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Delfin midget submarine

The Delfin [Dolphin] is Cubas sole submarine. This midget submarine is only about 70 feet long with a displacement of around 100 tons. This is large enough for a five-person crew and a small diesel engine. This dimunutive design seems to have more in common with narco-submersibles than "real" submarines. In the evident absence of anything resembling a snorkel, instead a crude inverted u-bend type exhaust is visible at the back of the sail, operations would either be confined to semi-submerged running, or brief sprints under battery power. Midget submarines are relatively small submersible boats which are used for purposes of recreation and underwater research, and which are designed for accommodating only a small number of people.

In 1988, the Cuban Navy boasted 12,000 men and three submarines. After the old Soviet submarines were put out of service, Cuba sought help from North Korea based on the DPRK's experience in midget submarines. North Korean defectors claim to have seen Cubans in mid to late 1990s at a secret submarine base. A single photograph of a small black submarine in Havana harbor appeared in public some years later. It was rumored to be called 'Delfin' and possibly armed with two torpedoes. The design appears original, though influenced by North Korea and Soviet designs. Only a single boat was initially in service, but as many as four units may be in service by 2020.

Delfin [via H.I.Sutton] Delfin [via H.I.Sutton] Delfin [via H.I.Sutton]

Japanese midget submarines took part in the attack on Pearl Harbor in 1941. Midget submarines were first used in the Pearl Harbor attack in December 1941, all five participating craft being lost in the operation. During 1942 they were used in small-scale attacks on shipping inside the harbors of Sydney, Australia, and Diego Suarez, on Madagascar Island, and also operated in the Solomons area during the fight for Guadalcanal. Limited cruising range, low speed, difficulty in launching from the mother submarine, and inadequate power of the torpedoes carried so reduced the effectiveness of these craft that a new type of midget submarine, with a cruising range of 300-350 miles, was developed. Sixteen of this new type, designed to operate from shore bases, were built between 1942 and 1945.

Probably the smallest submarines in the world belonged to the ex-German Seahound class (later in Soviet possession). These swimmer delivery vhicles were 49 feet long and displaced only 15 tons. The Germans made use of three different types of midget submarines (3514). These were the "Biber," the "Molch," and the "Seehund." The "Seehund" was the largest of the midget submarines and was prefabricated with an overall length of 39 feet, a depth of 6 feet, and a displacement of about 16 tons. This craft had a surface speed of 8 knots and a submerged speed of 3 or 4 knots. Propulsion was by diesel engine and electric motors. The "Seehund" carried two 21-inch modified electric torpedoes. The range of the submarine at 8 knots was 275 miles plus 50 miles at 3 knots submerged. The "Biber" was the smallest of these submarines and was a one-man boat. Its overall length was 29 feet with a beam of 4 feet 9 inches.

Somewhat heavier, but still in the midget submarine class, were the US Navy's X-1 and the British Shrimp class. The X-1 was less than 50 feet long and displaced 25 tons. Boats of the Shrimp class were slightly longer and displace 30 to 5 tons. The midget submarines of the British Navy, spoken of as X-craft, spent many hours submerged reconnoitering off the Normandie beaches on D-day. Three British X-craft torpedoed the giant German battleship, Tirpitz in a Norwegian fjord.

The rule while submerged was to avoid exertion and lead a languid existence. Food was cooked in an electric pot and electric kettle. Most of the meals consisted of sandwiches washed down with orange juice or condensed milk. The toilet was situated in the escape chamber and known as "wet and dry" because it could be flooded and pumped dry at will. It was hardly ever dry. It was described as an unsalubrious spot in which there was little temptation to dally and only just room to move. The tank was pumped out only at night. Washing was limited to shaving and brushing the teeth. Many men took a swim at night to get clean. The first lieutenant of one of the boats indulged in a swim overside during the Tirpitz adventure. Members of the crew became accustomed to each other's odor and tended to be avoided by submarine tender crews until they had taken a bath. The inside of the boats was wet with condensation from hot drinks and water brought by men from the watch into the interior. There were meager bunking facilities in the battery room and the engine room. The bunk in the control room was usually filled with food supplies.

Ghadir is a class of midget submarines built by Iran specifically for cruising within the shallow waters of the Persian Gulf. It has a surface displacement estimated at about 115 long tons (117 t). The Ghadir class is probably better described as a coastal or littoral submarine, similar in concept to the Italian Sauro class, though significantly smaller. The Ghadir class is based on the North Korean Yono-class submarine. North Korea's 300-ton Sang-o-class coastal submarine is smaller than Romeo- and Whiskey-class subs, but larger than a midget submarine. It is apparently intended for use in coastal defense missions, minelaying and special forces insertion. Midget submarine infiltration and the armed espionage infiltration at Mukho in June and July of 1998 respectively, followed the Kangnung submarine infiltration in 1996. The 26 March 2010 sinking of the South Korean navy corvette Cheonan brought more details of DPRK's midget submarine fleet into focus.

