Chinese Anti-Submarine Warfare
One topic of current perpexity relates to the patrol concept of operations for ballistic missile submarines. The first four Yype 094 boats were presumed to use the 3,500,000 square kilometer South China Sea as a patrol area, with the recently constructed fortified islands and reefs a string of unsinkable aircraft carriers a key component in the defense of this bastion against Western ASW forces. China's obsession with the South China Sea probably has as much to do with creating a defensible bastion for its ballistic missile submarines as with any of the other euqities in play in that region.
But possibly the PLAN will dispense with such Green Water bastions, and have its SSBNs "break through the first island chain" to the Pacific. This would marks a shift from a bastion concept of operations "with Soviet characteristics", to an operational concept "with American characterisics" of open ocean patrols.
Greg Torode and David Lague writing for Reuters suggested in 2019 that "In the north, the Yellow Sea is too shallow to conceal big, ballistic missile submarines. The East China Sea is deeper but it’s confined by the Korean Peninsula, Japan’s island chain and Taiwan. ... Japanese and U.S. forces can deploy advanced anti-submarine warfare ships and aircraft based in Japan to closely monitor these waters and the channels that pass out into the Western Pacific, where the submarines are ultimately headed. The Chinese need to reach these waters to be in a position to fire on the United States.... The South China Sea, by contrast, is much bigger and in parts deeper, making it more suitable for concealed submarine operations.... China would need to get its submarines out of Hainan, past surveillance and into seas east of the Philippines for their missiles to be in striking range of the United States...."
This analysis represents the conventional wisdom that Chinese planners aspire to put their boomers into the deep waters of the open ocean. This is probably not the case. The relatively shallow waters of China's continental shelf exclusive economic zone represent a challenging ASW environment constituting a defensible bastion from which the PLAN could confidently exclude Western ASW forces. Far from cconsituting an inferior operating domain, the shallow coastal waters are a Chinese killing ground, with heavily instrumented fixed sensor arrays complmented by Marine Survey Vessels providing real time updates on accoutic propagation conditions. Intruding Western attack submarines would have none of this support, but would be harassed by Chinese ships and aircraft that would have few if any Western counterparts deployed so close to mainland airfields and SAM sites. This Chinese anti-access / access denial capability is not simply a general purpose defense of the homeland, but a very focused pro-SSBN defense of the Chinese secure strategic reserve.
Anti-submarine warfare is divided into surface ship anti-submarine, aviation anti-submarine and satellite submarine to search, block, restrict or eliminate enemy submarines that have entered a certain sea area. Anti-submarine warfare is one of its most important missions. Surface ships are on the surface and face serious threats from underwater, so almost every combat ship is equipped with anti-submarine detection and attack equipment.
The anti-submarine of surface ships is usually dominated by special anti-submarine ships, while other ships are mostly equipped with self-defense anti-submarine equipment. Anti-submarine surface ships include submarine hunting, anti-submarine frigates , and anti-submarine destroyers. Anti-submarine warship major equipment include hull sonar, variable depth sonar, towed sonar and other equipment exploration potential, as well as anti-submarine depth charge, anti-submarine torpedoes, anti-submarine mines , anti-submarine missiles and other weapons to attack potential targets.
In addition to their strong anti-submarine combat capabilities, anti-submarine ships usually carry 2 to 3 anti-submarine helicopters to increase the effectiveness of anti-submarine operations. Aviation anti-submarine warfare is an operational operation in which anti-submarine aircraft use anti-submarine detection equipment to detect, identify, and locate underwater submarine targets, and use anti-submarine weapons to carry out attacks. It is an important part of modern anti-submarine warfare.
The main advantages of aviation anti-submarine are: anti-submarine aircraft has high speed, long range, large ammunition load, and flexible maneuverability; anti-submarine operations cover a wide sea area, and the efficiency of search and anti-submarine is high; attack. Aviation anti-submarine equipment is mainly composed of anti-submarine aircraft, anti-submarine detection equipment and anti-submarine weapons.
