Japanese Submarine Evolution "stronger, longer, more silent " and Operational Life

Above is the last page of the document History of submarine in our country - stronger, longer, more silent that S is referring to. Above is a Harushio-class submarine (left), second Oyashio-class (center) and Soryu-class (right).  

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On 15/3/16 9:27PM  S provided a Summary here (Pete has further translated and provided the links  below) of History of submarine in our country - stronger, longer,more silent :

Title: History of submarine in our country - stronger, longer,more silent 

[dated?]

[You will find the document is 15 pages of overheads (with photos, text, tables and diagrams) all in Japanese. If you right-click mouse - select "Translate to English" much is translated. Unfortunately the text seems to be lost if converted to .jpg pictures] 

Author: Toru Sato (Department of Naval Systems Development, Technical Research and Development Institute, Japanese Ministry of Defense [MOD]: 

Feature: The history of submarine built after WWII in our country will be reviewed from a technical standpoint.

Abstract: [the Japanese Navy] JMSDF has built about 50 submarines from the first Oyashio-class [a one submarine “class” SS-511, Laid down December 1957] which was [Japan’s first post war domestically built] submarine to the latest Soryu-class.

In hull form, from 195[7?] to1966, the:

-  first Oyashio-class [Laid down December 1957],

-  Hayashio-class [Laid down 1960, small, 59m long] 

-  Oshio-class [Laid down 1963], 

were underwater cruising-oriented submarines based on the pre WWII hull form.

 Graph similar to page 3 of the Japanese document. The steady evolution of Japan's submarines. Long history by class, elsewhere in Submarine Matters here. (Graph courtesy Australia's news-com-au)  

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From 1967, Uzushio-class, Yushio-class and Harushio-class were continuously built with tear drop shaped hulls, which were underwater speed-oriented. From 1993 to present (2012), [the second Oyashio-class and Soryu-class] with cigar shaped hulls were built. A partial single hull structure was adopted.

[Over the 1957 to 2012 period] various technical evolutions have been experienced, i.e:

- increase in submerged depth by improvement of steel welding technology and others;

- improvement in battery performance;

- extension of submerged period by using  AIP and other measures;

- equipment of [towed array sonar system] TASS and flank array sonar;

- [combat system improvements in terms of] improvement of sonar search and detection attack abilities by increase in processing speed;

- reduction of underwater radiation noise by reduction of equipments and adoption of damping steel alloy and material.

Our submarines have continuously evolved depending on the operation aspects, considering request of operators [Japanese Navy customer] and taking in latest technology. The direction of this evolution can be expressed as “stronger”, “longer” and “more silent”.

On that day, from a technical standpoint, all submarines of JMSDF will be visually introduced. [This is expressing the technical evolution of Japanese Navy submarines in visual terms].
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[On the Relatively Short Operational Life of Japanese Submarines]

S comments:

“Many people think short commission period of Japanese submarine is due to its short life time caused by degradation, fatigue, corrosion, and so on. But they are perfectly wrong, the short commission period results from require for continuous evolution. 

From standpoint of material science and design, designing and building of the weak structure which regularly degrades within defined period are much more difficult than those of the strong structure. In the former structure, perfect control and insight of key elements including prediction of future warfare, which are extremely difficult, is needed. 

As Japan unfortunately has not such high technology and insight, it can only build the strong structure.”

S (with some further translation and links by Pete)