Diving Depth- how common do modern subs go really deep- and how useful is it?

[tippership]

Been thinking about this since my Sub Command days(i only just transitioned to DW) -


In -game , the subs can go pretty deep...well, the 688I's are a bit lacking compared to the others, but that's one of the faults of lots of stuff, from rickover's philosphies, to HY-80 being used, costs.....etc,etc....


Anyway, the Akulas and Seawolves can dive pretty deep- so can subs like Alfas....

Not everywhere in the ocean can you get 2000 ft deep onwards..

but in a blue water mission, or just in areas where the ocean is that deep- how often would a modern skipper decide to travel that deep?

It surely IS harder to pick up a seawolf running at 2000+ ft deep
- and while it is probably a bit risky travelling near crush depth- i'd think there'd be advantages, like if you go at full or plus speeds, it's hardest to detect you- and even harder to shoot at you. Not all moderm torpedoes can go that deep , although many can...

And in a shooting gallery- why not operate at deep as possible?

Going deep stresses the hull , but there are still some very serious advantages to moving like that, right?



Seems to me, it'd be a good idea to design a advanced sub that uses titanium/HY 100 steel or greater (I know brittleness starts to become a factor ..)and can sit at 3000++, or ....let's shoot for the stars...5000 ft deep or so (Now he can say hello to DSRV's at 5000 ft in their face before blowing them up for the lulz :yeah: )
- and engage subs or surface ships with near impunity if not actual impunity due to hostile torpedoes not being able to operate in this range.(Adcaps and 65 CM's have depth limits- and adcaps were built to be able to chase Alfas, but go past 3500 ft into DSRV territory and they're done)
or them being able to detect you, for that matter.

You'd need special torpedoes built to operate at these depths- but that'd come with the sub..

the volume of water would also start to hamper your own sensors detecting things- but if thermal layers occur deeper than 2000 ft anywhere in the ocean and don't level off permanently after a depth point at one degree , and stay that way all the way down to ...marianas 30,000 ft levels - It'd be one easy way to travel silent, no?
And someone actively pinging away with a mil sonar isn't finding you at those depths no matter what he does, almost.


Finally, how often do YOU take your sub in DW/SC deep?
Do you flirt with crush depth a lot?




Hm...shooting at a DSRV's.....at 5000ft deep...at his depth level... :har:

[Dr.Sid]

Usually there is no reason to go deep. To go bellow layer yes. But deeper ?
With peace time missions there are also safety margins. If you are near max depth, you cannot recover from flooding or controls jam that easily. Emergency blowing is way slower at high depth, and so on.
You would use maximum depth when evading threats you know about. As for weapons, I have no idea, but I guess that it's easier to make torpedo run well at large depths, than it is to make a sub operate there.

[Nexus7]

I played with crush depth yesterday, with the Kilo. Basiclly i went deeper and deeper until message informing me we are approaching crush depth. The silly idea was to reproduce a situation similar to K-18 movie test trials, as said, silly idea.
Layer and cavitation depth are the factors i care for. SPP too, but that's a complex topic and I lack the theorical fundamentals to make maximal use of it.
Dunno if sitting on the bottom can help somehow.

btw Dr. Sid, how's your project on sub simulator going?

[tippership]

Usually there is no reason to go deep. To go bellow layer yes. But deeper ?
With peace time missions there are also safety margins. If you are near max depth, you cannot recover from flooding or controls jam that easily. Emergency blowing is way slower at high depth, and so on.
You would use maximum depth when evading threats you know about. As for weapons, I have no idea, but I guess that it's easier to make torpedo run well at large depths, than it is to make a sub operate there. That bit about emergency blowing being slower at deep depths is a bit...surprising. Seems to run counter to what one might expect....:hmmm:

I woonder if there's more than one layer one would encounter as they go deeper and deeper.


Doing some research on this- (of course there's little info on these boats)-

Alfa's are rumored to be 900 m capable with some account of a captain of one of them taking his boat down to 3000 to regularly lose tailing 688I's and make them look like a extreme joke - but Alfa's seem to be actually in the 700 m range give or take..

Sierras... seem to crush at 900 m + - the 3000 ft regime- that's the limit of ADCAPs- and they're still active.

There was that one Mike class boat which could hit the 4000s ...and would crush at 5000- that had the accident..

Since the Sierras are STILL running around even now- I figure it's reasonable to assume the Russians aren't going to forsake the idea of building more deep diving subs- and if they build another in the vein of the Sierra/Mikes...

