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To elaborate on the at sea charging idea..

China uses civil-military fusion, we see it all the time, eg in the new villages near the Indian border.

A similar thing will happen at sea, China is colonizing the marine environment.

This means, that to support civilian infrastructure there will need to be a marine electric network.

This is what SSK’s can plug in to.

However, I believe that the best way to recharge an SSK, is with an SSN.

Edit: check this “recharging“ cable..

Why invent a solution for a problem that doesn't exist in the first place?
All modern SSKs have main diesel engines, precisely for this purpose. And they have had them for well over a hundred years.

Gloire_bb said:

Why invent a solution for a problem that doesn't exist in the first place?
All modern SSKs have main diesel engines, precisely for this purpose. And they have had them for well over a hundred years.

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The problem does exist, there are many disadvantages with SSN’s. China has the technology and the innovation ability to transform submarine technology.

They don’t need to rely on 100 year old technology like their adversaries do.

Of course, their doctrine probably ensures large numbers of diesel electrics will still be built, new platforms will emerge, such as the sail-less sub.

Gloire_bb said:

To have such speeds as silent speeds you have to go waterjets - and this is simply inefficient/counterproductive for SSK.
The only SSK which even tried was the unlucky Attack design - and, frankly speaking, it was a non-proliferation weirdo sub design.

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Yes, I forgot to mention the pump-jets. From what I can see you can do about 20knots without cavitation.
And also that ducted pump-jets are more efficient at most speeds, but inefficient at very lower speeds when compared to a propeller.
With a normal propeller, you might get 10? knots without cavitation.

But with much better batteries, my gut tells me that the inefficiency of a pump-jet at low speeds is a good trade off, when combined with the greater efficiency of the pump-jet at higher speeds and the greater amount of time spent at those higher speeds.

Gloire_bb said:

The biggest issue for SSKs was that everything that requires energy is the enemy. It's the same even on Li-ion subs with their impressive energy density, energy maneuvering capability, and, among other, impressive speeds of recharging. It's also the same for AIP submarines, which can't even go full "lights on" on their AIP alone.
The biggest difference with SSNs there is that their designers for the large part don't even need to concern themselves with it - energy onboard is limitless* - be it for propulsion/sensors/processing/whatever. Psychological pressure (of limited battery) is just as crucial, perhaps - and while severely relaxed - it is by no means gone.

*it's more complicated for combat maneuvering, but mentioning it is enough for simplicity's sake.

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Yes. Energy management is still a concern.

But if you have 39hours@20 knots on a full battery, in many scenarios, you will always have at at least 12hours of reserve battery power at 20knots for combat manoeuvring at any point. That's enough time to successfully locate, engage and then completely disengage at maximum speed.

In comparison, an equivalent weight of lead-acid batteries would give you less than 2 hours at 20knots when disengaging.
And if you look at other AIP submarines, yes, they can't get to 20knots underwater.

At the moment, the Taigei batteries are rated at 300Wh/kg.
But in 5-10 years, you could be looking at 500Wh/kg, which is 67% more available power for the same weight.

Andy1974 said:

To elaborate on the at sea charging idea..

China uses civil-military fusion, we see it all the time, eg in the new villages near the Indian border.

A similar thing will happen at sea, China is colonizing the marine environment.

This means, that to support civilian infrastructure there will need to be a marine electric network.

This is what SSK’s can plug in to.

However, I believe that the best way to recharge an SSK, is with an SSN.

Edit: check this “recharging“ cable..

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Click to expand...

I disagree.

Using an SSN as a battery pack to recharge a SSK is grossly inefficient and also risky.
Diesels on board the SSK are a better option.

Having a marine electricity charging network may be useful for smaller UUVs, but not for an SSK.

AndrewS said:

Yes, I forgot to mention the pump-jets. From what I can see you can do about 20knots without cavitation.
And also that ducted pump-jets are more efficient at most speeds, but inefficient at very lower speeds when compared to a propeller.
With a normal propeller, you might get 10? knots without cavitation.

But with much better batteries, my gut tells me that the inefficiency of a pump-jet at low speeds is a good trade off, when combined with the greater efficiency of the pump-jet at higher speeds and the greater amount of time spent at those higher speeds.



