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

[latenlazy]

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?

Hmmm. Keep in mind that the nuclear reactor doesn’t generate electricity that directly feeds into a battery but has to turn a generator via a thermal cycle, so even if it’s stored as electricity you’re not avoiding thermal cycle limits.

EDIT: Unless I misread and the initial 30% figure you brought up was referring to the thermal cycle efficiency.

 

[tphuang]

Hmmm. Keep in mind that the nuclear reactor doesn’t generate electricity that directly feeds into a battery but has to turn a generator via a thermal cycle, so even if it’s stored as electricity you’re not avoiding thermal cycle limits.

EDIT: Unless I misread and the initial 30% figure you brought up was referring to the thermal cycle efficiency.

I was talking about thermal cycle efficiency. 200 mwt becomes 60 mwe for acpr50s

 

[Hitomi]

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.

Is this in comparison to a natural circulation reactor or one with coolant pumps?

Actually is it even possible to build a reactor smaller than contemporary submarine reactor with natural circulation?

 

[dingyibvs]

View attachment 117568

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

The first row is also interesting. The SSKN is supposed to be low pressure/low temp and uses "unibody" reactor, as opposed to the SSN's high pressure/high temp reactor. I suppose by "unibody" it means it doesn't need a separate containment vessel, possibly due to its lower pressure and temperature?

Is this in comparison to a natural circulation reactor or one with coolant pumps?

Actually is it even possible to build a reactor smaller than contemporary submarine reactor with natural circulation?

Surface area to volume ratio should increase with decreasing size, so I would think a smaller reactor/sub should have radiators with relatively more surface area to allow for natural circulation.

 

[taxiya]

Actually is it even possible to build a reactor smaller than contemporary submarine reactor with natural circulation?

yes if it is sub-critical which does not need forced circulation. I suspect the SSKN reactor is sub-critical by the look of its low temperature and low pressure.

 

[tphuang]

why are people so concerned about natural circulation? That's not the main source of noise for SSNs. It's in the coolant pumps and all the other equipments in the machine room iirc.

I do wonder about one thing though. Will this SSKN than use nuclear reactor as the primary generator of electricity & diesel engine as the backup?

 

[Blitzo]

why are people so concerned about natural circulation? That's not the main source of noise for SSNs. It's in the coolant pumps and all the other equipments in the machine room iirc.

Natural circulation means that (at the speeds where it works), you don't need the pumps and additional machinery to cool the reactor, meaning you can be quieter while still underway at a useful speed (albeit not top speed of course).

That said I'm not sure if it is relevant for the mini-Nuke/SSK-N

 

[Atomicfrog]

System like that would be perfect for ambush. Placing themselves in some good choke points before the conflict and waiting silently for way longer period of time than diesel ones.

Quite nice if they are quiet enough to follow some cargoships to place themselves without being detected.

 

[ACuriousPLAFan]

View attachment 117568

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

Full table:

Features	SSN	SSK-N
Nuclear power unit	High temp, high pressure reactor	Low temp, low pressure integrated/unibody(?) reactor
Nuclear unit structure	2 loops	3 loops
Primary propulsion	Turbine propulsion	Electric propulsion
Speed	High	Low
Noise level	High	Low
Endurance	Unlimited	Unlimited
Safety level	Medium/normal	High

 

[FairAndUnbiased]

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

SSKN will always be quieter than a full SSN because there is no gearbox, which is a huge source of noise and also a headache for Chinese industry, which has always been weaker on precision mechanical assemblies than electronics. Imperfections in the gears can cause noise, and as the gears rotate, the noise is periodic. This creates a detectable signal for the specific gearbox. bad.

SSKN mechanically decouples the engine from the drive shaft. This means no large, hull coupled gearbox needed, and no source of noise other than the reactor itself.