The New Attack Submarine (NSSN)
–codenamed Kurohana (Black Flower)- is an advanced stealth, multi-mission,
nuclear powered attack submarine for blue ocean anti-submarine warfare and for
littoral (shallow or brown water) operation. The NSSN will be quieter than
anything the U.S. or the Soviet Union can build, at speeds higher than that of
the Oyashio class, and at costs
two-thirds less than a Tenshio class.
Much of the security of the Japanese
Empire lies in the hands of the IJN submarine force. The original and ultimate
stealth weapon, modern Japanese submarines have preserved Japanese naval
dominance in the western Pacific for more than forty years. The current primary
attack submarine is the Kuroshio class. The first of the Kuroshio class boats
was commissioned in 1976, with twenty-one more planned in the series to follow.
For the last 20 years, the Kuroshio class has remained unmatched in stealth
capabilities. But three of these submarines have been decommissioned and the
rest are scheduled to follow around 2006 at a rate of four a year as they reach
the end of their thirty year service life.
By 2013, the attack submarine fleet will
fall below the numbers thought to be the minimum consistent with future
national security requirements. In the eighties, the Tenshio Attack Submarine
was born on the architect’s table, designed to be a superior replacement to the
Kuroshio class. It was bigger, faster, had more firepower, more advanced
tracking and surveillance gear, and was widely reputed to be "as quiet at
cruising speed as a Kuroshio class at the pier." There was a catch,
however. After years of testing, tooling up, and construction it became evident
that the Tenshio class boats would exceed cost expectations. Indeed, the prohibitive
unit cost of approximately 400 billion yen effectively limited the Tenshio
class to a run of three units. The dilemma: how to design and construct a fleet
of high-tech attack submarines in numbers sufficient to ensure the security of
the country and still not squander regional stability.
Then the Kurohana appeared. Tenshio class
quieting is being incorporated in a smaller hull while military performance
will be maintained or improved. With a focus on the littoral battlespace, the
Kurohana will have improved magnetic stealth, sophisticated surveillance
capabilities, and Special Warfare enhancements. The Kurohana is being
engineered for maximum design flexibility. Its responsiveness to changing
missions and threats, and the affordable insertion of new technologies, ensures
that it will be a potent warship well into the 21st century. Integrated
electronic systems with Commercial-Off-The-Shelf (COTS) components facilitates
state-of-the-art technology introduction throughout the life of the class and avoids
unit obsolescence.
Revolutionary cost controls have been
arranged to build this new class at reasonable prices. In 1995, the Diet
directed the Imperial Navy to submit a plan which would allocate the first four
New Attack Submarines to the Mitsubishi Boat Company and the Hitachi
Shipbuilding on an alternating basis. Mitsubishi Boat Corporation and Hitachi
subsequently announced that they had reached a teaming agreement to
cooperatively build the Imperial Navy's new class of attack submarines (NSSN). The
teaming was later approved in the Diet.
Based on the demonstrated success of the
design/build process, the Kurohana design will be far more mature than other
submarine designs at the beginning of construction. This greatly reduces the
risk of design changes during ship construction -- traditionally, a major cause
of cost increases. The nuclear reactor core has been designed to power the
submarine throughout its entire operational life without refueling. This will
result in a factor of two decrease, compared to previous classes of submarines,
in the amount of spent nuclear fuel requiring disposal. Not having to refuel
will also result in multi-million yen cost avoidance for each submarine.
Powered by a Toshiba Pressure Water Reactor R10H, 2 turbine engines with one
shaft and a pump jet propulser, the Kurohana will retain the high speed
characteristics of the Tenshio class. The claimed speed is 28 knots dived.
Additionally, this powerplant is possibly the quietest of its kind in the
world. The noise level of the Kurohana is equal to that of the Tenshio, with a
lower acoustic signature than the Soviet Improved Akula class and U.S. 4th
Generation attack submarines currently under construction.
The Kurohana will be armed with a variety
of weapons; carrying the most advanced heavyweight torpedoes, mines, Long Lance
cruise missiles, and Unmanned Undersea Vehicles (UUVs) for horizontal launch.
In addition, Long Lance missiles will be carried in vertical launch tubes. It
also features an integral special lock-in, lock-out chamber for special
operations and will host a special operations mini-sub.
The Kurohana will be the first Japanese
submarine built with a visual imaging capability that does not require a mast
to penetrate the pressure hull. The sail configuration houses two new photonics
masts for improved imaging functions, an improved electronics support measures
mast, a HF sonar array, and multi-mission masts that cover the frequency domain
for full-spectrum, high data-rate communications. The sail is also designed for
future installation of a special mission-configurable mast for enhanced
flexibility and combat performance.
It's sonar system will include a 15-foot
bow array, a HF array in the sail, and a UC-30 thin-line towed array which will
improve detection of threats in shallow waters or in areas with high background
noise. The plans could also call for a UC-61 towed array, a bow conformal array
and/or a wide aperture array. Using modular hull-section design, the boats
could be more easily configured for special operations, including the ability
to carry 200 troops for covert action, in excess of 100 cruise missiles, or
perhaps even the older M-IV missiles.
The submarine's Command Center will be
installed as one single unit resting on
cushioned mounting points. The submarine's control suite is equipped
with computer touch screens. The submarine's steering and diving control is via
a four-button two axis joystick. Advanced design, state-of-the-art technology,
multi-faceted operational capability; the Kurohana will continue a proud
tradition and ensure Japan's dominance in the Pacific ocean.
Kurohana's Characteristics:
|
Length |
115 meters |
|
Beam |
10.5 meters |
|
Displacement |
7,700 tons |
|
Speed |
28+ knots |
|
Payload |
38 weapons, including
Vertical Launching System and Special Operations Forces |
|
Weapons |
Four 21-inch torpedo tubes 12 Vertical Launching System
tubes Long Lance Land-Attack
Cruise Missiles NL-84 Advanced Capability
Torpedoes |
|
Sonars |
Spherical Active/Passive
Array Light Weight Wide Aperture
Arrays UC-30 and future towed
arrays High-frequency Active Arrays |
|
Countermeasures |
Internal (reloadable) 14 external (non-reloadable) |
|
Propulsion |
R10H pressurized water
nuclear reactor Steam turbine, single shaft |
