History of the Japanese Submarine(After WWII)

Defense Plan and Submarines

      Japan had constructed 242 submarines in the Imperial navy era (1869 - 1945), and operated 3530 ton(6560 ton in submerged) I-400 submarine carry three floatplanes during the World War II. However, 58 submarines that remained with the defeat in 1945 were taken over by the Allies Forces and have been dismantled or sunk in the Pacific Ocean.

      By outbreak of the Korean War in June 1950, the National Police Reserve(Later Ground Self-Defense Force) was born in August. While, in April 1952 the Maritime Security Force was organized in the Maritime Safety Agency, and in August the Maritime Self-Defense Force(Hereafter JMSDF) was reformed from the Maritime Security Force and independent from the Maritime Safety Agency.

      During the cold war era, the mission of the JMSDF was aimed the command of the sea of the west Pacific in cooperation with the U.S. navy, against Soviet navy as one of the west side navy, influenced by the confrontation between the east and west. But after surrender the Pacific War, as Japan was enforced by the Allied Occupation Forces to accept the constitution, which declared renunciation of war, as a sovereign right of the nation and the threat or use of force as means of settling international disputes. By this historical background, and strong anti-military feeling among the peoples, the National Defense Council draw up the Basic Policy for National Defense and it was approved by the Cabinet in May 1957. This policy declared Japan has been making efforts on its own initiative to build a modest defense capability under the Constitution in accordance with the fundamental principals of maintaining an exclusively by defense-oriented policy of not becoming a military power that might pose a threat to other courtiers. Though the Maritime Self-Defense Force esteemed to strengthen operational capability of anti-submarine and mine sweeping operation as allies that the U.S. navy is lacking in the northeast Asia area.

        By this defense policy, the main mission of the JMSDF submarine was surveillance and interception of Soviet combatants in major straits. In order to ensure the safety of Japan’s maritime transportation, the JMSDF needs to maintain the posture capable of deploying two submarines each in the three straits of Soya, Tsugaru and Tsushima, where necessary. In order to maintain such capability, it was necessary to possess six divisions with 16 submarines, taking into account geographical relations between submarine bases and sea areas where engage in surveillance and interception operation.


        However, early stages of the 1950s, there were strong opposition to have submarine by left wing political party and peoples. They opposed that submarine is an aggressive weapon and violate what is called “Peace Constitution”. By these oppositions, the construction of the submarine was delayed in comparison with the surface combatants, such as a destroyer and escort ship. So, the JMSDF had to ask the assistance for the U.S. navy for the target submarine needed for ASW training. Then fleet type submarine Mingo(SS-261) of U.S. navy was lent, on the basis of the Japan-U.S. Weapon Loan Agreement that was concluded in August 1955 and she was turn-over to the JMSDF and named Kuroshio(SS-501).Thus after 10 year’s interval of defeat of the Pacific War, Japanese new navy ? the JMSDF could hosted the Rising?Sun flag again to the sale of the submarine.

        Thereafter, Kuroshio carry our the duty as the underwater target boat and submarine’s crew OJT(On the Job training) ship, as the sole submarine of the JMSDF for about 5 years until the first domestic submarine come out and take over this role. As there was very strong anti-military feeling among peoples of Japan, the JDSDF could not use the word of submarine, so it was called as “an underwater high-speed target” for budge requirement and public announcements. These feeling still continued and Japanese submarines are still imposed several fateful restriction from the time of the birth to nowadays.

        From FY1958 to FY1977, the JMSDF was reinforcing by Five Years Defense Built-up Program four times, accordance with the Basic Policies for National Defense. This Basic Policies for National Defense include an exclusively defense-oriented policy, and also, adherence to the Three Non-Nuclear Principles, -- “Japan do not make or use any nuclear weapons and do not permit to bring into any nuclear weapon in Japanese territories”, also maintaining firmly the Japan - U.S. security arrangements.

         But in 1970s there aroused the strong opinion that Japan should restrict armament accordance with the world situation of the U.S and Soviet peace talk, the National Defense Policy and National Defense Buildup Program Outline were reviewed in October 1976. Further more as a result of the collapse of the Soviet Union, the defense power of the necessary minimum as an independent state which means not to become over the unstableness in our country periphery and self "becomes the blank of power” was decided by the National Defense Council and approved by the Cabinet in November 1995. Accordance with this new National Defense Buildup Program Outline, first Mid-Term Defense Built-up Plan (FY1980-FY1983) was adopted in December 1979.

