Make Way for South Korea’s Underwater Drones

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Make Way for South Korea’s Underwater Drones

The ROK’S “Smart Navy” is a vital project, but will require more than just new technology.

Make Way for South Korea’s Underwater Drones

Republic of Korea Submarine Chang Bogo (SSK 61) heads out to sea during the 2004 Rim of the Pacific (RIMPAC) exercise.

Credit: U. S. Navy photo by Photographer’s Mate 1st Class David A. Levy

President Moon Jae-in of South Korea is pursuing an ambitious program known as “Defense Reform 2.0,” as part of which the Republic of Korea Navy (ROKN) is implementing an innovative vision for a “Smart Navy.” This concept prioritizes the development of state-of-the-art underwater technologies over simple threat assessment, intending to create a strong maritime force by means of revolutionary technologies. But this concept, by itself, is not enough to develop an innovative, flexible, agile, and adaptable naval force: it is also essential to create an operational framework that allows the integration of this new technology into the existing understanding of warfare.

Countermeasures Against the Growing North Korean Threat

The ROKN is responding to the recent successful testing of North Korea’s Pukkuksong-3 submarine-launched ballistic missile (SLBM) in three ways: first, by acquiring Boeing’s P-8K Poseidon Multi-Purpose Maritime Aircraft (MMA) to enhance multidomain anti-submarine warfare (ASW); second, by constructing attack submarines to follow on from the KSS-III (Chang Bogo III-class) batch 3 project; and third, by acquiring unmanned underwater vehicles (UUVs).

Some commentators anticipate a new phase in underwater operations against North Korea based on integrating threat perception, operational capability, and innovative technology. The ROKN has ordered six Boeing P-8K Poseidons to replace its aging P-3C Orions, which have recently been conducting combined ASW operations as part of the multilateral Sea Dragon 2020 exercises held near Guam. In addition, the KSS-III batch 2 submarines are being fitted with Air Independent Propulsion systems using lithium ion batteries, and these will enter service 2020-7. But now that North Korea has SLBMs, the KSS-III batch 3 project is expected to be nuclear-powered, which would move the ROKN closer to becoming a true blue water navy. Despite U.S. opposition, the ROKN last year set up a special study group to consider the construction of SSNs. Problems include: how to acquire suitably enriched uranium fuel, how to dispose of the waste products, how to coordinate the operations of this formidable strategic platform with NATO and the United States, and how to deal with the likely reactions from neighboring countries.

Disruptive UUVs

The ROKN is also exploring the potential use in underwater warfare of unproven revolutionary technologies from the so-called Fourth Industrial Revolution (4IR), though it is unclear whether these can really deal with the threats posed by North Korea. 4IR encompasses artificial intelligence (AI), big data, and autonomous operation, paving the way for UUVs with unmatched reliability and performance. Indigenous small UUVs as well as extra-large UUVs (XLUUVs) are under development, and these new unmanned autonomous technologies may well transform ASW and underwater operations in general. Based on underwater technologies from the civilian industry, UUVs are relatively inexpensive to produce, rapidly increasing in sophistication, and easy to operate and deploy. Current KSS-class submarines can act as a mothership for UUVs, which may be useful against a variety of underwater threats, in particular against sea mines, submarines, and SLBMs.

Unfortunately, it seems likely that operating UUVs will disrupt the entire conceptual framework of naval warfare upon which the Combined Forces Command ROK/US (CFC ROK/US) relies, and which is fundamental for the ROK’s national defense. Since the Armistice Agreement was signed in 1953, as part of preserving peace on the Korean Peninsula, ROKN submarine operations have not crossed the de facto maritime boundary between two Koreas. But the introduction of UUVs will radically disturb the whole scenario of underwater warfare, likely leading to unexpected and unplanned encounters between the two Koreas, and to underwater conflicts that would also affect allies, such as the Japanese and U.S. navies.


At present, very little is definitely known about the ROKN’s UUV projects, since the operational concepts and the nature of the proposed platforms remain classified, though the ROKN Magazine has revealed that the ROKN vision of a Smart Navy relies upon a variety of autonomous underwater platforms. The ROKN has, however, announced a long-term project to develop UUVs at MADEX-2019, with the initial platform being a Remote Mine-hunting System (RMS) to be used by mine-hunters and minesweepers for explosive ordnance disposal operations to protect security in sea lines of communication (SLOC). The RMS operates down to 200 meters, at 7 knots, for 3 to 20 hours, utilizing side-scan sonar, underwater cameras, and EO sensors.

In the medium term, it seems that the ROKN plans to develop medium-to-large UUVs capable of carrying more weapons and communication systems. These will connect to land-based or satellite communications, and to other surface assets, to allow joint coordination for underwater operations. The ROKN hopes to develop something like the U.S. Orca XLUUV, and by adopting an operational concept similar to the current KSS-class submarines, these will be integrated with P-8Ks and other surface combatants into a “platform of platforms.”

The ROKN appears to consider its XLUUV projects as essential to the future of ASW and submarine operations. These XLUUVs would focus on command and control functions in support of other deep sea assets; on intelligence, surveillance, and reconnaissance missions; and on collecting the acoustic data that are so crucial to underwater warfare, including ASW. More than any other country, the ROK faces a variety of imminent underwater threats, and XLUUVs, which are likely to displace about 10 tonnes and operate down to 300 meters, would make a valuable contribution to the ROKN’s submarine fleet.