Well, for one- wouldn't they routinely take advantage of their deep diving capability? I wonder how well you could shadow a US CVBG from a mile deep... And they don't need to zoom around at 40 -50 knots that deep- they could with impunity, but if they don't -they aren't getting detected unless they go right over a SOSUS relay. And, detection is all you could even do at that.

the other thing is- It makes me wonder what in the world the US would do in a fight with something like this. The 688's and I's have already been a bit...outmanuevered by Alfas reportedly...but against Sierras and Mikes at a depth like that- the Virginas (being Littoral orientated)couldn't hack it, and the Seawolves which can go almost half a mile deepif they're feeling risky - have the best chance of detecting and intercepting one i suppose , but their ADCAPS don't play a mile deep. :nope:
- In a deepwater fight , wouldn't we be screwed beyond belief going up against boats like this? Just sit out of ADCAP range and lob torpedoes ? Of course, being able to move 40-50+ knots is almost just as good, and when combined with that depth- makes you untouchable. And you're harder to detect at all speeds, if you are even detectable at all.


This reminds me of the capability effects of fighter planes right now, in that the SSN21's are similar to F-22's and the SSN 774's are similar to F-35's in that they have advanced capabilities, but our :cheaper: alternative can't match up for certain reasons or in a shooting war won't have the efficency of the more advanced platform, while the more , expensive weapon can rule the day, but is hyper-limited in numbers(although that's where the comparisons end, as you can somewhat-easily choose to toss a IRST on a F-22 and it's efficency rises to the best on the planet against its peers which are also low-observable, whereas I don't ?think? They could take the SSN21's and refit them to be able to dive a mile+ deep.


..Maybe we do need to think about DSRV's with ADCAPs strapped to them heh.... or on a more serious note, plans for when we get out of a littoral focus and the Virginas are done, for a Seawolf successor that can chase these boats down to a mile deep and beyond.

..Now i'm curious what yield steel it'd take to match the Ti boats of the Russians...Best we have are the HY-100 Seawolves ..might be time to seriously consider titanium. OR a blend

[Dr.Sid]

Even with mile deep .. sub game is mostly 2D game. 1 mile away from enemy is WAY too close. And if you are 10 miles from enemy, 1 mile up or down wont do much difference. So from geometry point of view, there is no real sense.
Getting under the layer is important .. but layer is usually a lot shallower. And if it is deep, it's not so strong.
With mile of depth and so you could reach isothermal water, where lies the main speed of sound minimum and where strong sound channel is formed. That can be good for listening, but bad for your own stealth.
For preventing cavitation depth is good.
As with buoyancy .. you should not think that since the pressure is huge, the sub will be 'expelled' from water more. It is the case in air, but that's because air also changes density with pressure, while water for all practical purposes does not. On the other hand the submarine will be squeezed a bit at large depth .. which lowers it's volume, which actually lowers buoyancy. Sub trimmed neutral at periscope depth will want to sink near crush depth.

As for the blow .. HP air is stored in fixed volume pressure bottles. When they are full, the pressure is usually around 300 atmospheres. That is pressure at depth 3000 meters.
At 100m, the ratio of bottle pressure and water pressure is 300:10 or 30:1 .. and the tanks can be blown as long as there is at least 10 atmospheres, or 3% of air in the bottles.
At 1000m, the ratio of pressure is only 3:1, and you can blow air into the tanks only if there is at least 100 atm in the bottles, ie. at least 33%.
This difference in ratio means, that:
1) air will fill tanks a lot slower, even given volume at 1 atmosphere.
2) because of the outer pressure, the air will be compressed 10 times more, so for every cubic meter of air volume you have to pump 10 times more air in. So the speed of getting 'free buoyancy' can be 50 or more times slower near crash depth. There might not even be enough air to empty the tanks completely at crush depth. Air will expand during ascent, and any excess air will eventually leave the tanks through lower openings, but you want to leave the large depth ASAP. Because ..
3) With any leak, water will flow in a lot faster at large depth. Maybe not 10 times faster, speed of flooding is rather complex problem, but easily 5 times faster.

Also, as I mentioned, there is problem of controls jam. At periscope depth, if sub controls jam during 5 degree dive at 5 knots, you have relatively lots of time. At least you can blow fast to overcome dynamic forces. You might also be able to fix the problem.
Same things happens near crash depth at 20 knots while diving 20 degrees .. before you know you are beyond crash depth.
So depth does also affect safe speed, and maneuvers.

