In this blog post, we’ll examine the principles behind stealth technology applied to modern warships and the various ways it’s implemented, and explore what this technology means for naval power.
The Power of Stealth Demonstrated by Submarines
“We have lost more men than Admiral Nelson lost in all the battles he fought throughout his entire life.”
This remark is said to have been made by the then-Chief of the Naval Staff of the British Navy after the loss of three British ships and approximately 1,500 naval personnel due to attacks by German U-boats during World War I.
During World War I and World War II, the German Navy built over 1,000 U-boats, which sank approximately 5,000 warships and merchant vessels, etching the power of submarines into the global consciousness. Even today, submarines are operated as a core capability by many nations around the world. The reason U-boats were able to play such a significant role in the war was their ability to evade detection by the enemy—that is, their “stealth” capabilities.
In fact, stealth is not a concept that has emerged only recently. In a narrow sense, it refers to the ability to avoid detection by enemy surveillance equipment, but in a broader sense, it encompasses all concealment techniques designed to prevent detection by the enemy. Soldiers applying camouflage cream or wearing camouflage fatigues are also examples of methods used to enhance stealth capabilities.
The better the stealth capabilities, the more effectively attacks can be carried out without being exposed to the enemy, and the higher the likelihood of safely completing the mission and returning after engagement. For these reasons, stealth technology has been considered a crucial element in the military field from the past to the present. Even today, countries around the world continue to research and develop various stealth technologies. So, what technologies are actually used on warships to improve stealth performance?
Technologies to Reduce Radar Reflection
First, warships employ technologies to reduce RCS (Radar Cross Section). RCS quantifies the extent to which radar waves are reflected back from a target; the smaller the value, the lower the likelihood of detection by radar.
The primary methods for reducing RCS can be divided into the use of RAS (Radar Absorbing Structure) and RAM (Radar Absorbing Material). RAS is a technology applied during the design of a ship’s exterior that disperses the direction of reflection so that radar waves do not return toward the detection equipment.
Applying a certain angle of inclination to the hull’s surface or minimizing protruding structures can significantly reduce radar reflection. Additionally, designing the hull surface to be as smooth as possible also helps reduce the amount of reflection.
However, simply modifying the exterior shape is not enough to eliminate all radar reflections. Strong reflection signals may still occur at certain angles, and there are areas where reflections are structurally concentrated. To compensate for these limitations, a technology known as RAM (Radar Absorbing Material) is used in conjunction to absorb radar energy and further reduce the amount of reflection.
Technologies to Reduce Infrared Detection
Second, warships employ technologies to reduce the infrared signals emitted by the hull. Since ships use fuel for propulsion, they inevitably generate heat. Infrared signals are emitted directly as high-temperature exhaust gases are released, and heat generated by the engine room and various equipment is also transferred to the outside through the hull.
In modern warfare, infrared detection equipment is widely used alongside radar, so reducing these thermal signatures is crucial.
To achieve this, methods such as mixing exhaust gases with cold outside air to lower their temperature before discharge, or discharging exhaust gases underwater, are employed. Additionally, technologies that block heat transfer using insulation, improve ventilation, or cool the hull using seawater are also being applied.
Noise Reduction Technologies
Third, technologies designed to reduce noise are employed.
Submarines are undoubtedly the military vessels with the most outstanding stealth capabilities. Since submarines operate underwater, they are difficult to identify with the naked eye, and in the deep sea, the effectiveness of radar and infrared detection equipment is significantly limited. Furthermore, because light barely penetrates these depths, optical equipment is also difficult to use.
In such environments, acoustic detection becomes the most critical means of detection. The noise generated by submarines originates from propellers, propulsion systems, and various mechanical equipment, and each vessel has its own unique characteristics. Because of these characteristics, experts can identify the type of submarine based solely on acoustic signals.
To minimize this noise, various technologies are employed, such as optimizing propeller shapes, implementing designs that reduce cavitation, and reducing vibrations in propulsion systems. Technologies such as the Masker System, which reduces noise by forming air bubbles around the vessel, are also in use.
How will stealth technology evolve in the future?
As we have seen, modern warships incorporate a variety of stealth technologies, including optimized exterior design, radar-absorbing materials, thermal insulation, infrared reduction, and noise reduction. In addition, research and development into various other advanced technologies is ongoing.
Stealth technology has been a cornerstone of military technology from the past to the present and is expected to continue evolving. Next-generation stealth technology—combined with AI-based sensor fusion, new radar-absorbing materials, and low-noise propulsion technology—is highly likely to become a core element of future naval capabilities. Accordingly, stealth technology is projected to play an increasingly important role not only in terms of military value but also in international security and the defense industry.
