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Undersea

Neither Fish nor Fowl: China’s Development of a Nuclear Battery AIP Submarine

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By Dr. Sarah Kirchberger and CAPT Christopher P. Carlson, USN (Ret)

On September 27, 2024, news broke that a previously unreported new type of Chinese nuclear-powered submarine, dubbed the “Type 041,” had suffered a major mishap at its fitting out pier at the Wuchang shipyard in Wuhan, according to unnamed Pentagon sources. Submarine expert Thomas Shugart had previously spotted an unknown submarine with a distinct x-shaped stern at Wuchang Shipyard from satellite imagery taken on 26 April 2024, and days later reported unusual crane activity at the same pier location from June 2024 imagery, speculating that the new boat suffered a serious incident.

Even more intriguing and consequential than the question of whether a submarine incident of some sort actually did occur at Wuchang or not, is however another issue: What type of “nuclear-powered submarine” could this new design possibly be?

China watchers were quick to point out that the Wuchang Shipyard in Wuhan had not hitherto built any nuclear submarines, although the shipyard’s facilities were completely rebuilt at a new location (from 2012-2020) and massively enlarged. All Chinese nuclear-powered attack submarines (SSN) and ballistic missile submarines (SSBN) have so far been constructed exclusively at the Bohai Shipyard at Huludao. The imagery of the new submarine makes it clear it is too small for a SSN, and is similar in size to China’s Type 039A/B/C Yuan series of conventionally powered submarines. Another interesting indicator was the reported type number – “041” – which is a continuation of the traditional numbering scheme carried by China’s diesel-electric submarines. By contrast, China’s nuclear-powered subs, whether SSNs or SSBNs, all have official type numbers starting with “09.” The next-generation Type 095 SSN and Type 096 SSBN are possibly already under construction at the Bohai Shipyard in Huludao, and there is no plausible suggestion that the smaller, unknown boat observed in Wuhan could represent either of those two platforms, given the larger estimated displacement of the Type 095 and Type 096 compared with the previous generation of Chinese SSNs and SSBNs.

A new type of nuclear battery AIP propulsion?

It would have been easy to dismiss the news of a supposedly nuclear-powered Type 041 submarine built in Wuhan as misinformation, were it not for the fact that several years earlier Chinese sources had hinted at a project for developing small, low power auxiliary nuclear reactors for conventional submarines, replacing the Stirling engine air-independent power system (AIP) that China developed based on a technology transfer from Sweden during the 1980s. A 2017 report by Richard D. Fisher described some details of such a plan based on slides from an academic lecture given by retired Rear Admiral Zhao Dengping.

Despite successfully developing a Stirling engine-based AIP system, China is known to have struggled with developing a more advanced, fuel cell-based AIP system as is currently in use with the German, South Korean and Singaporean navies, among others. Neither has China deployed lithium-ion batteries aboard its submarines, as pioneered by Japan. Here, Chinese analyses have stressed unresolved issues regarding the danger of thermal runaway, which poses heightened risks of a severe fire aboard a submerged submarine.

In light of such technical challenges, China may have decided to forgo developing high power density fuel cells or even more powerful Stirling engines for submarine applications, even though lithium-ion batteries are probably still on the table, opting for a different solution altogether by developing a nuclear battery.

Interestingly, as reported by R.D. Fisher, Rear Admiral Zhao Dengping’s lecture slides described just such a nuclear battery project. Of the presentation slides posted online, three dealt specifically with a small-scale nuclear reactor for conventional submarine platforms. One slide showed a basic schematic diagram that depicted a possible layout of the nuclear-powered electric propulsion plant. The reactor itself is described as a low pressure, low temperature design that employs natural circulation in the primary loop. Steam is generated, however, through an intermediate loop that appears to be in a separate compartment, which is then sent to a secondary loop with a conventional steam driven turbine generator in yet another compartment. While this design suggests an emphasis on safety, it does so at the expense of internal volume requirements and thermodynamic efficiency.

It is reasonable to ask if these slides accurately reflect Chinese intentions. With the benefit of hindsight, the response would be a confident “yes” because every slide posted from RADM Zhao’s lecture showed a platform or system that was then in service, undergoing testing, or was in the advanced research and development stage. For example, Zhao presented a slide that discussed a large deck amphibious assault ship – larger than the Type 075. The computer-generated graphic on the slide is very similar to the Type 076 currently under construction at the new Hudong-Zhonghua shipyard on Changxing Island. Another slide depicted an anti-ship ballistic missile (ASBM) engagement launched from a surface ship. This too has come to fruition when a video of a Type 055 launching an ASBM was posted in April 2022. These two examples of a platform or system that hadn’t been known to exist in 2017, but became evident years later, demand that the small reactor concept be taken seriously.