PS. Oh yes .. my poor subs. Well it's not officially dead at all. I'm doing minor stuff on it. But it's more like to keep it up to date with my computer. I don't have much time for it at the moment. There also seem to be little concern really. As the progress is scarce, I moved the project on facebook, it's easy to find, so I suggest you join it there, to be in touch. There is some progress on active sonar, which proved a bit more complicated then I thought. If I find some time and will, in two weeks of work I could do new release I guess.

[LoBlo]

Even with mile deep .. sub game is mostly 2D game. 1 mile away from enemy is WAY too close. And if you are 10 miles from enemy, 1 mile up or down wont do much difference. So from geometry point of view, there is no real sense.
Getting under the layer is important .. but layer is usually a lot shallower. And if it is deep, it's not so strong.
With mile of depth and so you could reach isothermal water, where lies the main speed of sound minimum and where strong sound channel is formed. That can be good for listening, but bad for your own stealth.
For preventing cavitation depth is good.
As with buoyancy .. you should not think that since the pressure is huge, the sub will be 'expelled' from water more. It is the case in air, but that's because air also changes density with pressure, while water for all practical purposes does not. On the other hand the submarine will be squeezed a bit at large depth .. which lowers it's volume, which actually lowers buoyancy. Sub trimmed neutral at periscope depth will want to sink near crush depth.

As for the blow .. HP air is stored in fixed volume pressure bottles. When they are full, the pressure is usually around 300 atmospheres. That is pressure at depth 3000 meters.
At 100m, the ratio of bottle pressure and water pressure is 300:10 or 30:1 .. and the tanks can be blown as long as there is at least 10 atmospheres, or 3% of air in the bottles.
At 1000m, the ratio of pressure is only 3:1, and you can blow air into the tanks only if there is at least 100 atm in the bottles, ie. at least 33%.
This difference in ratio means, that:
1) air will fill tanks a lot slower, even given volume at 1 atmosphere.
2) because of the outer pressure, the air will be compressed 10 times more, so for every cubic meter of air volume you have to pump 10 times more air in. So the speed of getting 'free buoyancy' can be 50 or more times slower near crash depth. There might not even be enough air to empty the tanks completely at crush depth. Air will expand during ascent, and any excess air will eventually leave the tanks through lower openings, but you want to leave the large depth ASAP. Because ..
3) With any leak, water will flow in a lot faster at large depth. Maybe not 10 times faster, speed of flooding is rather complex problem, but easily 5 times faster.

Also, as I mentioned, there is problem of controls jam. At periscope depth, if sub controls jam during 5 degree dive at 5 knots, you have relatively lots of time. At least you can blow fast to overcome dynamic forces. You might also be able to fix the problem.
Same things happens near crash depth at 20 knots while diving 20 degrees .. before you know you are beyond crash depth.
So depth does also affect safe speed, and maneuvers.

PS. Oh yes .. my poor subs. Well it's not officially dead at all. I'm doing minor stuff on it. But it's more like to keep it up to date with my computer. I don't have much time for it at the moment. There also seem to be little concern really. As the progress is scarce, I moved the project on facebook, it's easy to find, so I suggest you join it there, to be in touch. There is some progress on active sonar, which proved a bit more complicated then I thought. If I find some time and will, in two weeks of work I could do new release I guess.

Excellent explaination. Thanks.

[ACR]

the actual depth ratings for current nuclear subs are classified so we can only use general information .

and we have to clarify what exactly depth rating we are talking , maybe also available data mixes the different depth ratings .

basicly we have :

test depth which has a big margin to the actual crush depth, the margin depends on the different navies . afaik thats the maximum depth which is approved for normal peacetime operations .

maximum operating depth : the maximum depth a sub can operate in extreme combat conditions. afaik this depth results in a high stress and wear on the hull and systems and is so only approved on wartime scenarios otherwise the life expectancy of the hull would be very low.

design depth : the calculated maximum pressure the hull will cope with , but without quarantee the systems on the boat will work and pipelines/ fittings etc will make it . there is also a small margin to the crush depth to cope with hull wear when the boat gets older.
this depth is not approved for any situation

crush depth : well, the depth the hull will be crushed when stressed beyond any limits , also calculated and never ( intentionally ) tested.

