[Reading Science] North Korean Drones That Claim to 'Block Everything' Actually Have No Countermeasures?

Senior Government Official from a Ministry Expresses Concerns After Consulting Private Experts
Technical Limitations in Both Radar Detection and Interception Make Defense Difficult
Continuous Technology Development and System Establishment Needed
Claims of Exaggerated Threats and Calls for Realistic Response Also Emerge

[Asia Economy Reporter Kim Bong-su] "In fact, it is impossible with current technology to completely block the infiltration of small drones. When members of the National Assembly ask (the minister), just tell them that we are diligently researching."

This is the reality of North Korea's unmanned aerial vehicle (UAV) defense capabilities revealed by a senior government official from a ministry. He consulted experts, including heads of government research institutes and respected civilian scholars, to brief the minister ahead of a National Assembly appearance on countermeasures for the North Korean UAV infiltration incident that occurred in December last year. However, contrary to government announcements promising "complete blockade" and public expectations, the general consensus among science and defense technology experts was that "100% interception is practically impossible," so he had no choice but to report this as is.

What exactly is happening? Experts contacted by Asia Economy gave similar assessments. Radar detection and counter-weapons currently have clear technical limitations. Trying to block all North Korean drones risks wasting the budget like "pouring water into a bottomless jar." Since the security threat is not that significant, some opinions suggest that instead of blindly investing due to public opinion, it might be better to simply "ignore" the threat.

North Korean drone discovered in Inje, Gangwon Province on June 21, 2017. [Image source=Yonhap News]

Detection is difficult from the start

It is very difficult to detect small flying objects under 4 meters, including the 2-meter UAV used by North Korea. Although the drone detection radar network of the Capital Defense Command detected the North Korean UAV that infiltrated Seoul last December, it repeatedly disappeared and reappeared due to obstacles such as mountainous terrain and power plants. Existing radars have long wavelengths, making it hard to detect small objects like small drones. Ku-Band radars operating at 12?20 GHz are required to detect small objects.

The problem is that these short-wavelength radars have a narrow detection range of about 4 km. Recently, the Defense Acquisition Program Administration (DAPA) developed technology with Daegu Gyeongbuk Institute of Science and Technology (DGIST) to detect ultra-small drones up to 8 km. This is cutting-edge technology using Active Electronically Scanned Array (AESA) radar and artificial intelligence (AI). However, it will take time to commercialize and deploy it in the field, and challenges remain regarding high costs and accuracy.

Some suggest tracking the drone control signals and striking the origin directly. However, like the recent North Korean UAV, which pre-programmed its target location and flew automatically using GPS, there is no need to exchange signals between the drone and controller, making this approach meaningless.

Of course, to completely block North Korean UAV infiltration, even if the detection range is narrow, anti-drone radars could be densely deployed nationwide. However, this requires an enormous budget, raising efficiency concerns. For example, the drone countermeasure equipment recently piloted at Incheon International Airport costs about 3 billion KRW. Deploying similar equipment along the 230 km Demilitarized Zone (DMZ) would require about 60 such units spaced every 4 km.

Even if deployment is limited to expected drone infiltration routes such as coastlines and high-risk areas like airports, nuclear power plants, and gas storage facilities nationwide, the cost would easily reach several hundred billion KRW. Kang Wang-gu, head of the Unmanned Mobility Project Group at the Korea Aerospace Research Institute (KARI), said, "Installing drone detection radars across the entire country would cost an enormous amount," and added, "If DAPA extended the detection range to 8 km, it means they increased the radio wave power or used long-wavelength waves, which could cause issues like surrounding interference and accuracy loss."

Cha Ji-hoon, head of the Next-Generation Unmanned Mobility Research Lab at the Electronics and Telecommunications Research Institute (ETRI), said, "Drones have a very small radar cross-section (RCS), only a few thousandths that of fighter jets, so the reflected signal is minimal. This requires high-performance radars, but they are either too expensive or too large, so currently, drone-specific radars with ranges of 3 to 8 km are being developed." He added, "It is impossible to block 100%, and realistically, the concept is to intercept 7 to 8 times out of 10. Like the U.S., a multi-layered drone defense system of about five layers centered on critical facilities should be established to form multiple defense barriers."

