Small submarine: an underwater Hunter ■ Ma Xiaojing sails For more than 70 years after the end of World War II, submarines have become the key equipment for the development of navies of various countries. Among them, there are not only large and medium-sized submarines with large shape and expensive cost, but also small submarines with small tonnage and different uses. Countries attach importance to the development of large and medium-sized submarines. It is easy to understand why the development of small submarines is also popular, and set off a new round of development upsurge at the beginning of the 21st century, and the momentum has not declined so far? See the interpretation. For a long time, people used to call conventional submarines with normal displacement less than 1000 tons and nuclear submarines with normal displacement less than 3000 tons small submarines. Now, some experts believe that the definition of small conventional submarines should be adjusted to a normal displacement of less than 2000 tons. During the first World War, hundreds of submarines from all over the world were put into naval warfare. In view of this, after the war, countries paid more attention to submarines and tried to improve their combat effectiveness. The development and use of small and micro submarines is one of the choices. Stand by concealment and small size From the development process, in addition to small submarines, there are micro submarines that have attracted extensive attention all over the world. To some extent, some micro submarines are not even submarines in the strict sense. In December 1941, the Italian Navy successfully carried out an attack with micro submarines - three "triumph" micro submarines seriously damaged and sank many British warships in Alexandria, Egypt. At this time, the "triumph vehicle" micro submarine is similar to a human operated torpedo, and the displacement is only 1.5 tons. In this World War I, the impression of small and micro submarines "haunting" and "small and broad" was engraved into people's memory. During World War II, Britain, Japan and Germany also designed and built small and micro submarines and used them in actual combat. In 1943, the British Army used a micro submarine "group" to seriously damage the German battleship tilpitts hiding in the Norwegian fjord. In 1945, the Japanese Navy's heavy cruiser Kaohsiung was sunk with a micro submarine. The Japanese army used micro submarines many times in the Pacific battlefield. During the sneak attack on Pearl Harbor, micro submarines participated. Although the German seal class micro submarine was put into actual combat relatively late, the war results were not small, and even sank a large destroyer. From these examples, the function of the small and micro submarine developed at that time was to attack the ship in the form of surprise. Due to the limited endurance of such submarines, they have to rely on other platforms to reach the target sea area and then fight in the water. In the face of large surface ships, the reason why micro submarines dare to "be small and broad" is that they are small and secret. In a sense, small and micro submarines are underwater hunters who rely on concealment and small size. As time enters the 21st century, the development of small submarines has set off a new upsurge. The main reason behind this phenomenon is that offshore and shallow waters have gradually become important battlefields for underwater operations. In this kind of naval warfare environment, small submarines are superior. First of all, "demand" is the biggest traction force for the development of small submarines. Iran's Kadir class small submarine has a displacement of about 120 tons. Today, this type of submarine is the submarine with the largest number of equipment in Iran. In the Persian Gulf where the sea water depth is not large, especially in the Strait of Hormuz with complex underwater environment, agile small submarines are more suitable. The increasing threat of underwater forces from offshore, shallow and narrow waters objectively requires some countries to obtain a response means commensurate with the operational environment - small submarines. Secondly, "really effective" is a strong driving force for the development of small submarines. Compared with the previous situation of "home ownership" of micro submarines, the current development of small submarines shows a corresponding increase in tonnage, which makes it possible to equip them with more and stronger weapons and equipment. With the increasing power of weapons and equipment equipped with small submarines, its deterrent power is further improved. The application of various advanced sensors makes it more competent for reconnaissance, survey and other tasks. The quieter and more concealed characteristics will help to improve the success rate of special operations. Thirdly, "enough economy" makes it an easily available equipment for the navies of some countries. Generally speaking, compared with the production of large and medium-sized submarines, the design process of manufacturing small submarines is relatively simple. Many small submarines use the mature technology used in the development of large and medium-sized submarines. For example, smx-23 submarine of French DCNS company uses 70% of the technologies and systems already used on Sebaste class submarines, so it has less investment. Due to the low production cost, the price of arms sales is also relatively low. If we want independent research and development, it is not as difficult as large and medium-sized submarines. In addition, it has the advantages of simple operation, less personnel and convenient transportation. Of course, small submarines also have shortcomings and shortcomings. The most important thing is that they lack endurance due to their limited size. French Sebaste class submarine Ability to continuously strengthen and expand Smx-23 submarine is a new concept offshore submarine launched at the "European Naval Equipment Exhibition" in 2006, with a displacement of more than 800 tons. French smx-23 submarine (CG diagram) Why did DCNS company, which has always acted frequently in guiding the new trend of submarine design in the world, suddenly throw out the concept of small submarine? The reason is the result of the company's Market Research - the navies of many countries are attracted by the performance and cost advantages of small submarines. Not only DCNS, but also other countries have noticed this change. At this time, German tkms company also analyzed the market research and evaluation results, and concluded that the navies of some countries do need smaller and affordable submarines. It is not difficult to see that some countries choose small submarines. First, economic factors play a role and try to "do big things with small money"; Second, we hope to obtain some functions and combat power of large and