Yes. Energy management is still a concern.

But if you have 39hours@20 knots on a full battery, in many scenarios, you will always have at at least 12hours of reserve battery power at 20knots for combat manoeuvring at any point. That's enough time to successfully locate, engage and then completely disengage at maximum speed.

In comparison, an equivalent weight of lead-acid batteries would give you less than 2 hours at 20knots when disengaging.
And if you look at other AIP submarines, yes, they can't get to 20knots underwater.

At the moment, the Taigei batteries are rated at 300Wh/kg.
But in 5-10 years, you could be looking at 500Wh/kg, which is 67% more available power for the same weight.

Click to expand...

Ideally, the batteries will be easily replaced with higher density versions over time. But you can also just add more of them.

A large SSK full of blade batteries is a bit future proof, because today it could patrol effectively island chains 1 and 2, but after a simple upgrade they will be able to patrol all they way to the US. The PLA doesnt even need to pay for much R&D.

Andy1974 said:

Ideally, the batteries will be easily replaced with higher density versions over time. But you can also just add more of them.

A large SSK full of blade batteries is a bit future proof, because today it could patrol effectively island chains 1 and 2, but after a simple upgrade they will be able to patrol all they way to the US. The PLA doesnt even need to pay for much R&D.

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From China to the USA is over 10000km. A round trip would be over 20000km.
Most SSKs have been designed for half this range (at most) in terms of fuel, supplies, etc etc

And unless you want SSKs to spend most of their time travelling at slow speeds in order to cover vast distances across the Pacific, SSNs are the way to go.

With a Taigei, you could get to 10000km on a single charge, but it would be at 5knots and take 87days.
At 20knots, you get 39 hours and 2500km in range

The problem with running diesels to recharge batteries is that diesels are noisy.

SSKs are ambush predators since they do not have the speed or endurance to actively chase down prey like SSNs can.

These two factors added together gives you a problem. Because if you use your diesels engines, you give away your location, and then you don’t have the speed or endurance to get very far very quickly.

Modern high energy density batteries and AIP greatly help with these issues, but does not and cannot fully mitigate them.

The key is to understand and accept the fundamentally different role and use for SSKs rather than go in a futile direction trying to make SSKs into SSNs.

For submarines, the next major limiting factor after power is crew consumables like air, water and food. Air and fresh water you can make (at a cost in energy), but there is no getting around the food limitation without seriously moral damaging costs). That is significant for SSKs because they face the trade-off between getting on station totally silent and time available on-station once they get there. Since the total length of time the sub can remain out at sea is capped by its provisions supply. Which in turn becomes a trade-off between speed and stealth.

This means undersea charging points can be a significant boost for SSKs because having them allows your sub not have to make a choice between speed and stealth by allowing your subs to run at higher speeds and then be able to recharge without using diesels and giving away their position.

The key difficulty with having charging points is going to be keeping them secret and secure, since they will become obvious ambush points for enemy sub hunters to lurk and wait for your subs.

The idea of using an SSN as a sub refueller for SSKs is actually a pretty good one. Since that eliminates the vulnerability of having fixed charging points with minimal cost (power lines can be easily run using the same existing winch tech as is used for TAS); and connection to the SSK would not be a massive technical challenge.

You could potentially even use this concept to develop a piggy back rapid deployment method for SSKs, where an SSN could be rigged up to connect to one or even several SSKs at port with charge cables (that can also run a data line for sub-to-sub comms). This would allow the SSKs to run at near full speed without depleting their battery power so would have full charge once on station to maximise both time on station and operational flexibility.

plawolf said:

The problem with running diesels to recharge batteries is that diesels are noisy.

SSKs are ambush predators since they do not have the speed or endurance to actively chase down prey like SSNs can.

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But here are the specifications.

29days@5knots for ambushing. Plus another 24hours@20knots for combat manoeuvring

plawolf said:

These two factors added together gives you a problem. Because if you use your diesels engines, you give away your location, and then you don’t have the speed or endurance to get very far very quickly.

Modern high energy density batteries and AIP greatly help with these issues, but does not and cannot fully mitigate them.

The key is to understand and accept the fundamentally different role and use for SSKs rather than go in a futile direction trying to make SSKs into SSNs.

