@Michaelsinodef They are probably talking about the AIP system which uses a Stirling engine. It is used to increase range underwater. But more modern Japanese submarines dispense with the AIP system altogether and just use the space to put more lithium-ion batteries. Electric drive is typically really quiet, more than nuclear.
I c
Stirling engine is relatively silent with the only vibration source being the piston - it doesn't have an explosion in the combustion chamber but rather is continuous burning (and in fact can use any heat source and heat sink). It also increases AIP range greatly compared to lithium ion batteries because chemical fuels have a far higher energy density vs. lithium. It's less quiet than fuel cell which has the best of both worlds (zero moving parts but chemical fuel storage). It's also more survivable than lithium ion batteries which (except BYD blade batteries) explode when punctured.
I c, well it was just some offhand comment I saw in a video (also talked about stuff years ago, so if it was true, might have been fixed since then as well.)
That's the usual baseless speculation of click-baiting online grifters.
Soryus were rejected because Attack-class was an Australian jobs program while Soryus are a Japanese jobs program.
Southern Australia is a swing region with strong Labour presence and Attack was Labour creation - the decision was taken during Kevin Rudd's government. Coalition wanted to keep those votes so they continued the program initially but Coalition is an American vassal and their loyalty is to American imperial interest so it was only a question of time before the French order would be cancelled. The continuing raising of demands and complaints about rising cost was just a preparation. This is also what was confirmed in the recent leak. France knew it was getting dumped and has known it for some time. They're not stupid. The rest is for show and manipulating the public perception just as AUKUS is.
Unlike the French design the Soryu could not be built in Australia because if you look at the rate of production of submarines in Japan it becomes obvious that the rate of replacement is slowing down. It seems that Oyashios will serve 25 years as Taigei subs are already being built at a slower rate. That increases the cost of retaining skilled workforce.
Japan submitted their bid because Attack was meant to be a source of additional orders for Japanese companies. Australia on the other hand wanted as much as possible of the technology and production to be transferred to Adelaide. France didn't object as long as it worked out financially. Japan refused any substantial transfer. Let's not forget also that Attack would be the first foreign sale of a Japanese warship after WW2 while France has an already established model of technology export that they use to gain advantage competing against the US.
See above, but even if they meant the engine then it couldn't be the problem.
Here's the always useful table of maximum detection distance for passive sonar (right column) depending on difference of noise level between the source and the sonar carrier (left column).
Example: a source of noise that is 15dB louder (in low frequencies - 20Hz and below) than the sonar carrier can be detected from no farther than 31m.
This is a very simplified approach but it is enough to explain why Stirling is not a factor.
Stirling engine is just the energy source - like the batteries. Everything else is the same and the only change is the rate of movement of the shaft, propeller etc. On diesel propulsion the rate of movement and the resulting speed is high, on batteries traditionally it never exceeds a couple of knots. This is a much more important factor in noise generation than the engine itself.
Diesels use explosive combustion to exert pressure on the pistons which raises the arm generating force. The arm is then returned to position by gravity and mechanics. The limit on the energy generated by single explosion determines the number of pistons and the rate of movement of the mechanical parts. This is why diesels are noisy - they are generating energy by explosion and movement at high frequency which is like a row of guns firing in harmonic pattern.
Stirling generates energy through a process of slow energy transfer between two volumes of gas which exerts pressure on the moving parts. Because of that there is no limit on the size of the piston because the pressure exerted is much lower unlike in explosive combustion. This is why Stirling engines have very few moving parts moving at slower rate and that causes Stirling to be not much louder than batteries compared to a regular diesel. The noise depends almost entirely on the shaft and the propeller.
So even if the sub has "characteristic signature" that signature can be heard at distances which do not change much tactically because before you hear the Stirling you already most likely have the signature identified based on the main moving parts.
From 2005 to 2007 the USN has extensively tested the Swedish submarine "Gotland" which uses Stirling engine as AIP. This is where the news of Gotland sinking the USS Ronald Reagan on exercise comes from. The Swedish sub operating with Swedish crew evaded detection by all ASW measures including American SSNs and unlike the previous infamous sinking by German subs - this was not a one-off ambush. Thanks to the Stirling engine Gotland was able to operate submerged for a very long time. It sunk the carrier repeatedly. The Swedish submarines are very proud of it and the Americans understandably worried.
Besides the technology being easy to implement Stirling engine was used by Swedes because its mode of operation is very useful for small coastal areas within range of enemy forces. Swedes operate in the Baltic protecting their shores and the first Stirling-powered subs were designed at the end of Cold War as a counter to the Soviet Baltic Fleet.
If you look at the Baltic and Swedish coast and the waters inside first island Chain and Chinese coast you can easily see why PLAN chose Stirling for their AIP subs. Chinese conventional subs operate in "own waters". The key to Chinese tactics is staying covert all the time - just like the Swedes did - because it was assumed that they would be operating with the threat of enemy advantage in aerial and surface ASW. Having AIP subs of any type and in larger numbers is essential to PLAN doctrine while having AIP subs with fuel cells is not. The purpose of AIP technology for China is not competition on export markets but defensive capabilities against enemy forces.
