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Old 05-10-2019, 11:10 PM
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How strong is the glass window on military submarines?


Assuming that what I am seeing is, in fact, a window (for instance, submarine here) - how strong is the glass used, and is it a weak point compared to the rest of the steel hull, at the pressure of depth? Does a crewman go there to look out the window from time to time, especially if near or on the water's surface?
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Old 05-10-2019, 11:18 PM
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The sail is flooded when submerged, so the glass doesn't have to be very striong.
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Old 05-11-2019, 10:37 AM
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The sail is flooded when submerged, so the glass doesn't have to be very striong.
I don't understand your explanation because I don't know what you mean: "The sail is flooded when submerged". Can you please explain?

TIA
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Old 05-11-2019, 10:39 AM
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The sail fills with water when submerged, so is only accessible when the sub is surfaced.
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Old 05-11-2019, 10:42 AM
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Sorry, missed the edit window. Since the sail is full of water at the same pressure as the surrounding ocean water, the glass doesn't need to be very strong.
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Old 05-11-2019, 10:45 AM
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What I'm getting at is, what is the SAIL? is it the conning tower? or what? I'm not connected with the military so I don't know these terms.
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Old 05-11-2019, 10:48 AM
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The sail is the structure sticking up out of the main hull of the submarine. At least the space immediately behind the windowed area is open to the sea (I can't imagine the whole structure is) so, when the sub submerges, water of equal pressure is on both sides of the glass. No pressure difference, no particular strength is needed.*

Imagine submerging a box made of window glass vs. simply dipping a pane of glass in the water.

*Enough strength to withstand pressure due to the sub's motion in the water would be needed but that's much lower than the difference between water at n-meters depth and an air-filled space behind.

ETA: The conning tower is generally contained in the sail but is not necessarily the whole sail.

Last edited by DesertDog; 05-11-2019 at 10:50 AM. Reason: I'm a slow typist
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Old 05-11-2019, 10:51 AM
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DesertDog, thank you for your patience with my question and giving me an answer I understood.
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Old 05-11-2019, 11:46 AM
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ETA: The conning tower is generally contained in the sail but is not necessarily the whole sail.
What's the difference?
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Old 05-11-2019, 11:48 AM
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It's possible to design a window to withstand the pressure if they really needed to. This submersible has a huge window and can go down to 3900 ft, deeper than most military submarines.
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Old 05-11-2019, 11:50 AM
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Per Wiki:

As improvements in technology allowed the periscopes to be made longer it became unnecessary to raise the conning station above the main pressure hull. USS Triton (laid down 1956) was the last American submarine to have a conning tower. The additional conning tower pressure hull was eliminated and its functions were added to the command and control center. Thus it is incorrect to refer to the sail of a modern submarine as a conning tower.
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Old 05-11-2019, 11:54 AM
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[ninja'd]

Last edited by Walken After Midnight; 05-11-2019 at 11:55 AM.
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Old 05-11-2019, 12:02 PM
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Why does a submarine need a sail, anyway?
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Old 05-11-2019, 12:25 PM
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Beats rowing.
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Old 05-11-2019, 12:33 PM
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Originally Posted by beowulff View Post
The sail is flooded when submerged, so the glass doesn't have to be very striong.
This is the right answer.
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Old 05-11-2019, 01:30 PM
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It's possible to design a window to withstand the pressure if they really needed to. This submersible has a huge window and can go down to 3900 ft, deeper than most military submarines.
Yes but that may not fair well with underwater explosives.
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Old 05-11-2019, 04:29 PM
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Beats rowing.
Seriously, though. Why does a submarine even need a superstructure? Why can't it just be a smooth, symmetrical cylinder? Seems to be that taking the lump away would make it more hydrodynamic and stealthy. So what's it there for?
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Old 05-11-2019, 04:35 PM
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Seriously, though. Why does a submarine even need a superstructure? Why can't it just be a smooth, symmetrical cylinder? Seems to be that taking the lump away would make it more hydrodynamic and stealthy. So what's it there for?
It could be as you say.

The reason is to have something that sticks well out of the water when surfaced.

If it was a bullet shaped tube no one would be able to exit the sub except in the calmest of water.
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Old 05-11-2019, 05:31 PM
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Okay, let's go one step further. Why doesn't the lens in the periscope implode? Is the periscope pressurized with the rest of the sub, or is the lens just that tough? How about the beacon, etc.?

Last edited by Kent Clark; 05-11-2019 at 05:31 PM.
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Old 05-11-2019, 06:32 PM
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Okay, let's go one step further. Why doesn't the lens in the periscope implode? Is the periscope pressurized with the rest of the sub, or is the lens just that tough? How about the beacon, etc.?
Periscope lenses are pretty thick and tough and aren't likely to implode. Besides, nowadays periscopes are replaced with electronic masts that basically have "cameras on a stick"

The periscope was an incredible piece of engineering -- it wasn't just a lens at the top and a lens at the bottom with a couple of mirrors to redirect the light. That whole tube was crammed with relay lenses and the like. Each lens had to be anti-reflection coated, or else Fresnel losses at that many surfaces would cause all the light to be reflected away.