The submarine that carried out the attack) was the North's Yeoneo-class midget submarine belonging to the RGB. The South Korean investigation team said that a North Korean Sango Class Submarine and Yono Class Submarine had left a naval base on the West Sea some two to three days prior to the attack and returned to base two to three days after the attack. They determined that the Yono Class Submarine carried out the attack. A Sango, Shark Class Submarine, weighs 300 tons, while a Yono, Salmon Class Submarine, weighs 130 tons.

A submarine has a unique advantage in naval battles. It can dive to a certain depth, cover itself with a natural barrier, a seawater cover, and then launch a sudden attack, causing an unexpected attack to the enemy. However, the submarine also has its own disadvantages. When investigating the situation on the sea surface, it needs to rise to the perimeter depth and observe the sea surface with a periscope. This depth is called "dangerous mode" in submarine operations. The submarine floats up and exposes the periscope, which is easy to expose. His position was detected by enemy radar or anti-submarine aircraft, and he suffered a fatal blow.

At the same time, the submarine underwater communication has also plagued the development of submarines in various countries. Due to the "skin effect", high-frequency signals attenuate sharply when entering the sea surface and cannot penetrate the sea. Therefore, the submarine needs to float to the surface to get in touch with the ground. Although low-frequency and very low-frequency communications are highly penetrable, submarines need long antennas to receive signals, and the ground station is huge in construction and extremely costly. The low-frequency communication band is narrow, the capacity is small, and the transmission rate is low.

To increase the accuracy of the navigation of an underwater vehicle, so that the advantages of both the GPS and inertial navigation system, the relatively common practice to use a combination of GPS navigation system INS added, i.e. underwater vehicle using its own most of the time INS carried autonomous navigation, for each navigation period of time, aircraft float to the surface receives a GPS signal, the GPS correction information by the positioning and eliminate the accumulated error over time before the aircraft.

This approach is effective in most of the time, but the demand for stealth or poor water seakeeping underwater vehicle, each float has certain risks. In case of adverse sea conditions at the time of floating the water, it could have serious consequences equipment damage or even sinking.

Such submersibles suffer from many deficiencies. One such deficiency is the sole use of variable buoyancy. In the case of catastrophic failure of a variable buoyancy system, the corresponding submersible will generally sink. Another deficiency is that conventional submersibles maneuver using a static system of ballast adjustment and vectored thrust. The use of such systems result in submersibles that are slow and bulky, and that are without advanced maneuvering capabilities such as, for example, aircraft. As a result, undesirable emergency situations such as, for example, entanglements, can occur with some frequency, and the ability to avoid such situations is diminished.

The boat needs to have a horizontal thruster for enabling the boat to travel forward or backward. In designing a submersible boat, a difficulty is found in the fact that in a surfaced condition of the boat, the thruster should be arranged at a level on the boat that is low enough for the thruster to be in the water. However, in a submerged condition of the boat, a low level of the thruster is disadvantageous. The fact is that in such condition, it would be ideal to have the thruster at the level of the centre of gravity of the boat , in order to avoid pitch behavior of the boat when the thruster is powered, and thereby to avoid measures for compensating such behavior.

An important issue in the field of submersible boats is buoyancy, and the design of means for taking the boat to a desired level in or on the water and keeping it there until another decision regarding the level is made. One such means may comprise two buoyancy chambers which are arranged at opposite sides of the submersible boat. In a possible embodiment, each of the chambers comprises a resilient inflation bladder. To provide buoyancy, the bladder is filled with a fluid having a lower density than water. In a practical situation, the fluid may be air such as can be provided by standard scuba air tanks. To decrease buoyancy, the fluid is evacuated from the bladder. To this end, a valve may be used, which is put to an opened position when evacuation of the fluid is required. A consequence of being underwater which is advantageous in this context is that ambient pressure is relatively high and may operate to collapse the bladder, eventually forcing out any inflation fluid contained therein. It is possible to have a passive system, i.e. a system according to which only water pressure is used for emptying and collapsing the bladder.

Hence, when a chamber comprising a bladder as mentioned in the foregoing is used, a downward movement of the submersible boat is associated with deflation of the bladder, and an upward movement of_ the, submersible boat is associated with inflation of the bladder. Although the use of the chamber comprising the bladder has proved to be functional, there are disadvantages associated with it. A notable disadvantage resides in the fact that when the submersible boat is underwater and the bladder is in a deflated condition, the chamber constitutes a considerable portion of the total weight of the boat, as it is filled with water in that situation. On the basis of this fact, the mass inertia of the boat is higher than is desirable and its maneuverability is lower than is desirable.




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Page last modified: 04-03-2020 14:17:20 ZULU