Japan has a different requirement. Japanese subs were traditionally meant to deal with Soviet navy and especially Soviet submarines. They also have a different area of operations which includes the open Pacific on the eastern side of the first island chain. They need to move fast if necessary and Stirling is awful at generating energy spikes. It is great for long periods of consistent low energy production. For week-long crawling. This is why Japan chose LiIon batteries which can be reloaded fast under snorkel and can store far more energy allowing for fast movement for up to couple of days rather than a few hours. On LiIon subs can in theory sprint (20kts) for as long as 12 or even 24 hours. A Kilo can sprint for less than 50 kilometers.
As for AUKUS it is pretty obvious that it is a political move to officially confirm Australia as a member of the anti-China alliance and an American vassal state. Whether any SSNs will come out of it is irrelevant. Australia is important to America in the same way that Iceland is despite having no military and yet being the founding member of NATO. It is important because of geography and because it works as a tripwire in case Taiwan fails. Americans might not feel compelled to come to aid of some Asians who are named "Republic of China" anyway but a threat against fellow anglos? News Corp will go into overdrive as will the GOP and suddenly it's the next Pearl Harbor. That's the real purpose of AUKUS and any rationally thinking Australian should be justified in their fears.
It was a conscious decision to increase the fleet.
The previous approach of writing down essentially modern subs was found to be simply too lavish.
Thanks for finding those values! But what publication/person is author of those dB/distance figures?
Also, do you happen to know a source that could shed light on the following question:
If a sound happens outside water, say a jet flying 100 feet above water, what noise level will it have made to have been heard by a 90 dB submarine that's 100 meters below water, at various distances from the sound?
My three cents for today:
I made a spreadsheet for an alternative scenario with service time of all submarines at 25 years. I won't link it because just as in the previous instances it won't be legible. What it demonstrated was this: assuming the same build orders Japanese submarine force plateaus in 2005 at 25 ships and last Harushio is retired in 2022. Which means that the only thing that is different in that alternative scenario is a 50% greater maintenance and personnel cost of the submarine fleet between 1987 and 2017.
Historically during that time Japan built more capable helicopter carriers and destroyers. Because Japan has a politically-determined ceiling for military spending at 1% GDP unchanged since 1960 and a legal cap for active personnel the funding for additional submarines would have to come from the funds for surface fleet. Submarines are a wartime fleet. A peacetime fleet is a surface fleet. Japan used the "Toyota way" for their naval strategy and it was the right choice because it modernized its surface fleet while retaining industrial capacity to expand its submarine fleet when necessary.
Besides those older submarines were hardly modern so their retirement was not a major loss:
The size of Japanese navy was largely constant since the 80s when it was supposed to augment USN against Soviet Pacific Fleet. Table below includes all domestically-built ships but all the US-made ships were retired in the 1970s.
As Russian navy collapsed in the 90s Japan had the second largest and most potent naval force in the Pacific until China started its rapid naval expansion in the 2010s. For political reasons JMSDF operates as a vassal force to the USN so it should never be considered in separation to the 7th US Fleet. It will only be in this decade that PLAN takes over WestPac USN and JMSDF in terms of potential.
It is questionable if more submarines are the right choice for the future. What would they possibly change in the strategic equation? Japan's weakness lies entirely in its geography and economy. It's a case of Taiwan - just on a larger scale. Japan can double or even triple their navy and it won't matter.
I've seen comparisons between Japan and Britain but Britain's rise in the 19th century happened on the back of unprecedented industrial and economic growth. Britain in 19th century was a growing economic power and it improved its position globally in the same way that America did in the 20th century also on the back of rapid economic growth. Japan is a declining economic power past its historical peak.
As the balance of power in western Pacific shifts Japanese security interest will follow the economic shift toward China. Japan is not a meaningful adversary for China because that has to come from natural economic potential. If Japan retains its alignment with the US then a more likely outcome is a breakup of the nominal alliance between Japan and Korea which exists under their vassalage to Washington. Korea will naturally shift toward China and Japan may choose an adversarial stance against Korea as these two occupy the same political, economic and military space. Korea would become a proxy tool for China and Japan a proxy tool for America.
Furthermore the key to any long-term strategy against China is Russia. As long as Russia remains neutral toward China the shift in the balance of power toward China will continue. The only thing that can stop it is a change in geopolitical attitude in Moscow which at this moment doesn't seem likely. It may happen in the 30s as China's economic expansion continues but I doubt it would be openly adversarial as the preferred partners for Moscow in balancing Chinese influence are the European and west Asian countries, not America. If America weakens sufficiently that Russia can renegotiate its relationship with Europe it might also choose to renegotiate its relationship with Japan. This would lead to an Orwellian scenario of Eastasia vs Eurasia vs Oceania which matches resource producers with capital producers in a manner that is stable in the long term and paradoxically beneficial to everyone as it would be sustainable. The current situation is precarious because American hegemony is not sustainable. It therefore has natural dynamic toward correction which America will attempt to prevent through war.
In my view this is also one of the reasons for AUKUS:
To do so a strong separation between economies of Australia and China has to be achieved and that can only be justified with arguments of national security on both sides.
