Project 877/636: Kilo class SSK

Not really.

They don't have two pressure hulls, they have one pressure hull and an outer hull that is flooded and not meant to hold anything out or in.

On the Oscar class SSGNs the gap between the inner pressure hull and the outer hull was where the main Granit missiles were stored... 12 on each side.

The outer hull looks thick but it is sound baffling material.... it is not armour or a pressure hull, it is just the outer skin.

By definition any armour layer that gets penetrated and for the contents of the penetrator to be over 300kgs of HE and the armour actually works against the vehicle by containing the explosion temporarily... intensifying the damage inside and ensuring the entire crew die.

If you want to blow up a tree stump you drill a hole into it and put the charge inside the tree.

If you have to put it outside the tree or object you strap something on the outside for the explosion to push against to damage the thing you are trying to blow a hole through.

For instance to blow a hole through a brick wall you get two flat bits of wood like 4x2s and tape or nail them together in the form of a cross and put plastic explosives at the ends of each of the pieces of wood and put the explosive up against the wall to blow a hole through.

If you were trying to bring down the building with a huge HE charge just open the door and place it in the centre of the building near the structural supports.

Anyway, there is NO one pressure hull WITHIN another, but abreast and on top, as they were constructed to survive a direct hit of US Mk.48 torpedo.

To protect a target from a HE explosion what you need are air pockets. The outer layer of the outer hull carries tiles to reduce noise and the reflection of noise from the outer hull, if they were smart (and they are smart) inside that layer they can have an air pocket and then things like missile tubes or bladders containing ballast water for manouvering and then another air pocket and then the pressure hull if the inner hull.

A blast on the outer hull would crush the outer hull but the air pockets inside would collapse and compress and absorb the blast wave... the way water can't... because water does not compress. In fact the problem is so bad that the US don't use blast HE torpedo warheads any more for their anti sub torpedoes... their anti sub torpedoes for quite some time have been HEAT designs intended t blow a small hole through deep armour to try to reach that inner pressure hull because if they don't reach it they really don't cause substantial damage to the sub despite the rather large weapons they use.

George1 wrote:Οnly 3 old Kilos under service? Also, Alrosa in BSF has been always in repairs from the time I remember myself in RMF

https://twitter.com/GrangerE04117/status/1735382807990681636

According to these guys https://russianships.info/eng/today/

- Baltic - 1
- Black Sea - 1
- Northern - 4
- Pacific - 4

They have been commissioning the new 636.3 subs at a rate of like one a year.
Next year they should have replenished the Pacific Fleet with six such subs. After already adding six such subs to the Black Sea Fleet.

The Alrosa should still be in service. They finished overhaul and put it into service in the Black Sea Fleet around last year.

They also have two 977 subs in trials which are going to the Northern Fleet.

Japanese experience with AIP SSKs is that they are not powerful enough... when submerged you need a lot of systems to be working all the time, even more systems if you actually want to be an operational sub that can move and detect targets and sink them if needed. A diesel generates noise and has to be run near the surface, but generates an enormous amount of power meaning you can run all your systems and fast charge your batteries while operating at snorkel depth.

On a 30 day deployment in an SSK you might leave port at full charge so you have two weeks of underwater operations where you can sneak around and be a hunter before you need to approach the surface and make some engine noise for 6-8 hours, but after doing that you are good for another two weeks of hunting and operations.

You can plan your mission so you spend your two weeks quiet in enemy or neutral waters and then when you need to snorkel you can head back to friendly waters and even enter a friendly harbour and recharge amongst the running diesel engines of a dozen other civilian ships. In the wild you could simply find a civilian ship to snorkel behind... the noise of the civilian ship will disguise the noise you are making and any diesel fume sensors will detect the fumes from the civil ship and might not even notice the fumes you are producing.

In comparison these fuel cells don't generate enough power to fully operate all the essential systems let alone the combat systems while at the same time fast charge the batteries. This means you essentially shut down all but essential systems, but the reduced power the cells generate means it might take a day or two to charge the batteries.

The Japanese, with their experience with AIPs (and they make AIPs as good as anyone in the west) they realised that actually replacing all their old batteries with new lithium ion batteries... but also replace the AIP with even more batteries actually gives much better performance. Remember these AIPs need large tanks of Oxygen and tanks of Hydrogen too to actually work. Carrying large volumes of oxygen is dangerous. Most ports do not have oxygen and hydrogen handling facilities.

The several design flaws in the Kilo.

Hahaha... it is normal for them to want them to stop making Kilos and start making the newer Ladas...

Kilos are made easier and faster because they have been in serial production for a long time while Ladas are new... think of it in terms of making Panthers and making Panzer 4s... for every Panther they could have made four or five Panzer 4s and when they changed from one to the other they weren't getting any tanks. At a time when the Soviets were making T-34s in enormous numbers.