In this blog post, we’ll explore the technological competition between the “seeker” and the “hider” in future warfare—from the principles of radar, which uses electromagnetic waves to detect objects, to stealth technology designed to reduce the likelihood of being detected by radar.
World War II is considered one of the most tragic events in modern history. However, from the perspective of technological advancement alone, there is an ironic truth: World War II served as a catalyst for even more rapid technological progress across various fields. To win the war—or simply to survive—nations desperately focused on technological development. One of the technologies developed and advanced during this time was radar, designed to detect enemy aircraft and warships in the vicinity. The Allied nations, including the United Kingdom and the United States, which had secured radar technology, were able to pinpoint enemy positions, and this technology contributed significantly to the Allies’ victory in World War II. Subsequently, technologies to evade radar also began to develop, and research and development on stealth technology continues to this day.
To understand stealth technology, one must first understand the principles of radar; and to understand the principles of radar, one must first understand electromagnetic waves. The existence of electromagnetic waves was predicted by Maxwell’s theory; they are waves in which electric and magnetic fields are coupled and propagate together. Electromagnetic waves consist of two components: an electric field and a magnetic field. Changes in the electric field generate a magnetic field, and changes in the magnetic field, in turn, generate an electric field. As this process repeats, the electric and magnetic fields of the electromagnetic wave constantly change, and these changes propagate through space.
Radar utilizes the property that electromagnetic waves are scattered or reflected by objects. Since electromagnetic waves are waves, they are reflected or scattered when they interact with objects, and depending on the conditions, they may also diffract. When a radar emits electromagnetic waves, they propagate through space; when these waves reach an object, such as a fighter jet, a portion of them returns toward the radar. Since no reflection signal originating from the object would be received if the object were absent, the radar can determine the presence of an object by analyzing the returned electromagnetic waves. Furthermore, as electromagnetic waves are scattered by an object, their energy is dispersed in various directions, and the strength of the signal received by the radar depends on the object’s shape and material, the distance between the radar and the object, the frequency of the electromagnetic waves, and the angle of incidence. A key metric representing an object’s radar reflectivity is RCS (Radar Cross Section). RCS is not a value that simply represents the actual physical size of an object; rather, it is an effective cross-sectional area that indicates how strongly radar electromagnetic waves are reflected from a specific direction. Therefore, RCS varies depending on the object’s structure, material, and surface characteristics. Even if two objects are at the same distance from the radar, their RCS values may differ if they have different structures and materials. Under the same conditions, an object with a high RCS tends to produce a stronger reflected signal toward the radar than an object with a low RCS. The radar receiver detects these returned electromagnetic waves to determine the presence and location of the object. Generally, all other conditions being equal, the stronger the reflected signal received by the radar, the easier it is to detect the object from a greater distance.
Stealth technology can be defined as the process of designing and manufacturing objects specifically to reduce this RCS. Generally, because fighter jets and warships are large, they can generate significant radar reflections based on their size alone. However, by appropriately designing the object’s shape and surface to minimize the strength of the electromagnetic waves reflected back toward the radar receiver, and by using radar-absorbing materials to reduce the reflected energy, the likelihood of being detected by radar can be lowered. In this way, minimizing RCS weakens the signal appearing on the radar screen, making detection more difficult. Consequently, fighter jets or warships equipped with stealth technology can carry out their missions while reducing the likelihood of being detected by enemy radar networks. However, it is important to note that stealth is not a technology that renders an object completely invisible, but rather a low-observability technology that reduces the probability of detection.
No matter how advanced stealth technology may be, it cannot completely render an object invisible to radar surveillance. Although stealth aircraft are sometimes mistakenly believed to be completely undetectable by radar, stealth technology is designed to reduce radar reflections, thereby making detection and tracking more difficult—it does not make the object disappear from radar entirely. In particular, as the distance between the radar and the object decreases, the received reflected signal can become stronger, increasing the likelihood that even a stealth aircraft will be detected. Therefore, the performance of stealth technology is not evaluated simply in terms of “whether it is detected by radar or not,” but rather through a comprehensive assessment of various factors, including how low an RCS it can maintain under specific conditions and at what distance it can make detection and tracking difficult. Furthermore, the likelihood of detection can vary depending on the radar’s power and frequency, the antenna’s performance, and the detection environment.
Stealth techniques can be broadly categorized into two approaches: one that reduces radar reflection by utilizing the object’s shape and structure, and another that employs materials capable of absorbing electromagnetic waves. The former is commonly described as designing the shape to reduce radar reflectivity, while the latter involves the use of radar-absorbing materials (RAM). In the shape-based approach, the object’s surface and angles are meticulously designed so that electromagnetic waves received from the radar are scattered in other directions rather than being strongly reflected back toward the radar. For example, using a surface with a specific shape can guide electromagnetic waves to reflect in a direction other than that of the radar receiver. However, this method does not produce the same effect in all directions, and the reflected signal may increase at certain angles and under specific conditions. The RAM method involves applying materials that absorb or attenuate a portion of the electromagnetic waves to the surfaces of aircraft or naval vessels to reduce the signal returning to the radar. In actual stealth aircraft, various technologies—such as aerodynamic design, radar-absorbing materials, and surface treatments—are applied in combination. The F-22 Raptor fighter jet, developed by the United States, is a prime example of a fighter that achieves stealth performance by utilizing such low-observable shapes and radar-absorbing materials.
In modern military operations, radar serves as the “eyes” for detecting the enemy’s position and movements. Stealth is a technology designed to prevent one’s presence from being easily detected by the enemy’s “eyes.” Making it difficult for the enemy to pinpoint one’s position and movements can yield extremely powerful military effects on a different level from the destructive power of the weapon itself. However, radar technology is also continuously advancing, and research is underway on technologies to detect and track objects from even greater distances, as well as various methods to detect stealth aircraft. Ultimately, it is unlikely that only one of these technologies—radar or stealth—will advance in isolation; rather, it is highly probable that a cycle of competition will continue, with technologies emerging to neutralize the opponent’s capabilities, followed by the development of new technologies to counter them. In future wars as well, the fierce technological competition between radar—which seeks to detect—and stealth—which seeks to hide—will be one of the key factors.
