Japan uses a continuous build (1 new submarine per year) system. New classes (the Taigeis are the latest) are created every 10 years or so. Production is shared between Kawasaki Heavy Industries (KHI) and Mitsubishi Heavy Industries (MHI). There are gradual improvements (often in diesel, snorkel, sensor and weapon systems) within classes and between classes.
Also see SubMatt's Updated History & Photos of Japanese Submarines After WWII of January 17, 2015 at https://gentleseas.blogspot.com/2015/01/history-of-japanese-submarine-after-wwii.html It contains a vast amount of Japanese originated information on Japanese submarines. From the end of WWII (September 2, 1945) to June 30, 1960 Japan had no operational submarines.
From December 1957 Japan restarted submarine production based on US experience (eg US Gato class) and based on long institutional experience building advanced submarines for the former WWII Imperial Japanese Navy.
+++++++++++++++++++++++++++++
TABLE
This Table is unique to Submarine Matters mainly created by "S"/Anonymous and Pete.
Japan's Diesel-Electric Classes of Submarine (SSKs)
The 2nd Oyashio class, Soryus & Taigeis as at October 18, 2025.
SS No. Diesel Type Motor | Build No Name | Pennant No. | Ministry of Finance (MoF) approved Ministry of Defense Budget in Billions of Yen (¥B) | LABs + AIP: or LIBs | Laid Down | Laun -ched | Comm ission ed | Built By |
8105 + 8106 Oya shio means currents | ¥52.2B FY1993 2 x 12V25/25S diesels for all Oyashio class (each diesel 2,000kW) | LABs only | 1994 & 1995 | 1996 & 1997 | Built at KHI | |||
7SS-15SS 8 active Oyashios 10 subs SMC-7? | 8107 -8115 various | SS-591-600 | ¥52.2B per sub FY1994-FY2003 | LABs only | 15SS Feb 2004 | 15SS Nov 2006 | 15SS Mar 2008 | MHI & KHI |
16SS Dragon class Mk I | 8116 | SS-501 | ¥60B FY2004 Mk.1 LAB+AIP Soryus have 2 x Kawasaki + a SMC-8 motor | LABs + AIP | Mar 2005 | Dec 2007 | Mar 2009 | Built at MHI Home Port Kure |
17SS | 8117 Unryū | SS-502 | ¥58.7B FY2005 | LABs + AIP | Mar 2006 | Oct 2008 | Mar 2010 | KHI Kure |
18SS | 8118 Hakuryū | SS-503 | ¥56.2 FY2006 | LABs + AIP | Feb 2007 | Oct 2009 | Mar 2011 | MHI Kure |
19SS | 8119 Kenryū | SS-504 | ¥53B FY2007 | LABs + AIP | Mar 2008 | Nov 2010 | Mar 2012 | KHI Kure |
20SS | 8120 Zuiryū | SS-505 | ¥51B FY2008 | LABs + AIP | Mar 2009 | Oct 2011 | Mar 2013 | MHI Yokosuka |
21SS LIBs Concept Research Project | No 21SS built. It was an 8 year research project on LIBs. 1st LIBs sub launched was 27SS in 2018. | |||||||
22SS | 8121 Kokuryū | SS-506 | ¥52.8B FY2010 | LABs + AIP | Jan 2011 | Oct 2013 | Mar 2015 | KHI Yokosuka |
23SS | 8122 Jinryu | SS-507 | ¥54.6B FY2011 | LABs + AIP | Feb 2012 | Oct 2014 | 7 Mar 2016 | MHI Kure |
24SS | 8123 Sekiryū | SS-508 | ¥54.7B FY2012 | LABs + AIP | KHI Kure | |||
25SS | 8124 | SS-509 | ¥53.1B FY2013 | LABs + AIP | 22 Oct 2013 | 12 Oct 2016 | MHI Yokosuka | |
