Speed and quiet - 1/3 vs 2/3 vs full stop

[PurpleCow]

I usually try to crawl around at 1/3rd (5 knots) but it is often too slow to maneuver into attack position. Just how loud are the U.S. subs when traveling at 10 knots (2/3rds)?

For example, say a Sturgeon skipper knows there is an enemy sub in the area. Will he slow down to 5 knots or will he feel safe continuing to cruise at 10 knots?

Also, if I am comfortable where I am is it better to go full stop or would it be better to stay at 5 knots? Just wonder if full stop overs any advantages?

[Julhelm]

It really depends on what the enemies are doing, what sensors they have, if you're in a duct, if there's a layer in between, etc. It is quite possible to stalk enemies up to 20kts if the variables are in your favor. Use the signature analysis to determine this. If engaging surface ships, observe their sprint and drift behavior, then use that to your advantage. Being stealthy does not necessarily mean being slow.

[PurpleCow]

... Use the signature analysis to determine this.

Thanks!. I was about to ask you to talk further about signature analysis but I did some searching and found this nice video from JiveTurkey that covers it. Nice explanation JiveTurkey!

https://www.youtube.com/watch?v=7CqCRNxIjbk

[FPSchazly]

Here's a nice tutorial from my buddy ramjb on why being stealthy doesn't mean you have to be slow.

https://www.youtube.com/watch?v=clhxFImfH9I

[Raptor_Pilot]

Being stealthy does not necessarily mean being slow.

This is a lesson I am forced to re-learn, time, after time, after time.

[Shadow]

Basically, you've to use the Signature Analysis panel to gauge just how detectable you are versus a specific contact. As long as you're not over 10 dB on any enemy sensor at a given speed, you should be safe.

However, it's a gamble to run above 2/3 speed unless you're more or less certain the enemy won't be detecting you (i.e. you're in their baffles), considering the faster you go, the deafer you are. That can make you lose contacts and prevent you from noticing (and adapting to) changing circumstances. Which can very well happen given escorts and submarines occasionally change course and/or slow down to listen in where they couldn't earlier.

Another thing to consider is that you can't measure yourself against what you haven't detected, so again, caution is advised unless you're fairly sure every enemy is accounted for.

[schurem]

Aren't Narwhal and the 688's the only boats that have natural convection reactors that don't need to actively pump their coolant when running slowly? Is it modelled that they make a big step in quieting when going 1/3rd?

Also Rickover was a dick lol.

[Kazuaki Shimazaki II]

Aren't Narwhal and the 688's the only boats that have natural convection reactors that don't need to actively pump their coolant when running slowly? Is it modelled that they make a big step in quieting when going 1/3rd?

AFAIK, there's only one "kink" in the system right now, and that's an jump when you cavitate. Beyond that it is linear with speed.

Perhaps it'll be a good idea to change the text file format to allow for aknot by knot noise value which the game just looks-up. Then we can program in however many kinks we feel is realistic. Pumps on/off, pumps switching to high speed, another pump being brought into the game, the raft being locked on some subs at high speed ... etc.

[The Bandit]

Aren't Narwhal and the 688's the only boats that have natural convection reactors that don't need to actively pump their coolant when running slowly? Is it modelled that they make a big step in quieting when going 1/3rd?

Also Rickover was a dick lol.

The 688s use an S6G reactor which isn't natural convection, you're probably thinking of the Ohio's S8G.

[Kazuaki Shimazaki II]

The 688s use an S6G reactor which isn't natural convection, you're probably thinking of the Ohio's S8G.

I've been told the S6G can also nat-circ, but you have to be STOPPED (hotel load only).

[The Bandit]

I've been told the S6G can also nat-circ, but you have to be STOPPED (hotel load only).

Well in theory if sound is that important just about any boat could be SCRAM'd and run off the battery for some time, as long as enough power is reserved to do a reactor start up again. Screw that up and you're back in the 1950s and its time to raise the snorkel.

Would also be pretty cool if you could put the boat into turbo-electric mode or use the EPM. My understanding is that the EPM is pretty loud though.

[Shadriss]

My understanding is that the EPM is pretty loud though.

