Submarine cloak

[bumfire]

:D Sry, I don't buy it.

 

 

 

Range is not normally given by listening. In simple geometry, you don't know when the sound left the target, only when it reaches you, so you can't have the range. AFAIK the Seawolf can do an estimation on range, must be something like signal strength, don't know exactly.

You can also determine the course even if you don't have range, but you have to know the speed. (which you can get from the propeller sounds).

Of course you can get the solution, but you don't get it as soon as when using active sonar, and second, if the target makes changes in course, you have to start from the beginning with your calculation.

 

You do know that certain sounds travel thousands of miles under the ocean and in some instances right around the world ?, the lower the frequency the more distance it travels, so if the passive sonar is good enough, I quite believe that it is possible to pick up ships that far away.

 

I cant say if it has those capabilities, its just what was on TV when they were building it, but I do believe that long range detection in the thousands of miles is possible.

[Pilotasso]

Dont think a sub or a warship is among the sounds you can catch that far.

 

Subs usualy lurk within just a few miles to record other military vessels signature.

[bumfire]

You can catch a ship that far only if its padling furiously with a half exposed prop out of the watter. Ships wanting to be silent will have to be much much closer to be detected.

 

Agreed that it wont be picking up say subs or anything designed to be stealthy at that range, but the mere fact that they can hear certain frequencies that far off is nothing but astonishing, I spose all new subs have similar capabilities and similar detection ranges, but being able to hear something 2-3000 miles away really is something, just think back 60/70 years when a couple KM's were the max distance.

 

EDIT:

 

I said Vanguard in my previous post, its not Vanguard, its the Astute Class boats that were said to be able to do that, I got mixed up with the Vanguard Boomer and the Astute hunter subs, vanguard being in service from 1993 and Astute in service last year, and some idiot has crashed it already :)

 

http://www.global-military.com/tag/hms-astute

 

Where it lists Sonar Capability as 3000 miles.

Edited January 27, 2011 by bumfire

[EtherealN]

Range is not normally given by listening. In simple geometry, you don't know when the sound left the target, only when it reaches you, so you can't have the range.

 

AFAIK the Seawolf can do an estimation on range, must be something like signal strength, don't know exactly.

 

http://en.wikipedia.org/wiki/Standard_candle

 

Given, that there is in astrophysics, but the principle should apply:

 

1) You hear the target.

2) You identify the target, and engine RPM through screw sounds

3) You should then know the absolute sound strength of the track.

4) Since you also have the apparent sound strength of the track, you have range.

5) Depending on the sensitivity of your equipment, doppler shifts in the sound gives you closing/receding.

6) Bearing change and your own movement completes the picture and you have target heading.

 

Of course you can get the solution, but you don't get it as soon as when using active sonar, and second, if the target makes changes in course, you have to start from the beginning with your calculation.

 

But you can do this while maintaining EMCON, which is the whole idea of submarines. Sending out a big "hello here I am!" to an enemy is a very bad idea when your platforms entire idea is to be hidden... And normally the only case where a naval formation would change course is either if it is anticipating attack or has reached a waypoint. And all of the steps necessary, assuming that the sonar equipment is sensitive enough (quite classified stuff), are a matter of computation. I expect the errors to be more about various water temperatures and layers distorting the signal in unpredictable ways rather than an inherent inability to get detailed information through passive sonar.

[bumfire]

Yup ethereal, dunno if any of you play dangerous waters, but you can get all the info you need for a stealthy attack from the passive array only, given enough time, no need for a ping, which in most cases isnt needed and is likely to come back and bite you.

[EtherealN]

I haven't played Dangerous Waters, but I know swedish sub commanders tried out Harpoon way back in 95 (that was such a good game), and they seemed to agree with that game's ability of giving good tracks on passive sonar only. (They then proceeded to accidently sink the very submarine they were sitting in IRL with a very hasty attack orders to some aircraft. :D )

 

Was a looong time since I read the article though - I think it was the October '95 issue of High Score.

[asparagin]

Correct, but that is not enough to give you a firing solution, you will further need location, bearing and speed. This equation can be solved when only using passive sonar (you only have bearing and maybe range) if you have enough data.

 

What are we actually debating here?

[Groove]

You can get a perfect firing solution with passive sonar only.

 

Subs use active sonar only as last line of possibilites, because it will instantly give your position away which in war times is equal to being sunk ;)

[sobek]

Given, that there is in astrophysics, but the principle should apply:

 

1) You hear the target.

2) You identify the target, and engine RPM through screw sounds

3) You should then know the absolute sound strength of the track.

4) Since you also have the apparent sound strength of the track, you have range.

5) Depending on the sensitivity of your equipment, doppler shifts in the sound gives you closing/receding.

6) Bearing change and your own movement completes the picture and you have target heading.

 

You might be able to get something out of spectral band specific attenuation also, that is, spectral composition of the signal at range compared to what it would be at close. Although i don't know right now if water is as nonlinear a medium for sound as air is.

[Maximus_G]

Sono buoys are used on helicopters. Ships have their own embeded ones.

Wasn't that obvious?

There are buoys using active sonar technology to detect subs. They are normally used for that purpose, i complex with the other means. They are not something exceptional. A...difference you've found doesn't change that fact!