        By this new National Defense Buildup Program Outline, defense capabilities and major units and main equipment of the JMSDF were again reviewed, and due to the deterioration of finances, necessary expenses were significantly reduced in December 1997. The submarine forces were also reviewed by this new National Defense Buildup Program Outline, but six divisions sixteen submarines were maintained, thought about 10% of the JMSDF forces were reduced by the policy of streaming, making it more efficient and compact.

Oyashio class:First home built submarine
                       
          The idea of the construction of the domestic production proceeded as an alternation of Kuroshio in early 1954. The construction idea of the shift Kuroshio sprouted three types of boats, 1,000 tons class(10 knot on surface, 20 knot in submerged), 500 tons class(9 knot on surface 17 knot in submerged) and 250 tons class(9 knot on surface, 13 knot in submerged) and these three plans were examined by the Under Water Weapon Study Committee of the Maritime Staff Office .
However, on that time, it was difficult to get 20 knot in underwater as lack of space to install big engines, so finally 1000 tons plan was adopted in December 1957 by the Maritime Staff Office. Construction began at the Kawasaki Heavy Industries Ltd. Kobe Shipbuilding Yard from December 1957, she launched in May 1959 and after half year’s sea trial, she joined the Fleet in June 1960, as the name of Oyashio(SS-511).

        During construction stages, there aroused many difficulties, as technical blank of not constructing submarine for 10 years. Though basic design was adopted from the high-speed submarines I-201 class(1070ton, Lx79m, Wx5,8m, surface 2750 horsepower 15,8 knot, underwater 5000 horspoer 19 knot) of the Imperial Japanese navy. And also technology of the Imperial navy such as the automatic depth holding system was adapted, but the snorkel and other new devices were introduced from the U.S. navy sending technical missions and submariner to the U.S. navy, and learned not only technology, but also submarine operation and tactics.

        The JMSDF learn from the U.S. navy and also the submariners were tamed to the devices and system of the U.S navy through the Kuroshio, so if there was not big difference between Japan and America, applied the U.S. navy’s methods. During the construction increased 130 tons, and finally displacement became 1130 tons. She equipped four tubes for 533mm torpedoes. Power system was diesel-electric, two diesel Kawasaki MAN type of V8V22/30MATL, 2700 horsepower, two main motors of 5900 horsepower and two shaft, speed was 13 knot on surface, 19 knot in underwater , the battery was 4 groups of 120 cells. NS 46 high tension steel was used in hull, this high tension steel NS46 means 46kg pressure on 1mm square.

        On that time, as there were no training facilities for submariners in Japan, there aroused a demand to dispatches submarine to Hawaii to use the U.S. navy’s training facilities, and to learn tactics. This training is continued from 1968 to now and expanded to the LimPac Exercise including not only submarines, but also surface ships and air plain to improve tactical level and closer relations between the JMSDF and the U.S. navy.

Characteristics of Oyashio
● Displacement 1130 ton(double hull) NS 46 high tension steel.
● Length 79 m×beam7.0 m×depth 5,9 m×4,6m, L/D(Length/Depth Ratio) 13,4,
● Power Plant:Diesel-electronic, 2 diesel engine(Kawasaki V8V24/30AMTL) 2700 horsepower 13 knot on surface, 2 main motor 5900 horsepower 19 knot in submerged(Battery 120 set 2 groups)
● Armament 533mm torpedo tubes x 4
● Complement 65
● Contractor Kawasaki Heavy Industries Kobe
Remarks 1:The name of submarine of the JMSDF was name after from oceanographic phenomenon of “Shio(Tide)” in Japanese
Remarks 2: Submarine is constructed at the ex-Imperial navy’s main submarine Contractor of the New Mitsubishi Heavy Industries Kobe and the Kawasaki Heavy Industries Kobe alternately at a rate of one per two years in fiscal year.

Hayashio/Natsushio class:Small type submarine

          The plans for next submarine Hayashio(SS-521) begin with 700 tons but it become 750 tons, and first Hayashio class boats begin construction in June 1960 at New Mitsubishi Heavy Industry Kobe and lunched in June 1962, other was constructed by Kawasaki Heavy Industry in Kobe in June 1960 and also lunched in June 1962, and two more Natsushio class boats constructed in 1963. Hayashio class was firstly esteemed for coastal defense and for blocking the three straits as a attack-submarine(SSK) in war time, and also aimed to be under-water target submarine for ASW training in the peace time.

