Stealthier periscopes/masts

[ETR3(SS)]

There's so much here I'm going to have to multi-quote it for my reply to make any sense.

I can imagine that the periscope exterior has the same temperature as the interior of the sail, or slightly warmer (some conductive heating from the sub's interior). And that temperature, in turn, reflects the water temperature of the water layers the sub has travelled through in the recent past. That could be both warmer or colder than the surface temperature at the moment the periscope is raised above the surface. If the temperature of the periscope externals is different from that of the water surface (and due to radiative cooling, it likely will be in a short time even if it started out the same), there will be a detectable contrast for thermal imaging systems.

Ok lets start with this. The sail is a free flood area. Therefor the parts of the periscope outside of the hull are the same temp as seawater. Hence you don't go looking for periscopes using thermal imagery.

Now, if you gave the exterior a capillary network of water pipes where surface water was pumped through continuously at all times when the scope is not in its down position, that would virtually eliminate the temperature contrast, making detection much more difficult.

Scopes + water inside = Bad. This pump would have to be inside the hull, wouldn't work very well outside. So that means two additional hull penetrations. The less hull penetrations the better. Also this pump would be another sound source.

Visual stealth could probably be achieved by covering the exterior with some kind of light-emitting material (fiber optics perhaps?) capable of adapting to the surrounding environment. A detector would record the current light level, color temperature and directional differences, and alter the visual signature accordingly.

To the best of my knowledge James Bond is the only one that has adaptive camouflage available. Also weapons and sensors tech has gotten to the point where you don't have to close to within 1000yds of your target to hit it. So if no one knows you're there, who's looking for a scope in the water?

Finally, radar stealth. Extensive use of RAM, non-conductive materials and careful shaping would probably be able to defeat most radars. Newer, LPI radars specialized in detecting such small objects would be harder to fool, but reducing the strength of returns still limits detection range.

I'm curious to know how much you know about the subject of radar? But if you want to find a periscope using radar, this is what you would use. http://www.raytheon.com/capabilities/products/aps137b/

[bottomcrawler]

Originally Posted by ETR3(SS)

Ok lets start with this. The sail is a free flood area. Therefor the parts of the periscope outside of the hull are the same temp as seawater. Hence you don't go looking for periscopes using thermal imagery.

While it is free flooding, the actual tube is probably thermally connected with the interior, at least partly. If it's made of metal, it conducts heat very well. And as soon as a metal object is raised out of the water, it changes its temperature fairly quickly and rapidly develops a thermal contrast.

I thought that thermal imaging was extensively used to hunt subs in shallow waters.

Originally Posted by ETR3(SS)

Scopes + water inside = Bad. This pump would have to be inside the hull, wouldn't work very well outside. So that means two additional hull penetrations. The less hull penetrations the better. Also this pump would be another sound source.

The pump would not have to be inside the hull per se. It would merely have to be inside the external tube of the periscope. And noise with things out of the water is hardly an issue. Peristaltic pumps are really quiet, and would suit this application well.

Originally Posted by ETR3(SS)

To the best of my knowledge James Bond is the only one that has adaptive camouflage available. Also weapons and sensors tech has gotten to the point where you don't have to close to within 1000yds of your target to hit it. So if no one knows you're there, who's looking for a scope in the water?

Adaptive camo can be made very complicated, but what I had in mind is more of a color/brightness matching to minimize the visual signature.

Originally Posted by ETR3(SS)

I'm curious to know how much you know about the subject of radar? But if you want to find a periscope using radar, this is what you would use. http://www.raytheon.com/capabilities/products/aps137b/

Oh, I know a fair amount. That's why I suggested it. I'm mainly familiar with it within the world of aviation, but the principles are universal. Again, if you reduce the intensity of returns, you decrease detection range.