This is why Australia suddenly declares its preference toward nuclear submarines. The word nuclear is what generates arguments of national security. If that doesn't succeed in splitting the two then war will be instigated for that purpose. If Australia falls into Chinese sphere of influence sufficiently that it becomes a non-US aligned territory then the only way American navy can move between the two most important oceans is through the Americas - Panama or Cape Horn.
I made a spreadsheet for an alternative scenario with service time of all submarines at 25 years. I won't link it because just as in the previous instances it won't be legible. What it demonstrated was this: assuming the same build orders Japanese submarine force plateaus in 2005 at 25 ships and last Harushio is retired in 2022. Which means that the only thing that is different in that alternative scenario is a 50% greater maintenance and personnel cost of the submarine fleet between 1987 and 2017.
Historically during that time Japan built more capable helicopter carriers and destroyers. Because Japan has a politically-determined ceiling for military spending at 1% GDP unchanged since 1960 and a legal cap for active personnel the funding for additional submarines would have to come from the funds for surface fleet. Submarines are a wartime fleet. A peacetime fleet is a surface fleet. Japan used the "Toyota way" for their naval strategy and it was the right choice because it modernized its surface fleet while retaining industrial capacity to expand its submarine fleet when necessary.
Besides those older submarines were hardly modern so their retirement was not a major loss:
- Uzushio were built 1968-1978 and most were withdrawn from service by 1991. The only modern thing was the teardrop hull.
- Yushio were built 1976-1989 and were equivalents of the Dutch Zwaardvis class which Taiwan also uses (Hai Lung). They had better electronic systems compared to their predecessors but not much more. They were modern in the same sense that a Kilo is modern compared to a Foxtrot.
- Harushio were built 1987-1997 and were an improved design similar to the Dutch Walrus class but they would require a costly overhaul to be able to serve for additional 10 years and they still wouldn't match the performance and capabilities of Oyashio and especially Soryu.
The size of Japanese navy was largely constant since the 80s when it was supposed to augment USN against Soviet Pacific Fleet. Table below includes all domestically-built ships but all the US-made ships were retired in the 1970s.
As Russian navy collapsed in the 90s Japan had the second largest and most potent naval force in the Pacific until China started its rapid naval expansion in the 2010s. For political reasons JMSDF operates as a vassal force to the USN so it should never be considered in separation to the 7th US Fleet. It will only be in this decade that PLAN takes over WestPac USN and JMSDF in terms of potential.
It is questionable if more submarines are the right choice for the future. What would they possibly change in the strategic equation? Japan's weakness lies entirely in its geography and economy. It's a case of Taiwan - just on a larger scale. Japan can double or even triple their navy and it won't matter.
I've seen comparisons between Japan and Britain but Britain's rise in the 19th century happened on the back of unprecedented industrial and economic growth. Britain in 19th century was a growing economic power and it improved its position globally in the same way that America did in the 20th century also on the back of rapid economic growth. Japan is a declining economic power past its historical peak.
As the balance of power in western Pacific shifts Japanese security interest will follow the economic shift toward China. Japan is not a meaningful adversary for China because that has to come from natural economic potential. If Japan retains its alignment with the US then a more likely outcome is a breakup of the nominal alliance between Japan and Korea which exists under their vassalage to Washington. Korea will naturally shift toward China and Japan may choose an adversarial stance against Korea as these two occupy the same political, economic and military space. Korea would become a proxy tool for China and Japan a proxy tool for America.
Furthermore the key to any long-term strategy against China is Russia. As long as Russia remains neutral toward China the shift in the balance of power toward China will continue. The only thing that can stop it is a change in geopolitical attitude in Moscow which at this moment doesn't seem likely. It may happen in the 30s as China's economic expansion continues but I doubt it would be openly adversarial as the preferred partners for Moscow in balancing Chinese influence are the European and west Asian countries, not America. If America weakens sufficiently that Russia can renegotiate its relationship with Europe it might also choose to renegotiate its relationship with Japan. This would lead to an Orwellian scenario of Eastasia vs Eurasia vs Oceania which matches resource producers with capital producers in a manner that is stable in the long term and paradoxically beneficial to everyone as it would be sustainable. The current situation is precarious because American hegemony is not sustainable. It therefore has natural dynamic toward correction which America will attempt to prevent through war.
In my view this is also one of the reasons for AUKUS:
- it puts a resource-rich continent in the "Oceania" sphere of influence
- it provides a logistical base for any power projection into Antarctica
- it provides a flank to shield against any power projection into South America
- it prevents cutting off American movement between Pacific and Indian oceans.
To do so a strong separation between economies of Australia and China has to be achieved and that can only be justified with arguments of national security on both sides.
This is why Australia suddenly declares its preference toward nuclear submarines. The word nuclear is what generates arguments of national security. If that doesn't succeed in splitting the two then war will be instigated for that purpose. If Australia falls into Chinese sphere of influence sufficiently that it becomes a non-US aligned territory then the only way American navy can move between the two most important oceans is through the Americas - Panama or Cape Horn.