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

[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 gives the maximum operating depth of the Los Angeles class as 650 feet (200 m),[9] while Patrick Tyler, in his book Running Critical, suggests a maximum operating depth of 950 feet (290 m).[

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.