        The speed decreased 14 knot in submerged with 2300 horsepower and surface 11 knot with 900 horsepower. Battery system was 120 shell and 2 groups. Due to the small boat, torpedo tubes were limited only six, but from this class hydrographic launching tubes were introduced from air launching tubes. Also from this class, two sonar systems were adopted, one is passive bow sonar, and the other was active sonar under the sail covered by FRP dome for ranging. The big difference of Hayashio and Natsushio is length, from Natsushio class canning tower were expanded 1.5 m for astern and overall length became 59m to 61m and displacement increased 790 tons.

        The JMSDF constructed three classes of ten submarines by the First(FY1958 - FY1962) and the Second (FY1962 ? FY1967) Defense Built-up Programs. But, as Hayashio was constructed after long blank of construction, there were many malfunctions and troubles, and that Hayashio class was too small for stable snorkeling in the rough sea around Japan, and also as restricted in endurances capability because of poor habitability. By theses reasons, small size submarine 750 ton class were not considered in Japan after Hayashio class. Hayashio class constructed 4 boats,

  Characteristics of Hayashio(Natsusio)class
● Displacement 750(790) ton(double hull, partly single in astern section),NS 30 high tension steel
● Length 59(61) m×beam 6,5 m×depth 6,4×draft 4,1m, L/D 9,2
● Power Plant Diesel-electronic, 2 diesel engines(Mitsubishi Kobe 6LDA25B), 900 horsepower 11 knot surface, 2 main motors, 2300 horsepower 14 (15)knot in submerged(Battery 120 set 2 groups)
● Armament 533mm torpedo tubes x 3
● Complement 40
Name(Commissioned/Decommissioned)
Hayashio(SS-521) (Commissioned 1962)(Decommissioned 1977) (Mitsubishi)
Wakashio (SS-522)(Commissioned 1962)(Decommissioned 1979)(Kawasaki)
Natsushio(SS-523)(Commissioned 1963)(Decommissioned 1978)(Mitsubishi)
Fuyushio(SS-524)(Commissioned 1963)(Decommissioned 1980)(Kawasaki)

Ooshio/Asashio Class:Ocean type submarine

 From operational experiences of small submarines, these small submarines were lacking operational stability in the rough sea, especially in snorkeling. Next submarine was considered for large multipurpose submarine for patrol, surveillance, reconnaissance and crew’s training. Ooshio class went to the sea in March 1965, then Asashio of 1650 tons improved type of Ooshio was commissioned in October 1966.
      By enlargement of displacement, eight 533mm torpedo tubes in bow and two short range homing torpedo tubes in stern which aimed as the counter-attack for anti-submarine ships(Later short range torpedo tubes were take off). Bow Torpedo tube became from air pressure launching to hydraulic launching. New steering and engines automation systems and auto-course holder were adapted. From this class provided a steering system became aircraft type stick control at the diving stand.

        This class was expected, as an underwater target use, so boat was esteemed high speed to carry out may services with a few submarines, so compromised with 18 knots in underwater with main motor of 6300 horsepower, 14 knot on surface with Man V8V24/30AMTL 2900 horsepower, two shafts. From these reasons underwater performance as a submarine was not realized until appearance of tears drop submarine. The L/D ratio become 11,7 in this class while Hayashio class was 9,2. From Asashio class screw propeller become 5 blades and safety depth increased by high tension steel NS 46.

 Charactlistics of Ooshio(Asashio)class
● Displacement:1600(1650) ton (double hull, partly single in astern section),NS 46 high tension steel
● Length 88 m×beam 8,2 m×depth 7,5×draft 4,7(4,9)m (L/D 11,7)
● Power Plant:Diesel-electronic, 2 diesel engines(Kawasaki V8V24/30AMTL), 2900 horsepower×2 14 knot on surface, 2 main motor 6300 horsepower, 18 knot in submerged(Battery 120 set 4 groups)
● Armament 533mm torpedo tubes×8, 533mm Anti Submarine Torpedo×2 astern
● Complement 82
Name(Commissioned/Decommissioned)
Ooshio(SS-561)(Commissioned 1965)(Decommissioned 1981)(Mitsubishi)
Asashio(SS-562) (Commissioned 1966)(Decommissioned 1983)(Kawasaki)
Harushio(SS-563)(Commissioned 1967)(Decommissioned 1984) (Mitsubishi)
Michishio(SS-564)(Commissioned 1968)(Decommissioned 1985) (Kawasaki)
Fuyushio(SS-565)(Commissioned 1969)(Decommissioned 1986) (Mitsubishi)