26SS | 8125 | SS-510 | LABs + AIP | 2014 | 6 Nov 2017 | KHI Kure | ||
27SS a Soryu "Mk II" as it has LIBs. 1st Soryu Mk II | 8126 | SS-511 | ¥64.4B FY2015 with 2 12V25/25SB diesels (totaling 4,240kW) agree it has 640 LIB/SLH modules], other improvements | LIBs only (SLH type) | Nov 2015 | 4 Oct 2018 | 2020 | MHI Kure |
28SS Soryu Mk II, final Soryu | 8127 | SS-512 | NCA? LIBs | Jan 2017 | KHI Yokosuka | |||
29SS 1st Taigei Class means Whale 3,000 tonne (surfaced) | 8128 Taigei "Big whale" Used as test sub. Not opera- tional | SS-513 | says 640 LIB/SLH modules, Anon says 720.] | SLH LIBs maybe 960 | 14 Oct 2020 | 9 Mar 2022 | MHI Home Port Yokosuka | |
30SS 2nd Taigei Class | 8129 Hakugei "White whale" First opera- tional Taigei | SS-514 | SLH LIBs | KHI Home Port Kure | ||||
| 8130 Jingei "Swift whale" | SLH LIBs maybe 960+ | 8 Mar 2024 | MHI | |||||
02SS 4th Taigei Class | 8131 Raigei Thunder whale | SS-516 | Impro ved SLH LIBs | 26 Mar 2021 | KHI | |||
03SS 5th Taigei Class | SS-517 | LIBs | 19 Apr 2022 | Planned 8 March 2026? | MHI | |||
04SS 6th Taigei Class | SS-518 | LIBs | 28 Mar 2023 | Mar? 2027 | KHI | |||
05SS | 8134 | SS-519 | LIBs | 17 Apr 2024 | 2026 | ? Mar 2028 | MHI | |
06SS | 8135 | SS-520 | ¥95.00FY2024 enhanced sensors page 24 [1] | LIBs | 2025 | 2027 | 2029 | KHI |
07SS | 8136 | SS-521 | ¥B? FY2025 | LIBs | 2026 | 2028 | 2030 | MHI |
08SS | 8137 | SS-522 | ¥B? FY2026 | LIBs | 2027 | 2029 | 2031 | KHI |
¥***B = Billion Yen. MHI = Mitsubishi Heavy Industries, KHI = Kawasaki Shipbuilding Corporation of Kawasaki Heavy Industries.
at https://www.mod.go.jp/en/d_act/d_budget/pdf/20240607a.pdf
25 comments:
Hot off the press:
https://www.channelnewsasia.com/singapore/multi-role-combat-vessel-mrcv-navy-warship-mindef-5414746
so this is why it was so unexpectedly quick (1 year from award to launch)
the hull needs to be launched so it can be moved to another yard where the superstructure can be fitted
Hi retortPouch at 10/21/2025 9:03 PM
I'm envious. Contract award until launch was only 2 1/2 years https://en.wikipedia.org/wiki/Republic_of_Singapore_Navy#Future_procurement_plans reports :
"Contract for the procurement for six multi-role combat vessels (MRCV) was signed between ST Engineering Marine Ltd and SAAB on 28 March 2023"
It would have taken Australia 10 years.
Cheers Pete
Oh yeah, what the heck was I saying? It's 1 year from keel laying to hull launch, but the MRCV has been stewing for a long while... meanwhile, whither the JMMS!
Hi,
here some new information about German submarine production capacity:
"TKMS habe überdies angekündigt, ab 2027 etwa drei bis vier Boote pro Jahr produzieren zu können."
"TKMS has also announced that it will be able to produce about three to four boats per year starting in 2027."
https://www.hartpunkt.de/pistorius-wirbt-fuer-einstieg-der-kanadier-bei-u-212-cd/
The article is about the 12 submarines for Canada. Also worth translating.
