Type 091 Han-class - Design

In March 2007 Seapower Magazine published an article based on information supplied in December 2006 by the US Office of Naval Intelligence (ONI), and subsequently obtained under the Freedom of Information Act. According to ONI, The HAN-class SSNs, of which retirement of the lead units has already begun. are relatively noisy submarines based on 1950s and 1960s technology. Although the class has benefited from several upgrade programs, it remains limited by short range weapons and noise.

The nuclear submarine has a total of 7 compartments. The first compartment is a torpedo compartment, the second the the command compartments, third compartments is the front auxiliary compartments responsible for emergency power, fourth compartments is the reactor compartment, fifth compartments is the control compartment with auxiliary machinery, and six compartment is the main machinery compartment, and seven compartment is the tail compartment.

With a fully loaded displacement of 5,5000 tons, this class is armed with six 533mm torpedoe tubes. Given that China's first-generation nuclear submarines were developed against this backdrop, it is hardly surprising that their operational performance was considerably inferior to that of contemporary American or Russian vessels. The Han-class SSNs are noted for problems, including high internal radiation levels and an inability to fire missiles while submerged, which compromise their operational effectiveness and their wartime utility against ASW-competent adversaries.

The lead boats (401 & 402?) suffered radiation problems which were thought to have been solved after extensive refit. But since the late 1990s they appeared to have become inoperational. According to some reports, as of 2000 only two of its Han-class SSNs remained operational, despite the extended re-fits to the units of this class. The reports of tehir demise appeared premature, with Chinese sources reporting all in service until late 2003.

From 403 onwards the hull was extended 8 meters aft of the sail. These three boats were erroneously reported to have been lengthened to accommodate tubes for six YJ-1 SSM launchers to the rear of the sail. The upgraded design was thought by some sources to include the ability to launch YJ-8 SSMs from the 533mm torpedo tube [it is unclear whether this capability has been demonstrated in practice].

After the first two ships of the Type 091 attack nuclear submarine were built, the Chinese Navy made partial improvements and upgrades to the subsequent boats in response to problems in its use. An anechoic tile was added to upgrade various devices. As the 401 and 402 boats found excessive noise during the voyage, starting from the No. 3 boat, the subsequent improvements were made to the Long March 3rd to 5th boats. The hull increased by 8 meters, and the noise was changed from the original 160-170 decibels dropped to about 140-150 decibels.

In the "09-I" reform project in the 1990s, a better-effect anechoic tile was installed; the shape of the water hole of the hull was improved, and the longitudinal shape of the original boat from the raft to the front and rear of the raft was The flow hole was changed to a row of square holes with a gap; the old model sonar was replaced with a newly designed integrated sonar. The new sonar system adopts advanced technologies such as Kalman filtering, adaptive noise cancellation and optimal linear prediction, which makes the new sonar system have the functions of torpedo alarm, multi-target automatic tracking and low-frequency line spectrum detection, which greatly enhances China's first generation nuclear submarine.

In the shape of the hull, compared with the conservative conventional line type adopted in the design of the first generation nuclear submarine in the United States, the Soviet Union’s first-generation nuclear submarine was combined with conventional water droplets. The hybrid line type, the 091 type attack nuclear submarine bold breakthrough, using advanced water droplet line design.

The hull adopts double-shell structure, which has the advantages of large reserve buoyancy, high damage resistance and strong anti-seismicity. The ballast water tank, buoyancy adjustment cabin, fuel oil tank and intake and exhaust piping system are arranged between the two shells. The equipment such as the high-pressure gas cylinder group saves the internal space and is also beneficial to improve the smoothness of the surface of the submarine. Due to the double-layered shell, when the submarine is launched, the pressure-resistant shell and the non-pressure-resistant shell are soaked with water, so as to ensure that the remaining water between the two shells flows out in time when the submarine floats up, it will not affect The free-flowing water hole is provided for the speed and stability of the floating, but this water hole increases the sailing resistance of the submarine and increases the navigation noise.