Uzushio class: The first tears drop type submarine
                         
         Uzushio class was the historic mile stone for the Japanese submarine that changed the application of the submarine which esteemed the surface ability than underwater ability. Ten kinds of models were made, to design the hull that demonstrated underwater performance, and conducted the water tank experiment to collect data for design of submarine figure and could get tears drop type submarine with one axis, L/D changed from conventional submarine 11,7(Oyashio class) to 7,1 in tear drop type. Also, the development of new steel necessary to expand safety depth was started.

        First boat of the Uzushio class began construction in January, 1971 and seven boats were constructed in the Third Defense Build-up Programs (FY1967-FY1972), and the Fourth Defense Build up Programs (FY1972-FY1977). By the adoption of tears drop type, underwater performance increased largely in comparison with the conventional submarine. Power plant was diesel-electric propulsion with two Kawasaki MAN V8V24/30AMTL diesel engines and speed was 12 knot by 3400 horsepower, output of main electric motor was 7200 horsepower, and estimated speed was 20 knot pulse in the under water. Battery became 240 set 2 groups from this class.

       New high tension steel NS63 was used on hull to increase the safety submerge depth to 300m(est). Increased tonnage brought space, deck becomes three layers, and this improved not only habitability of performance but also could equipped many devices. Carbonic acid gas absorbent air cleaner, the emergency blow system(Main blow tank), installation of spare torpedo, and could equipped the steerage device, trim and depth adjustment automatic controller, automatic direction holder, and automatic steerage of three dimensions.

       From the Uzushio class increased tonnages to 1850 ton, torpedo tube in bow was removed to the mid-ship section to install large sonar ZQQ-1 in bow(from Isoshio ZQQ-2, from Takashio ZQQ-3), also plane removed from bow to the sail. This plane characterized the tears drop style submarine from external form. In Japan, when the Uzushio commissioned, some member of the opposition political member pursue question in the Diet that the JMSDF was aiming to use nuclear power to submarine contrary to the "The three Non-Nuclear Principles", if an engine was changed to nuclear reactor, it could convert to nuclear submarine easily.

 Characteristics of Uzushio class
● Displacement:1850 ton(double hull, partly single in astern section),NS46 high tension steel
● Length 72 m×beam 9,9 m×depth 10.1 m×draft 7,5m(L/D 7,1)
● Power Plant Diesel-electronic, 2 diesel engines(Kawasaki V8V24/30AMTL), 3400 horsepower 12 knot, 1 main motor 7200 horsepower, 20 knot in submerged
● Armament 533mm torpedo tubes×6
● Complement 75(80 Takashio and Yaeshio)
Uzushio(SS-566)(Commissioned 1971)(Scraped 1987) (Kawasaki)
Makishio(SS-567) (Commissioned 1972) (Scraped 1988) (Mitsubishi)
Isoshio(SS-568) (Commissioned 1972)(Converted ASU-8001 1989)(Used as a target of
new torpedo and then scraped in 1992) (Kawasaki)
Narushio(SS-569)(commissioned 1973)(Converted ASU-8002, 1990)(Scraped 1993)
(Mitsubishi)
Kuroshio(SS-570)(Commissioned 1974)(Converted ASU-8003 1991)(Scraped 1994)
(Kawasaki)
Takashio(SS-570) (Commissioned 1976)(Converted ASU-8004 1992)(Scraped 1995)
(Mitsubishi)
Yaeshio(SS-572) (Commissioned 1978)(Converted ASU-8005 1994)(Scraped 1996)
(Kawasaki)

Yushio class:Second Tears Drop type Submarine

Yushio class submarine was the second generation of tear-drop boats, from FY1975 to FY1985, 10 boats were constructed. This class is double hull structure and used new high tension steel NS80 and safety depth increased 400m(est). The main engines are Kawasaki MAN V8V24/30ATMTL type, 12 knot at snorkel, and 20 knot in the water. From this class, high capacity new battery were installed, screw rotation are lower than Asashio class with five blades husky propeller. Automatic steerage system of three dimensions, automatic depth and direction holder system were equipped. VLF communication was also possible, net-work-centric combat systems were incorporated in operation room, which enhance adaptability of operations.