Price tag for Germany for 4 Type 212 CD is 4.7 billion Euro and additional 2.44 billion Euro for special equipment requests. That's in total 12.8 billion AUD or $8.3 billion.
Regards,
MHalblaub
Meanwhile, South Korea launches a new Submarine of its own:
"It is equipped with 10 vertical launch systems (VLS) capable of
carrying submarine-launched ballistic missiles (SLBM) such as
Hyunmoo-4, doubling the firepower compared to the Dosan Ahn
Chang-ho-class (6 VLS)."
Source:
https://www.chosun.com/english/national-en/2025/10/23/44T7V23CT5HWXLLFRZ4JQN64YI/
Thanks MHalblaub at 10/23/2025 1:50 AM and Anonymous at 10/23/2025 4:48 AM
I suspect Germany with Norway versus South Korea's bid for Canada's replacement submarine competition will be fought for several months, or years, to come.
It is unfortunate for Canada that the US prevents Canada from having nuclear subs. https://en.wikipedia.org/wiki/Canada-class_submarine#American_opposition
Canada, in a war with Russia or China, will have severely limited under ice performance. The anti-submarine forces using advanced satellite sensors of Russia or China merely need to wait for a month for a VERY SLOW MOVING Canadian diesel-electric-AIP sub having to snort and LOUDLY use diesels to recharge its batteries. Then a hypersonic long range missile will destroy it.
Or a fast moving Russian or Chinese SSN could chase a slow moving Canadian SSK while under the ice. The Canadian sub's batteries and AIP will be exhausted after 1 or 2 days of moving around 20 knots.
Pete
Dear Pete,
I must lower your expectations for advanced satellite sensors. To be effective these sensors must be close to the surface in low earth orbit (LEO). Then you would require a huge number of satellites to detect a submarine at any time. Even China can’t afford that number. A submarine just needs to use the time gaps without a satellite overhead. These gaps are very predictable because it’s very fuel consuming to change orbits.
Do really you think a running diesel engine on a Type 212 is louder than a fast moving nuclear-powered submarine? Speed kills and size matters. A small Type 212 can go where no fat SSN can go. Just look at the fractured northern Canadian coastline. Ideal hunting ground for a small submarine looking for a big whale.
“I suspect Germany with Norway versus South Korea's bid for Canada's replacement submarine competition will be fought for several months, or years, to come.”
I doubt Canada needs more time for a decision than Australia. Singapore ordered their Type 218SG in 2013 and commissioned the first two ships in 2024. Australia started in 2009 and may receive new submarines in 2040 or later. Canada wants its submarines in 2035. I expect a decision before the end of 2026 due to the momentum for military acquisition of the Ukrainian war. Maybe there will be the opportunity for Australia to get some Victoria-class submarines as an interim solution.
I can’t see a reason why a Canadian submarine would need a dedicated land attack capability. Where could Canada strike in a conflict?
Regards,
MHalblaub
Hi MHalblaub at 10/23/2025 11:42 PM
Yes our opinions are largely unprovable in the secret submarine world.
Regarding your opinion:
"To be effective these sensors must be close to the surface in low earth orbit (LEO). Then you would require a huge number of satellites to detect a submarine at any time. Even China can’t afford that number. A submarine just needs to use the time gaps without a satellite overhead. These gaps are very predictable because it’s very fuel consuming to change orbits."
Here is just such a constellation with "a huge number of satellites" that are "close to the surface in low earth orbit (LEO)" that just one US company has deployed. There are no gaps. https://en.wikipedia.org/wiki/Starlink
"SpaceX began launching Starlink satellites in 2019. As of May 2025, the constellation consists of over 7,600 mass-produced small satellites in low Earth orbit (LEO) [already] that communicate with designated ground transceivers. Starlink comprises 65% of all active satellites.[11] Nearly 12,000 satellites are planned, with a possible later extension to 34,400."
If the those satellites had sufficiently sensitive electro-optical sensors they may be able to see a submarine's snorkel and periscopes/photonic masts.
