Semi submersible: floating and sinking freely "offshore flat car" ■ Yang Shan, Wang Haofan, Li Tao Submarines, destroyers, cruisers... What should these larger warships do in case of an accident? At this time, it is necessary to invite "sea porters" - semi submersible ships to "carry" the failed ships back to the shipyard or base with maintenance capacity. In recent years, the number of semi submersible ships owned by various countries has increased and their functions have been continuously expanded. Among them, the Netherlands, Norway, South Korea and the United States have achieved remarkable results in the development and use of semi submersible ships. Some semi submersible ships are also equipped with troops, which has attracted much attention. So, what kind of ship is a semi submersible? What are its functions? Where will the future go? See the interpretation. Cape monteford mobile landing platform, information picture With the strong pull of maritime demand, semi submersible ships came into being Semi submersible ship is a large special marine ship whose loading deck can surface or sink underwater. Unlike submarines, semi submersibles can not fully submerge into the water. Even if the deck can be immersed deep below the water surface, some hull or structures are still exposed on the water surface. With the help of this sinking and floating function, it can make it easier to load, unload and carry large equipment such as offshore drilling platforms, ships and submarines. To some extent, the birth of most equipment is the result of filling the demand gap. The emergence of semi submersible ship is no exception. Its earliest "stage" is the civil field. For quite a long time before the 1970s, countries mostly used other ships for the transportation of "lying down" large ships. Although this method is primitive, it is simple and easy to use. After that, with the development of economy, the types of seaborne goods have changed greatly. The weight, volume and height of some goods are much higher than before, the center of gravity is high and the stability is poor, so it becomes difficult to drag them, loading and unloading is not easy, and accidents will occur if they are careless. The shipping industry urgently needs a ship that can transport super large goods to ensure the safety, economy and stability of transportation. In 1979, the world's first semi submersible ship, super employer 1 semi submersible ship, was born in the dock of Sumitomo heavy industry in Japan. Strange shape, huge hull and amazing carrying capacity... Once the semi submersible ship came out, it has attracted much attention. Subsequently, some countries followed suit and set off an upsurge in the development of semi submersible ships. Why can a semi submersible perform like this? In the final analysis, it comes from its strong handling capacity formed by the law of buoyancy. The semi submersible has obvious external characteristics. The bow and stern are high and convex, and the middle is low and flat. It is a wide deck, that is, the cargo area. This configuration can maintain the stability and balance of the hull to a certain extent, so that when the loading deck dives into the water, its bow and stern remain on the water surface, so as to better complete the task of commanding and dispatching loading. The key to the free floating and sinking of semi submersible ship lies in the adjustment and use of ballast water. It is designed with a ballast tank that takes up a lot of space. When diving is required, the operator will inject water into the ballast tank to immerse the deck of the semi submersible into a suitable position under the water. Then, the cargo to be shipped is dragged above the loading deck that has dived underwater. When the semi submersible ship is going to float up, start the drainage device - load regulating pump or air compressor to discharge the ballast water in the semi submersible ship, so that the ship body and the load-bearing goods on the deck surface, and then bind and fix it. Compared with traditional tugs, semi submersible ships have unique advantages in handling convenience and transportation capacity. For example, it generally does not need to separate and load oversized goods, is insensitive to the height of goods within a certain range, and has large oil tank and long endurance time. Especially when loading and unloading goods, due to the large proportion of hull immersed in water, it is not easy to be affected by sea waves and can maintain better stability. Therefore, it is also known as "offshore flat car". If you sail in the water by semi submergence, due to the low center of gravity, high floating center and small position change, the deck is not far from the water surface, so it has strong ability to resist strong winds and waves and good stability. It can not only easily load and transport super large goods by floating and sinking the hull, but also load and unload goods by rolling, sliding and hoisting with the help of wharf facilities. It also has good maritime stability, ocean navigation capacity and amazing transportation capacity... With the emergence of these advantages of semi submersible ships, the plan to use them in the military field was soon put on the agenda of some countries. Blue marlin semi submersible. Data picture Strong transportation capacity highlights military application potential Due to the amazing transport capacity, many countries are interested in semi submersible ships, but from a worldwide perspective, there are not many countries that can develop and own such ships. Including the Netherlands, Norway, South Korea, the United States and other countries, the total number of semi submersible ships built and equipped is only dozens. On the one hand, although semi submersible ships are "tall", they are only suitable for some marine countries; On the other hand, it is because the semi submersible ship has a huge hull, high requirements for development technology and technology, and a lot of capital investment. The subsequent system upgrading and maintenance are also a lot of expenses, which can not be borne by ordinary countries. In this regard, the development of semi submersible ship industry in the Netherlands is more representative. Several shipping companies in the country have a number of semi submersible ships. Among them, the Dutch blue marlin semi submersible has a length of 217 meters and a loading deck area of 7215 square meters. Even this volume is not comparable to the semi submersible of the daokewei sentry, nor to the semi submersible of the ROK Boca pioneer. It can be seen that the semi submersible ship has a large volume. The difficulty in the development of semi submersible ships comes not only from the huge hull. Because it has the functional characteristics