        Serial improvement were tried on Yushio class, while constructing 10 boats, from 1984 Nadashio (SS-579) equipped Harpoon missiles launcher with 533mm torpedo tube, by this new system, displacement increased 50 tons and become 2250 tons from 2200 tons. From 1981 Mochishio(SS-574) installed masker, in 1987 from Okishio (SS-576) equipped TASS(Towed Array Sonar System), Hamashio(SS-578) installed modified bow sonar ZQC-4 and attack sonar(active) in the sail in 1986, inertia navigation system was adapted in 1991, sixth boats are still active among ten constructed.

       The reason why Japanese submarine increased displacement constantly are installation of many kind of the weapons aiming a various functions for one submarine, as the total number of submarines are limited within 16 by the National Defense Buildup Program Outline. By this limitation, the JMSDF must decommissioned all boat which passed 16 years then assigned reserve, consequently all Japanese boat served sixteen years of front line, then assigned an axially training submarine for three years, then scraped and finished 19 years life. Furthermore as Japan strictly adopts a firm policy of banning prohibiting the exportation of a submarine or any weaponry, so mass production of auxiliaries equipments are push up high price because of small production, this also enforced effective usages of defense expenditures and oppressing defense budget.

 Characteristics of Yushio class
● Displacement 2250 ton (Complete double hull, partly single in astern part),NS80 high tension steel
● Length 76 m×beam 9,9 m×depth 10,2 m×draft 7,4 m(L/D 7,5)
● Power Plant Diesel-electronic, 2 diesel engines(Kawasaki V8V24/30AMTL), 3400 horsepower 12kt on surface, one main motor, 7200 horsepower 20 knot in submerged (screw 5 high-skew blades)
● Armament 533mm HU603 type tubes for torpedo and Harpoon×6
● Complement 75
Present states of Yushio class(Constructed 10 boats)
Yushio(SS-573)(Commissioned 1980)Converted 1996 ASU-8006(Scraped 1999) (Mitsubishi)
Mochishio(SS-574) (Commissioned 1981)Converted 1997 ASU-8007(Scraped 2000) (Kawasaki)
Setoshio(SS-575) (Commissioned 1982)Converted 1998 ASU-8008(Scraped 2001) (Mitsubishi)
Okishio(SS-576) (Commissioned 1983)Converted TSS-3603(Scraped 2001) (Kawasaki)
Nadashio(SS-577) (Commissioned 1984) (Scraped 2002) (Mitsubishi)Active
Hamashio(SS-578) (Commissioned 1985)Converted 2002 TSS-3604(Kawasaki)
Akishio(SS-579) (Commissioned 1986) (Mitsubishi)
Takeshio(SS-580) (Commissioned 1987) (Kawasaki)
Yukishio(SS-581) (Commissioned 1988) (Mitsubishi)
Sachishio(SS-582) (Commissioned 1989) (Kawasaki)

Harushio class:Third Tears drop type submarines

        The Harusio class is the third generation of the tear-drop submarine construction began from FY1986 to FY1992, and seven boats were constructed. Harushio class followed fundamentally adapted design of Yushio class, but increased 250 tons in displacement. This type was esteems improvement of the underwater maneuverability, expanded search and attack ability. The main motor’s rotation is slower than Yushio class with seven blades high-skew propeller.
       
          The various measures have been carried out to improve noise and tried to make silent submarine cut on noise of not only main engines but also auxiliary machines. Main engines and main motor were fitted on emission double anti-vibration rubber to reduce of a noise, pipe system, gears, and gaskets were improved, and also snorkel noise are reduced. Harushio class became a considerably quieter boat adapting noise-cut in auxiliary machines, while underwater speed, underwater endurances, safe submerge depth are greatly improved. High tension steel NS110 is adopted with a double shell hull and safety depth is extended 500 m(est). New inverter of electric power transformation(CVCF), which transform of 400 Hz and 60 Hz of the power supply, this help noise reduction and also saving electric power. From this type, torpedo/USM tubes were equipped from constriction stages, fitted with ZQQ-5 sonar system(From Nadashio ZQQ-5B type) combined with TASS and side-array-sonar as a unit. The reception of the communication became possible at the submerged states by the introduction of VLF receiver.