EPM and SPM both. Does the term, "Screaming Banshee" mean anything to you? :)

[jerseytom]

I'm curious from an implementation standpoint - more a developer question - is noise level based more on reactor setting or knots?

So let's say we've got a Skipjack and a Sturgeon. Sturgeon is, by the game files, a quieter noise level boat. But is that at equivalent speed, or equivalent reactor setting?

For example, both boats going 20 knots. Skipjack may only have to be at Standard to achieve this, Sturgeon at Full (just guessing, without verifying in game). Will the Sturgeon be quieter at equivalent speed? Or is that nullified by the fact that it's running at a higher reactor setting?

[Capt Jack Harkness]

Not to nitpick but it's more of a throttle setting than a reactor setting.

[The Bandit]

I'm curious from an implementation standpoint - more a developer question - is noise level based more on reactor setting or knots?

So let's say we've got a Skipjack and a Sturgeon. Sturgeon is, by the game files, a quieter noise level boat. But is that at equivalent speed, or equivalent reactor setting?

For example, both boats going 20 knots. Skipjack may only have to be at Standard to achieve this, Sturgeon at Full (just guessing, without verifying in game). Will the Sturgeon be quieter at equivalent speed? Or is that nullified by the fact that it's running at a higher reactor setting?

I don't believe relative plant noise is factored into the game. You have your ownship noise level as specified in the .txt file for the ship, which is then modified by whatever speed the ship is running at. So for something like a Skipjack or a November, that noise is going to be through the roof no matter what it is doing. Ditto for stuff like the Los Angeles or Narwhal being quiet.
The trouble is, this makes certain things (like the claims that the Alfa was actually a quiet boat until it was cranked up, or the "blade-rate" related noise suffered by the early Skipjacks and Permit class with 5 blade screws at certian speeds) impossible to replicate.

What I'm not sure about is whether or not Silent Running will bring you below the base noise-level or just down to it, but other than that you'd have ownship noise + speed modifier.

[Bubblehead Nuke]

I've been told the S6G can also nat-circ, but you have to be STOPPED (hotel load only).

Nope.. Pumps have to be on all the time while critical.

There is enough thermal head to provide emergency cooling after a scram if the pumps have to be turned off.

[Bubblehead Nuke]

Well in theory if sound is that important just about any boat could be SCRAM'd and run off the battery for some time, as long as enough power is reserved to do a reactor start up again. Screw that up and you're back in the 1950s and its time to raise the snorkel.

Would also be pretty cool if you could put the boat into turbo-electric mode or use the EPM. My understanding is that the EPM is pretty loud though.

We actually did this once down in AUTEC. We entered the range and scrammed the plant out. We turned almost everything in the boat off, including the fans.

With the EPM you are not going to be winning any speed races and you are VERY range limited but you will be a hole in the water. They tracked us by the LACK of noise in the water. We ran the range and then had to recover the plant and bring the boat back on-line quickly. It was quite the experience.

It was QUIET in the engine room. Scary quiet.

The outboard?? That would be for maneuvering in port. In theory you COULD use it to go somewhere if you have a propulsion train casualty, but that would be a LONG, LOUD, and SLOW. That was a screaming banshee as someone said earlier.

[Bubblehead Nuke]

This is something that is NEVER simulated correctly in any subsmin I have tried.

Basically the speed to noise curve is not a linear progression as it is always seemed to be modeled.

This is going to be a very general discussion for obvious reasons.

Here we go:

You have to look at what is going on.

The main noise you have on a boat is the propulsion plant in a nuclear powered vessel. It is the ONE thing that has to be on all the time. It is the single biggest creator of noise on the platform.

Now, with the plant running critical sitting at the pier, you may be using 25% of your reactor power to just keep the lights on and such. We call the 'hotel load' It is a constant amount of power that is required to operate the various equipment on the boat. This means that the remaining 75% of the available power is used to turn the screw.

A simplistic way to thing about speed is that each 'bell' is a doubling of power. Note that I did NOT say speed. Power is a cubed function in relation to speed. In essence, to double your speed you have to have 4 times the power to attain it.

