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

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..

07-24-17, 06:09 PM	#9
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..