I feel this concept makes sense. Wherever you need a conventional sub, this one should work too. And with AUKUS, I think China may export it as well.
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- Thread starter Jeff Head
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Just to replace conventional subs.
Where can one read about it ? Very good if true. The waste heat can be channeled to Li ion battery packs to improve their performance. There are studies (in sweden) to use heat conductors to improve LI ion performance in frigid waters and found that Diesel engine heat can't be effectively channeled.
Sorry, I didn't save them. Just google "小堆AIP" or something like that.
What exactly would be the usefulness of such submarines?
SSNs are characterized by unlimited underwater range independent of speed which means that they can change position relatively fast while avoiding detection. That makes them a strategic asset for global power projection at any place - limited only by the duration of transit.
A SMR submarine travelling at 10knots is only twice as fast as an AIP submarine travelling at 5 knots. It is also at half as fast as a modern large SSN traveling at "quiet" speeds.
Let's use this image as visual aid - it is an approximation of travel times at speeds of 14, 21 and 28 knots of USN vessels transiting the Pacific. Zoom in if necessary - it's 1600x738 pixels.
SMR submarines will be useless for missions performed by regular SSNs. Their only potential use would be to replace conventional AIP in coastal submarines. This statement is most important. The SSKs are no "conventional submarines". Conventional submarines were ocean-going vessels in the past but now they are coastal submarines because they are so outmatched by nuclear submarines that they have to limit their operations to coastal areas. SMR does not provide sufficient energy to change that. Therefore SMR submarines will still be coastal submarines.
At the same time SMR submarines will still be nuclear submarines which means all the security precautions of building and operating a nuclear submarine apply. They will still be significantly more expensive than conventional submarines. Conventional subs will be cheaper while nuclear subs will be more capable. SMR submarines seem to be stuck in "neither cheap nor capable" region.
So what about AIP? Is SMR worth the cost?
AIP was implemented on conventional submarines not because batteries had limited capacity being able to move at 5 knot for two weeks without surfacing was revolutionary.Before AIP conventional submarines had to be essentially static and had to surface after approximately 7 days at the most because battery power was used for life support as well. A submerged Kilo can travel 400 miles at 3 knots which is 133 hours (5 days 13 hours) of operation. It can also sprint at maximum speed at distances of less than 50 miles. An AIP submarine can absorb ASW assets for at minimum 2,5 times as long and remain an active threat at the same time - something a traditional SSK maxing out battery life can't do. It completely changed the tactics of ASW operations against such submarines. Now ASW ships have to keep the distance and use more resources to find the submarine. A single AIP SSK is worth 2-3 traditional SSKs. That was the nature of AIP revolution.
But that revolution did not occur in a vacuum. It was a solution to a very specific problem. AIP (Stirling) was first introduced in Sweden, which relied on submarines for defense against a hypothetical Soviet invasion. The distance between Sweden and USSR is equivalent to the Taiwan Strait. Being able to remain submerged for many days was a fundamental advantage, especially that Soviet submarines were not capable of the same. The first AIP submarines entered service only in 1996 but they were ordered before 1991. The next AIP solution was introduced in Germany which had a similar requirement during the Cold War. The first 212A entered service in 2005 but was ordered before 1998. Germany was also a major submarine exporter and selling the cheaper 214 it promoted PEM fuel cell and AIP in general. France developed its MESMA solution for export but it is easily the worst AIP solution available. The only reason anyone would buy a Scorpene with MESMA is if they got bribed but had "AIP" in tender requirements. Arguably that's the story of every Scorpene tender. Pakistan ordered MESMA for their Agosta 90B because they provide second strike capability.
Note that nobody decided to build larger conventional submarines with AIP. AIP did not replace nuclear. That's because low energy output of AIP makes it uneconomical for propulsion of larger submarines. This is also why France built small SSNs - they were limited by the power of their reactors. K48 generated 48MW of power which translated to 7MW of steam power. To build larger SSNs they would need to put two K48 reactors in each which would be both more difficult and expensive. To optimize they reduced the size of the submarine with all the consequences to noise level and crew comfort. Rubis (even upgraded as Amethyste) is a bit of a joke SSN. New K15 reactor has triple the power and is used on new SSBNs, new SSNs and the Charles de Gaulle and should finally give proper SSN to Marine Nationale.
Replacing AIP with SMR will not solve the issue of limited power. And even if it did there's no point in building larger submarines which are not full SSNs because there is no use for large volumes in your own waters. What are you going to put there that you can't put on land? Increasingly it might be more practical to have land-based ASROC or land-based long-range torpedoes if you can't put ASW aircraft in the air because of enemy air superiority.
Coastal submarines don't need to be large. They need to be numerous.
This logic is reflected in every naval procurement anywhere. Either a country is buying a few submarines to have submarines as unique capability, or it is buying a lot of submarines. And by a lot I mean as many as it can afford.
Similarly with SSNs - either you have the necessary minimum or you go for broke. Look at Britain - at one point they had almost twenty SSNs but now they are down to six-seven. This rule is also reflected in Chinese nuclear deterrence. Either the minimum deterrent or the maximum deterrent. There is no middle ground. That is the inherently unstable nature of strategic systems. Strategic systems change strategy. And strategy - not tactics, not operations, not faith in victory or confidence in leadership - determines whether there is a war or not.
SMR technology might be valuable on its own. The research might lead to improvements in reactor design in general. To replace conventional propulsion SMR breakthrough would have to be truly revolutionary - to the point where SMR will start to replace all propulsion on every major warship. And when that happens will SMR provide sufficient power to operate new weapon systems like railguns or DEW?
And that leaves completely the fact that increasingly unmanned systems will be replacing manned submarines in coastal duties. Technically already at some point in the calculus, when your posture is purely defensive, subs can be replaced by seabed sonar providing targeting data for land-based weapons. But most countries like to have the offensive option as well so they keep submarines. When large underwater drones become efficient the cost of maintaining a crewed submarine will become a problem. It already is to an extent.
Finally when you realize how much of submarine work is collecting signatures and testing hydrographic survey data in practice, how boring, routine and time-consuming it is, you will see how easily most of it can be replaced by autonomous systems. The only element that will stay crewed is nuclear-armed vessels and how many of those are there?
In my view the future of coastal undersea warfare is not "small modular and reactive" but very cheap, very plentiful and very unmanned.
And I've already written too much today. You take care while I take a break.
The same answer to the question why PLAN still build conventional subs.
by78
General
Mr. Zhu Kun, a missile expert, doing a presentation. Note the concentric canister launch system (CCL) in the image.
Summary of the text: Mr. Zhu overcame a 20-year (domestic) bottleneck and achieved a breakthrough where all other countries had failed. In accordance with strategic requirements, Mr. Zhu successfully developed a generation of missiles that are smaller yet more powerful than their counterparts. He's once in a generation talent...
Mr. Zhu Kun has just been awarded the title of "Outstanding National Technical Talent" (全国杰出专业技术人才) for his breakthrough contributions in key missile programs.