The reactor compartment is the heart of a nuclear submarine. It consists of a 90 MW pressurized water reactor and a primary loop system. The reactor is filled with high-temperature, high-pressure pure water, so it is called a pressurized water reactor. The nuclear reactor is mainly composed of a pressure vessel, a core and a control rod; the primary loop system is mainly composed of a main circulation pump, a voltage regulator and a steam generator. The rear auxiliary engine room is mainly equipped with a reactor secondary circuit system, the first circuit system produces saturated steam, and the second circuit uses steam to drive the host or auxiliary equipment. The secondary circuit system is mainly composed of a steam turbine generator set, a condenser, a condensate pump, a feed water heater, a deaerator, a feed water pump, a steam generator, a steam-water separation reheater and the like.

The Type 091 attack nuclear submarine has six 533mm torpedo tubes, a hydraulically balanced launch system, and 18 spare torpedoes. There are 6 inside the tubes, and a total of 24 torpedoes or 36 mines can be carried, and fish- 1 torpedoes and fish-3 torpedoes or mines can be launched . The torpedo adopts the hydraulic balanced launching system. Although the structure is complex, it is not limited by the working depth, the launching noise is small, and no bubble is exposed to the position of the submarine. The high-pressure gas during the pneumatic launch is not required to be recovered from the boat, so it will not harm personnel.

The improved Type 091 attack submarines on the weapons and equipment, and speculation has been using wire-guided torpedo sound from fish-3 improved guide features and fish -6 thermodynamic wire-guided torpedoes instead of behind the performance of early torpedo, and from The Type 091 attack nuclear submarine began with the No. 403 boat, and a missile launcher was installed behind the shell of the command post. It can be used to launch the Eagle-82 submarine-launched anti-ship missile, which significantly improved its operational power.

The sonar system of the Type 091 attack nuclear submarine is an intermediate frequency passive search and attack hull sonar using large array technology. This sonar uses a digital scanning display device with the ability to simultaneously track multiple targets and guide torpedo or missile attacks. Equipped with the French "Trout Cheek mounted active" / "DUUX-5" low frequency passive sonar. The integrated passive low-frequency sonar is installed in the lower pressure-resistant casing of the torpedo launching port, and is equipped with a system accepting a transducer matrix, also called a sonar array, which uses hundreds of sonar transducers as a matrix unit. The elements are arranged along the cylindrical surface, and the beam is formed by the compensator and beam scanning is realized, which can effectively improve the radiation power and the spatial gain, improve the directivity, and improve the orientation accuracy.

An IF communication sonar and hydroacoustic interference equipment are installed in the sonar fairing. It is mainly used for underwater communication, enemy identification and cooperative ranging. It is used for submarine underwater formation or meeting with surface ships, surface ship search, to identify the own submarine, etc., the call distance is about 5-10 nautical miles, the notification distance is about 15 nautical miles, and the identification distance between the enemy and the enemy is about 4 nautical miles.

The improved 091-type attack nuclear submarine is also equipped with arrays on the side of the ship. The three white collision lines at the same position on the hull clearly calibrate the installation position of the sonar array, which significantly increased the distance of the Chinese submarine to track moving targets. The detection accuracy and improved tracking improve the capabilities of the weapon system.

The electronic equipment of the Type 091 attack nuclear submarine includes multi-purpose combat data and command systems, I-band search radar and 921-A radar warning system. [34] Type 091 observation equipment: attack periscope and airborne periscope, communication equipment: short wave, ultrashort wave transceiver, very long wave receiver, satellite communication and underwater acoustic communication equipment, command equipment: torpedo shooting commander, attack display and torpedo Launch control device, navigation equipment: magnetic compass, gyro compass, log, depth sounder, sextant, track self-drawn instrument. Others include radio, starlight, satellite, inertial navigation equipment, integrated air conditioning systems, and anti-ship missile fire control systems that are installed on the 403 boat.

There are more than three meals per person per day. Compared with other arms, the standard is quite high. Some people call it "buy life money." Counting up late, serving four meals a day. However, when it comes to the sea, it is limited to conditions. The food is mostly dehydrated vegetables and canned food. It is difficult to eat fresh vegetables. Bread and steamed bread are often mildewed.