Some seven years after RADM Zhao’s slides became public, on 24 April 2024, a Chinese news article claimed that, in honor of the 75th birthday of the PLA Navy, a “new nuclear-powered submarine installed with a domestically produced small nuclear reactor” and based on the hull design of the conventionally powered “Type 039C” AIP sub was in development at the Wuchang shipyard in Wuhan. Note, this article came out a mere two days before the satellite images of the shipyard were taken and subsequently analyzed by Tom Shugart. The article compares the new Type 041 submarine design to an enlarged French Rubis class and states that its submerged displacement would be around 4,000 tons and thus larger than the Rubis, allowing it to integrate more capable sensor and weapon systems. The article describes the small auxiliary reactor as a “low-temperature, low-pressure, subcritical nuclear reactor” to “directly charge” the boat’s battery rather than drive the propeller. This describes a nuclear battery AIP system that allows the battery to be charged continuously while the boat is submerged and would eliminate the need to surface every 20 days as in the case of China’s Stirling AIP submarines.

The article goes on to say the first one or two units of the Type 041 would likely be used as prototypes for weeding out technical issues before any further units would be produced. It speculates that if the development is successful, even older conventional submarines could be gradually retrofitted with a nuclear battery AIP system. The article states that this could potentially transform China’s conventional submarine fleet into a fully nuclear-powered fleet. Despite some questionable technical conclusions by the author, the article is consistent with Zhao’s lecture material.

What is a nuclear battery?

The reference to a “small” reactor on the Type 041 should be understood in the context of existing submarine reactors, which produce between 70 – 190 megawatts of thermal power (MWt) depending on the design and all belong to the category of microreactors. These reactors are defined by the International Atomic Energy Agency as having a power generation capability of less than 50 megawatts of electrical power (MWe), or approximately 220 MWt. Most microreactors are in the 1 – 20 MWe (≈6 – 125 MWt) range; the nuclear battery resides at the bottom end of this category. Nuclear batteries are loosely defined as nuclear reactors that produce up to 20 MWt or approximately 3 MWe. These reactors are indeed “small” in comparison to those on larger SSNs and SSBNs and can fit into a Type 039A/B/C submarine pressure hull that is about 7.1 meters in diameter.

While rather scarce, nuclear batteries have been used in submarine and submersible designs before: the American NR-1 (≈1 MWt), the Soviet Project 651E Juliett with the VAU-6 (4.9 MWt) boiling water reactor, the Project 20120 Sarov, and the collection of deep-diving submersibles of the Soviet/Russian Main Directorate of Deep-Sea Research or GUGI, including Project 1851 X-Ray, Project 1851.1 Paltus, Project 1910 Uniform, and Project 1083.1 Losharik, reported to have a pressurized water reactor in the 10 – 15 MWt range. Lastly, Canada conducted considerable research in the late 1980s to develop a “baby nuke” submarine using an Autonomous Marine Power Source or AMPS-1000 powerplant with a maximum design power of 10.8 MWt.

Based on RADM Zhao’s description that the small reactor being considered operates at low pressure and low temperature, it is reasonable to assume a maximum thermal power rating of 10 – 11 MW – consistent with Soviet and Canadian experience. The thermodynamic efficiency would be on the low side for historical nuclear batteries, around 12% – 13%, due to the losses involved with the additional intermediate steam generation loop as shown in the system diagram slide. Despite the low efficiency, such a nuclear power plant could generate about 1.3 MWe, four to five times that of any conventional AIP system. The hull size of the Type 041 revealed in satellite imagery is sufficiently large to accommodate the design as shown, but even with the additional 7 meters in length, the Stirling engines and cryogenic oxygen storage would have to be removed to free up additional volume.

Operational advantages of a nuclear battery

All types of advanced conventional AIP propulsion systems, whether fuel cell, Stirling engine, or steam turbine based, offer extended submerged endurance to small and medium size submarines when compared with traditional diesel-electric propulsion systems, such as that fitted to the Project 636M Kilo-class China imported from Russia. The latter typically needs to come up to snorkeling depth every day for two to three hours to recharge its batteries, assuming a 10% – 12% indiscretion rate, thus greatly increasing the risk of detection. At best, a Kilo-class submarine can stay submerged at slow speed for about three days before needing to snorkel. Chinese analysts have in the past lamented the fact that this limitation exposes Chinese submarines to adversary anti-submarine warfare (ASW) forces just when they are about to reach deeper diving depths in the Okinawa Trough after leaving port in East China. Any AIP system would help to alleviate this predicament, but the maximum submerged transit speed of a submarine utilizing a conventional AIP system is still only 4 – 6 knots. A nuclear battery AIP system as described above could support submerged transit speeds of up to 9 – 10 knots while meeting all hotel loads and the electrical power requirements of the nuclear plant auxiliaries.

Another advantage that is often not discussed is that there is ample electrical power available to outfit a Type 041 with a full spectrum of atmospheric control equipment. Conventional AIP boats still need to ventilate daily to renew the atmosphere with fresh air, unless the crew relies on a limited supply of consumable chemical systems to purge carbon dioxide and carbon monoxide from the atmosphere. Oxygen isn’t a problem as the crew can vent off a little from the AIP cryogenic oxygen tank to support their needs. A Type 041 can feasibly be fitted with compact oxygen generators, carbon dioxide scrubbers, and carbon monoxide-hydrogen burners, thereby giving the submarine complete independence from outside air.

