October 18, 2022 · Analysis China

Analysis: Nuclear-Powered Undersea Swarms



▶︎ Two key drivers of China's undersea weapons development are the convergence of torpedoes, mines, and autonomous underwater vehicles (AUVs), and a desire for an underwater swarming capability to augment offensive mine warfare.

▶︎ Chinese scientists are actively seeking ways to overcome AUV endurance and range limitations in order to enable missions such as persistent, wide area ISR (Intelligence, Surveillance, and Reconnaissance), and standoff attack.

▶︎ Chinese scientists are exploring the use of nuclear energy as a power source for conventionally armed torpedoes, and recently published a conceptual design for a small nuclear reactor intended to power a standard (533mm or 21 inch) diameter torpedo.

▶︎ While the endurance and range of a nuclear-powered torpedo would provide China with a significant operational advantage, attendant technological challenges, such as communication and navigation, would need to be addressed before such weapons could be deployed over long distances.

▶︎ Given the current scale of nuclear microreactors, it is highly unlikely that China will develop and operationalize a nuclear-powered standard torpedo within the next ten years.

▶︎ While a nuclear-powered standard torpedo may be beyond China's technical capability, novel methods of energy production are either currently available or under development, making it increasingly likely that China will develop high-endurance, long-range AUVs within the next ten years.

▶︎ If China successfully overcomes AUV energy limitations, this will dramatically enhance the People's Liberation Army Navy (PLAN) mine warfare capability, enabling it to threaten U.S. maritime forces in home waters, as well as beyond the littorals in deep ocean regions.

On July 20, 2022, the South China Morning Post (SCMP) published an article claiming that Chinese scientists had "completed the conceptual design" of a small nuclear reactor to power a standard (533mm/21 inch) heavyweight torpedo, what the article describes as a "mini version of the Russian Poseidon unmanned submarine" (a reference to the Russian development of a nuclear-armed, nuclear-powered torpedo/AUV). The SCMP article made several claims regarding the design and capabilities of the reactor, as well as operational concepts for a nuclear-powered standard torpedo, including:

The SCMP article references two scientific papers published in the Journal of Unmanned Undersea Systems, a publication of the China State Shipbuilding Corporation. An overview of each paper and an analysis follows.

NOTE: English translation was obtained by importing the text of the papers into Google Docs and using the "Translate Document" tool. Any resulting translation errors or distortions could contribute to erroneous conclusions.

▶︎ Concept of a Nuclear Reactor Power Supply for Unmanned Underwater Vehicles
Journal of Unmanned Undersea Systems (JUUS)
July, 2022
Guo Jian, Yu Rongjun, An Weijian, Wang Ao, Li Gao, Jian Xiaohui
Affiliation: China Institute of Atomic Energy, Beijing


The Guo paper presents a conceptual design for a miniaturized, water-cooled, thermal-neutron nuclear reactor that can be used to power a standard 533mm diameter heavyweight torpedo.



▶︎ Discussion on Intelligent Decision-making Requirements and Methods for Underwater Unmanned Vehicle Torpedo Attack
Journal of Unmanned Undersea Systems
July, 2022
Ma Liang, Guo Liqiang, Zhang Hui, Yang Jing, Liu Jian
Affiliation: Navy Submarine Academy, Qingdao


The Ma paper highlights current Chinese thinking on the development and employment of AUV swarms ("UUVcluster," ""cluster operations") in "intelligent strike" missions, with a particular emphasis on "torpedo attack decision making," as "[this] ... is the premise and basis for unmanned equipment to form self-organized cross-domain coordination, autonomous cluster confrontation and other combat capabilities."

(Quoted in their entirety.)


The convergence of torpedoes, AUVs, and sea mines is a key driver in the development of undersea weapons both in the United States as well as the People's Republic of China. It is clear to naval strategists of both nations that mobile, swarming mines would pose a serious operational dilemma for an adversary, and could potentially hold warships at risk in nearly any region of waterspace, not only in the littorals, but on the high seas as well. The latter was highlighted in the 2021 Asia-Pacific Regional Security Assessment published by the Institute for Strategic Studies, in a scenario involving the use of electrically-powered Yu-9 torpedoes acting as a swarm to attack a U.S. Navy carrier strike group in the Phillippine Sea. (Strikepod Systems provided research for the scenario.)