Regards Pete
Hi Pete
Just want to throw some thoughts.
For the concern that the fuel cell AIP might not be able to provide sufficient energy for extended patrol at sea
I've read a doc from early 90s that compare several type of AIP, it seems the methanol reformer+AIP yield the best volumetric power density.
For a 7.6m diameter pressure hull, an 18 m-long AIP module can carry of reformer+fuel cell system + 108t of methanol+163t of LOX.
A more ambitious design that extend the diameter out to 10m could perhaps store close to 300t of methanol and 450t of lox ? That could yield a potential total capacity of 600-700MWh.
For fuel cell, the new FC4G from TKMS is quite compact
https://euro-sd.com/2023/12/articles/34972/developments-in-lithium-ion-batteries-and-aip-systems-for-submarines/
according to the article, this could yield about 320kW of output. If true, about 20 of them can put out 6.4MW, that could probably be sufficient for 20 knots dash + onboard sensor load for a 3000-4000t SSK.
https://jmstt.ntou.edu.tw/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1152&context=journal (See figure 2 for speed-power curve)
Assume this hypothetical SSK require about 6MW for 20 knots and other load, the above system could carry on for at least 4-5 days before the reactants is totally exhausted. A more realistic scenario will probably be patrolling at 10-12 knots. Here the power requirement would be 5-6 times less, so a month at 10-12 knots is highly possible.
And this didn't take into account of any onboard Li-ion capacity, however i don't think LIBS would be nearly as crucial in this case as the AIP.
For much more enclosed area like north atlantic or arctic, i can see this become a reasonable alternative to SSN. Ofc, SSN will still hold a significant advantage in endurance in very long patrols.
Dear Pete,
to track something from orbit reliably on earth you can't use optics due to a phenomenon called clouds. Clouds are also a problem detecting diesel smoke particles from orbit. Therefore something else is required like a synthetic-aperture radar (SAR). E.g. German SAR-Lupe satellites orbits at 500 km just like Starlink. The problem to detect a snorkel with SAR are twofold: the snorkel is quite the minimum size X-band SAR can resolve, about 50 cm x 50 cm and radar absorbing materials on snorkels (since Type XXI). Did China invent something else to detect submarines? The problem is basic physic: angular resolution even for opitcs
Here you can see the coverage area of starlink and look where Hudson Bay is located. https://upload.wikimedia.org/wikipedia/commons/1/1a/Starlink_SpaceX_1584_satellites_72_Planes_22each.png
There are many shallow bays or passages in the north of Canada where a SSN can’t follow a small SSK. No problem running a silent diesel engine there. Is Garden Island-Hedemora a silent diesel engine?
Hi Anonymous at 10/24/2025 10:50 PM
Yes what you say about optical sensors looks right.
But satellites using some types of radar might detect snorkels and periscopes/optronic masts. See https://gentleseas.blogspot.com/2012/08/satellite-detection-of-submarines.html
Cheers Pete
Hi Anonymous at 10/24/2025 2:02 PM
An SSK with AIP might move at 20 knots for about 3 hours maximum because it needs to keep some AIP and battery power in reserve for life and death emergencies.
AIP providing companies occasionally argue that AIP is a substitute for nuclear. But an SSN might move at 25 knots for weeks while an AIP equipped submarine might move at 25 knots for about 2 hours until its AIP and batteries are fully depleted.
Sustaining higher speeds is not a linear power matter, rather squaring or cubing power electrical capacity is probably more accurate.
Another consideration is increasing noise as a submarine moves underwater more quickly. An SSN equipped with a pumpjet might be far quieter at at speeds above 15 knots, than a SSK all of which use propellers (due to heavy weight of pumpjet considerations).
This is because an SSK with a propeller is more prone to experience noisy cavitation https://en.wikipedia.org/wiki/Cavitation above 15 knots. While an SSN with a pumpjet (too heavy for an SSK to use) is quieter above 15 knots.