Lastly, despite what the advertising brochures say, conventional AIP systems do not charge submarine storage batteries well. They can keep a fully charged battery topped off, but recharging a battery that has been significantly discharged is really not a viable option. Russian brochure data on the Project 636 Kilo states that it would take about 12 hours to recharge a completely discharged battery; this is with most of the output of two 1.5 MW DC generators run by the diesel engines. A conventional AIP system would be hard pressed to produce even a tenth of the power that diesel-driven DC generators can provide – this means multiple days to fully recharge a very low battery. A nuclear battery AIP system would be more capable of recharging a battery, but it will still take longer than using the diesel-driven DC generators. The main advantage in this case is the nuclear AIP system could support sufficient speeds to move the submarine clear of a possible ASW threat so that the diesel generators could be used to recharge the battery.

This severe limitation is why most AIP submarine crews tend to operate their boat like a traditional diesel-electric submarine for as long as they can, holding the AIP system in reserve for those tactical situations that demand greater stealth. By contrast, a nuclear battery AIP system turns this operating concept on its head. The crew can rely on the reactor to meet all their operating needs, allowing them to hold the battery in reserve to deal with those rare occasions where higher speed sprints are required to approach a target. In other words, a “SSn,” if you will, can patrol like a larger nuclear attack submarine, but because it lacks high-speed endurance would have to resort to conventional submarine approach tactics as the situation demands.

Due to their smaller size and comparative quietness, a SSn is better suited than larger SSNs to area-denial missions in shallow, coastal waters where the environment would make it difficult to detect a nuclear battery AIP platform; this makes them likewise useful for intelligence and mining missions. Whenever greater speed and longer steaming distances are required, however – for instance when hunting an adversary carrier strike group or tracking and trailing SSBNs on the high seas – their limitations render the SSn unsuitable. China, in light of its complex maritime geography of shallow littorals, does have an enduring requirement to operate both smaller coastal submarines for area denial missions in the Near Seas, as well as larger SSNs and SSBNs for its nuclear deterrence and missions in the Far Seas.

Could China have developed a nuclear battery AIP alone?

China has had difficulties in designing modern, reliable, and safe nuclear reactors for its next generation SSNs and SSBNs and reportedly has turned to Russian assistance in the recent past. This raises the question whether Russian help was also involved in developing China’s nuclear battery AIP submarine propulsion. Although open-source information falls short of a definitive answer, some indications hint at Russian assistance.

Firstly, the Soviet Union, and later Russia, have the most operational experience with this type of propulsion plant. The Soviet and Russian navies have operated nine relevant submarines, including the Project 651E Juliett and the Project 20120 Sarov, with the majority assigned to GUGI. Given that most of these nuclear battery plants were designed and built in the 1980s, Russia’s defense establishment would likely feel comfortable in sharing detailed design information on the older systems as well as providing technical support to China’s endeavors.

Secondly, Russia has previously transferred other types of nuclear propulsion technology to China. CMSI reported in 2023 that an agreement concluded in 2010 between Rosatom and the China Atomic Energy Agency for the expansion of Russian-Chinese joint nuclear power programs – including floating nuclear power plants – gave China “access to detailed technical information on the nuclear reactors Russia was installing on their nuclear power barges and new icebreakers.” These reactors either didn’t fully address China’s military needs or were too large for installation aboard a submarine, but nonetheless this transfer indicates a general willingness of Russia to provide China sensitive nuclear reactor technology.

Thirdly, there have been announcements that China and Russia are collaborating on a novel type of small submarine design. Already in 2015, reports indicated a Chinese interest in procuring four Lada-class submarines from Russia – a purchase that was never followed through in light of the Lada-class’s vexing technical issues. However, on August 25, 2020, quoting an official representative of the Federal Service for Military-Technical Cooperation (FSMTC), Russian state media announced that Russia and China were “jointly designing a new generation non-nuclear submarine.”

Although no further public information about this new type of jointly developed conventional submarine has since been disclosed, in October 2020, Vladimir Putin gave an intriguing answer to a question on Russian-Chinese relations at the 17th Valdai Annual Meeting:

“We have achieved a high level of cooperation in the defence industry—I am not only talking about the exchange or the purchase and sale of military products, but the sharing of technologies, which is perhaps most important. There are also very sensitive issues here. I will not speak publicly about them now, but our Chinese friends are aware of them. Undoubtedly, cooperation between Russia and China is boosting the defence potential of the Chinese People’s Army, which is in the interests of Russia as well as China.”

Though the nature of these “very sensitive” technologies remains unclear, submarine technology certainly fits the description, and in September 2024, news reports indeed indicated that Russia was supporting China with improving the nuclear propulsion plant of its next-generation Type 096 SSBN.

