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11 Apr 2016 | Sumio Kusaka, Ambassador of Japan to Australia.
[pictured is Soryu submarine SS-505, which is Zuiryu "Sword Dragon"]
At the end of November last
year, Japan submitted to the Australian government its proposal for Australia’s
future submarine program.
The Japanese proposal is low
risk and meets Australia’s needs. It’s a proposal based on our accumulated
experience and the proven technologies of the Soryu-class submarine, which is
the world’s largest conventionally powered submarine. Seven Soryus are already
in use by the Japanese Maritime Self-Defence Force.
Several key questions have been
posed about whether our proposal will be able to meet Australia’s future
The following two posts will
seek to explain to the greatest extent possible the truth about the capability
of the Soryu-class and the reasons why the Japanese proposal is low-risk.
Japan’s proposal meet Australia’s cruising range requirement?
There’s a concern, promulgated
in some quarters, that the Soryu-class submarine won’t be able to match
Australia’s requirements regarding cruising range. Such a concern is mistaken,
for in Japan’s pre-concept design, every effort was made to ensure that Australia’s
cruising range requirements would be met.
Given that cruising range can
be determined by the quantity of fuel expended and fuel consumption efficiency,
the Soryu-class submarine was the basis of a comprehensive study on an internal
layout made in order to ensure effective use of space by extending the hull and
re-designing partitions. That study led to the conclusion that by increasing
the capacity of the fuel tank and working on its positioning, as well as
extending the hull design, the pre-concept design will be able to meet
Australia’s cruising range requirements without any problems.
internal space of the Soryu-class submarine too narrow?
The size of the reserve
buoyancy compared to submarines from other countries and the double hull structure
has led to questions about whether the internal space of the submarine is
The estimated surfaced
displacement of the Soryu-class submarine is approximately 3,600 tonnes, while
its dived displacement is around 4,200 tonnes. So in relation to the reserve
buoyancy of the Soryu-class submarine, there’s no reason to believe that it
possesses an excessive amount of reserve buoyancy compared to submarines of
Moreover, although it’s true
that one section of the Soryu-class submarine consists of a double hull
structure, a highly space-efficient outfitting using 3D digital mock-up
technology and design techniques that prevent reinforcement structures such as
beams from restricting space have created a wide internal space while avoiding
a growth in the size of the submarine itself. Furthermore, the extension of the
hull has allowed a much wider internal space than in the Soryu-class submarine.
The internal space of the
Soryu-class submarine has been shown to a large number of Australians familiar
with the internal space of the Collins-class submarine. So far, there hasn’t
been any comments which indicate that the internal space of the Soryu-class is
lifespan of Japanese submarines too short when compared to Australian boats?
Until recently, Japanese
submarines were used for a period of 18 years before being retired. The
operational lifespan of the submarines was determined by the National
Defence Program Guideline (NDPG) taking into consideration
factors such as not exceeding the pre-set number of submarines to be retained
by Japan (originally 16), technical obsolescence, and the introduction of new
submarines incorporating technical improvements.
Japan decided to increase its
submarine fleet to 22 vessels based on the 2007 NDPG, so a decision was made to
extend the service life of our submarines by six years.
It’s not true to say that
Japanese submarines can’t endure for long periods of time. If the Royal
Australian Navy desires to use the submarines over a long period of time, the
same level of technological checks that we carry out on our own vessels now
will enable such desires to be met.
Some have said that corrosion
of the double hull structure is the source of the submarine’s shorter lifespan,
but that’s simply not true. The construction of the Soryu-class submarine in
sections allows for an appropriate level of anti-corrosive maintenance. Japan
has never experienced any major fault’s which have interfered with the
operation of its submarines.
anti-corrosive technologies were developed to allow our submarines to operate
in a range of environments, even in harsh warm waters conducive to corrosion.
Japan believes that such technologies will guarantee the effectiveness of
Australian submarines which will also operate in the same maritime
Sumio Kusaka is the Ambassador of Japan to Australia"