How do huge surface ships evade sensitive radar?

With the development of modern detection equipment, the probability of ships being discovered is increasing, and their survivability and combat effectiveness are seriously threatened. In order to enhance the survivability of surface ships, ship stealth technology has become the mainstream of warship protection technology development in various countries.

Radar "transparency" is the mainstream

How to avoid radar monitoring is the primary problem of stealth for surface ships. Modern ships mainly reduce the effectiveness of enemy radars and radar-guided weapons by reducing their radar cross section (RCS). In the stealth design of surface ships, the RCS value is generally reduced by changing the hull design and the shape of the superstructure. For example, the side is tilted to avoid being perpendicular to the water surface, so that the illuminated surface is anisotropically reflected to reduce the reflected energy of the echo; the surroundings of the superstructure and adjacent joints avoid right angles, and arc transitions are used as much as possible to prevent sharp-angle diffraction, and the exposed area is minimized.

Theoretically, the RCS of the Zumwalt-class destroyer is equivalent to that of a small fishing boat (Image source: Baijiahao)

At the same time, using absorbing materials to pass radar waves to reduce RCS is theoretically the most suitable for the stealth requirements of ships. At present, the technology of ship stealth materials is developing rapidly, from the earliest ferrite materials to nanomaterials and biomaterials. However, absorbing materials still have problems such as narrow adaptability band and low efficiency, so they are usually used together with appearance design.

Noise reduction and temperature reduction are a must

Since ships have strong infrared radiation capabilities during use, they are themselves a huge infrared source and can be easily detected by enemy infrared detection equipment. Therefore, reducing the infrared characteristics of ships is also an important aspect of ship stealth. By spraying seawater on the entire ship, the surface temperature of the ship can be reduced, thereby achieving artificial destruction of the ship's thermal imaging graphics, making it impossible for the enemy to find an accurate target for attack. The current technical level can reduce the surface temperature of the ship to a state similar to the ambient temperature in about 10 minutes. At the same time, coating the hull surface with insulating paint that reduces infrared radiation and using an insulating layer are also effective methods. However, due to the high requirements for materials (or coatings) in naval warfare environments, such as not only requiring low emissivity and temperature control capabilities, but also low solar energy absorption capabilities, and being compatible with radar stealth requirements, although many countries have been researching in this field for many years, there has been little progress.

The warship itself is a huge infrared source (Image source: Tencent)

In addition, in order to deal with torpedoes and enemy submarines, ships must also achieve acoustic stealth by reducing their own radiated noise. The current acoustic stealth methods mainly include reducing the intensity of the noise source and controlling the noise transmission process. Common methods include using low-noise shapes, electric propulsion, magnetohydrodynamic propulsion, floating valve isolation, cabin suspension, shock absorber shock absorption, adding soundproof covers to the power units of ships, laying sound-absorbing coatings or anechoic tiles, etc.

In addition to traditional radar, infrared, and acoustic methods, plasma stealth technology is also one of the development directions that has received more attention. Plasma stealth technology refers to a new stealth technology that forms a plasma cloud on the surface of a ship and uses it to avoid radar wave detection. It mainly uses the jet of plasma airflow to cause a plasma cloud to surround the ship, thereby absorbing radar waves and attenuating reflected signals to achieve stealth. This technology has the advantages of wide absorption bandwidth, high absorption rate, long service life, and controllable switches, and its stealth effect is good. This method can be mainly divided into two types: full plasma stealth technology and local plasma stealth technology.

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: Fei Boyu (senior military content editor)

Planning: Jin He