Fourth and lastly, Russia and China have for several years steadily enhanced their collaboration in sensitive anti-submarine warfare related technology areas – including fiber-optic hydrophones and underwater communication. This could be related to a general trend in their subsurface warfare cooperation.

Could the jointly developed Russian-Chinese “new generation non-nuclear submarine” be the Type 041? The apparent contradiction between the Russian statements and the arguments presented in this article could be accounted for if neither the Chinese nor the Russians consider this a traditional nuclear submarine, but a conventional submarine that uses a nuclear battery AIP system. Semantics? Perhaps, but this premise would also provide a rationale as to why the Type 041 was constructed at Wuchang instead of Huludao.

At this stage, it is not possible to determine whether the reported nuclear-powered Type 041 submarine spotted at Wuchang is related to the joint submarine collaboration that was announced in 2020. This new submarine could be solely a Chinese project, or a Chinese project that received some technical aid from Russia. None of these possibilities can be excluded.

The mutual benefits of collaboration on sensitive submarine technology

Russia, despite its superiority in the field of building nuclear submarines, has long struggled to develop AIP propulsion for its smaller conventional submarines. Russian industry representatives have envied China’s successful Stirling engine-based AIP system, going so far as to admit that the Rubin Design Bureau, when trying to develop fuel cell AIP and lithium-ion battery technology at the same time, was spreading itself too thinly and therefore did not succeed.

China, for its part, has lagged behind Russia in nuclear propulsion technology and has in the past received help from Russia in that area. The known transfers of Russian nuclear reactor technology might therefore just be the tip of the iceberg. There are thus clearly potential synergies that could be exploited. Joining forces to improve Chinese AIP with a small auxiliary nuclear reactor might be a project in which both sides could bring their respective strengths to the table while each profiting from a common submarine design. This hypothesis needs to be evaluated in the light of future information as it becomes available.

Since at least 2023, there has been speculation about the possibility that Russia might opt to rejuvenate its war-depleted fleet by ordering naval vessels from Chinese shipyards, which can offer competitive prices and superior production capacity, even for highly complex warships, when compared with cash-strapped Russian yards. On July 5, 2023, a Chinese news article reported a visit by Russia’s Navy Commander-in-Chief Yevmenov to the Jiangnan shipyard in Shanghai. The article frankly discussed the possibility that Russia might opt for Chinese shipyard orders to solve its production capacity problems – noting however that this would be possible only “if Russia can overcome its pride.” A joint submarine design could, however, be produced in parallel by Chinese and Russian shipyards.

Opting for an advanced, nuclear battery AIP design would also make operational sense for Russia, not least because the whole concept originated from the Soviet Union in the 1970s.

Russia is at a disadvantage vis-à-vis NATO submarines in the shallow and confined undersea domain of the Baltic Sea, where its traditional nuclear-powered submarines can’t operate as efficiently as in deeper water. For that theater alone, a more capable, smaller AIP submarine would be desirable – and likewise for the Black Sea, Barents Sea, and parts of the Arctic Ocean, where Russia also routinely encounters NATO navies. In particular the recent Norwegian-German Type 212CD class submarine cooperation would be a serious concern for Russia on its northern flank. The pressure of having to meet those challenges, against the backdrop of Russia’s increasingly lopsided dependency on Chinese political and economic support due its war against Ukraine and Russia’s reduced shipbuilding production capacity, may have induced Russia to agree to a joint development of nuclear battery AIP submarines.

Even without an official agreement, there is the possibility that Russia’s arms industries could be faced with a brain drain of Russian specialists towards China, as Russia’s economic crisis worsens. There could thus be informal, behind-the-scenes Russian involvement even in a “purely indigenous” Chinese submarine program.

Conclusion

So far, the limited information on a new Type 041 submarine spotted on satellite imagery at Wuchang Shipyard yields more questions than answers. The above musings should be treated as hypotheses, to be revised as new data emerges. However, given the rapid modernization of China’s military, and particularly its navy, it seems advisable to keep an eye on the likelihood that the Type 041 submarine could be sporting a novel, auxiliary nuclear powerplant in place of the Stirling engine previously employed in its AIP propulsion system. Furthermore, such an improvement may have been derived from Soviet (and now Russian) technology, which pioneered auxiliary nuclear batteries for submarines during the 1980s. And if that were the case, the Type 041 may be the outcome of a Russian-Chinese collaboration on a new type of conventional submarine as announced by Russian state media in 2020.

Lastly, even if the Type 041 is indeed a novel kind of nuclear-powered small submarine, the Chinese SSN and SSBN programs (Type 095 and 096) will almost certainly continue because they are independent submarine development projects that are designed for distinctly different operational roles. Indeed, suggestions that the reported flooding casualty suffered by the Type 041 constitutes a major setback in China’s nuclear submarine program is overstated. The development of a smaller nuclear AIP submarine is completely segregated from the Type 095 and 096 production effort – an effort the Huludao Shipyard was enhanced to meet. At worst, the Type 041 mishap is a minor speedbump in China’s overall submarine modernization plans.