Here are some basic numbers:

Ahead 1/3 is 5 knots
Ahead 2/3 is 10 knots
Ahead standard is 15 knots
Ahead full is 25 knots
Ahead flank is 30 knots

If you worked BACKWARDS, ahead flank is 100% reactor output. That is all out get the hell out of dodge thermal limit on the plant.

Ahead full is HALF of the amount of power, ahead standard is HALF of the power used for ahead full, and so on and so on.

So what is the difference between ahead 1/3 and ahead 2/3? Not very much if you do the math.

Now.. WHY is this important? Because you can increase your speed and have basically no increase in own ships noise up to a point.

What you DO have is a degradation in your sensors to DETECT the other guy. So while he may still not be able to hear you, you lose the ability to hear HIM and thus you have to get even closer to detect him.

The whole issue is about trading maneuverability and time for expediency. How much ocean can you cover and find the bad guy.

I wish they had some kind of simplistic model of reactor plant ops. Give you, the captain, some kind of tactical option. You can go into an area in low power mode. You are quieter, but you are speed limited. You can go in at high power ops and while you are noisy, you have better acceleration and higher speeds. Make it so that if you have to shift to power states you make HUGE 'here I am' transients. That way you have to think about what you are doing and how you are going to approach things.


Sorry for the ramble..

[jerseytom]

Ramble on! I was close-ish to going into a nuclear engineering program in college ~15 years ago, but opted the mechanical route instead. Interesting to hear the insight.

[FPSchazly]

Yes, please ramble on haha. I do nuclear engineering for transport packages but I'm always interested to hear the reactor side of things. Isn't the power required to overcome drag proportional to the cube of velocity?

[Shadriss]

This is something that is NEVER simulated correctly in any subsmin I have tried.

Basically the speed to noise curve is not a linear progression as it is always seemed to be modeled.

This is going to be a very general discussion for obvious reasons.

Here we go:

You have to look at what is going on.

The main noise you have on a boat is the propulsion plant in a nuclear powered vessel. It is the ONE thing that has to be on all the time. It is the single biggest creator of noise on the platform.

Now, with the plant running critical sitting at the pier, you may be using 25% of your reactor power to just keep the lights on and such. We call the 'hotel load' It is a constant amount of power that is required to operate the various equipment on the boat. This means that the remaining 75% of the available power is used to turn the screw.

A simplistic way to thing about speed is that each 'bell' is a doubling of power. Note that I did NOT say speed. Power is a cubed function in relation to speed. In essence, to double your speed you have to have 4 times the power to attain it.

Here are some basic numbers:

Ahead 1/3 is 5 knots
Ahead 2/3 is 10 knots
Ahead standard is 15 knots
Ahead full is 25 knots
Ahead flank is 30 knots

If you worked BACKWARDS, ahead flank is 100% reactor output. That is all out get the hell out of dodge thermal limit on the plant.

Ahead full is HALF of the amount of power, ahead standard is HALF of the power used for ahead full, and so on and so on.

So what is the difference between ahead 1/3 and ahead 2/3? Not very much if you do the math.

Now.. WHY is this important? Because you can increase your speed and have basically no increase in own ships noise up to a point.

What you DO have is a degradation in your sensors to DETECT the other guy. So while he may still not be able to hear you, you lose the ability to hear HIM and thus you have to get even closer to detect him.

The whole issue is about trading maneuverability and time for expediency. How much ocean can you cover and find the bad guy.

I wish they had some kind of simplistic model of reactor plant ops. Give you, the captain, some kind of tactical option. You can go into an area in low power mode. You are quieter, but you are speed limited. You can go in at high power ops and while you are noisy, you have better acceleration and higher speeds. Make it so that if you have to shift to power states you make HUGE 'here I am' transients. That way you have to think about what you are doing and how you are going to approach things.


Sorry for the ramble..

There's the nuke side - the SONAR side of it adds even more complexity. Another thing that is rarely modeled well (if at all) is how O/S noise increases with speed. Not the equipment side that Nuke talked about, but simple flow noise across the hull.

Really, there's two numbers here to worry about. The first is ambient noise (which CW does use), basically the noise that's there as background. The second is O/S noise, which changes based on any number of large factors. These both matter greatly in speed selection. Why? Simple: I go slow enough that O/S noise doesn't significantly add to overall background, and I'm good. Any slower, and I gain nothing. I go fast enough that I can still hear. Any faster, and I gain nothing.