A breakthrough in AUV range and endurance would be key to advancing the development of undersea swarms, and the Guo paper's proposed nuclear-powered torpedo is indicative of what is likely a broader Chinese effort to overcome this limitation. While neither the Guo nor Ma papers refer to any organized Chinese effort to develop undersea swarms, they do indicate that Chinese scientists are willing to engage in "out of the box" thinking in pursuit of novel AUV energy solutions to enable this capability, and that Chinese naval strategists believe that such a capability would provide China with the means to significantly blunt enemy maritime power.

Based on a reading of these papers, we can conclude the following with respect to China's efforts to acquire an undersea swarming capability:


Chinese engineers are actively seeking ways to overcome the limitations of current AUV energy storage and power generation technologies in order to enable long-range, wide area, persistent autonomous underwater operations, including mobile, swarming minefields.


Chinese scientists and engineers have identified and are working to overcome key data collection, processing, and transmission challenges related to undersea vehicle autonomy.


Given the technological challenges involved in scaling down a uranium-fueled, water cooled nuclear reactor to fit inside of a 533mm diameter torpedo, it is highly unlikely that China could develop a working prototype, test, and operationalize a standard nuclear-powered torpedo within at least the next ten years.

The claim that a nuclear-powered torpedo could attack targets with little or no human intervention is true.

While the SCMP article claims that the nuclear-powered torpedo would be conventionally armed, the Guo paper makes no specific claim with respect to the nature of the warhead.

While a nuclear-powered standard torpedo may be largely conceptual, there are currently technologies that could extend the operational range and endurance of heavyweight torpedoes and provide China with a rudimentary undersea swarming capability.


Chinese strategists view undersea swarms as a logical extension (or evolution) of offensive mine warfare.

While in theory a salvo of nuclear-powered torpedoes could "transi[t] from Shanghai to San Francisco in a matter of weeks," it is unlikely that nuclear power would be used to "drive a swarm of torpedoes across the Pacific"

The most likely CONOPS of high-endurance, long-range AUVs, such as nuclear-powered torpedoes, would involve salvo launches from standoff range by manned Chinese submarines or extra-large AUVs (XL-AUVs) operating in the Pacific ocean.


The following scenario illustrates how China could employ long range, high endurance AUVs, such as a nuclear-powered torpedoes, against the United States.

The U.S. island territory of Guam is located approximately 3300 miles west of Hawaii, and 1500 miles east of the Phillippines. It is home to Naval Base Guam, where five Los Angeles-class attack submarines (Submarine Squadron 15) are currently homeported, and Andersen Air Force Base, a critical node for U.S. heavy strategic bomber (B-1, B-2, B-52) operations. Naval Base Guam is also a logistics and stopover hub for a wide range of U.S. and allied/partner surface and subsurface assets, including cruisers, destroyers, aircraft carriers, as well as attack (SSN), guided missile (SSGN) and ballistic missile (SSBN) submarines. Both bases are key to U.S. power projection in the Indo-Pacific region, and would be of critical importance for the United States during a sustained, high intensity conflict in the Western Pacific.

Given its strategic importance for the the United States, Guam would likely be the target of a Chinese ballistic missile attack during the opening stages of conflict. Guam's current missile defense is provided by a combination of Arleigh Burke guided missile destroyers (DDGs) and Ticonderoga-class guided missile cruisers (CGs) equipped with the Aegis Ballistic Missile Defense (BMD) system. Prepositioned mobile mines could be directed to attack these ships in advance of a missile attack, cutting off a critical means of defense. These mines could also attack ships sortieing from Guam should the United States receive advance warning of a Chinese missile attack, or while still moored inside Apra Harbor.

Deploying the Minefield
Several weeks prior to a planned offensive, China deploys three Type-039B Yuan-class submarines¹, each armed with 16 (estimated) nuclear-powered heavyweight torpedoes to engage in a two-pronged attack on Guam.² With an estimated range of 6500 to 8000 nautical miles, and an endurance of 60 days, the submarines, operating out of Daxie Dao or Luhan submarine bases, transit to a location within 1000 miles northwest of Guam, beyond the range of U.S. Navy ASW patrols, where they launch a salvo of 48 torpedoes. Assuming they transit at an average speed of 15 knots, the torpedoes arrive on station off the coast of Guam anywhere from 33 to 67 hours later, and assume a patrol which they can sustain from 104 to 123 days, surfacing periodically to obtain navigational fixes and to maintain communications via satellite with human operators.³ Should the offensive be delayed, the torpedoes would reach their max endurance, then scuttle and sink to the seabed, and the minefield could be reseeded by a future mission.⁴


