Service ships have played an important role in past naval battles and daily activities. Its development has attracted the attention of navies of various countries. During the 25 years from 1920 to 1945, the total displacement of naval vessels in service of the United States, Britain, France, Germany, Italy and Japan increased from1650,000 tons to1776,000 tons, an increase of 9.7 times, and the ratio to combat vessels was 0.3:. 1982, during the Falklands War, Britain dispatched 1 18 ships, including 76 service ships, transporting 9,000 troops, more than 400 planes and helicopters, and a large number of ammunition, fuel and dry goods. The ratio of service ships to combat ships reaches 1.8: 1. Since the 1960s, with the development of modern science and technology and the changes of national marine strategy and naval construction policy, new types of service ships have emerged continuously. The United States, the Soviet Union, Britain, France, China and other countries have all modified or built space tracking and measuring ships, recycling and salvage ships, and comprehensive supply ships. , displacement of more than ten thousand tons. As of 1987, the total tonnage of service ships of the US two-ocean fleet is 860,000 tons; The total tonnage of Soviet navy service ships is 6.5438+0.73 million tons; China Navy also has a variety of service ships, which initially constitutes a maritime service support system, which can provide comprehensive support for the formation of COSCO Sea. In order to meet the needs of offshore operations, the performance of service ships is also constantly improving. For example, the American "dove" class submarine lifeboat and "Hayes" ocean research ship adopt catamarans with good stability; The latest sonar monitoring ship in the United States and the diving operation ship of the Japanese navy both have full-load displacement of more than 3300 tons, and both have successfully adopted semi-submersible small waterplane catamarans; German training ships use gas turbines; Some icebreakers in the Soviet Union use nuclear power devices; Adjustable pitch propeller, head propeller, fin stabilizer, anti-rolling tank and air conditioner are widely used. It is equipped with advanced navigation radar, theodolite, inertial navigation, computer and satellite terminal, and some are also equipped with helicopters.