This happens in most subsims as pure chance - at least on the high side. The area that tends to be lost is the slow side - slow is not always quieter. There is a point where going any slower does not make you quieter... but it does cost you in terms of your control of the local tactical situation.

So, between the two... well, what I'll say is that I'd far rather cruise around at 10-ish knots than the 5 that CW's 'silent running' forces me into.

[Bubblehead Nuke]

There's the nuke side - the SONAR side of it adds even more complexity.

I was actually expecting a sonar weenie to chime in. :salute:That is why I left that whole discussion out.

FYI. I was a nuke who actually QUALIFIED as a sonar operator. It made section tracking party MUCH easier as I knew what the heck they were actually talking about and could ask specific questions that were actually helpful.

I did not want to get into the sonar side as I am more comfortable beating around the bush on the engineering side and not giving away a capability or operational information by accident.

I am sure there are TONS of things you and I could nit pick and bellyache on. If they only implemented a tenth of the things we are generalizing about most peoples head would explode from the workload

[Capt Jack Harkness]

All that said, it seems like making the own ship noise have a minimum background level and scale on a curve would be pretty simple to implement in a basic fashion, no? And scaling flow noise would be similar but without the added constant.

Do we know that noise actually does ramp linearly in game currently?

Also, should ultra-quiet be limited to ahead ⅓ or would it be more acccurate for it to be independent of bell?

[The Bandit]

This is something that is NEVER simulated correctly in any subsmin I have tried.

Basically the speed to noise curve is not a linear progression as it is always seemed to be modeled.

This is going to be a very general discussion for obvious reasons.

Here we go:

You have to look at what is going on.

The main noise you have on a boat is the propulsion plant in a nuclear powered vessel. It is the ONE thing that has to be on all the time. It is the single biggest creator of noise on the platform.

Now, with the plant running critical sitting at the pier, you may be using 25% of your reactor power to just keep the lights on and such. We call the 'hotel load' It is a constant amount of power that is required to operate the various equipment on the boat. This means that the remaining 75% of the available power is used to turn the screw.

A simplistic way to thing about speed is that each 'bell' is a doubling of power. Note that I did NOT say speed. Power is a cubed function in relation to speed. In essence, to double your speed you have to have 4 times the power to attain it.

Here are some basic numbers:

Ahead 1/3 is 5 knots
Ahead 2/3 is 10 knots
Ahead standard is 15 knots
Ahead full is 25 knots
Ahead flank is 30 knots

If you worked BACKWARDS, ahead flank is 100% reactor output. That is all out get the hell out of dodge thermal limit on the plant.

Ahead full is HALF of the amount of power, ahead standard is HALF of the power used for ahead full, and so on and so on.

So what is the difference between ahead 1/3 and ahead 2/3? Not very much if you do the math.

Now.. WHY is this important? Because you can increase your speed and have basically no increase in own ships noise up to a point.

What you DO have is a degradation in your sensors to DETECT the other guy. So while he may still not be able to hear you, you lose the ability to hear HIM and thus you have to get even closer to detect him.

The whole issue is about trading maneuverability and time for expediency. How much ocean can you cover and find the bad guy.

I wish they had some kind of simplistic model of reactor plant ops. Give you, the captain, some kind of tactical option. You can go into an area in low power mode. You are quieter, but you are speed limited. You can go in at high power ops and while you are noisy, you have better acceleration and higher speeds. Make it so that if you have to shift to power states you make HUGE 'here I am' transients. That way you have to think about what you are doing and how you are going to approach things.


Sorry for the ramble..

Ramble on! I was close-ish to going into a nuclear engineering program in college ~15 years ago, but opted the mechanical route instead. Interesting to hear the insight.

2nd that, awesome explanation.
Also with the speed/noise curve. I think an outboard would be nice just for the circumstances / scenarios it could open up (thinking Cold is the Sea, Ned Beach's Cold War book about a crippled boomer stuck under the ice with just outboard propulsion) and it could probably be animated similarly to a periscope / any other retractable mast.

