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

PurpleCow · 07-20-17, 06:32 PM

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 · 07-20-17, 06:46 PM

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 · 07-20-17, 06:56 PM

Quote:

Originally Posted by Julhelm

... 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!

FPSchazly · 07-20-17, 07:00 PM

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

Raptor_Pilot · 07-22-17, 03:20 PM

Quote:

Originally Posted by Julhelm

Being stealthy does not necessarily mean being slow.

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

Shadow · 07-22-17, 03:52 PM

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.

jerseytom · 07-24-17, 07:14 AM

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 · 07-24-17, 12:35 PM

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

The Bandit · 07-24-17, 01:00 PM

Quote:

Originally Posted by 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?

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 · 07-24-17, 06:09 PM

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 · 07-24-17, 06:51 PM

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 · 07-24-17, 07:58 PM

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?

The Bandit · 07-25-17, 02:05 AM

Quote:

Originally Posted by 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..

Quote:

Originally Posted by 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.

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.

Shadriss · 07-24-17, 09:55 PM

Quote:

Originally Posted by 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..

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 · 07-24-17, 10:13 PM

Quote:

Originally Posted by Shadriss

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

I was actually expecting a sonar weenie to chime in.

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

07-20-17, 06:32 PM	#1
PurpleCow A-ganger Join Date: Nov 2004 Posts: 75 Downloads: 23 Uploads: 0	Speed and quiet - 1/3 vs 2/3 vs full stop 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?

07-20-17, 07:00 PM	#4
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	Here's a nice tutorial from my buddy ramjb on why being stealthy doesn't mean you have to be slow. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

07-22-17, 03:52 PM	#6
Shadow Torpedoman Join Date: Oct 2005 Location: Buenos Aires Posts: 112 Downloads: 10 Uploads: 2	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. __________________ Shadow's Cold Waters mods (JSGME-friendly) = Longer Campaigns: Marathon Edition = 500-yard MAD range

07-24-17, 07:58 PM	#12
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Beantown Posts: 776 Downloads: 15 Uploads: 1	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? __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

07-20-17, 06:46 PM	#2
Julhelm Seasoned Skipper Join Date: Jul 2007 Location: The Icy North Posts: 693 Downloads: 189 Uploads: 0	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.

07-24-17, 07:14 AM	#7
jerseytom Watch Join Date: Jul 2017 Posts: 19 Downloads: 0 Uploads: 0	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?

07-24-17, 12:35 PM	#8
Capt Jack Harkness Samurai Navy Join Date: Nov 2007 Posts: 567 Downloads: 210 Uploads: 1	Not to nitpick but it's more of a throttle setting than a reactor setting.

07-24-17, 06:09 PM	#10
Bubblehead Nuke XO Join Date: Feb 2006 Posts: 435 Downloads: 5 Uploads: 0	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..

07-24-17, 06:51 PM	#11
jerseytom Watch Join Date: Jul 2017 Posts: 19 Downloads: 0 Uploads: 0	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.