      Length of the ship become longer than Yushio class by 1.2 m and increased 190 tons and become finally 2,490 tons. Main engine are adopted newly developed Kawasaki MAN 12V25/25S, output became 3,100 horsepower, main battery were 240 shells of 2 groups. The IR detection and ESM devices and comfortable habitability of the crew were also improved. For weapons torpedo are changed to Type 89 torpedo in 1989.The tears drop submarine’s construction began from 1971 and constructed 7 Uzushio class, 10 Yushio class, 7 Harusshio class, totally 24 tear-drop boats to the fleet until 1990.

Characteristics of Harushio class

● Displacement 2450 ton(Asashio 2500 tons) (Double hull, partly single in astern part)NS110 high tension steel
● Length 77 m×beam 10.0 m×depth 10.5 m, draft 7.7m(L/D 7.3)
● Power Plant:Diesel-electronic, 2 diesel engines(Kawasaki 12V25/25S, 3400 horsepower 12kt on surface, one main motor 7200 horsepower 20knot plus in submerged
● Armament 533mm Hu603B type torpedo tubes for 89 type torpedo and Harpoon×6
● Complement 75(Asashio 71)
Same type ships(Commissioned)
SS-583 Harushio(November 30, 1990) (Mitsubishi)
SS-584 Natsushio(March 20, 1991) (Kawasaki)
SS-585 Hayashio(March 25, 1992) (Mitsubishi)
SS-586 Arashio(March 17, 1993) (Kawasaki)
SS-587 Wakasio(March 1, 1994) (Mitsubishi)
SS-588 Fuyushio(March 7, 1995) (Kawasaki)
SS-589 Asashio(March 12, 1997) Converted TSS-3601(March 2000) (Mitsubishi)

Oyashio type:Cigarette type submarine

        Oyashio class is the successor of the Yushio class, and the first submarine of the cigarette type submarine in the JMSDF. While planing Harushio, there began two studies for next submarine. One is material for secrecy from active sonar to absorb reflection. Another is automatic steering, trim control system which were also carried out in parallel in these studies. From 1991 to 1992, integrates submarine operation(Fire control) system was discussed by the Next Term Submarine Technology Examination Committee, member of a committee was Technical, Equipment, Defense Department of MSO, Submarine Fleets and Technology Research Center. These studies are applied to new tactical integrated operation(fire control) system.

        From this class to improve search ability, new ZQQ-5(from Michishio ZQQ-5B, Makishio ZQQ-6) sonar was equipped in bow and passive detecting sonar was top of the sail. Also developed array sonar fitted on hull and TASS sonar was fitted astern part. By these sonars capability of the detection in a long-distance was greatly expanded. Main engine is same as Harushio class, but output of main motor is increased 550 horsepower. From Arashio(SS-586) screw changed 5 to 7 blades with high-skew propeller. For weapon new 89 type torpedo and six torpedo/USM(Harpoon) combined tube are in bow and two automatic mine launchers are fitted on stern part. The big different of Oyashio class is changed hull structure to the simple shell partly from double shell with new high tension steel NS110. Torpedo tubes in bow were removed to mid-ship section, and for anti-detection stealthy for reflection hull is slanted and also sail is covered noise absorptive tile. Main engine is same as Harushio, Kawasaki 12V25/25S, but output power increased 550 horsepower.

       Construction of the first Oyashio class began January 1994, and commissioned in March 1998, and now six are in active and more two are under construction. During construction, in 2000 from Uzushio(SS-594) the solid aminn carbonic acid gas absorption device was adopted, and from Isoshio(SS-593) floating antenna was introduced.From 1960 to now the JMSDF constructed 40 diesel powered submarine, 10 were pre-tear-drop type boats, 24 were tear-drop type boats and 6 were cigarette type boats. But as there is the restriction of "The Non-Nuclear Three principle" ,nuclear engines are not allowed to use, so the JMSDF started next population Project of the AIP(Air Dependent Propulsion) engine from 2000, installing Stirling engine of the Swedish Kockums Co. ITD. , fitted on Asashio (TSS-3601) and started test from December, 2001.