Add to that the fact that if you use a periscope while the sub is underway it will be pushed backwards by the drag of the water. This can cause the whole thing to go out of alignment. And that at all times you want to avoid humid air from inside the sub getting into the periscope tube as well as water from the outside -- because if those intermediate lenses fog up you won't be able to see anything. So they pack dessicants in there, too.

A lot went into classic periscope design. Even though the periscope was invented before submarines became practical (they were used to see above the tops of military trenches without getting shot), it was a long time before all the problems were addressed. No wonder Jules Verne didn't put a periscope on his [Nautilus.
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Old 05-11-2019, 10:05 PM
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Also, there is wide variation in whether or not you put windows in the sail. In this other class of sub, you may notice, the sail itself is windowless so while surfaced the watch-standers (and smokers) get to poke their heads above the top old-style, with a pop-up barrier to keep them from getting splashed too badly. Meanwhile in the OP sub you can see that you have that going on at the very top, plus then the level with windows immediately below, probably to accommodate surfaced watch standing in bad weather.
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Old 05-11-2019, 10:26 PM
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The dorsal fin of marine animals helps stabilize the animal against rolling, as well as assisting in sudden turns. Does a submarine's "sail" - called a "fin" in European/Commonwealth usage - assist the submarine at all in these areas?
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Old 05-12-2019, 12:40 AM
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It could be as you say.

The reason is to have something that sticks well out of the water when surfaced.

If it was a bullet shaped tube no one would be able to exit the sub except in the calmest of water.
When does a modern nuclear sub ever need to surface outside a dock?
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Old 05-12-2019, 03:53 AM
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Also, there is wide variation in whether or not you put windows in the sail. In this other class of sub, you may notice, the sail itself is windowless so while surfaced the watch-standers (and smokers) get to poke their heads above the top old-style, with a pop-up barrier to keep them from getting splashed too badly. Meanwhile in the OP sub you can see that you have that going on at the very top, plus then the level with windows immediately below, probably to accommodate surfaced watch standing in bad weather.
The Russians will often need their lookouts to have protection from the elements in Murmansk and Vladivostok. The American donít at Pearl Harbour and even at Groton or Norfolk, a heavy jacket and mittens will suffice.
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When does a modern nuclear sub ever need to surface outside a dock?
As stated the tower is for the lookouts. Subs will need to surface when the local water depth in insufficient for safe underwater operations, like in coastal areas, straits or when transiting canals.
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Old 05-12-2019, 04:35 AM
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As stated the tower is for the lookouts. Subs will need to surface when the local water depth in insufficient for safe underwater operations, like in coastal areas, straits or when transiting canals.
Why not just put some cameras on retractable mast? Why do you need Mark 1 eyeballs up top?

Also, do missile subs ever enter shallow waters? Why? Isn't staying hidden their number one priority?
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Old 05-12-2019, 08:47 AM
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Why not just put some cameras on retractable mast? Why do you need Mark 1 eyeballs up top?



Also, do missile subs ever enter shallow waters? Why? Isn't staying hidden their number one priority?


1. Heck if I know, ask the Navy. But I suppose same reason surface vessels don’t go to just 360-round cameras fed to the command room and still have topside lookouts - redundancy and, it is hoped, human ability to recognize something wrong. Even then they don’t always manage to prevent the Loud Crunching Sound.

2. Nearing and entering port. Which in turn means you may be around traffic, in a low-profile dark vessel so the more you want to see them in time.
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Old 05-12-2019, 08:51 AM
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What's the difference?
The sail is the whole thing sticking above the hull. The conning tower is (was, actually) the part where the people lived. The rest of the sail was filled with stuff that didn't mind getting wet.
Quote:
Originally Posted by Wiki
As improvements in technology allowed the periscopes to be made longer it became unnecessary to raise the conning station above the main pressure hull. USS Triton (laid down 1956) was the last American submarine to have a conning tower. The additional conning tower pressure hull was eliminated and its functions were added to the command and control center. Thus it is incorrect to refer to the sail of a modern submarine as a conning tower.
If you read the whole article I linked to, you'll find that surface ships had a conning tower too, once upon a time. It was just not as obvious, being buried in the superstructure.
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Old 05-12-2019, 09:49 AM
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The periscope was an incredible piece of engineering -- it wasn't just a lens at the top and a lens at the bottom with a couple of mirrors to redirect the light. That whole tube was crammed with relay lenses and the like. Each lens had to be anti-reflection coated, or else Fresnel losses at that many surfaces would cause all the light to be reflected away.
Periscope engineering was indeed a highly developed art. I have looked through the periscopes of https://www.historicdockyard.co.uk/s...s/hms-alliance and the optical quality and the brightness of the image were stunning.

