Stealth submarine shaping - Type-212CD, etc

[covert_shores]

Hi, starting to put some info out there about the Type-212CD and other 'stealth shaped' submarines. You'll actually see similar lines in other submarine classes of certain countries

Radical New Stealth Submarine, Type-212CD, Will Be Much Larger - Naval News

Submarines rely on stealth to maintain the element of surprise and escape threats. For decades this has focused on reducing the noise emitted by the submarine. A resurgence of using active sonar to locate submarines now means that new stealth measures may be required. German submarine builder...

www.navalnews.com

 

[covert_shores]

Dreadnought maybe, a bit?

 

[Foo Fighter]

A common theme for future submarines has been going totally sail less. That or extendable types. Would it make the hull stronger in that area if the hull form was to have greater circumferende to allo the sub to ride higher and achieve the same effect as a sail/conning tower?

 

[covert_shores]

I am better that most submarines won't be sailless, although some might (not Chinese experimentation in that area, and US stated interest).

 

[Dilandu]

Hm. Wouldn't such shapes of submarine hull conflict with laminar flow, thus essentially cancelling the whole advantage?

 

[Volkodav]

Interesting.

I wonder if this design owes anything to the feed back from the Australian submarine program in which the Germans were advised their design was deficient in terms of acoustic signatures.

 

[kagemusha]

Here there's a paper by Thyssenkrupp Marine Systems (TKMS) about stealth-shaped submarines.

https://pub.dega-akustik.de/ICA2019/data/articles/000046.pdf

 

[Cjc]

Lockheed definitely considered it back in the 80's although the navy didn't really like the design

http://www.hisutton.com/Lockheed-Stealth-Submarine-Design.html

Interestingly enuff this wasn't the first time Lockheed worked on a sub project, they were part of the "aircraft" sub concept back in the 50's (aircraft in this case meaning number biult not the aircraft carrier sub concept) with there design being called empire.

 

[quasar61]

Interesting.

I wonder if this design owes anything to the feed back from the Australian submarine program in which the Germans were advised their design was deficient in terms of acoustic signatures.

Stealth shape and acoustics are two different things. In this regard, Australia cited the 216-class freestanding propeller as one reason, but the real reasons are more political, as Australia was really looking for reasons why they should not be German or Japanese boats. Ultimately, Australia also found political reasons to give France the boot.
Stealth technology was considered by tkMS (HDW) as a variant for the Type 800 as early as around 1997. This variant looked very similar to the current form for 212CD.

 

[Scott Kenny]

Pardon me, the "Similar Threads" sidebar brought me here...

A common theme for future submarines has been going totally sail less. That or extendable types. Would it make the hull stronger in that area if the hull form was to have greater circumferende to allo the sub to ride higher and achieve the same effect as a sail/conning tower?

Before the Virginia class and the fiber-optic "photonics mast" periscope, it just wasn't possible to go without a sail. The traditional periscope is a single tube that is however long. Hull diameter, maybe plus some. It doesn't telescope, it's just 40ft long or whatever. It gets raised by hydraulic power to bring the eyepiece end up to the control room, and then stick up however far that is above the top of the sail.

So there are 5 holes in the hull under the sail. 2 for the periscopes, one for the bridge access hatch, Snorkel Mast (air in), and diesel exhaust (air out). The periscope holes are tiny in comparison, maybe 10"/25cm across.

You're not getting rid of the other 3 holes. You have to be able to get up to the top of the sail, that's where the bridge is on the surface. You have to have the snorkel mast to take air into the boat. And you have to have the diesel exhaust to get air out.

On something like a Virginia-class, the Snorkel Mast is 18" in diameter, exhaust is less than that. On an Ohio-class, the snorkel mast is a 36" diameter hole in the hull...

 

[Scott Kenny]

Hm. Wouldn't such shapes of submarine hull conflict with laminar flow, thus essentially cancelling the whole advantage?

I don't believe so in practice, submarines very rarely move with a significant "angle of attack" relative to the flow of water.

But it would have to be examined for interactions at 0-10deg positive and negative angle of attack for sure. If a sub is doing more than a 10deg bubble, you no longer care about noise. Less than that, you'd be at periscope depth in bad weather or heading deep.

 

[TomS]

Before the Virginia class and the fiber-optic "photonics mast" periscope, it just wasn't possible to go without a sail. The traditional periscope is a single tube that is however long. Hull diameter, maybe plus some. It doesn't telescope, it's just 40ft long or whatever. It gets raised by hydraulic power to bring the eyepiece end up to the control room, and then stick up however far that is above the top of the sail.

CONFORM thought otherwise and proposed a sail-less sub with hinged rather than telescoping masts and periscopes, and even a retractable conning bridge. Might not have been practical but it wasn't immediately rejected.

Edit: Wow, clearly the wrong link there! Try this one:

https://www.secretprojects.co.uk/threads/us-navy-conform-submarine.7792/

 

[A Tentative Fleet Plan]

CONFORM thought otherwise and proposed a sail-less sub with hinged rather than telescoping masts and periscopes, and even a retractable conning bridge. Might not have been practical but it wasn't immediately rejected.

Are we sure they would be conventional periscopes for the sail-less variants of CONFORM? I know the SUBIC program (which predated CONFORM and was associated with a much more ambitious program for various submarine designs planned for FY65, which were initially intended to use small, lightweight reactors derived from the nuclear-powered aircraft program) looked at television periscopes. Given that one of the planned innovations intended for CONFORM was the combat system and sensors, perhaps some of that earlier SUBIC work survived to be part of CONFORM?

Certainly later on, the CONFORM design seems to have also looked at conventional sails, either Thresher or Sturgeon-sized.

 

[TomS]

Are we sure they would be conventional periscopes for the sail-less variants of CONFORM?

Nope. I suspect they would have been cameras (what we'd nowadays call an optronics mast). Running an optical path through a hinge like that (while holding against pressure) would have been nightmarish. My point was just that they had already explored ways to do without a sail.

 

[Scott Kenny]

Nope. I suspect they would have been cameras (what we'd nowadays call an optronics mast). Running an optical path through a hinge like that (while holding against pressure) would have been nightmarish. My point was just that they had already explored ways to do without a sail.

I mean, the Virginia class run a fiber optic through the mast, which would be easier to deal with. When did optic fibers really start being used? *wikidive* Looks like there were fiber optics being used in the Apollo cameras in 1965, so a folding periscope based on fiber optics would absolutely be an option for the CONFORM subs.