If the theories on the nuclear battery propulsion system presented above are confirmed, then the Type 041 SSn is neither fish, nor fowl. It would possess some, but not all, of the benefits associated with a traditional nuclear-powered attack submarine. In short, it would be a tertium quid – a third something – designed to specifically address China’s geographical and geopolitical concerns in the Near Seas.

Dr Sarah Kirchberger is Director of the Institute for Security Policy at Kiel University (ISPK) and Vice President of the German Maritime Institute (DMI). She is the author of Assessing China’s Naval Power and editor of Russia-China Relations: Emerging Alliance or Eternal Rivals?. Formerly an Assistant Professor of Sinology at the University of Hamburg, she has also served as a naval analyst with shipbuilder TKMS. She holds a M.A. and a PhD in Sinology from the University of Hamburg. 

Christopher Carlson is a retired U.S. Navy Reserve captain and Department of Defense naval systems engineer. He began his navy career as a submariner and transitioned to the scientific and technical intelligence field in both his reserve capacity and in his civilian job. He is one of the co-designers, with Larry Bond, of the Admiralty Trilogy series of tactical naval wargames – Harpoon V, Command at Sea, Fear God & Dread Nought, and Dawn of the Battleship. He has also authored numerous articles in the Admiralty Trilogy’s bi-annual journal, The Naval SITREP, on naval technology and combat modeling.

Featured Image: A PLA Navy submarine steams during a training exercise in the Yellow Sea. (PLA photo)

Shipbuilding

Japan’s Submarine Industrial Base and Infrastructure – Unique and Stable

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By Jeong Soo “Gary” Kim

The Japan Maritime Self Defense Force (JMSDF) possesses a modern and highly capable fleet, including light carriers, large AEGIS destroyers, and advanced conventional submarines which are renowned for their size and stealth. While individual Japanese naval vessels and their crews are certainly world class, Japan’s unique approach to naval industrial base strategy is often underappreciated, especially its submarine industrial base. This approach relies on three deliberate policy pillars:

  • Ensuring an extraordinarily stable production system for new boats,
  • Decommissioning operational boats with plenty of service life left in them, and
  • Maintaining these retired submarines in training and ready reserve fleets.

This industrial policy admirably balances cost, readiness, and wartime surge capacity. 

Pillar 1: Stable Production Capacity

The JMSDF received its first submarine, the JS Kuroshio (ex-USS Mingo) as Foreign Military Aid in 1955. Soon after, the JMSDF started ordering domestically produced submarines based on both Imperial Japanese Navy and U.S. Navy designs. Starting in 1965, the JMSDF consistently built ocean-going fleet submarines, and by 1980 starting with the Yushio-class of submarines, Japan had established an incredibly stable submarine industrial base. Mitsubishi Heavy Industries and Kawasaki Heavy Industry’s shipyards in Kobe each produce one boat every two years. With the exception of 1996 (due to the great Kobe earthquake of 1995) and 2014, Kawasaki or Mitsubishi has delivered a submarine on March of every single year like clockwork. This production scheme has held steady through the massive expansion of the Soviet Navy during the 1980s, the peace dividend era of the 1990s and 2000s, and even through the PLA Navy’s surge in the 2010s and 2020s.

Another stabilizing leg of the JMDSF’s submarine industrial base is the forward-looking and well institutionalized research and development scheme. For example, detailed design for the current Taigei-class of submarines kicked off in 2004, even before the previous Soryu-class was laid down. Detailed engineering for a follow-on class, including such features as pump jet technology, was already in the works when the JS Taigei entered service in 2022. Furthermore, when the JMSDF implements new technology, like Air Independent Propulsion (AIP) or large lithium battery packs, it inserts these technologies into an existing class of submarines to validate technical maturity. For example, in 2000 the JMSDF retrofitted a conventional, Harushio-class submarine, JS Asashio, with a Sterling-type Air Independent Propulsion (AIP) module to test its effectiveness before applying the technology to the future fleet. Similarly in 2020, Soryu-class submarines JS Oryu and JS Toryu were fitted with large lithium-ion battery packs instead of the Sterling AIP modules in anticipation of the lithium-ion power pack transition in the Taigei-class. 

