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Pressureized Scope? - How do they do that..

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Postby Robse » Mon Jul 21, 2003 6:03 pm

Hi, all.

I was just wondering: A sub diving to a depth of about 1000 ft. is subjected to an enourmes pressure on the hull. I can understand how the pressure is held back by the several inch's of steel, hull shape etc, but....

How in the world is the scope keept tight? You have a metal tube, fitted with a piece of (thick) glass, and still the water does not enter. I can imagine that it's quite some job getting the glass and the metal tight, as the temperature expansion ratio's are different for the two materials, and yet it's gotta be tight. I can't imagine a water filled scope, as this would distort the image too much, and I can't imagine that the scope is at full pressure at all times, even when surfaced, as this would cause the same problem on the surface as when dived down, only the other way around. (The new Virginia class uses a CCD-TV scope, so this only applies to old fashioned scopes....I guess.)

Is the scope pressureized (and adjusted to match depth) when diving, with either normal air, or some kind'a gas? Or is the scope 'stowed' behind a pressure hatch when diving? How is dew prevented? Hope this is not silly Q's, but this sub technology is really getting interesting...

Anyone?




Edited By Robse on 1058825188
Yours Sincerely, Robert Holsting, Denmark
1/81 SSBN Ohio Class scratch builder, more at www.robse.dk

"Never be afraid to try something new; remember that it was amateurs who build Noah's Ark, and professionals who build the Titanic"
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Postby Seahawk » Mon Jul 21, 2003 9:56 pm

I'm not sure on the answer but I found this on a website while doing a quick search.

"2B1. Importance of watertightness. When periscopes are assembled at the factory, the greatest care is used to make sure that the contained nitrogen-air mixture is absolutely free of moisture. A periscope, when new, is charged with dry nitrogen-air mixture at a pressure of 7 1/2 psi and -50 degrees C to -69 degrees C dewpoint. Since the optical qualities of most of the periscopes presently in use are excellent, there is usually no reason for opening the periscope unless water enters. "

It came from an online WW II US Submarine Periscope Manual so it should probably have more information then what I quoted. Here's the link:


Submarine Periscope Manual
SubCommittee #2508
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Postby Robse » Thu Jul 24, 2003 9:20 am

Thanks, SeaHawk! There's all the answers. :D Pretty impressive tool, a scope..

Thx again, Sir.
Yours Sincerely, Robert Holsting, Denmark
1/81 SSBN Ohio Class scratch builder, more at www.robse.dk

"Never be afraid to try something new; remember that it was amateurs who build Noah's Ark, and professionals who build the Titanic"
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Robse
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Location: Denmark/Europe


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