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

further i think we talk wrong numbers and the actual depths current subs go are way less.

we can learn from tresher accident. the hull was build from HY-80, so the same like the 688I . and the hull crushed finally at 1300-2000 feet .

http://en.wikipedia.org/wiki/USS_Thresher_%28SSN-593%29

assuming the 1.5 safety factor of the US navy it would push tresher to roughly 800 feet test depth and maybe 1000-1200 feet maximum operating .

with the construction of the los angeles class rickover wanted speed at any cost and finally due to the weight of the massive powerplant he had to reduce hull thickness for saving boat mass to keep the boat floatable at all. he accepted it to keep speed because depth was not that important in his eyes.

build from the same material like the tresher i do not see any chance the 688 can dive deeper and with the hull thickness reduction there are good chances the dive depth of the 688 is lower .

how deep ? its classified , but you see on the internet depth ratings like here :

The U.S. Navy (http://en.wikipedia.org/wiki/U.S._Navy) gives the maximum operating depth of the Los Angeles class as 650 feet (200 m),[9] (http://en.wikipedia.org/wiki/Los_Angeles-class_submarine#cite_note-9) while Patrick Tyler (http://en.wikipedia.org/wiki/Patrick_Tyler), in his book Running Critical, suggests a maximum operating depth of 950 feet (290 m).[ (http://en.wikipedia.org/wiki/Los_Angeles-class_submarine#cite_note-10)

you also see in some sources a statement "max depth 800 feet"

so what ? what if all these depth numbers have some value but were mixed to different ratings ?

my best guess for the los angeles class is the following :

650 feet test depth ( this implies with the 1.5 us navy factor a design depth of 975 feet and crush of 1000-1200 )

800 feet maximum operating

950-975 feet design depth and maybe 1000-1200 feet crush depth .

when we see the HY-80 AND thicker hull tresher crushed at about 1300-2000 feet it seems plausible the crush depth of the 688 might be in the area of 1000-1200 as a rough guess.

when i,m roughly correct the 1475 feet max operating in dangerous waters of the 688 is only a myth . lets also rember max operating is still a good margin away from crush .

there were good statements made that deep diving has nearly no use in military sub operations and the silent and fast 688i is even with a low diving depth a powerful submarine .

best regards !

[Kapitan]

Alfa's are rumored to be 900 m capable with some account of a captain of one of them taking his boat down to 3000 to regularly lose tailing 688I's and make them look like a extreme joke - but Alfa's seem to be actually in the 700 m range give or take..

Sierras... seem to crush at 900 m + - the 3000 ft regime- that's the limit of ADCAPs- and they're still active.

There was that one Mike class boat which could hit the 4000s ...and would crush at 5000- that had the accident..



Heres whats what with the golden fishes

Alfa class project 705 and 705K were built as intercept submarines much like the mig25 foxbat designed to get somewhere fast, the main mission for an alfa is ASUW not anti submarines although yes its capable in the area to a limited degree.
after long time of studying designs and the backgrounds ect the roomer of the Alfas hitting 900m is a spoof, most of the time an alfa would not go below 450m because this caused cracking in their hulls and being a very expensive hull to build the soviets required them to last (hence why the first test boat was launched in 69 and scrapped in 74), the crush depth of alfa would be around 750m maximum operational 550m still deep enough for its role.

The sierras are quite different however again not so much in deep diving maximum operational would be around 650m and crush at 850m again made of a titanium alloy and based of the victor III, most of these boats are experimental Alfa Papa Mike and Sierra classes didn't really take off into a mass production like what we see with the other classes of submarines.

Despite spending a huge amount on defence the soviets couldn't afford to build and maintain large numbers of these boats so they restricted diving depths to extend hull lives, one alfa was still knocking about in 1995 as a test platform and as mentioned the sierras are still about.

The mike class is probably the only true deep diving submarine she did reach 1020m during several tests before she sank, however the cost for diving deep meant that only one submarine was built and later lost to fire in the norwiegen sea.

papa is basically a fast titanium hulled submarine (that the later steel hulled Charlie SSGN are copied from) what most people don't know or realise is that papa is actually faster than alfa and holds the speed record for fastest submarine 44.7knots sustained (alfas can hit 45knots but only in bursts usual maximum cruise speed 41knots)

Only the sierras remain active with the B230 carp a sierra I to be reactivated by 2016.

In terms of the 688 captain following an alfa to put it mildly as captain of the alfa I would have just gunned the throttle its unlikely that the 688 would be able to keep pace.

[Kapitan]

To be honest and answer the second point i don't generally go below 450m in the akula and 200m in the kilo but that said it does depend on the layer depth.

Speed and depth are not too important when stalking the greater the depth the torpedo doesn't even have to hit you and your dead atlaest at 200/300m you have some chance.

In regards to seawolf SSN21 if i remember rightly she is made of HY130 steel much like the UK Astute class this is more cost effective and also easier to maintain and build than a titanium hull.