Fish Type 6 (Yu-6)

Although the Chinese Navy's fish 3 series torpedo has been improved many times, the overall technical level is very poor. The maximum speed is only 35 knots. It is very likely that the straight pursuit can not catch up with the US and Russian nuclear submarines. Therefore, it is imperative to increase the speed. The maximum speed generally reached or exceeded 50 knots, so our army began to develop a new generation of fish-6 torpedo. In addition to increasing the speed of the fish-6, the fish-6 has improved the shifting function. Once the target is launched, it can be re-entered into the search mode after deceleration. After the target is found, the target will be chased again. This will bring more attack opportunities. The function brings great convenience to the submarine's underwater operations. However, the development of the fish 6 is not smooth sailing, and the rapid evolution of the combat environment and objects has brought great difficulties to the development, and even almost reinvented. However, the fish 6 eventually managed to finalize the equipment and become the main battle equipment of the new generation of navy submarines.

The Yu-6 is the 533mm wire-/acoustic-/wake-homing heavy torpedo designed by 705 Institute (also known as Xi’an Precision Machinery Institute), a R&D branch of the China Shipbuilding Industry Corporation (CSIC) in Xi’an, Shaanxi province. The Yu-6 is the most advanced and capable indigenous torpedo in service with the People’s Liberation Army Navy (PLAN), designed to engage both deep-diving submarines and surface ships. The torpedo entered the PLAN service in 2005, carried by the Type 039 (Song class) and Type 039A (Yuan class) conventional submarines, and possibly the newly launched Type 093 (Shang class) and Type 094 (Jin class) nuclear-powered submarines too.

In the mid-1980s, the PLAN decided to develop a new heavy torpedo for both anti-ship warfare (ASuW) and anti-submarine warfare (ASW) roles, by reverse-engineering a single Mk-48 torpedo recovered by Chinese fishermen in the late 1970s or early 1980s. The development project was later put on a halt after few prototypes were produced due to enormous technical difficulties and lack of funding. However, research on the Otto fuel II and wire guidance was continued by a small team.

As the PLAN realised that its current torpedoes were unable to meet its requirements for modern naval warfare, the Yu-6 project was officially revived in 1995, with Dong Chun-Peng appointed as the chief designer. The revised Yu-6 design has possibly incorporated some Russian technologies, particularly the unique wake-homing technology. A number of Chinese organisations were involved in the Yu-6 development, including Shanghai Jiaotong University that developed new alloy for the torpedo casing; Tianjin Rubber Research Institute that supplied the noise-reduction casing for the acoustic seeker; Harbin Electro Carbon Research Institute tasked to develop the graphite material used to make engine valves and other components; Yizheng Shuanghuan Piston Ring Co. Ltd. that developed the piston ring for the torpedo propulsion. It was reported that the Yu-6 adopts a combined wire + active/passive acoustic + waking-homing guidance for different types of targets. It guidance system reportedly uses an Intel 80486-class microprocessor. The Yu-6 was also the first Chinese torpedo designed with the concepts of modular design and open architecture software programming in mind, so that new technologies and programmes could be readily incorporated whenever they become available.

The Yu-6 533mm heavy torpedo is China's first torpedo designed with modular design and open software architecture. It uses liquid fuel to provide power, and its guidance system uses Intel 80486-class microprocessors. It can be guided by wire guidance, active and passive acoustic guidance or stern guidance. Among them, "stern guidance" is a more advanced guidance method. When detecting and passing through the wake of a ship (submarine), the rudder is turned at a certain angle so as to face the ship. This homing method makes the torpedo Will be like a snake, shuttle left and right to catch up with the ship.

Since its entry into service in 2005, this type of torpedo has been equipped with a large number of surface ships and naval aviation of the Chinese Navy, and used as a warhead for anti-submarine missiles. It can not only attack surface ships but also submarines in deep submerged state. It can be called China The most advanced domestic torpedo in active service.

China's Type 039 "Song" class and 040 "Yuan" class conventional submarines have been equipped with Yu-6 torpedoes. In addition, the newly launched Chinese Type 093 "Shang" class and Type 094 "Jin" class nuclear submarines may also prepare for this Type torpedo.

At the beginning, the development of Yu-6 did not go smoothly. When the Chinese navy discovered that the Chinese torpedoes at that time were no longer suitable for modern naval warfare, in 1995, Yu-6 was redesignated as a key target and Dong Chunpeng was appointed as the chief designer. The division is responsible for research and development. The article also speculates that the R&D work after 1995 may have absorbed some Russian technologies, such as stern guidance technology.

Yu-6 is the culmination of the hard work of Chinese scientific researchers. Although 705 institutes, namely Xi’an Precision Machinery Research Institute, are responsible for research and development, a large number of Chinese research institutes and even companies have joined the research and development of Yu-6, including , Shanghai Jiaotong University, responsible for the torpedo’s new synthetic shell; Tianjin Rubber Research Institute, responsible for the development of torpedo silencing coatings; Harbin Electric Carbon Research Institute, the development of wear-resistant and high-temperature graphite materials for torpedo engine valves and other components; Yizheng Shuanghuan Piston Ring Co., Ltd. is responsible for the development of the piston ring for the torpedo thruster.