of fork loading, floating ship and offshore supply ship, especially in the driving system and diving positioning control system, it is more difficult to develop. These technical and financial barriers make it difficult for semi submersible ships to be owned by more countries, and most of their users are dual-use. As a "maritime Porter" with amazing physical strength, semi submersible ship soon showed its potential in military application. When some ship producing countries deliver warships and submarines to purchasing countries, and some large ships are hard hit and cannot return by themselves, they often borrow semi submersible ships. In October 2000, the aegis missile destroyer Cole was attacked in Yemen. The ship weighing more than 8000 tons was transported back to the United States for repair by the blue marlin, a semi submersible chartered by the U.S. military from the Netherlands. In June 2009, the United States rented this semi submersible ship to transport the sea-based X-band radar, which is about 90 meters high and weighs about 30000 tons, to Hawaii for anti missile test. The biggest pride of the blue marlin semi submersible is to transport the Australian aircraft carrier Canberra back from Spain. In addition, the ship also participated in the transportation of Viktor class III nuclear submarines of the Russian navy. With the increase of military demand, the navies of some countries began to train semi submersible ships in order to make them more effective. The Cape monteford mobile landing platform installed by the U.S. military is a semi submersible ship to a certain extent, and the subsequent such platforms in the country are still under construction. From dual-use to special train loading, this change is not only reflected in the adjustment of users, but also reflected in the increase of functions and performance of semi submersible ships. How to determine the applicable indicators for the construction of semi submersible ships on the premise of pre judging the operational environment? How to keep up with the speed of Shanghai warship formation? How to integrate into the existing perception and combat system of ship formation? These are the urgent problems to be solved by semi submersible ship developers. Blue marlin semi submersible. Data picture It may play a variety of roles in the future battlefield Theoretically speaking, the semi submersible ship "joining the army" has its natural advantages. On the one hand, compared with most surface ships, semi submersible ships can be partially immersed in the water when needed, and the exposed volume is reduced. At this time, it can effectively reduce the radar reflection area, weaken the infrared characteristics, eliminate certain noise, and reduce the hit rate of anti-ship missiles launched by opponent surface ships. On the other hand, according to the principle of hydrodynamics, the semi submersible state helps to eliminate the wave making resistance and maintain the situation awareness similar to that of surface ships. At the same time, in some shallow water areas, it can also float to the surface to increase the passing rate. In view of this, some countries began to vigorously explore the military effectiveness of semi submersible ships. Over the years, the U.S. military has made great efforts to build mobile landing platforms such as Cape monteford into floating forward bases at sea, acting as a mobile port; Mitsui sea mobile landing platform launched by Japan has four heavy helicopter take-off and landing points marked on the open deck. It can also be used to transport air cushion landing craft, main battle tanks, various vehicles and materials in large quantities, and carry out aviation control and amphibious operations according to the situation. In addition to acting as a mobile base at sea, semi submersible ships can play a variety of roles in the future battlefield, such as turning into a marine emergency repair and maintenance station, acting as a marine dock and carrying out rapid maintenance of damaged ships and equipment; Variable missile launching platform, especially in the arrangement of vertical launch system, the related problems of missile launch and guidance are easier to solve than those on submarine, and the bomb load is larger. However, the requirements for wave resistance and corrosion resistance of weapon systems are greatly improved, and further research is needed. Some experts predict that semi submersible ships will play an increasingly important role in the future. At present, the development of semi submersible ships has shown the following trends: Large hull. In the future, large tonnage transport ships will still be the marine equipment that countries will focus on. Under the condition that the combat situation and system can ensure the safety of semi submersible ships, the loading deck of large tonnage semi submersible ships is wide, which is conducive to transporting more combat materials in place and into the battlefield in a short time. The fact that semi submersible ships can be refitted from some super large civil ships also determines that the volume of semi submersible ships invested in wartime will not be small. The large hull can also effectively reduce the economic cost of transporting goods in wartime. Diversified functions. As a large transportation platform, this function of semi submersible ship will be further expanded. By finding out the type, configuration and transportation requirements of transportation objects, military semi submersible ships in the future may improve methods and enrich the types of vehicles, further improve the ability to transport a variety of super large weapons and equipment, and realize accurate transportation and efficient loading and unloading. At the same time, the functions of semi submersible as a maritime support platform will be deeply excavated and enriched. As a weapon and ammunition launching platform, semi submersible ships may even obtain other new role positioning. Modular design. At present, some countries have incorporated modular design into the top-level planning of semi submersible ships. The modules developed by cohesion in various countries mainly include hull shell, propulsion system, transportation system, fuel storage system, etc. Once these modular designs are put into use, they will effectively shorten the manufacturing cycle of semi submersible ship, improve the utilization rate of hull space, shorten the wartime maintenance time, and realize the leap of comprehensive capacity. In short, in the foreseeable future, the comprehensive capacity of semi submersible ships, including loading capacity and delivery capacity, will be greatly improved, and can more effectively play the role of "offshore Porter". Photo: Yangming (outlook new era)