 

Modern subs and torpedoes dont require a lock on previous to launch

...Torpedoes can be guided by cable before their own sensors can achieve a lock on, whats so funny about it??

Well, a "lock on previous to launch" when it comes to torpedoes is #$%ing ridiculous, they're LOAL since WWII :music_whistling:

[EtherealN]

Good point sobek, didn't think of that.

[Groove]

Wasn't that obvious?

There are buoys using active sonar technology to detect subs. They are normally used for that purpose, i complex with the other means. They are not something exceptional. A...difference you've found doesn't change that fact!

 

 

Well, a "lock on previous to launch" when it comes to torpedoes is #$%ing ridiculous, they're LOAL since WWII :music_whistling:

 

Yes, it's always LOAL, but basically you feed it with as accurate data as possible before launch. Usually you turn it onto "Pitbull" mode quite some time after it left the tube, for example if you need to get it through a termal layer.

[asparagin]

Although i don't know right now if water is as nonlinear a medium for sound as air is.

 

This ->

 

I expect the errors to be more about various water temperatures and layers distorting the signal in unpredictable ways rather than an inherent inability to get detailed information through passive sonar.

 

Salinity plays also a role. That is why it is difficult to get an exact range. And as stated before, not all subs are carrying the hardware to do this.

[EtherealN]

Difficult to get exact ranges, sure. But you don't need to know whether the other guy is 512km away or 546km away - in both cases it's just too far away for a shot.

 

When the target track is close enough for a firing solution, all those variables have diminished dramatically. Especially since you do not need an exact track. You need a track with good confidence of the torpedo being able to find the target once it goes active, and you are obviously able to give it updates as you go along.

 

And sure, maybe not all subs can do it, and different types will have differing success, but I haven't heard of an attack submarine this side of the 70's that is unable to effectively prosecute a target while relying on passive sensors only. Obviously a lot depends on which target it is - an Ohio or Gotland would obviously be harder than the Jahre Viking, but in those cases I'm not sure you are better off starting to work with active sensors - if you aren't already dead they probably don't have a solution on you, so why help them unless you are really desperate? :P

[Case]

Given, that there is in astrophysics, but the principle should apply:

1) You hear the target.

2) You identify the target, and engine RPM through screw sounds

3) You should then know the absolute sound strength of the track.

As with astrophysics, all the uncertainty is in calibrating point 3. Getting absolute sound strengths is probably very hard an may be very dependent on the aspect of the target sub with respect to you. Add in the fact that range goes quadratically and any uncertainty in the absolute strength will dramatically increase the uncertainty in the range.

 

So yes, in principle this is possible, but in practice there will be very many caveats.

[asparagin]

but in those cases I'm not sure you are better off starting to work with active sensors - if you aren't already dead they probably don't have a solution on you, so why help them unless you are really desperate? :P

 

I'm quite sure using active sonar is a bad call. If you are a sub. It's giving away your main advantage.

If you are OHP, different story. Your target sub knows already you are there, because you are a lot noisier then a sub, so there's no reason why not to use the active sonar. And I think for this, they are looking for cloaks.

[bumfire]

Obviously a lot depends on which target it is - an Ohio or Gotland would obviously be harder than the Jahre Viking :P

 

LoL, that Jahre viking is some slippery target, really quick and stealthy and can turn on a dime to evade torpedo's. :lol:

[EtherealN]

As with astrophysics, all the uncertainty is in calibrating point 3. Getting absolute sound strengths is probably very hard an may be very dependent on the aspect of the target sub with respect to you. Add in the fact that range goes quadratically and any uncertainty in the absolute strength will dramatically increase the uncertainty in the range.

 

So yes, in principle this is possible, but in practice there will be very many caveats.

 

Agreed, but it's not like a submarine has to compute firing solutions over millions of light years. Now obviously I'm not a sonar operator so I don't know the real limitations exactly, but I have a hard time thinking that this will be a problem considering the relatively limited range of torpedoes compared to the detection ranges of passive sonar.

[RIPTIDE]

Too many SH4/5 players here. :D

[Pilotasso]

Never tried them, or any other for that matter. :)

 

My coments come from a local navy forum.

[Case]

Agreed, but it's not like a submarine has to compute firing solutions over millions of light years.

That doesn't matter. The relative uncertainties are the same size...

[EtherealN]

Relative, yes - but shorten the range and you end up at a place where you can launch a LOAL weapon.

[Case]

Relative, yes - but shorten the range and you end up at a place where you can launch a LOAL weapon.

As the uncertainties are relative, this is obviously true.

[LordWolf]

Too many SH4/5 players here. :D

Sh3 is far better than both of those two combined :P

[raynor]

For US submarines passive SONAR can only provide bearing to the target, everything else after that is obtained from repeated recordings of the same target to get speed, range, target bearing, and target course. Submarines do not "lock" targets they simply have a fire control party that gets the ADCAP to a specific area ( since it is wire guided ) and the ADCAP will take care of the rest as it has a high freq sonar array built in for terminal guidance. If active sonar was required SSBN's wouldn't even carry torpedoes because they are not equipped with any HF arrays.

 

The US wants to lease a Gotland class submarine because it is diesel and because our most current threat ( china ) has a lot of diesel submarines. A crucial part of any submarines work up trials is submarine to submarine combat against your expected foe.