Rudimentary plant operation would be pretty cool, and who knows, if they ever decide to add diesel boats with their associated "control panel" for battery charging and whatnot it may be a possibility.

[The Bandit]

All that said, it seems like making the own ship noise have a minimum background level and scale on a curve would be pretty simple to implement in a basic fashion, no? And scaling flow noise would be similar but without the added constant.

Do we know that noise actually does ramp linearly in game currently?

Also, should ultra-quiet be limited to ahead ⅓ or would it be more acccurate for it to be independent of bell?

Believe so, I can recall looking at one of the config files (not just for the sensors flow noise) and seeing something for noise per knot.

In some ways flow-noise could get tricky because again, some of the LOUD boats, specifically the Echos and Juliets, are that way primarily because of their added flow noise from having all sorts of limber holes and big missile tubes recesses (I imagine that Halibut and the Greybacks would have behaved the same way) created all sorts of issues which would be nearly non-existent at slow speeds.

The Soviets started getting crafty later on and putting spring-loaded doors on all their limber holes. The sea-pressure would eventually overcome the spring and close the doors at depth.

[jerseytom]

If they only implemented a tenth of the things we are generalizing about most peoples head would explode from the workload

Probably the most important thing here. As with anything that exists for entertainment, you can take the fun factor out of it by making it too much like a job. Probably don't need to go as far as "Game Over: You have failed to qualify on virtual submarines." ;)

Another consideration - a simple boat_noise = 132 in a configuration file is a lot more accessible from the standpoint of tuning things in a relative sense for gameplay, and also in keeping a mod community alive and well with future growth.

From an implementation standpoint I'd think it would be fairly trivial to have a table lookup for noise level versus speed. I would think though that there's got to only be a very limited number of people floating around here that could even subjectively describe what that curve should look like for any number of boats.

If it were me, and my experience from developing professional simulation software, my MO would be to ask - what all do we really need to capture as far as characteristics across a broad range (of diesel/electric and nuclear submarines in this case), and what's the absolute most simple way to implement it.

[Shadriss]

FYI. I was a nuke who actually QUALIFIED as a sonar operator.

A rare breed indeed. In 20 years of submarining, I can count the number of nuke-qualified SONAR operators I've worked with on no hands. Yes. That few. In which case, respect.... and mind your stack, Broadband. :)

Probably the most important thing here. As with anything that exists for entertainment, you can take the fun factor out of it by making it too much like a job. Probably don't need to go as far as "Game Over: You have failed to qualify on virtual submarines." ;)

Another consideration - a simple boat_noise = 132 in a configuration file is a lot more accessible from the standpoint of tuning things in a relative sense for gameplay, and also in keeping a mod community alive and well with future growth.

From an implementation standpoint I'd think it would be fairly trivial to have a table lookup for noise level versus speed. I would think though that there's got to only be a very limited number of people floating around here that could even subjectively describe what that curve should look like for any number of boats.

If it were me, and my experience from developing professional simulation software, my MO would be to ask - what all do we really need to capture as far as characteristics across a broad range (of diesel/electric and nuclear submarines in this case), and what's the absolute most simple way to implement it.

The way it's implemented here isn't bad, it's just very much overly pessimistic.

For Silent Running aka Ultra-Quiet, you have to understand that it's a machinery line up condition, and therefore, less the plant operations, speed independent. So yes - should definitely be unshackled from the 5 knot restriction. There will be a point where it's pointless to set ultra-quiet if you're going to go so fast (likely Standard Bell, for the purposes of this game), but even so there is no direct correlation between speed and ultra-quiet.

As for the speed-noise curve... it needs to be loosened up a bit. It's not as bad as I had originally thought, but after playing around a bit more, I can usually pull 10 knots and still be fine on most approaches.

[jerseytom]

Makes sense.

Should there be any other gameplay penalty to silent running? As it is the only thing is you can't reload weapons, I think. Seems like that's not quite as much of a penalty with fast reloads - if in a pinch you really need to reload, you can do so in ~30 seconds.

[Shadriss]

You ask a question that I reply with another question to:

Why should we penalize a submarine for doing what it's supposed to do?