No suitable weapons either

Even if drones are detected, there are no practical means to shoot them down. Drone countermeasure weapon systems are broadly divided into three types: physical neutralization, electronic neutralization, and control authority takeover. Physical neutralization involves destroying drones with anti-aircraft machine guns or small missiles. Nets, adhesives, or even birds are sometimes used, and methods to cause drones to collide with each other exist. Research and development (R&D) on high-power laser weapon systems to destroy drones is also active. Electronic neutralization includes radio frequency (RF) jamming, GPS signal jamming, and electromagnetic pulse (EMP) attacks, while control authority takeover refers to GPS spoofing and hacking.

The problem is that all these anti-drone attack methods have clear limitations with current technology. Anti-aircraft machine guns and missiles have very low hit rates against small drones and poor cost-effectiveness. They are practically unusable in urban areas due to grenades and shrapnel risks. Even in suburban areas, early detection and trained anti-aircraft shooting skills are required. The only somewhat feasible technology is high-power lasers that burn and destroy drones. However, current technology requires continuous laser irradiation for at least 30 seconds to over a minute, making it impossible to hit and destroy fast-moving drones.

Accordingly, South Korea recently began developing a weapon system at Gwangju Institute of Science and Technology (GIST) that fires femtosecond (one quadrillionth of a second) ultra-high-power laser pulses to destroy drones. Kim Hyung-taek, a researcher at GIST's Advanced Optics Research Center, explained, "Current laser drone strike systems use tens of kW-class fiber lasers to precisely track and concentrate laser beams on moving objects for several seconds or more, which limits response to fast-flying drones. We are developing technology that fires ultra-strong lasers about 10 times per second in the air to ionize and destroy key components of drones and small missiles to shoot them down."

Electronic neutralization technology also has limitations. These technologies require understanding the radio frequencies and circuit characteristics used by the opponent's drones to mount tailored attacks. If the opponent uses systems unknown to us, there is no way to block them. Jang Jun-ha, a doctoral student at KAIST who developed technology to disable enemy drone circuits with electromagnetic waves, said, "If the radio technology and circuit manufacturing methods used by the opponent are not pre-listed, response is impossible," explaining, "This is a limitation of all electromagnetic wave technologies."

Side effects are severe as well. They cause the same damage to all surrounding electronic devices indiscriminately. In the case of GPS jamming, most drones continue flying according to pre-programmed information when signals are lost, making it often ineffective. GPS spoofing technology can harm all aircraft flying near the target drone, so it cannot be used recklessly.

Kang said, "Jamming or spoofing affects various electronic devices besides drones, so they cannot be used in urban areas. Guns and cannons are problematic due to collateral damage, and laser weapons currently have limitations. For now, intercepting drones with interceptor UAVs that capture them with nets or shooting them down with small anti-aircraft guns might be possible methods."

On the 13th, at the Mugun-ri training ground in Paju, Gyeonggi Province, a reconnaissance drone is performing missions such as enemy detection during the AmTiger demonstration brigade joint training. Photo by Jinhyung Kang aymsdream@

System maintenance and calm response needed

Experts advise that since anti-drone systems are currently at the stage of developing individual technologies by field, efforts should be made to mature and integrate them to build proper systems. Cha said, "Anti-drone systems require a wide range of technologies such as radar, image processing, AI, radio wave tracking, and high-power lasers, but so far development has focused on individual technologies. Even if individual performance is good, they may not operate organically when combined. Efforts are needed to manage the entire system cohesively."

There are also voices calling for realistic responses by acknowledging the North Korean UAV threat as it is. Yang Wook, a research fellow at the Asan Institute for Policy Studies, said, "North Korea's drones do not have wireless modules, so real-time control is impossible, and their bomb payload is small, so they cannot be considered a significant military threat at present. The threat is greatly exaggerated." He added, "We need to check whether the Air Defense Command and Control and Alert System (C2A) projects, introduced by the Ministry of National Defense in 2019 (30 billion KRW) and 2021 (180 billion KRW), have fulfilled their roles." He also said, "Defense budgets are limited, so postponing existing planned investments to respond to drones is unreasonable."