The Type 039 submarine (NATO reporting name: Song-class) is a class of diesel-electric submarines of the People's Liberation Army Navy. The class is the first diesel-electric submarine to be fully developed within China and also the first Chinese diesel-electric submarine to use the teardrop hull shape. Design The submarine uses a modern teardrop-shape hull for underwater performance. The hull incorporates four rudders and is propelled by a single propeller. The engine is imported from Germany. For quieter operation, the engine was mounted with shock absorbers and the hull is plated in rubber tiles for sound deadening. Development was not without problems, as a lengthy testing period for the first vessel (320) attests. Problems with noise levels and underwater performance led to revisions in the design and only a single boat was ever built to the original specification. Improvements led to the specification for the Type 039G, which became the bulk of production, with seven of the type entering service. Elimination of the stepped design for the conning tower is the primary visual cue for identification of the G variant. This class has two versions: the original Type 039, Type 039G. The most obvious visual difference between the two types is the conning tower. The Type 039s conning tower is stepped, rising aft. In an effort to shrink the submarine's acoustic signature, the Type 039Gs conning tower was given a more conventional shape without any step. Weapons Primary weapon for the Type 039 is the 533 mm Yu-4 torpedo, a locally produced passive homing torpedo based on the SAET-50 and roughly comparable to the SAET-60. Surface targets may be attacked at up to 15 km. Yu-6 wire-guided torpedoes may also be used for targeting submarines. It is also likely that the Type 039 is capable of carrying the YJ-8 anti-ship missile, a cruise missile which can be launched from the same tube as the boat's torpedoes, and can target surface vessels at up to 80 km. The missile is subsonic and carries a 165 kg warhead. For mining operations, in place of torpedoes, the submarine can carry 24 to 36 naval mines, deliverable through the torpedo tubes. The general designer of the torpedo and missile launching system is Mr. Sun Zhuguo (孙柱国, 1937-), and the launching system is compatible with AShM, ASW, torpedoes of both China and Russian/Soviet origin. Although Type 039 has successfully test fired the CY-1 ASW Missile under