SUBSIM Radio Room Forums - You know I've ben whining about passive detection range until I read this

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- - You know I've ben whining about passive detection range until I read this (https://www.subsim.com/radioroom/showthread.php?t=144408)

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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

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Originally Posted by Bubblehead Nuke

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Originally Posted by 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.

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.

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Originally Posted by Bubblehead Nuke

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Originally Posted by 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.

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:

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.

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

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Originally Posted by Bubblehead Nuke

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.;)

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

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Originally Posted by Hitman

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

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

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

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.

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 ;).