In order to distinguish between day and night, the timepiece on the boat is 24 hours. The boat was on four shifts and was on duty. After 4 hours of work, the crew rested for 8 hours. Unlike surface ships, nuclear submarines do not have a fixed bed, and wherever the bed is empty, sleep. Two or three large dormitories, similar to the train's sleeper compartments, each with 12 beds and a length of 170 cm, most of the crew can only curl up and sleep. The width is one-fourth narrower than the train berth, and the spacing is narrower. You can only reach into one leg first, then extend the handrail into the second leg, and then send the upper body. When lying on the side, the body is only a dozen centimeters away from the bed above.

After sleeping for 4 hours, crew must get up and get to work. This gives 4 hours of free time. There are horizontal bars, dumbbells and other fitness equipment on the boat, books, and 8.75mm miniature film projectors. But long-term underwater navigation is devastating, and most people have no mental exercise and entertainment. Leaders sometimes force crew to exercise.

Every day, the crew must do 5 minutes of UV exposure. An ultraviolet lamp on the ceiling of the conference room was opened. Everyone sat on the sofa, and the whole body was stripped. They only wore underwear, put on sunglasses, and sat for 5 minutes.

According to the regulations, the four-cabin (reactor compartment) must be closed at will and a quick walk. The corridor on the left side of the four compartments is less than one meter wide. There is a probe for detecting the radioactive concentration on the top and a metal cover outside. Once, the one-meter-high Cheng Wenzhao striding over the meteor, he did not pay attention to the metal cover, and was arrested for half an hour before being discovered, leaving behind the concussed sequelae.

The trial time is usually two to three days to one week, depending on the test subjects in the training program, whether to sail on the surface or underwater. When performing a surface navigation mission, the water surface may be in a bad situation or encounter a strong wind or a large wave and cannot dive; when performing a submarine mission, it generally sails at a working depth of 100 to 200 meters underwater.

The crew generally had a good amount of alcohol, because the treatment is higher, every Saturday night meal, drink, beer tube is limited to white wine. Every time, the political commissar will raise a glass: "Comrades, raise the cup, cheer for our cause!" When crews go out to sea, they often drink alcohol because of work needs.

When sailing on the surface, there must be three commanders and one soldier on duty at the bridge. The captains, deputy captains, voyage chiefs, and rudders of the squadron often go to the bridge to observe the situation. The temperature on the sea surface is very low, the wind is strong, and there are often seven or eight winds that set off waves of more than ten meters. The submarines are all in the sea, and the thick military uniforms and raincoats will be penetrated.

The crew's winter uniform is a Su-style cotton jacket. The outside of the knee has a pocket for wine. The crew on the bridge will put a bottle of special green bottle Wuliangye inside. When it is too cold, drink two to resist the cold.

The nuclear submarine was equipped with a surface water toilet and an underwater toilet. When sailing underwater, only underwater toilets can be used. The used toilet paper should be thrown into a pressure-resistant steel toilet. When flushing the toilet, first activate the switch, completely seal the toilet with a watertight and airtight lid, open the valve, let the seawater influx from the water inlet, open the high pressure blowing system, blow the sewage into the sea, and close the valve to block the seawater. Open the internal valve to make the toilet clean.

Once, a comrade who did not cover the toilet lid opened the valve that controls the ingress and egress of seawater. The powerful air pressure caused a large amount of seawater to flow in instantly, and the toilet was filled with sewage, so that everyone was angry and cleaned for a long time.

When a nuclear submarine sails on the surface of the water, the underwater toilet cannot be used. Only the water surface toilet on the side of the control tower can be used. The crew must report to the commander before going to the toilet: "The bridge! I want to be convenient!" Then I will get a sign. You can only issue up to 5 brands at a time, so that when the nuclear submarine encounters an emergency, you can judge whether there is anyone in the toilet or not, and whether you can immediately close the door and dive.

Excreta can be disposed of in situ in China's territorial waters, but enter the high seas, especially in hostile areas, to activate the dirt box. Otherwise, toilet paper and the like float on the surface of the sea, and it is easy to expose the target.