Rumoured "mini-nuke/diesel" Submarine SSK-N(?) thread

[Jason_]

The disadvantage being in open ocean it doesn't have the high top speed of a big SSN? Any other drawbacks?

A mini-nuke may be able to still reach the same top speed as a regular nuke but cannot retain that top speed indefinitely as a regular nuke can.

In a regular nuke the reactor output determines the top speed. In mini-nuke, the reactor replaces the AIP module in a conventional AIP sub. The reactor charges a battery which allows for 20+ knot bursts for several hours while also allows for <10 knot cruising indefinitely. This allows a smaller, cheaper, easier to maintain and possibly quieter reactor to be used.

 

[FairAndUnbiased]

The disadvantage being in open ocean it doesn't have the high top speed of a big SSN? Any other drawbacks?

short term endurance is limited by battery capability. A SSKN is a very quiet ambush predator with bursts of speed that can prowl around with almost unlimited underwater endurance, but has to rest to recharge in between bursts of speed. All moving parts are decoupled from the structure. A traditional SSN is more like an endurance predator that happens to be kind of stealthy, but is still noisier by nature due to the mechanical gears that actually make it move and the fact that the primary drive shaft must be mechanically coupled to both the engine and the hull, which transmits engine vibrations.

I guess it's kind of like tigers vs. wolves.

 

[tphuang]

The concern with sskn is just the noise level from machineries associated with the reactor. If they can lower the noise level of 093b to akula level, then getting sskn to that level is probably doable if they can make everything small enough to fit inside the current aip compartment and pad it with plenty of noise absorbers.

We will have to wait and see.

You also don't want sskn to move around that much. I think 20 knots even in burst mode is unnecessary.

Just have something that can sail to where it needs to go at depth that can't be easily detected from MPA or satellites, that will be a huge improvement over 039Bs

 

[The Observer]

Will SSKN need nuke tech onboard? If yes, that could be another bottleneck to think about.

AFAIK nuke means cost, and cost mean higher performance demand & lower total number/budget.

So the question becomes "Does the potential performance increase of SSKN over SSK AIP warrant the higher cost & complexity?"

 

[taxiya]

Will this submarine have a battery and/or AIP system like diesel electric subs? Or will it's sole means of power be the nuclear reactor?

All subs including big nuclear ones have battery. I think your question about battery is if the battery is used for propulsion. The answer is yes. The idea is to use the small reactor to constantly charge the battery. The propeller is driven by electrical motor from electrical grid that is fed by both battery and generator (driven by reactor).

The reason of using battery is because the reactor is low powered. The battery is acting as a cache for high speed. The reactor is to constantly charge the battery at low speed. The reason for low power reactor is its quietness and simplicity.

 

[taxiya]

The concern with sskn is just the noise level from machineries associated with the reactor. If they can lower the noise level of 093b to akula level, then getting sskn to that level is probably doable if they can make everything small enough to fit inside the current aip compartment and pad it with plenty of noise absorbers.

The whole idea of this design is that it is inherently quieter than ordinary SSN. The reactor has one more loop than ordinary pressurized water reactor, its pressure and temperature are all lower, it doesn't need main circulation pump, or rarely need it to run.

 

[taxiya]

	SSN	SSKN
reactor	2 loops	3 loops
noise	high	low
safety	so-so	high

 

[tphuang]

All subs including big nuclear ones have battery. I think your question about battery is if the battery is used for propulsion. The answer is yes. The idea is to use the small reactor to constantly charge the battery. The propeller is driven by electrical motor from electrical grid that is fed by both battery and generator (driven by reactor).

The reason of using battery is because the reactor is low powered. The battery is acting as a cache for high speed. The reactor is to constantly charge the battery at low speed. The reason for low power reactor is its quietness and simplicity.

Good points. Also note that electric motor should be slightly more efficient. I think it's something like 30% efficient in thermal to energy. Then if you put the latest electric motor, you get maybe 90 to 95% efficiency on that. So 28% efficiency overall.

Not bad

So iirc
A really power diesel engine generates 2 mw power and a striking plant generates 320 kw power. So for a nuclear plant, you just need it to be like 2mwt to generate enough power for 560 kw energy and that can probably sustain 5 knots and faster on shorter bursts. It's possible my calculations are wrong here and you need something like 4 mwt to do that, but you get the idea.

To put things in perspective, a modern nuclear sun needs 200 mwt reactor.

With a 2 to 4 mwt reactor, everything should be quite simple.

What do you think @latenlazy does that seem about right?

 

[tphuang]

The whole idea of this design is that it is inherently quieter than ordinary SSN. The reactor has one more loop than ordinary pressurized water reactor, its pressure and temperature are all lower, it doesn't need main circulation pump, or rarely need it to run.

Of course it has to be a lot quieter than your usual reactor on ssn, because it's a lot of smaller and the power requirement is like 1 or 2% of something you would expect on 095. On the other hand, 039b pressure hull is tiny compared to nuclear sub and you would want simple raft around it.

 

[taxiya]

Of course it has to be a lot quieter than your usual reactor on ssn, because it's a lot of smaller and the power requirement is like 1 or 2% of something you would expect on 095. On the other hand, 039b pressure hull is tiny compared to nuclear sub and you would want simple raft around it.

My reply was because you brought in both 093B and Akula in your post #13, both are regular SSNs. So I thought it shouldn't be relevant to compare with this SSKN. Maybe it was a typo that you actually meant 039B?