SS Yushio Class
The SS 573 Yushio class represents an enlargement and improvement of the Uzushio (Whirlpools) class tear drop model submarines. A total of ten were built starting in 1975, and was the largest class of submarines built for the Maritime Self Defense Force. It is called a tear drop model submarine of the 2nd generation, but because the peripheral technology progressed over the decade during which they were under construction, the earliest unit and the latter units were almost different types of ships. The 5th and later units are improved in order to fire to be able to discharge the Harpoon USM (the underwater launched anti-ship missile) from the torpedo tube, and the displacement was increased somewhat.
Improvements included the ability to launch the Harpoon missile, and in later units the control navigation system was improved. The NS80 steel was adopted to the pressure-resistant boat hull, which permitted operations at a depth that was presumed to be approximately 400-450 meters. A propeller of seven blades was adopted for the screw, which meant that the submarine became quieter. The computer and information processing ability was improved. The result of the increase of cruising power and periscope depth range and the large-sized computer conversion of the direction device, resulted in a displacement increase of about approximately 400 tons relative to the earlier Uzushio class.
The construction budget of the first unit was 23,724,000,000 Yen, but with the final unit it had reached 31,950,000,000 Yen.
The Yushio class has been retrofitted with TASS (type not announced but most likely ZQR-1A). Yushio utilized the active portion only of the original AN/SQS-36.
The Japanse policy is to keep a constant number of submarines -- 16 in total -- in commission. But, in order to maintain submarine construction technology at fixed level, it was decided that it was necessary to build one new submarine every year. Thus the time in commission of the submarines was extremely short, and four became auxiliary vessels less than two decades after being commissioned. On 01 August 1996 SS 573 Yushio became ATSS-8006.
The Japanese Maritime Self- Defense Force (JMSDF) continued a steady modernization as it reduced the size of its submarine components through attrition without replacement. With the transfer of the second Yuushio-class diesel attack submarine, the Mochishio, to training duties as ATSS 8007 on 8 August 1997, the submarine force dropped to its new level of 15 first-line boats.
On 10 March 1999 SS 575 Setoshio became a training submarine [ATSS-8008], and was redesignated TSS-3602 on 09 March 2000. When the Setoshio was decomissioned, SS 576 Okishio became TSS-3603 on 29 March 2001. These ships typically served as training submarines for two or three years before being finally decommissioned.
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