Anti-submarine patrol aircraft, also known as maritime patrol aircraft, are mainly divided into shore-based and ship-based types. Shore-based anti-submarine aircraft are usually modified with large civilian transport aircraft, so the battery life is very long, generally up to more than ten hours, and more than 20 hours in individual cases. Due to the large fuselage, a large amount of anti-submarine detection and attack equipment can be accommodated in the cabin. Generally, shore-based large-scale anti-submarine patrol aircraft are equipped with sonar buoys , magnetic detectors and other underwater acoustic, optical and electromagnetic submarine detection equipment, as well as torpedoes , deep bombs and other submarine attack weapons, which can patrol a large area of sea in a short time, It is the main force of strategic antisubmarine.
Ship-borne anti-submarine helicopters are the main force for tactical anti-submarine operations. They mainly carry anti-submarine detection equipment such as sonar buoys, suspended sonars, and magnetic detectors, as well as torpedoes, deep bombs and other submarine attack weapons for anti-submarine operations. Anti-submarine helicopters are widely equipped with various types of combat ships above naval frigates, and are the most widely used and powerful anti-submarine force.
Aviation anti-submarine detection equipment is equipment used to detect, discover, identify, and locate enemy submarines. It is divided into acoustic detection and non-acoustic detection. Due to the small propagation loss and long range of sound waves in seawater media, acoustic detection equipment is the main detection equipment widely used in aviation antisubmarine, and non-acoustic detection equipment is used as auxiliary detection equipment.
When the submarine is cruising, it will cause the current to fluctuate and form a wake. This wake will spread to the sea and will form a large area of characteristic ripples. Synthetic aperture radars deployed on satellites can detect this characteristic ripple. In addition, submarine activity may also cause subtle changes in ocean temperature, which are captured by infrared detection satellites.
The traditional method of reconnaissance submarines is to deploy sonar and other equipment on the seafloor and surface ships to search for the sound waves emitted by the submarine while cruising . However, the United States is vigorously developing the "non-acoustic detection and hunting potential" project, mainly focusing on the use of laser , infrared and satellite technology to hunt for potential.
As early as the mid-1980s, the United States had discovered the potential of satellite dive hunting. In 1984, US naval oceanographer Paul Scully Bauer boarded the space shuttle "Challenger" and successfully detected the ripples of submarines in other countries. "Asia Times" also disclosed that the US "Challenger" space shuttle has also performed space antisubmarine missions.
According to the plan of the US military, the anti-submarine network should link the reconnaissance satellites and submarine, surface ships, unmanned underwater craft, maritime surveillance aircraft, and unmanned aerial vehicles to integrate into a huge “underwater dynamic library” Used by anti-submarine forces. The US military is also very interested in anti-submarine high-altitude airships. A project jointly carried out by Japan and NASA is also trying to network reconnaissance satellites with maritime detection buoys, with obvious anti-submarine intentions.
At present, China has the largest submarine force in Asia, and the growth rate of the submarine force is second to none in the world. According to a report released by the US Naval Intelligence Office in July 2009, China’s nuclear submarines are easier to detect because of the greater noise. The conventional diesel-electric submarine has a good mute effect and is difficult to detect.
Of course, satellite antisubmarine also faces some technical difficulties. Although the satellite can detect the wake formed by the submarine, it cannot track for a long time. To make up for the shortcomings of satellite submarine hunting technology, the US Navy is considering networking other satellite diving methods with satellites to form a huge submarine hunting system.
Western submarines operating in the East China Sea and the Yellow Sea face challenges because this area is very shallow, from the Chinese coastline to the Okinawa Trough in Japan. Most of the seas are only 50 meters to 100 meters deep. A great variety of marine environments occur in the shallow, runoff-freshened reaches of the Yellow Sea and East China Sea. The Kuroshio Tsushima Current System complexly branches and distributes warm, saline waters to the Sea of Japan, and Yellow Sea after transport through and mixing within the East China Sea. The latter two basins have vast areas of shallow water with strong tidal activity, severe atmospheric forcing events, and among the largest freshwater and fine-grained-sediment fluxes on the globe. In these shallow-water regions and adjacent shelf edges, horizontal mixing is extremely important as runoff from coastal regions encounters and is mixed with the equatorial waters of the Kuroshio-Tsushima system. The vigorous winter-season cooling processes destratify the water column, forming oceanic fronts between shallow and deep waters and waters of northern versus southern origin.