Charactlistics of Oyashio class
● Displacement: 2750 ton, (double hull partly simple hull in astern)NS110 high tension steel)
● Length 82 m×beam 8,9 m×depth 10.3 m×draft7.9m(L/D 8,0)
● Power Plant Diesel-electronic, 2 diesel engines(Kawasaki 12V25/25S,3400 horsepower 12kt on surface, one main motor one shaft 7700 horsepower 20k plus submerged with 7 blades propeller
● Armament 533mm type 87 torpedo Hu603B type tubes with Harpoon×6
● Complement 70
Same type of boat(Commissioned)
SS-590 Oyashio(March 16, 1998) (Kawasaki)
SS-591 Michishio(March 10,1999) (Mitsubishi)
SS-592 Uzuishio(March 9, 2000) (Kawasaki)
SS-593 Makishio(March 29, 2001) (Mitsubishi)
SS-595 Isoshio(March 14,2002) (Kawasaki)
SS-595 Narushio(March,15, 2003) (Mitsubishi)
SS-8111(SS-596) under construction(March, 2004) (Kawasaki)
SS-8112(S-597) under construction(March, 2005)(Mitsubishi)
SS-8113(SS-598) under construction(March, 2006) (Kawasaki)

Submarine Organization

        In February, 1960 in accordance with the increase of submarines, submarine base was opened at Kure in the Inland Sea of western part of Japan, in there Kure Submarine Education Department was established as the attachment of the Kure Submarine Base. In 1961 submarine rescue ship ASR Chihaya (1340 tons diving bell type) was commissioned and in August 1962, the First Submarine Division was formed to conduct submarine operation and submarine rescue operation. In February, 1965 accordance with increase of submarines, the First Submarine Division reformed to the First Submarine Flotilla.

       In 1981 along with the reinforcement of the submarines, the Submarine Fleet was newly formed in Yokosuka, under the Self Defense Fleets with the 1st and 2nd submarine Flotilla, the Submarine Education and Training Division(SETD) and the 1st Submarine Training Division. The Submarine Fleet commander is responsible to all operations of submarine including the submarine rescue activity and also unification of submarine tactics. Each submarine flotilla consists of a submarine base and 2 or 3 submarines divisions. The Submarine Flotilla Commander is type commander and responsible to the training, the Submarine Base commander is responsible for logistics support.

       Submarine Education and Training Division(Kure Base) has a detachments in Yokouska, Submarine Education and Training Division has Submarine diving simulation trainer, Submarine Tactics Simulatio Trainer and navigation Simulation trainer which help level up of tactical skill. Yokosuka Tactics Support Division(YTSD) operate DSRVT(Deep Submergence Rescue Vehicle Trainer) for rescue crew of DSRV craft. The escape training installation and fire-water fighting facility located at the First Service School (Etajima) in the Inland Sea, opposite side of the Kure Submarine Base.

Submarine Organization chart
 Defense Fleet(Yokosuka)
 Submarine Fleet(Yokosuka)

 1st Traing Submarine Division (Kure)Asashio (TSS-3601) Hamashio (TSS-3604)
 Submarine Education and Training Division(Kure)
 Submarine Education and Training Detachment (Yokosuka)

 1st Submarine Flotilla (Kure)
   Submarine Rescue ship Chihaya(ASR-403)(Kure)
   First Submarine Division(Kure) Michishio (SS-591) Makishio(SS-593) Isoshio(SS-594)
   3rd Submarine Division (Kure)Hayashio (SS-585) Arashio (SS-586) Fuyushio (SS-588)
   5th Submarine Division (Kure) Akishio (SS-579) Harushio(SS-583)Natsushio(SS-584)
 Kure Submarine Base
 
 2nd Submarine Flotilla(Yokosuka)
   Submarine Rescue ship Chiyoda(ASR405) (Yokosuka)
 2nd Submarine Division(Yokosuka)Oyashi(SS-590) hamashio(SS-578)
 4th SubmarineDivision(Yokosuka)Takeshio(SS-580) Uzushio(SS-592) Narushio(SS-595)
 6th Submarine Division(Yokosuka)Wakashio(SS-587) Sachishio(S-582)
 Yokosuka Submarine Base

 Remarks:ASR Chihaya(5400 tons), ASRChiyoda(3650 tons) both installed
   DSRV (Deep Submergence Rescue Vehicle)