[Popular Science of Chinese Military Technology] How does sonar "illuminate" the dark seabed during naval battles?

Modern naval warfare has long encompassed three areas: air, surface, and underwater. In underwater combat, since electromagnetic waves attenuate at a very high rate in water, they cannot be used as a source of detection signals. Therefore, using sound waves to detect objects under the water surface has become the most widely used means. Sonar is another technology or equipment that uses the propagation and reflection of sound waves in water for navigation and ranging.

Widely used "underwater radar"

Sonar technology has a history of 100 years. It was invented by Lewis Nixon of the British Navy in 1906. The first sonar he invented was a passive listening device, mainly used to detect icebergs. This technology was applied to the battlefield during World War I to detect submarines. After years of development, sonar has become the main equipment used by the current navy in underwater monitoring, which can further detect, locate, classify, and track underwater targets, and conduct underwater navigation and communication.

Schematic diagram of the working principle of sonar used by the military and navy (Source: Sohu)

Sonar devices are generally composed of three parts: array, electronic cabinet and auxiliary equipment. The array is composed of underwater acoustic transducers arranged in a certain geometric shape. Its appearance is usually spherical, cylindrical, flat or linear. There are receiving arrays, transmitting arrays or combined transmitting and receiving arrays. The electronic cabinet generally has subsystems such as transmitting, receiving, displaying and controlling. Auxiliary equipment includes power supply equipment, connecting cables, underwater junction boxes and amplifiers, lifting, rotating, pitching, retracting, dragging, hanging, and releasing devices that match the transmission control of the sonar array, as well as sonar deflectors, etc.

Among them, the transducer is an important component in sonar. It is a device that converts sound energy into other forms of energy, such as mechanical energy, electrical energy, magnetic energy, etc. Its working principle is to utilize the piezoelectric effect or magnetostrictive effect of certain materials that expand and contract under the action of electric or magnetic fields.

The transducer can both transmit and receive sound waves underwater. When the transducer is used to transmit and receive sound waves at the same time, the sonar is active. Active sonar mainly calculates the echo by emitting ultrasonic waves in the detection water area. It is suitable for measuring underwater mines, fish schools, reefs, sunken ships, etc., and can calculate hidden submarines that have turned off their engines. When the transducer is used exclusively for receiving sound waves, the sonar is passive. Passive sonar passively receives the signals emitted by the target or some radiated noise generated by the target, analyzes the data, and judges the characteristics and position of the target. It can detect external activities without exposing itself.

The intelligence backbone of the underwater battlefield

Due to the development of modern digital signal processing algorithms and computer technology, the information processing capability of sonar has been significantly improved. The open, standardized and modular system architecture has promoted the rapid embedding of new sonar technologies and promoted the continuous improvement of the functional integration of sonar systems. The new generation of sonar systems integrates the side, bow, towed, active/passive, and multi-band sonars, and has multiple functions such as target detection, tracking, identification, hydrographic reconnaissance, underwater communication, navigation, information comprehensive processing and display, torpedo control, and underwater acoustic confrontation, which greatly improves the detection performance and information combat capability of submarines and surface ships in deep and shallow seas.

Sonar is essential for underwater combat (Source: Sohu)

Among them, the US AN/BQQ-10 integrated sonar system is a representative of this type of equipment. This integrated sonar system is based on the AN/BQQ-5 and AN/BQQ-6 integrated sonar systems and is upgraded through the "Civil Acoustic Ready-made Technology Rapid Implantation Program". The AN/BQQ-10 integrated sonar system improves the submarine underwater precision mapping and navigation (PUMA) system. This improvement can provide submarines with the ability to map the seabed topography and record its geographical features, including mine-like object detection and 3-D mapping display. These digital maps can be compressed and transmitted to sea-based and land-based platforms for display. This ability to accurately map the seabed topography enables submarines to covertly carry out preparations for the seabed situation in the combat space, as well as safely conduct minefield monitoring and avoidance operations.

About the author: Lan Shunzheng specializes in research and theoretical writing on space strategy, military strategy, and international relations. While serving in the army, he edited and published his first military theory book, "Random Thoughts on National Defense by an Army Sergeant - Soldiers Going Out of the Frontier". While studying for a master's degree at the School of International Relations, he focused on space strategy. Now he often publishes related articles on online media and military magazines. In addition, his second monograph, "Zhenxing Dinghai - Building China's Future Space Military Strategy", has also been published.

Produced by: Popular Science of Chinese Military Technology

Producer: Guangming Online Science Department

Author: Lan Shunzheng (military science writer)

Scientific review: Peng Kun (senior military content editor)

Planning: Jin He