Yu-6 torpedo

Yu-6 (鱼-6) torpedo is the Chinese counterpart of the US Mark 48 torpedo. Guidance can be by wire, active and passive homing, or wake homing. Domestic Chinese sources have claimed that the Yu-6 torpedo is in the same class as the Mk 48 Mod. 4 torpedo, but official information on the Yu-6 torpedo is limited.

Background
At least one Mark 48 torpedo was reportedly recovered by Chinese fishermen in the late 1970s or early 1980s, and the government of China might have begun reverse engineering in the 1980s. However, due to the inexperience of the Chinese technological base at the time and the concentration on economic development, most of the reverse engineering project was put on hold after research had been completed on Otto fuel II, wire guidance and some other subsystems; some research continued on a much smaller scale. The Yu-6 torpedo development program was revived when the Chinese military realized that despite developing several torpedoes including the Yu-1, Yu-2, Yu-3, Yu-4, and Yu-5, the obsolete doctrine of having separate ASuW and ASW torpedoes was unsuited for modern naval warfare, and the Chinese navy needed a torpedo for both ASuW and ASW. As a result, the Yu-6 program was fully resumed in 1995 and 705th Institute was named as the primary contractor, with Dong Chunpeng (董春鹏) as the general designer.

Development
One of the difficulties encountered was that the Yu-6 torpedo had greater operating depth than all previous Chinese torpedoes, and Chinese arms manufacturers could not build the new casing needed. A brand new alloy was required to cast the outer casing of the Yu-6 torpedo; under the leadership of Ding Wenjiang (丁文江), professor of material science at Shanghai Jiao Tong University, the problem was solved when ZLJD-1S alloy was successfully developed and used to cast the casing for Yu-6 torpedo. He Yuyao (贺昱曜) was in charge of developing the power module for the newly developed computer of the Yu-6 torpedo, which took three years, from 1999 to 2001.

Another obstacle was the casing for the acoustic seeker required new materials to build, but Chinese arms manufacturers had never had any experience in this field when the reverse engineering was first attempted. When most of the reverse engineering was put on hold, research in this field continued and Tianjin Rubber Research Institute (also known as Tianjin Municipal Rubber Industry Research Institute (天津市橡胶工业研究所) was tasked to develop the rubber needed for the acoustic seeker casing. A team of seven scientists, Shen Yingjun (申英俊), Hou Yehua (侯月华), Zhang Jianguo (张建国), Ma Gangying (马刚英), Zhang Lixia (张立侠), An Jiazhu (安家柱) and Zhang Suqin (章素琴), was formed, and eventually developed new rubber and production techniques needed by October 1994, shortly before the Yu-6 program was fully resumed in 1995.  The resulting rubber exceeded the required specification, with density 1.098 ton per cubic meter, speed of sound 1,551 metres per second, and surface roughness 0.16 micrometres.

The propulsion system was the biggest obstacle in the development of the Yu-6 torpedo. A team of three scientists, Ms. Su Li (苏丽), Mao Yuanfu (毛元福), and Wang Lisong (王立松) of Harbin Electro Carbon Research Institute (哈尔滨电碳研究所), was tasked to develop the graphite material used to make engine valves and other components. By September 1998 the new graphite material, designated M130, had been successfully developed and then utilized for Yu-6 torpedo. The piston ring of the engine was developed successfully in December 2003 by Yizheng Shuanghuan Piston Ring Co. Ltd. (仪征双环活塞环有限公司). Wang Guozhi (王国治) was in charge of noise reduction, and his successful research in this field won him second place in the Chinese national scientific and technology advancement award in 1998.

Over two-thirds of the technologies used for the Yu-6 torpedo were new to Chinese arms manufacturers, and there were some serious doubts that they could complete the project on its own. Dong Chunpeng (董春鹏), a University of Science & Technology of China graduate in 1966 who worked for 705th Institute since then, completed the project, filing 18 patents including four in fields that China had had no experience in. After ten years of development, the Yu-6 torpedo was accepted into service in 2005; Dong Chunpeng (董春鹏) was awarded the 2006 Scientific and Technological Advancement Award at the end of February in Beijing.

One characteristic of the Yu-6 torpedo is its high-performance processor; most western torpedoes are believed to use old, but known reliable, processors. The microprocessor used for the Yu-6 is of approximately Intel 80486 class. Some Chinese sources have claimed that Loongson-1 is used for Yu-6 torpedo.

The transducer array of the torpedo's acoustic seeker is believed to have about the same number of transducers as the Mark 48 torpedo. The Yu-6 torpedo uses modular design and open architecture software programming, so that when new technologies and programs become available they can be readily incorporated. The first generation Chinese-made wire-guided torpedo Yu-5 torpedo, used acoustic guidance only in the final stage of an attack or if the wire was severed; in the new torpedo guidance can be switched between wire and acoustic at any time. If the wire is severed, the targeting information stored in the memory enables the computer onboard to calculate the approximate new location of the target, augmenting the acoustic homing to achieve a higher kill probability.

Specifications

 * Diameter: 533 mm
 * Guidance: passive / active acoustic homing + wake homing + wire guidance
 * Propulsion: Otto fuel II
 * Speed: maximum > 65 kt (for attack)
 * Range: maximum 45 km+ (at the cruise speed)

Yu-8 torpedo
Yu-8 (鱼-8) torpedo was developed as the electrically-powered counterpart of the Otto-fuel-II-powered Yu-6, with which it shares many components and technologies, with the exception of the propulsion system.

Domestic Chinese sources have said that the Yu-8 torpedo had become the test vehicle and subsequently the first torpedo to be armed with a new warhead developed by the Chinese naval research institute. The new warhead utilizes sodium hydride compounds / chemical reaction; on detonation a large amount of sodium powder is released, which reacts with seawater to produce large amounts of very-high-temperature hydrogen within a very short period of time, so that the temperature instantly increases to over 2,000 °C within a radius of a few dozen metres as the hydrogen reacts with oxygen, destroying the target even if not hit. During the test in East China Sea, a retired 12,000-ton ship was struck by two Yu-8 torpedoes, which completely melted the side of the ship within fifteen minutes.