Strike on AEGIS BMD Warships
Once the attack order has been given, target and navigation data is transmitted via satellite to any surfaced torpedoes, with the data propagating throughout the swarm using acoustic communication. An initial wave of torpedoes breaks away from the minefield and transits under remaining nuclear or stored electric power toward designated targets - Aegis cruisers and destroyers operating off the coast that are charged with defending Guam against ballistic missiles. With little or no warning, the torpedoes successfully kill their targets, significantly degrading Guam's ability to defend itself against missile attacks.


Simultaneous Attack on Naval Base Guam
As the initial wave of torpedoes dismantles Guam's BMD defense, a second wave of torpedoes receives target and navigation data for a simultaneous attack on ships and submarines moored at Naval Base Guam. The torpedoes break away from the minefield, and, using a combination of inertial navigation and AI, make their way into Apra Harbor to strike submarines moored at Polaris Point, or surface ships, such as cruisers, destroyers, tenders, strategic sealift ships, or even a CVN, moored at inner Apra Harbor. Surface ships may include additional, repurposed Aegis-equipped Ticonderoga-class cruisers that have been integrated into Guam's BMD, further degrading the island's defenses. Any remaining torpedoes continue to loiter offshore, forming a blockade to interdict reinforcements and resupply vessels, or to strike ships that have survived the initial strike and attempt to escape.


This is just one possible scenario involving Chinese use of prepositioned long-range, high-endurance torpedo-mines. Other possible missions include blockading ports, attacking submarines transiting strategic chokepoints, striking vessels inside Allied/partner ports, such as Sasebo or Yokosuka, interdicting U.S. strategic sealift or carrier strike groups, or loitering off the coast of key U.S. Pacific naval installations - Pearl Harbor, Hawaii, San Diego, California, or Kitsap, Washington - to strike ships in home waters.

Scenario Notes:
1 - China currently operates approximately 17 Type-039A/B Yuan-class SSP (air-indpendent power) submarines out of Daxie Dao and Lushun submarine bases. Given this vessel's range (which open source data indicate to be between 6500 and 8000 nautical miles, the estimated range of the Type-039B export variant, the S20), and the number of vessels available, it was chosen for this mission. Alternatively, a nuclear-powered submarine, such as the Type-091 Han-class, or the Type-093A Shang II-class, with its estimated loadout of 22 torpedoes, could also be used for this mission. However, with a total of three Hans and six Shang IIs in the PLAN inventory, with some undergoing maintenance or workups at any given time, or otherwise underway, they may be unavailable. In addition, while other classes of PLAN diesel-electric submarines could also potentially deploy the torpedo-mines, the Type-039B's AIP capability would provide greater stealth, as there is no need to snorkel and expose itself to possible detection.
2- In the absence of reliable estimates concerning the Type-039B torpedo loadout, the Type-039A loadout is used, which is estimated to be 16. It is possible that not all torpedoes would be used for the mining mission, and that space may be reserved for conventionally-powered torpedoes for self defense.
3,4 - The scenario assumes a transit speed of 15 knots, and relies on performance data derived using the Guo paper claim that a nuclear-powered torpedo could operate for 200 hours at 30 knots, or longer if operated at a lower power consumption. For simplicity, it was assumed that power generation would increase/decrease in a linear fashion - i.e. if 200 hours @ 30kts, then 400 hours at 15kts, 600 hours at 10kts, etc. Alternatively, if the torpedoes transited at a lower speed, they could be launched from a greater standoff range, and still operate in situ for an extended period of time.


China is actively pursuing a breakthrough in energy production that would extend the operating range and endurance of AUVs in order to enable persistent, wide area operations, including undersea swarming. While it is highly unlikely that China will develop and operationalize a nuclear-powered standard torpedo within at least the next ten years, given that other forms of energy production are either currently available or under development, it is likely that China will acquire an undersea swarming capability within that time period. This will dramatically enhance the People's Liberation Army Navy (PLAN) mine warfare capability, enabling it to threaten U.S. and Allied/partner maritime forces operating in home waters, as well as in deepwater regions of the ocean, well beyond the littorals.


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