medium-sized submarines. This makes the tonnage of small submarines developed by various countries in this period mostly between 1000-2000 tons. The development of small submarines for more than 10 years has basically followed a similar path. However, the positioning of small submarines at this stage is more and more suitable for a new description - Underwater attack and defense generalist. First, the content of underwater warfare is richer. Like the early small and micro submarines, the later small submarines also take torpedoes, mines and missiles as the "blade", which can be used for anti-ship, anti submarine and obstacle clearance. Different from the past, with the development of science and technology and the relative enlargement of the hull, the weapons and equipment that can be equipped by small submarines are increasing and continuously optimized, which increases the number of objects they can attack. In addition to anti-ship and anti submarine, some small submarines can attack land targets and some can also attack air targets. The standard displacement of the Russian designed p-750b submarine is about 1400 tons. The main weapon system is a 533mm torpedo launcher, which can launch heavy multi-purpose torpedoes, anti-ship missiles and mines. It is said that the submarine can also be equipped with a missile vertical launch system to launch submarine launched missiles to attack nearshore targets hundreds of kilometers away. The 800 shallow water submarine developed by hdw company based on the German Navy 212a submarine has a standard displacement of about 900 tons and can also launch anti-ship cruise missiles. German designers also tried to install optical fiber guided air defense missiles and small caliber automatic guns to deal with the threat of anti submarine aircraft and attack small surface ships. Second, the capability of underwater reconnaissance and anti underwater facilities has been improved. Underwater patrol, vigilance, surveillance and reconnaissance are important tasks for small and micro submarines, but countries choose to keep it secret in terms of surveying underwater terrain and anti underwater facilities. However, some clues can still be seen from the configuration of some small and micro submarines. NR-1 deep sea nuclear submarine is a small nuclear powered vessel of the US Navy, with an underwater displacement of less than 400 tons. This type of boat was retired in 2008. The front of the hull is a control and observation area. There are wheels at the bottom of the hull for traveling on the seabed. The hull is equipped with external lights, TV cameras, remote-control manipulators and sampling devices. Thus, the boat can carry out deep-sea operation, underwater environment monitoring, deep-sea search and rescue and other tasks. In this regard, since the 1970s, the "malachite" Marine Machinery Design Bureau in St. Petersburg, Russia, has successively designed and launched three types and seven as series deep-sea nuclear submarines, with a surface displacement of 550 ~ 1600 tons. The boats are equipped with manipulators and winches to grasp seabed items, which can be used for seabed survey, topographic mapping, underwater communication system Underwater acoustic monitoring system construction, underwater weapon test and rescue. It can be seen that this kind of small submarine is different from the general small and micro submarine. Generally, the submergence depth of small and micro submarines is limited, while NR-1 nuclear submarines and Russia's as series nuclear submarines are designed to "forge ahead" in the deep sea. Their diving and operation depth are basically more than 1000 meters. Today, with the development of science and technology and the application of new materials and new processes, the deep-sea operation capacity of such small submarines is still improving. It is said that the Russian 10831 rosarik small submarine, which "surfaced" due to an accident in 2019, has a maximum diving depth of 6000 meters. It can be inferred that such small submarines play a great role in studying seabed topography, circulation and water depth, and the measured data can be used for underwater navigation and meet more operational needs. Third, the conditions for special operations are more complete. Transporting special combat personnel and carrying out tasks such as destroying enemy port and shore facilities and important targets are the housekeeping skills of small and micro submarines. Therefore, the vast majority of small and micro submarines have the function of carrying "frogman". Some micro submarines are almost designed to transport special combat personnel. For example, the mark VIII vehicle used by the US navy seals is essentially a "wet" submersible, which means that the crew must wear respirators and diving suits when driving underwater. In April 2020, the "dry combat submarine" micro submarine developed by an American company was delivered to the US Navy special operations command. Compared with the mark VIII vehicle, its underwater endurance, concealment and mute effects, including comfort, are further improved. In order to improve the underwater operation capability, many small submarines are also equipped with advanced combat management systems, which realize the automatic control of combat information command system, weapon launch control system and submarine power propulsion system, so as to reduce the number of operators and improve the operation efficiency of submarines. Future development trend French Ruby class nuclear submarine As a representative of small attack nuclear submarines, France's Ruby class nuclear submarines have an underwater displacement of more than 2000 tons and a self-supporting capacity of 45 days. In some exercises organized by NATO and France in recent years, ruby class nuclear submarines successfully "sank" or "injured" several participating ships, including some aircraft carrier targets, in the face of the advanced three-dimensional anti submarine defense network. Therefore, ruby class nuclear submarine once represented a direction of nuclear submarine development in the future. However, the emergence of its successor, the Barracuda class attack nuclear submarine with a displacement of more than 4000 tons, makes the development prospect of small attack nuclear submarines confusing. So, is there a place for small submarines, including small attack nuclear submarines, in the underwater battlefield in the future? The answer is yes. First of all, there are a large area of offshore, shallow water and narrow sea areas in the world. Such sea areas have become hot spots of wrestling, providing a "hotbed" for the development of small submarines. Secondly, some tasks that can not be completed by large and medium-sized submarines still need to be completed with the help of small and micro submarines with good concealment performance and the advantage of large diving depth. Yi