For submarines, the next major limiting factor after power is crew consumables like air, water and food. Air and fresh water you can make (at a cost in energy), but there is no getting around the food limitation without seriously moral damaging costs). That is significant for SSKs because they face the trade-off between getting on station totally silent and time available on-station once they get there. Since the total length of time the sub can remain out at sea is capped by its provisions supply. Which in turn becomes a trade-off between speed and stealth.

This means undersea charging points can be a significant boost for SSKs because having them allows your sub not have to make a choice between speed and stealth by allowing your subs to run at higher speeds and then be able to recharge without using diesels and giving away their position.

The key difficulty with having charging points is going to be keeping them secret and secure, since they will become obvious ambush points for enemy sub hunters to lurk and wait for your subs.

Click to expand...

By definition, if there are undersea charging points for an SSK, the area is comparatively secure and also close to a Chinese base.
That means it should be safe enough to run a diesel or just go to a Chinese controlled port anyway.

plawolf said:

The idea of using an SSN as a sub refueller for SSKs is actually a pretty good one. Since that eliminates the vulnerability of having fixed charging points with minimal cost (power lines can be easily run using the same existing winch tech as is used for TAS); and connection to the SSK would not be a massive technical challenge.

You could potentially even use this concept to develop a piggy back rapid deployment method for SSKs, where an SSN could be rigged up to connect to one or even several SSKs at port with charge cables (that can also run a data line for sub-to-sub comms). This would allow the SSKs to run at near full speed without depleting their battery power so would have full charge once on station to maximise both time on station and operational flexibility.

Click to expand...

An SSN (such as the Virginia) costs $2.8 Billion for example. Yet it would be tethered to a SSK (such as the Taigei) that costs $0.6 Billion, and only has 39hours of endurance at 20knots. You're better off with the Virginia operating by itself in the attack role.

Also, if you're talking about SSKs operating in the Western Pacific, that is close enough to Chinese bases or Chinese fleets.
Then they can run their diesels and charge up the battery in safety.

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But what I can see happening in the future is a large submarine mothership which is nuclear powered.
It would be carrying smaller underwater surveillance and fighter drones, powered by rechargeable lithium batteries.

I also expect to see surface ships deploying similar underwater drones.

AndrewS said:

But here are the specifications.

29days@5knots for ambushing. Plus another 24hours@20knots for combat manoeuvring

Click to expand...

At 5 knots, you can only travel 222km per day. In reality it is going to be a lot less due to currents and the fact that you often don’t want to or even can’t just travel straight line while submerged.

Also you need to consider that under battery power only, you have a total mission endurance of 30 days. Whereas a sub that sized could easily have room for provisions for triple that length of time if desired. Sure it’s perfectly serviceable, but why not vastly reduce your transit time and increase your on station time?

AndrewS said:

By definition, if there are undersea charging points for an SSK, the area is comparatively secure and also close to a Chinese base.
That means it should be safe enough to run a diesel or just go to a Chinese controlled port anyway.

Click to expand...

Not necessarily. You could built charging points as far from your coast as you want, but the issue of security and secrecy is going to be hard to get around the further out you push your charging points. Which is why I don’t think fixed charging points is a good idea.

AndrewS said:

An SSN (such as the Virginia) costs $2.8 Billion for example. Yet it would be tethered to a SSK (such as the Taigei) that costs $0.6 Billion, and only has 39hours of endurance at 20knots. You're better off with the Virginia operating by itself in the attack role.

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What does cost have to do with it? I assumed it goes without saying, but the whole point of a SSN recharger is that the SSN can and will disconnect from the SSK once the batteries are charged back up.

Also, that 39h of endurance ould become meaningless if the SSK can run at 20Knots while using mains power supplied by the SSN in piggy back mode. In which case the SSK could theoretically run at 20Knots for as long as it’s motors can sustain that speed if power is no longer a constraint.

AndrewS said:

Also, if you're talking about SSKs operating in the Western Pacific, that is close enough to Chinese bases or Chinese fleets.
Then they can run their diesels and charge up the battery in safety.

Click to expand...

So rather than have a single SSN charge up SSKs, you want an entire surface fleet to go babysit it instead as it charges up using diesels on the surface?!