Apra Harbor, Guam (April 12, 2013) – Japan Maritime Self Defense Force (JMSDF) Soryu-class submarine Hakuryu (SS 503) visits Guam for a scheduled port visit. (U.S. Navy photo by Mass Communication Specialist 1st Class Jeffrey Jay Price/Released)

Pillar 2: Unique Utilization Strategy at the Operator Level

The JMSDF’s submarine utilization system is unique and may seem odd to American and other Western Navies. While Japanese submarines are well-built and likely could serve as long as their American counterparts (35-40 years), they serve around 18 years before being decommissioned or transferred to training status. While most navies try to sustain submarines as long as economically feasible, the JMSDF “prunes” serviceable submarines out of its operational fleet in order to maintain the number of boats required in Japan’s maritime strategy. For example, between 1980 and 2018, the national strategy called for 18 submarines in the operational fleet, therefore most submarines were decommissioned between the 17-20 years of service to achieve this fleet goal. Starting in 2019, in order to match China’s rising naval power (and perhaps to hedge against the U.S. submarine base’s sluggish production increase), Japan’s maritime strategy increased its submarine requirement to 22 submarines in the operational fleet, and the JMSDF raised the “retirement age” of its submarines from 18 to 22 years until annual submarine production rate allowed the fleet size to reach 22. Officers in the JMSDF’s ship repair unit describe maintaining older submarines as “more costly, but not particularly difficult”, implying that if operational needs dictate, they could increase the number of operational submarines without having to increase the production rate.

Figure 1. Historical JMSDF submarine fleet size and average age of fleet. Credit: Author’s work.

 

Figure 2. Age in which JMSDF submarines were decommissioned. (Author graphic)

Another unique aspect to the Japanese submarine industrial base planning is that submarines typically do not go into an extensive mid-life refit like their American counterparts. JMSDF leaders cite that overhauling older vessels can often be unpredictable and lead to schedule growth, as submarines can be in much worse material condition than anticipated. They admit that conducting a mid-life upgrade could save cost in peacetime, but the current system that prioritizes new construction ensures more stability in the submarine industrial base. On the ground level, JMSDF ship repair officers cite that cutting holes into a pressure hull and then replacing major components in already tightly packed submarine is time consuming, and believe that new submarine construction “delivers more submarine sea power per man-hour worked” than conducting a midlife overhaul. They jokingly called this practice similar to the “Shikinen Sengu”, which is a ritual where one of the most revered Shinto shrines in Japan, Ise Shrine, is traditionally torn down and rebuilt every 20 years.

Pillar 3: Consistent Supply of Reserve Submarines

Another benefit of consistent production and early retirement is the ability to keep several reserve submarines in good material condition on reserve prior to final decommissioning and disposal. Typically, when submarines are decommissioned from the operational fleet, they are transferred to the training squadron and then consistently sail to train and qualify sailors prior to assigning them to operational boats. The training submarine fleet not only helps supplying the operational fleet with sailors already equipped with sea time inside a submarine, but also allows boats to be quickly transferred back to the operational fleet whenever new construction and delayed decommissioning cannot meet requirements. While the JMSDF has yet to recommission a training submarine back to active service, it has transferred older destroyers, the JS Asagiri and JS Yamagiri, from the training fleet back to the operational fleet in 2011/2012 to meet increased operational surface vessel demand. It is not unimaginable that the JMSDF would be willing to use its training submarines in a similar manner during a period of surging demand.

Furthermore, when submarines stop sailing with the training squadron, they stay on a reserve status receiving a certain amount of maintenance until they are finally stricken and disposed of. The number of submarines kept in this status is not well known, but parts are typically not salvaged to sustain other boats for a number of years. If submarine demand were to outstrip operationalizing the training submarines, the reserve boats could possibly be put out back to sea after some period in maintenance. Consequently, the combination of operationalizing the training and reserve submarines could give the JMSDF the ability to surge up to four additional operational submarines without accelerating its build schedule, which would constitute an impressive 20% increase in capability from the current fleet of 22 boats. 

Conclusion

All in all, Japan sustains an advanced, powerful conventional submarine fleet staffed by dedicated, overworked sailors, and supported by a robust, stable shipbuilding industry. Considering how quickly a shipbuilding industrial base atrophies without consistent inflow of new construction orders, the Japanese method of consistent production and fleet size control through early decommissioning may prove to be a viable template that even the U.S. Navy can incorporate into its long-term naval shipbuilding plan.

Jeong Soo “Gary” Kim is a Lieutenant in the U.S. Naval Reserves and currently a student at the Lauder Institute at the Wharton School of the University of Pennsylvania earning an MBA and MA in East Asian studies. He previously served with the Seabees of Naval Mobile Construction Battalion 5, and with NAVFAC Far East in Sasebo, Japan. He graduated from Columbia University with a bachelor’s degree in mechanical engineering and a minor in history.

The author would like to give special thanks to LCDR Hiroshi Kishida of the JMSDF’s Sasebo Ship Repair Facility, and various junior officers serving in Sasebo-based ships for assisting with the research for this article.

References

Dominguez, Gabriel. “Recruitment Issues Undermining Japan’s Military Buildup.” The Japan Times, The Japan Times, 2 Jan. 2023, www.japantimes.co.jp/news/2023/01/02/national/japan-sdf-recruitment-problems/.

Kevork, Chris. “The Revitalization of Japan’s Submarine Industry, From Defeat to Oyashio.” NIDS Journal of Defense and Security, 14, Dec. 2013, 14 Dec. 2013, pp. 71–92.