Regards Pete
Hi pete
The SLCM development project currently being promoted by the ATLA is a separate project from the Type12SSM-ER development project. [1]
Therefore, it should not be assumed that the Type12SSM-ER will be deployed on the Taigei-class submarines.
Note that while development of this SLCM is not yet complete, the initial mass production contract was signed last month. [2]
Meanwhile, Japan recently saw a realignment of political parties and the formation of a new coalition government. The agreement between the ruling parties included the phrase “long-endurance submarines equipped with next-generation power plants and VLS and stand-off missiles” [3]
This is widely seen as referring to SSGNs.
In the distant future, “JUKUS-SSGNs” similar to “AUKUS-SSNs” may become a reality.
[1]https://www.mod.go.jp/j/policy/hyouka/seisaku/2022/pdf/jizen_11_honbun.pdf
[2]https://www.mod.go.jp/j/press/news/2025/10/07b.html
[3]https://o-ishin.jp/news/2025/images/624de5f22900f6e88e892abb49d3fc70ef3cac92.pdf#page=5
Regards
wispywood2344
Hi wispywood2344 at 10/26/2025 2:09 AM
Your comment is very important. I have removed mention of Type12SSM-ER.
I have also written article "Japan Long Term Planning ICBM as well as SSGN Capabilities?" of October 26, 2025 at https://gentleseas.blogspot.com/2025/10/japan-long-term-planning-icbm-as-well.html
Regards Pete
Thanks Pete and MHalblaub for the interesting thread. There is some open source data available on satellite ISR for a range of purposes. The cloud problem can be overcome by use of Infra Red photography from LEO satellites.
Papers have hypothesised that shallow cruising sub s(SSK or SSN) could be detected from the temperature differential of their wake by scanning infra-red photos. Not easy but possible on smooth seas.
https://www.quanhom.com/knowledge-cont-245
IMO the real threat of detection to SSKs when they are snorkeling is the potential for LEO satellites to detect the diesel exhaust plum. (Ironically this tech was developed to monitor greenhouse gases for climate agreements).
The paper below shows we can already isolate a plum as small as 60 metres square. Scan an ocean and anywhere there is a diesel plum with no ship below it is probably a snorkelling sub. The drawback is that this will take a few hours of data processing. Still, subs could be tracked at a strategic level if they snorkel.
https://www.sciencedirect.com/science/article/abs/pii/S0048969723054451
Hi Pete,
Regarding speed at certain power threshold. There's a pretty good formula for this from u/Vepr157 on reddit years ago:
U = (P/K)^1/3*V-2/9
where P: power
K: drag coefficient, we'll use 0.0108 for simplification
V: total volume in cubic metre
applying above for a hypothetical 2000t SSK running on full power at 3MW
V^{-2/9} = 2000^(-2/9) ~ 0.185
(P/K)^{1/3}=(3000/0.0108)^(1/3) ~65.25
U ~ 65.25*0.185 = 12.07 m/s ~ 23.46 kt
And i do agree with you that at higher speeds (above 20 knots) then SSK will likely be noisier than SSN, due to the absence of a pump jet(the exception would be the canceled attack class of the australian navy years ago, though i'm unsure how useful would a pump jet be on a diesel-electric using older LAB battery without any AIP system).
Though for the modern Yasen, according to Bruce Rule, the sub might have to switch to DC motor for true 'stealth' mode (< 8 kt), highly likely due to the absence of a pump jet:
[For patrol mode and for low-speed transits, the BOREY uses a 5,500 horsepower (hp) dc motor, exactly the same hp rating as the PG-141 dc propulsion motor installed on all KILO Class Russian diesel submarines. Use of this turbo-electric mode eliminates the acoustic vulnerability that planetary reduction gear associated noise represents at low speeds.]