The Bohai Gulf which Northern Fleet boomers might use as a bastion, has an area of 80,000 km2 (30,000 sq mi), but is enclosed on three sides by the east coast of mainland China. But the Bohai Gulf is quite shallow, with half of is area having a depth of less than 30 meters. The Yellow Sea, between mainland China and South Korea, is a bit better, with a mean depth of less than 50 meters, and surely often less than 100 meters. China might conduct patrols in the northern part of the Yellow Sea in the area above the 38th parallel, bounded by the Chinese and North Korean borders.
The East China Sea is located [not surprisingly] directly east of East China (hence the name), covering an area of roughly 1,250,000 square kilometers (480,000 sq mi). This area is dominated by the Chinese continental shelf, with a depth of only a few hundred meters.
For comparison, the Baltic Sea is a large body of relatively shallow water, with a total area of roughly 40,000 km2 (15,000 sq mi) and an average depth about 60 meters. The Persian Gulf has an area of about 240,000 square km [90,000 square miles]. The Gulf waters are overall very shallow, with a maximum depth of 90 meters (300 feet) and an average depth of 50 meters (160 feet).
Such shallow water areas present special problems for ASW operations, including high ambient noise levels, complex layering of waters of varying characteristics, reverberation from the Sea bottom and surface, and exposure of ASW forces to land based air attack.
Shallow water, for ASW purposes, is defined as ocean areas with depths less than 400 meters. In shallow water, sonar performance may be enhanced because the ocean bottom and surface boundaries act as a duct for the chan-neling of sound. Since no precise quantitative measure of the expected improvement is available, the ASW tactical commander could view the shallow water problem as one in which ambiguities may be created by him to mask the real composition and precise presence of his forces. One can even conceive of his active sonars being used in a bistatic mode, i.e., using one ship's sonar as an ensonifying source, and any other ship's sonar or sonobuoys being used as re-ceiving or detecting sensors. Bistatic geometry creates problems in establishing precise target location. Cross-layer detection is u-sually limited in range because of the refraction or bending of the sound rays.
Passive sonar has proven ineffective in shallow water due to the ambient noise overwhelming and masking any target noise. Non-nuclear subs were notoriously quiet and hard to find in shallow water. Ultimately, though, active sonar had proven effective. The “quietness” of a sub didn’t matter when active sonar was applied. It was usually just a matter of time before the sub was localized. Of course, the drawback to active sonar was that it provided the submarine with a precise fix on the hunting ship’s positions.
ASW forces need to be aware of the potential for night detection of bioluminescence; the light emitted from certain species of dinoflagellate plankton when disturbed by a moving submarine hull and its turbulent wake. This blue-green light, predominately in a 0.42 - 0.59 band, occurs in various water conditions and is most prevalent between 50 and 150 meters and where the water has steep temperature gradients. Visual detection in most cases requires a moon-less night and a relatively shallow target.
Raymond Wang in November 2017 wrote of the potential use of quantum communications technology for strategic communications with SSBNs. This optical communiations link would be significantly impacted by water clarity. He found the Bohai Gulf to be an unfavorable area for quantum communications. The northern South China Sea and the northern Yellow Sea are the most favorable areas. But SSBNs could patrol in murky areas and regularly go to clear areas to receive signals.
Owen Cote wrote "The enemy of all sonar propagation, passive or active, is shallow water... In shallow water, all acoustic energy tends to reflect repeatedly off the bottom and the surface, shallow waters are the littoral seas like the northern part of the South China Sea and the East China Sea where the continental shelf extends outward from China?s coast all the way to the First Island Chain, and where depths rarely exceed 100 fathoms (roughly 600 feet).... current American ASW capabilities are substantially less in Chinese coastal waters than elsewhere for two relatively intractable reasons: the Chinese can deny or greatly limit the access of opposing surface and air ASW platforms near its coast; and very shallow water greatly limits acoustic propagation and therefore detection ranges for both active and passive sonars, the primary ASW sensors... if for no other reason than that neither side will have a robust ASW capability in Chinese coastal waters, those waters will constitute a zone of “contested command” in which neither side can assure its use of the sea surface for either commercial or military purposes..."
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