Ogasawara, Rie. “Observing the Horrible State of JSDF Military Housing through Photos.” ダイヤモンド・オンライン, 27 Sept. 2022, diamond.jp/articles/-/310137?page=2.

Takahashi, Kosuke. “Japan Launches Fourth Taigei-Class Submarine for JMSDF.” Naval News, 17 Oct. 2023, www.navalnews.com/naval-news/2023/10/japan-launches-fourth-taigei-class-submarine-for-jmsdf/.

일본 신형잠수함 타이게이(大鯨)함 진수의 의미 (Implications of the JMSDF’s New Taigei Class of Submarines), Korea Institute for Maritime Strategy, 11 Dec. 2020, kims.or.kr/issubrief/kims-periscope/peri217/.

Featured Image: Launch Ceremony of SS Taigei. (Japanese Ministry of Defense photo)

Law of Warfare

Rules of Engagement and Undersea Incursions: Reacting to Foreign Submarines in Territorial Waters

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This article is part of a series that will explore the use and legal issues surrounding military zones employed during peace and war to control the entry, exit, and activities of forces operating in these zones. These works build on the previous Maritime Operational Zones Manual published by the Stockton Center for International Law predecessor’s, the International Law Department, of the U.S. Naval War College. A new Maritime Operational Zones Manual is forthcoming.

By LtCol Brent Stricker

“We have attacked, fired upon, and dropped depth charges on a submarine operating in defensive sea area.”–USS Ward (DD-139) December 7, 1941, Pearl Harbor, Hawaii.

Submerged foreign submarines in a nation’s territorial sea pose a unique situation that is inconsistent with the rule of innocent passage. Under certain circumstances, their concealed presence without the consent of the coastal state could be considered a threat to the territorial integrity or political independence of the coastal state. A modern submarine fulfills its peacetime mission and combat role while submerged. If the coastal state detects a submerged submarine in the territorial sea, it is faced with a dilemma on the appropriate measures that can be used to force the submarine to surface or leave the territorial sea. The recent sabotage of the Nord Stream pipeline and the vulnerability of the world’s vast subsea network of electricity and network cables highlights the danger posed by unknown submersibles.

Norway and Sweden have faced this problem for more than 50 years from suspected Soviet and later Russian submarines. Both countries have used warning shots in an attempt to signal the submerged contacts to surface or leave the area. Use of explosives in this manner, however, could be misinterpreted as an attack on the submarine. Balancing the protection of territorial sovereignty with avoiding escalation poses a predicament.

Innocent Passage

All ships, including warships, enjoy the right of innocent passage through the territorial seas of a coastal state without prior notification or consent. This rule was discussed in detail in the Corfu Channel case before becoming codified in the United Nations Convention on the Law of the Sea. The Corfu Channel is a narrow passage between Albania and the Greek island of Corfu. The United Kingdom’s Royal Navy was confronted by Albanian coastal artillery fire when transiting the channel in May 1946. In October 1946, two Royal Navy destroyers transited the channel while at action stations to be prepared to respond to coastal artillery fire or other threat posed by the Albanians. These destroyers struck naval mines laid in the channel. As a result, in November 1946, the Royal Navy conducted minesweeping operations to clear the channel.

The United Kingdom brought a case against Albania in the International Court of Justice seeking reparations for the loss of life and damages to its warships. The ICJ upheld the Royal Navy’s right of innocent passage through Albanian territorial waters, rejecting Albania’s arguments that the ships were not in innocent passage because they were sailing in formation and the sailors on board were at action stations. Rather, the Court found that sailing in formation and running at action stations were appropriate defensive measures. The Court found that the minesweeping operation was inconsistent with innocent passage and a violation of Albanian sovereignty, rejecting the British arguments that this was a measure of “self-protection.” Corfu Channel illustrates how innocent passage may include defensive measures. The case has long presented a conundrum because it determined that states are entitled to innocent passage, yet are restrained from taking defensive action, such as minesweeping, to exercise their right.  

Innocent passage is governed by the United Nations Convention on the Law of the Sea (UNCLOS). Norway and Sweden are signatories to UNCLOS, and the United States, while not a signatory, recognizes much of it as customary international law. UNCLOS codified the right of innocent passage in Articles 17-21. Innocent passage must “not be prejudicial to the peace, good order, or security of the coastal state.” A foreign vessel’s passage is not innocent if its actions constitute “any threat or use of force against the sovereignty, territorial integrity or political independence of the coastal State.” A special provision for submarines, Article 20, requires submarines engaged in innocent passage to “navigate on the surface and to show their flag.”