[At very low rotational speeds, for which reduced centrifugal force exists, the planets, because of gravity, will fall away from the ring-gear when they pass through the upper arc of the circle of rotation, and will fall toward the sun-gear. Thus, at low rotational speeds, which are low ship's speeds, less precisely machined planetary gears can produce impact energy from both tooth-slap and the positional changes – no matter how small – of the planets relative to the ring- and sun-gears. Thus, planetary gear systems can produce more noise at the very low-speeds typical of SSBN patrols than at higher speeds.]
https://pub10.bravenet.com/forum/static/show.php?usernum=774301397&frmid=32&msgid=1356633
https://www.iusscaa.org/articles/brucerule/potential_acoustic_vulnerability_of_borey_and_yasen_class_russian_nuclear_submarines.htm
In any case, my opinion is fuel cell AIP SSK now get to the point of being 'good enough' to challenge SSN in many situations rather than just being a glorified movable sea mine, as the case with older diesel-electric boats.
Hi Anonymous at 10/26/2025 5:37 PM
Indeed. You're on top of the maths.
Cheers Pete
Hi Anonymous at 10/26/2025 5:02 PM
You've located some very interesting references: https://www.sciencedirect.com/science/article/abs/pii/S0048969723054451 and especially https://www.quanhom.com/knowledge-cont-245 on the importance of frequently overlooked infrared sensors.
It is as though acoustic and magnetic anomaly are the ONLY sensors that count.
Cheers Pete
Cheers Pete
FYI, this is where i take the formula from :
https://www.reddit.com/r/submarines/comments/c5822p/comment/es087fy/
Regards
Thanks DopSeu at 10/27/2025 10:52 PM
Regards Pete
The detection of SSN via temperature differences might be possible but SSK have a power output 10 times less. Also less visible beneath ice.
CO2 detection via IR-Laser is a thing but it is also an active detection method like a sonar ping. The reflections of the beam are measured up in space. I could imagine they are detectable on the surface. Snorkels already have radar detectors. I’m even more optimistic according to detection speed. There is no need to process all the data as for environmental purpose. Only the peaks need to be analysed more thoroughly. This is a good option up in the northern part of Canada without much marine traffic. At any other part of the world a submarine just needs to snorkel behind any kind of vessel.
Is the information via CO2 detection sufficient to attack a submarine? I doubt it. How should a long range hypersonic anti-ship missile detect a submarine? A submarine would just dive in case detected by laser.
BTW in 2005 old Type 212A U32 travelled 4600 nm in 18 days submerged from Europa to the US.
Thanks Anonymous at 10/28/2025 12:32 AM
For your clear explanation.
I too recall in 2005 the German Navy's Type 212A U32 travelling 4600 nm 18 days submerged from Europe to the US, using its battery and fuel cell AIP.
Cheers Pete
Pete you are welcome. Note that I am stating what is possible with current technology. It might be enough to locate a sub at a strategic level but not tactically. By the time you have scanned and processed the data the SSK might have moved one hour's travel. So the satellite becomes a strategic locating tool and you then need local assets to track and generate a firing solution. If the sub (SSK or SSN) dove below the boundary layer and/or was not snorkeling, then I can't see much a satellite could do to find it. So don't sell those P8 Poseidon's yet!
Anonymous. No the IR signature stuff would not give an exact locational solution. It might locate subs with a few hundred metres. Also no exact depth. So you know where to drop the Sonobuoys, maybe a homing torpedo?
Hi Scott at 10/28/2025 2:21 PM
Once satellites have picked up near surface subs, the tactical narrow-downers, with active sonar, are:
- the RAAF P8s (with sonobuoys) until 2042 if not longer https://en.wikipedia.org/wiki/Boeing_P-8_Poseidon#Operators .
and
- the RAN's MH-60R Seahawks, also for ASW (with dipping sonar) and also sonobuoys possible.
Both aircraft types can fire homing lightweight torpedoes to narrow down the position and destroy subs.
Cheers Pete
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