[Yang Nak-gyu's Defence Club] The Conditions of Stealth That Make North Korea Nervous

[Asia Economy Yang Nak-gyu, Military Specialist Reporter] Our military is drawing attention as it plans to develop stealth technology that allows for covert infiltration independently.

According to the military on the 14th, the Joint Chiefs of Staff organized the acquisition of a 'low-observable reconnaissance unmanned aerial vehicle' as a long-term new requirement project in July last year and began studying its operational concept. 'Low-observable' refers to stealth technology that is difficult to detect. The Agency for Defense Development (ADD) has selected unmanned aerial vehicle technology with stealth capabilities as a 'core technology research project' and has been researching technologies to reduce radar cross-section (RCS), such as implementing stealth shapes for UAVs and developing stealth coatings.

Stealth technology has been applied to maritime and ground weapon systems since the late 1950s, starting with stealth aircraft. Recently, military powers have been working to equip submarines with stealth functions. Measures such as applying radar-absorbing paint or radar-absorbing structures to reduce radar cross-section and designing low-noise propellers to reduce noise are underway. The Polish tank PL-01 is known to be capable of radar concealment by applying infrared signal reduction technology and radar-absorbing paint.

Conditions required for stealth = The core of stealth is the 'radar cross-section' (RCS). RCS refers to the value of electromagnetic waves emitted by radar that bounce back after hitting an object. The RCS value varies depending on the aircraft's size, shape, material, azimuth, elevation angle, and wavelength. Friendly forces use this information to identify the type of aircraft and respond accordingly.

However, stealth reduces the RCS value, causing confusion for the enemy. The stealth bomber B-1B, known as the 'Death Swan,' is 44 meters long and 41 meters wide but has an RCS of only 10㎡. The stealth bomber B-2, which is 20.9 meters long and 52.1 meters wide, has an RCS of 0.75㎡, making it appear like a 'large bird.' Stealth fighters F-35A and F-22 have RCS values of 0.001㎡ and 0.0001㎡ respectively, making them look like 'golf balls.' This means they cannot be detected by conventional radar even during surprise attacks in enemy territory.

The exterior also differs from conventional aircraft. The stealth aircraft F-117 Nighthawk, produced by Lockheed Martin in 1983, has an angular shape. This design reflects emitted electromagnetic waves in different directions to prevent radar from receiving the signals. This technology is also applied to the 'Korean Next-Generation Fighter' (KF-X).

However, focusing only on the exterior can compromise flight performance. To compensate, special paint called radar-absorbing paint was developed. Known as stealth coating, the F-22 and F-35 use special coatings and graphite-infused composite materials on their exterior to absorb radar waves.

Stealth coating developed by a domestic SME = In June last year, at the 2019 Civil-Military Cooperation Requirements Development Seminar hosted by the Air Force Aerospace Combat Development Group, a domestic SME, ETL Co., Ltd., attracted attention by announcing the development of a radar absorber, a stealth technology that reduces radar signals.

At that time, the company stated, "Unlike the existing solid-type radar absorbers that are attached, we developed a liquid-type electromagnetic wave absorbing paint (RAP)," and explained, "Applying electromagnetic wave absorbing paint to weapon systems enhances their stealth effect." The company added, "Especially for small-scale vessels like high-speed boats, applying the absorber is expected to enable operations close to the coast."

To verify the performance of the paint developed by this company, a test was conducted in 2017 using the domestically produced supersonic advanced trainer T-50. The test involved painting ETL's radar wave absorbing paint on a precise model one-tenth the size of the T-50, followed by performance verification by the POSTECH Electromagnetic Wave Technology Research Team.