In a different league from ordinary binoculars etc.
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Old 05-12-2019, 02:31 PM
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The sail is the whole thing sticking above the hull. The conning tower is (was, actually) the part where the people lived.
Illustrated here. Above the conning tower were the exposed topside bridge, from which you drove the boat while surfaced, and masts for antennae, periscopes etc.
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Old 05-12-2019, 02:45 PM
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It's possible to design a window to withstand the pressure if they really needed to. This submersible has a huge window and can go down to 3900 ft, deeper than most military submarines.
Even our favorite, "two men, for twenty minutes," submersible, the bathyscaphe Trieste, had a window. It was a conical piece of Plexiglas 4.5 inches in diameter, and 5.9 inches thick. And it still famously cracked at about 31,000 feet deep during Walsh and Piccard's trip to the Challenger Deep.
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Old 05-12-2019, 03:38 PM
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Also, do missile subs ever enter shallow waters? Why? Isn't staying hidden their number one priority?
Since you said missile subs, the Russians do , or at least did for their bastion patrols. They would be entering shallow waters in a mine field, so the boomer would be riding higher.

Older generations of Russian boomers used the sail for housing the SLBM's.
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Old 05-12-2019, 03:55 PM
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Also, do missile subs ever enter shallow waters? Why? Isn't staying hidden their number one priority?
I read Big Red: Three Months on Board a Trident Nuclear Submarine by Douglas Waller not too long ago; the process of coming out of the submarine base at King's Bay here in Georgia is apparently fairly tricky (and definitely involves threading their way through some narrow and shallow channels). I would imagine the naval base over in Bangor, Washington (the other base where U.S. ballistic missile subs are home-ported) requires similar maneuvering. It's only after they're out to sea that they dive, and vanish.
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Old 05-13-2019, 07:01 AM
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Here's an idea: instead of a big, useless sail, bolt a cherry-picker onto the sub instead. Just get a guy to stand on a platform, have a hydraulic crane lift it up 10-20 feet, et voila - you've got a lookout.
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Old 05-13-2019, 03:29 PM
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What? No one is asking about the huge windows on the Seaview?
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Old 05-13-2019, 04:00 PM
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Seriously, though. Why does a submarine even need a superstructure? Why can't it just be a smooth, symmetrical cylinder? Seems to be that taking the lump away would make it more hydrodynamic and stealthy. So what's it there for?
It gives you a place to put antennas, periscope masts and the like that need to be above the waters surface to work correctly. A place that produces a less wake and is less obvious than the main body of a submarine.

Also, I know ordinary pleasure yachts are a lot easier to manuever from the upper bridge (which is ~10 feet above the normal bridge). I imagine the same is true for military subs.
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Old 05-14-2019, 12:58 AM
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What I'm getting at is, what is the SAIL? is it the conning tower? or what? I'm not connected with the military so I don't know these terms.
google "submarine sail"

It takes about 3 seconds.
Which is much, *much* less than showing your ignorance here.

Last edited by MarvinKitFox; 05-14-2019 at 12:58 AM.
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Old 05-14-2019, 01:55 AM
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Quote:
Originally Posted by MarvinKitFox View Post
google "submarine sail"

It takes about 3 seconds.
Which is much, *much* less than showing your ignorance here.
Telling someone to google something is not acceptable in GQ.

Maybe you should have taken a few seconds to read the General Questions FAQ:

Quote:
Originally Posted by General Questions FAQ
By the same token, we aren't interested in hearing about how stupid the question was because a search could have answered the question. Nor are we interested in hearing how simple it was for another poster to find the answer in a search engine. If it's that simple to find the answer, go ahead and post the answer.
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Old 05-14-2019, 09:15 AM
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google "submarine sail"

It takes about 3 seconds.
Which is much, *much* less than showing your ignorance here.
Oh Marvin, I don't mind showing my ignorance. I AM a civilian and an old lady, and I don't mind asking questions; that's how you learn things (except--in your case--manners, it would seem).
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Old 05-14-2019, 09:56 AM
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Oh Marvin, I don't mind showing my ignorance. I AM a civilian and an old lady, and I don't mind asking questions; that's how you learn things (except--in your case--manners, it would seem).
ETA: Maybe this is the part of the FAQ's he didn't read:

We have one guiding principle: Don't be a jerk.
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Old 05-14-2019, 10:47 AM
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(except--in your case--manners, it would seem).

Made me laugh!

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Old 05-14-2019, 11:48 PM
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Just to pile on; the OP photo is a Russian submarine My understanding is that the weather around Murmansk (their only European ocean access ice free port) gets cold, wet, and windy. And rough. US submarines don't go for the enclosed conning station anymore because even New England and Pacific NW weather is comfy by comparison.
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