I'm not even convinced there is a reason to stop torpedo loading during silent running, as everything involved in it is quiet unless the Trained Monkeys (TMs, AKA Torpedo Men AKA Horizontal Bomb Squad) manage to somehow drop a weapon... which is bad news of a different variety entirely.

Up until you actually shoot the tube, the whole process is a quiet one. So a better question might be, "Why are we penalizing a submarine for doing it's job?"

[Julhelm]

Well, it's ultra-quiet mode. Anyway, the torpedo reloads will be buffed up a bit. They'll still be around a minute on easier levels but around 3-5 minutes on realistic difficulty, depending on the boat. So can no longer spam weapons with reckless abandon.

[jmr]

I always enjoy reading first hand accounts of technical minutia from ex-submariners on this board. There used to be a blog called The Stupid Shall Be Punished that was operated by an ex submariner but he stopped updating it some time ago. The best part was reading the comments from former and active submariners.

[Shadriss]

Well, it's ultra-quiet mode.

Not to sound rude, but that means what exactly? Ultra-Quiet is a machinery line-up, but the machinery used in torpedo loading is always on... hydraulics cannot be shut off because too many critical systems use it. I've been in several 'shoot-outs' with other boats (and believe me, the bragging rights stakes are always high between crews in the same ports...), and we certainly were moving torpedos around in the room during them. Heck, Sonar Division is the primary author of a ship's Ultra-Quiet lineup, so I can say with some small amount of authority that on most ships, torpedo movement and reloads will still be permitted during that line-up... especially in a combat or expected combat situation. It simply doesn't add enough noise (barring a dropped weapon, which is extremely rare) to bother restricting it.

[Julhelm]

I'm sure you can do that in reality, but in terms of gameplay, if you can rig for ultra-quiet and still load weapons and conduct repairs, what's to stop players from just keeping the ultra-quiet mode on all the time? As we implemented it, it's an additional layer of stealth that comes at a cost, similar to how it is modelled in Silent Hunter.

[Kazuaki Shimazaki II]

I'm sure you can do that in reality, but in terms of gameplay, if you can rig for ultra-quiet and still load weapons and conduct repairs, what's to stop players from just keeping the ultra-quiet mode on all the time? As we implemented it, it's an additional layer of stealth that comes at a cost, similar to how it is modelled in Silent Hunter.

How about this? If we reload torpedoes during ultra-quiet, it'll take a "realistic" 15 minutes per torpedo and if we switch off the ultra-quiet we'll get the more gamey 4-5 minutes / torpedo.

[Capt Jack Harkness]

Or we leave out damage control and the pumps aren't as effective at controlling flooding?

[shipkiller1]

Not to sound rude, but that means what exactly? Ultra-Quiet is a machinery line-up, but the machinery used in torpedo loading is always on... hydraulics cannot be shut off because too many critical systems use it. I've been in several 'shoot-outs' with other boats (and believe me, the bragging rights stakes are always high between crews in the same ports...), and we certainly were moving torpedos around in the room during them. Heck, Sonar Division is the primary author of a ship's Ultra-Quiet lineup, so I can say with some small amount of authority that on most ships, torpedo movement and reloads will still be permitted during that line-up... especially in a combat or expected combat situation. It simply doesn't add enough noise (barring a dropped weapon, which is extremely rare) to bother restricting it.

I'm sure you can do that in reality, but in terms of gameplay, if you can rig for ultra-quiet and still load weapons and conduct repairs, what's to stop players from just keeping the ultra-quiet mode on all the time? As we implemented it, it's an additional layer of stealth that comes at a cost, similar to how it is modelled in Silent Hunter.

In actual operations, up North, we would rig for ultra quiet for hours on end. This would be dependent on what we were doing of course. As Shadriss stated, its an equipment lineup. Some equipment would be shut down during the rig... Sometimes the CO would modify this on the fly: "Rig for ultra-quiet with the exception of XXX".

[Capt Jack Harkness]

That makes sense, but to Julhelm's point, the game needs a trade off that players are impacted by. It sounds to me like making things realistic would mean removing the command entirely and assuming that we're always rigged for ultra quiet during combat, maybe with a call out from the XO at the start of the encounter.