Looking further ahead, advocates of 4IR see XLUUVs functioning as an adjunct to the current KSS-class submarines only for a transitional period. They envisage the ultimate replacement of all manned submarines by large and easily operable fully autonomous AI-controlled XLUUVs, including for offensive roles and missions. ROK defense industrial companies — such as Hyundai Heavy Industries, Daewoo Shipbuilding & Marine Engineering, Hanwha, and LIG Nex1 — have speculated about building XLUUVs with a displacement of 50 tonnes, which could operate autonomously underwater for more than 30 days, and with a range of 3,000 nautical miles.

UUV Challenges

Before UUVs can deployed routinely, there are some challenging operational and technical issues to be resolved. What about identification? Manned submarines do not require an Identification, Friend or Foe (IFF) system — contact with an unexpected vessel, within the assigned area and depth, is tantamount to identifying an enemy, which can therefore be attacked without prior warning.  UUVs, by contrast, face a very difficult task to distinguish manned and unmanned friendly and enemy vessels, and will need to use an IFF system for this purpose, which inevitably exposes their position and course, so that they cannot conduct stealthy operations.

Moreover, it remains unclear whether the rapidly evolving underwater technologies are sufficiently adaptable to perform all the tasks that skilled and experienced personnel are capable of in the submarine environment. XLUUVs may feature advanced core electronics, navigation suites, high capacity energy packs, and modular, open systems architecture, but it is entirely reasonable to doubt their ability to conduct fully autonomous C2 operations to the same standard as an expert professional human who is proficient in the concepts of underwater tactics and warfare. Much thought has been given to individual features that any type of XLUUVs will require to support the KSS-class submarines, such as long-endurance underwater operations, high speed for chasing North Korean SSBs, and more powerful strike weapons, but putting all these elements together may produce a vessel that exceeds the management capabilities of any AI system that we can build in the short or medium term.

The ROKN has so far been focused on technical development: creating innovative design and building methods; integrating government-owned organizations, such as the Advanced Defense Agency (ADD), into military-civilian defense industrial cooperation through start-up cooperation; and adapting the ROKN’s requirements for revolutionary underwater warfare. Now that the ROKN is urgently attempting to move toward a revolutionary Smart Navy, however, it is the right time to consider how UUVs would fit in, tactically and operationally, with the Smart Navy concept.

Some Recommendations

First, the ROKN should set up a permanent task force to both identify the best run-silent-run-deep underwater technologies for XLUUVs, including stealth, low-noise, and autonomous maneuvering, and oversee the development and optimization of hardware and software.

This task force should include marine scientists and acoustic engineers, but also operational submariners and naval architects. Together they must decide how XLUUVs will fit into future underwater operations, including ASW. How will the current submarine fleet cooperate with UUVs? Should UUVs be launched from a submarine mothership, or will they operate singly and independently, without direct support from submarines? In the latter case, IFF would be essential for safe navigation. Some government organizations, notably ADD, which is a South Korean research and development institute reporting to the defense ministry, have played a leading role in developing XLUUVs. But to fully exploit the power of 4IR, there are also some civil institutions and universities that have much to contribute, especially the Korea Advanced Institute of Science and Technology (KAIST), which dominated a recent algorithm contest and seminar hosted by the U.S. Office of Naval Research.

In addition, the task force should identify critical functionality for ASW-oriented underwater operations. To be effective, autonomous XLUUVs will require AI capable of search-detect-identify functions, which means integrated information processing systems capable of providing real-time detection and classification based on acoustics. This implies sophisticated high-definition sonar capable of recognizing underwater objects from any angle. Of course, autonomous XLUUVs must also be able to neutralize enemy submarines, so they will need to incorporate light or heavy torpedoes.

Finally, the task force should plan the future development of underwater warfare, which ideally will evolve into an integrated package as a system of systems controlling a platform of platforms. Taking into account the current state and likely development of AI, big data algorithms, imaging sensors, and real-time processing algorithms, as well as prevailing time pressures, the task force should determine the timing of the XLUUV project, and which aspects of it can be domestically developed. Perhaps it could be built after the KSS-III batch 2 project, but since this will continue into the late 2020s there is still time to design and incorporate XLUUVs within this project. One option under consideration is a hybrid design that would convert small UUVs into XLUUVs.


Since October 2, 2019, when North Korea demonstrated its SLBMs, military experts have debated how to counter this disturbing new threat. The consensus is that UUVs are the best approach to enhancing the ROK’s ASW capabilities, so as to defend against North Korean Sinpo-class SSBs. But many operational and technological difficulties must be overcome to develop truly effective UUVs. The ROKN’s UUV project certainly appears to moving in the right direction, but if the ROKN Smart Navy is to deserve the name, it cannot become obsessed with technology for its own sake: integration of UUVs with existing operational paradigms is also crucial. The ROKN should prioritize the deployment of UUVs, not just to deter North Korea, but also to deal with future potential threats from neighboring countries and regional powers.

Sukjoon Yoon (Captain, ROK Navy, retired) is currently a senior fellow at the Korea Institute for Military Affairs. The views expressed in this paper are author’s own and don’t represent any government organization, including the Korea Institute for Military Affairs.