Kairyu class submarine
The was a class of midget submarine
Midget submarine
A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to 6 or 8, with little or no on-board living accommodation...

s of the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

, designed in 1943–1944, and produced from the beginning of 1945. These submarines were meant to meet the invading American naval forces upon their anticipated approach of Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...



More than 750 of these submarines were planned and by August 1945 about 210 had been manufactured. Most of them were constructed at the Yokosuka shipyard. These submarines had a two-man crew and were fitted with two torpedoes along with a 600 kg (1,322.8 lb) explosive charge intended to be used on a suicide mission.

Most of the Kairyu submarines were based at Yokosuka to defend the entrance of Tokyo Bay
Tokyo Bay
is a bay in the southern Kantō region of Japan. Its old name was .-Geography:Tokyo Bay is surrounded by the Bōsō Peninsula to the east and the Miura Peninsula to the west. In a narrow sense, Tokyo Bay is the area north of the straight line formed by the on the Miura Peninsula on one end and on...

 in the event of a United States invasion of mainland Japan. Some of these subs were also stationed in the Moroiso
Moroiso is the name of an inlet in the Miura Peninsula south of Tokyo in Japan.- Prehistory :Moroiso was settled by Jōmon people by at least 3,000 BCE. Evidence from that period have been found, including sedentary to semi-sedentary housing, pottery, stone tools and fishing implements...

 and Aburatsubo
is an inlet on the west side of the Miura Peninsula facing Sagami Bay on the Pacific Ocean. It exits into neighbouring Moroiso inlet.-History:...

 inlets on the southern tip of the Miura Peninsula
Miura Peninsula
is a peninsula located in Kanagawa, Japan. It lies south of Yokohama and Tokyo and divides Tokyo Bay, to the east, from Sagami Bay, to the west. Cities and towns on the Miura Peninsula include Yokosuka, Miura, Hayama, Zushi, and Kamakura....

 where a training school had also been set up.

Due to Japan's surrender on August 1945, after the atomic bombing of Nagasaki and Hiroshima, none of these submarines ever saw action.

Technical details

All modifications of the Kairyu class are constructed from 3 sections of welded steel bolted together. The sections are the fore (warhead), mid (diesel engine, ballast, fuel, controls and batteries) and finally the aft (motor and control planes).

The bow section can be installed with or without a warhead.

Following on from the bow is the central section, first in this section are the batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

 for the electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

 and the air flasks. Then is the pilot area. He has numerous controls including controls for the fore and aft dive planes and rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

s, valves for oil, fuel and water and the periscope
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....

 raise/lower controls. Behind the pilot are the main ballast tank
Ballast tank
A ballast tank is a compartment within a boat, ship or other floating structure that holds water.-History:The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish or argonaut octopus, and the concept has been invented and reinvented many times by...

 and fuel tank.

Abaft the fuel tank and ballast tank is the in-line six diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 engine, followed by the aft trim tanks, gearbox and reduction motors and finally the electric motor and propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...


In the conning tower
Conning tower
A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....

 there is usually a large magnetic compass however in some early models there is a gyrocompass
A gyrocompass­ is a type of non-magnetic compass which bases on a fast-spinning disc and rotation of our planet to automatically find geographical direction...

in the boat itself.

Modification 3

While both the original and second modifications were practically identical, the third modification of the class had some notable differences.

The overall length is 160 centimetre longer. The forward dive planes have been moved forward of the conning tower. There is no external magnetic compass and the fuel tank is now installed before the pilots control area. There is also a second periscope aft of the conning tower.

This model could very well have been used for training purposes with a complement of 3.

External links

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