, I'm still curious as to sources on Soviet sonar kit :p

[Rip]

Humm that doesn't sound correct, I did a test long ago and a Kilo stopped and lying in the seabed was not heard by a Los Angeles even if at a few hundreds of yards :hmm: As it should be, BTW, because a stopped diesel-electric theoretically does not generate any noise.
It will not have any propulsive noise, however that does not mean it is silent.

Unless they are using direct DC powered gear (and that would be difficult), you are going to have the DC-AC Motor generators running that are providing power to the AC buses. You will have HVAC equipment running in order to maintain the proper temp in the boat. You will also have other ancillery gear running that is required to operate and fight with the boat and maintain habitability. All it takes is ONE piece of equipment to soundshort and you are royally screwed. That is where the 50/60hz tonals come from. The AC bus and the equipment that it runs.

It is these CONSTANT equipment noises that will give you away. Yes, you can raft and sound isolate most of this gear, but you have to remember: a diesel boat is SMALL and that limits what you can do. The more mass that a electric powertrain has to move, the shorter its legs. Thus they will scrimp and cut corners in that all important weight/effectiveness consideration. You also have to bring on FUEL. This is a LOT of mass that has to be considered into this equation. Thus as you can see there are a LOT more variables here than I think you realize. I could give some good real world examples and such, but I hope the point has been made.

With a nuke boat you have unlimited fuel. You do not have to worry about your underwater endurance. You can include the more comprehensive rafting and sound isolation considerations. You are not worried about the size of your boat because you have a LOT more power that will not run out on you. You then have OTHER considerations but the biggest one is solved and manageable.

A diesel boat is quiet. But it is not as quiet as you would believe.

Also, there is something BAD about being DEAD quiet. If you can isolate a line of bearing that is LOWER than background noise and is MOVING. Um.. guess what, you have found something that is trying to hide. That was becoming a problem when I got out. The sonar gear was getting so good you could do just this and they actually had to make sure that you did not get TOO quiet as a large moving object that is occluding background noise and moving at 8 knots can be a bad thing.

Ahh yes, much like exposing weakness in cloaking shields. Everyone hitting on the right areas. This is also without delving into readiness levels of respective units with regards to crew training/moral and the quality and frequency of some very critical maintenance. The seldom spoken truth that never gets factored into these discussion but IRL have had substantial effect on submarine mission and tactical performance. Even within our own service you can tell more about whether a boat will operate effectively and get results by these factors. When those inevitable sound shorts and such occur a well oiled crew handles them quickly and needs to less. While the better the quality of support the easier that makes it. There has been in history a substantial difference between the resources alloted a 688 or Seawolf and that typically available to a Kilo or like quanitity over quality sub. The 688 may have heard you but one of the three or four other Kilo's that would be with you now know exactly where he is.

[Rip]

yep, excellent points. How about coolant pumps? How noisy do you think they were? Lets say circa 1980's?
You know I can not get into that area of discussion, even in a roundabout way.

Strictly FORBIDDEN to even go into this area.

I can not even give you a rough list of the the constant running things that were NOT propulsion related. That stuff was on of those uber kill before reading type lists.

Way too much info for a sim.

WAY too much for general disclosure.

Indeed. The days of shutting a submarine down and having no power but battle lanterns are long gone. I can remember their being a great deal of reluctance to kill the power to things like the reactor coolant systems and such. Few people realize that these systems are not like a car battery. They require constant services, maintenance, and supervision. you don't flip off the swith at night, lock them up and go home for the night. There are two of everything important and one of them is almost always running from launch until you tie up at the scrapyard. I remember a chief told me like this. If it uses power it creates heat and needs cooled, and it makes noise as does removing that heat. There is also a need for doing things like cleaning/creating air, moving water around and of course houscleaning(sanitaries and trash). Which reminds me of a particularly sensitive mission where we could not dispose of trash or sewage and were very limited on making water. No showers and can full of garbage stacked up at every corner. Oh the thrills of sensitive missions.:roll:

[Bubblehead Nuke]

Once, just ONCE, we did the 'stealth thing'. We were in post availability shakedown doing sound cuts at a classified location. This place is LOADED with all kinds of acustic sensors used to profile a boat and show any potential problems.

We full scrammed the plant, secured EVERYTHING that could be turned off. We turned off gear so that we would turn off support gear. We turned off the redundant gear forward and aft, we shut the engineroom down except for ONE lube oil pump. We then answered the bell on the EPM. We crawled through the array so they could get the ultimate noise level of JUST the hull moving through the water.

We had only the absolute minimum gear running and you couold hear a flea fart it was so quiet.

It was actually a dangerous evolution. All we had was the ships battery and that is not much. As soon as we completed the run we had to snorkel in a hurry and restart the plant and the rest of the boat.

How did we do in the test? As it was told to me we started snorkelling and they told us we could begin our run in the array. They never heard us pass though.

[Pillar]

So that's how to beat SOSUS, you listening ruskies? Tow your subs behind freighters. :hmm:

[Rip]

Once, just ONCE, we did the 'stealth thing'. We were in post availability shakedown doing sound cuts at a classified location. This place is LOADED with all kinds of acustic sensors used to profile a boat and show any potential problems.

We full scrammed the plant, secured EVERYTHING that could be turned off. We turned off gear so that we would turn off support gear. We turned off the redundant gear forward and aft, we shut the engineroom down except for ONE lube oil pump. We then answered the bell on the EPM. We crawled through the array so they could get the ultimate noise level of JUST the hull moving through the water.

We had only the absolute minimum gear running and you couold hear a flea fart it was so quiet.

It was actually a dangerous evolution. All we had was the ships battery and that is not much. As soon as we completed the run we had to snorkel in a hurry and restart the plant and the rest of the boat.

How did we do in the test? As it was told to me we started snorkelling and they told us we could begin our run in the array. They never heard us pass though.

I am familiar with the place you refer. Some great places to have a port of call there but they never seem to want to let you unless a major issue is noted that can be corrected by a quick tie up. Visited those ports at other times but never on sound trial runs. Go figure. Also interesting is how well that whole area is monitored. I think they don't want anyone observing what is going on.;)

[Frame57]

Haaa! I got liberty there and i think i have son there now who is about 27 years old...:D

[LoBlo]

I have played also a lot with the 688i and I can hear Kilos moving at those 5 knots easier that I would think at first glance. Tests I have conducted with LWAMI seem to indicate however that with all stop and lying in the seabed, a 688 can go right over your conning tower and not hear you :hmm: , so it's probably a matter of rescaling a bit the curve of noise increasing with speed

Some of have been suggesting that the next iteration of DW (patch or otherwise) use a *nonlinear* sonar versus speed curve (meaning that noise generation becomes a bit more sophisticated) to address these sort of things. The noice of a boat in reality should not be linear to its speed.

http://www.fas.org/spp/eprint/snf_02.gif

[Bubblehead Nuke]

Boy would THAT change the way things are done in the sim.

[Hitman]

Oh, that would be fantastic :up: :up:

[Dr.Sid]

Well .. I would not expect anything from DW. The fact that SCS approved code mods (well, talking about them at least), means that they really don't plan much in this area. And I don't expect anybody to really be able to change THIS in the code.

On the other hand, you can expect even more complex model from me :hmm: Outlines of the sonar are being made in these very days.

[Castout]

Dr. Sid I hope your work could be like Open Falcon for Falcon 4.0. But then they didn't start from scratch.

I hope you get your sim done beautifully and as realistic as it could possibly be done ;).