A coastal state that discovers an unknown submerged contact in its territorial sea is faced with a dilemma. Examples from Norway and Sweden of submerged contacts lingering in their territorial waters are inconsistent with the definitions of both passage and innocent passage. The coastal state, under Article 25 of UNCLOS, may “take the necessary steps in its territorial sea to prevent passage which is not innocent.” There is no agreement on exactly what steps are deemed necessary. Furthermore, these measures are limited when applied to sovereign immune warships. Thus, while an unknown submerged contact is not exercising innocent passage, it is unclear what measures a coastal state can apply to exercise its rights under Article 25. Articles 30 and 31 of UNCLOS allow a coastal state to require the submerged contact to leave its territorial sea and places liability for any damages on the flag state of the submerged contact. Armed force against an unknown submerged contact, however, may only be used in self-defense under Article 51 of the UN Charter. In most cases, use of force would not be justified simply because the submarine is submerged or refuses to surface and the mere presence of the submarine does is not tantamount to an “armed attack.” This determination is complicated when the submerged contact’s intensions cannot be ascertained.

Norway

Norway has been dealing with suspected intrusions by foreign submarines for more than 50 years. These contacts in Norwegian fjords are difficult to track due to the mixing of fresh water runoff and salt water in the fjords which can provide cover for submarines from sonar detection. Acoustic detection is complicated by the fjord’s subsurface structure, currents, and civilian surface traffic. For two weeks in November 1972, Norwegian vessels aided by Norwegian and British aircraft attempted to locate and force to the surface an unknown underwater contact, believed to be of Soviet or Warsaw Pact origin, in the Sogne Fjord using depth charges. Hand grenades and then depth charges were used to signal to the underwater contact to surface. Ultimately, the Ministry of Defense was given permission to sink the contact if it did not surface and identify itself.

For the Norwegians to use force against the unknown submerged contact, they would need to articulate how an otherwise benign submerged vessel posed an imminent threat that would justify the use of force in self-defense. Violating Article 21 of UNCLOS in and of itself does not constitute such a threat of imminent attack, even if the submarine is engaged in an intelligence or reconnaissance mission. Such a mission may be illegal under Norway’s domestic law, but it does not imply an illegal use of force, let alone an armed attack.

In limited situations, the location and duration of the unknown submarine in territorial waters could be considered as a threat, as noted in the radio transmission of the USS Ward when it engaged an unknown submarine in a defensive sea area. The Norwegians would be more concerned by the location of the unknown submersible if it were in such an area or in close proximity to another sensitive military exercise or base. The longer the submarine remained at depth, the greater potential one might consider it laying in wait to attack. Nonetheless, the Norwegians employed an escalating use of force in 1972 with attempts to signal with hand grenades and ultimately culminating with firing anti-submarine missiles at the suspected target. The Norwegians were ultimately unable to force the contact to the surface, identify it, or sink it.

Norwegian experiences with unknown submarine contacts continued over the decades. The official Norwegian policy on the use of force remained somewhat ambiguous. In 1983, Brigadier Asbjorn V. Lerheim stated on the use of force, “It is a tough decision, it is still peacetime, and you can’t really destroy a submarine . . . it is not an attack on Norwegian soil.” Norway seems to have adopted a set of measures to escalate the use of force against these intrusions. The first measure is to signal the submarine to surface. If the submarine complies, it would be taken under escort. If not, depth charges would be dropped within 300 meters from the submarine with a two-minute interval to indicate this was a signaling measure, not an attack. If this failed to surface the submarine, Norwegian captains were authorized to attack with depth charges, but torpedoes were prohibited in the attack because of the potential of catastrophic damage to the boat and loss of the entire crew. It is speculated that the anti-submarine missiles fired in 1972 used homing devices and proximity fuses and were not a real attempt to hit the submarine.

Suspected Soviet incursions into Norwegian territorial waters continued as late as 1990. Norwegian authorities received reports of suspected submarines in the summer of 1990 at Skipton, a Norwegian bay twenty-five miles from the Russian border. The area was put under surveillance when, in November 1990, a mini-submarine was observed briefly on the surface. The sea floor was examined and a series of tracks were found that indicated a submersible crawler had been deployed. Similar tracks were discovered elsewhere in Sweden and Norway near military installations. The Soviet Northern Fleet possessed such miniature submarines at the time. It was speculated that the miniature submarine was launched from a nearby mother ship to conduct a Spetsnaz training or reconnaissance mission.

As late as 2021, Norway was subjected to an undersea intrusion by unknown submersibles. The Norwegian Institute of Marine Research operates a network of undersea sensors in northern Norway to monitor the marine environment. It can also be used to monitor submarines in the area. These sensors are interconnected by a series of fiber optic cables. In April 2021, it was discovered that 2.5 miles of fiber optic cable had been cut and stolen. Several of the sensors had been tampered with and moved. The reason for the intrusion is speculative but includes the potential for reverse engineering.

Sweden

Like Norway, Sweden has been troubled by intrusions of foreign submarines in its territorial waters for a similar period of time. Unlike Norway, Sweden has actually caught one submarine on the surface in the infamous “Whiskey on the Rocks” incident in 1981. This incident noted increased intrusions throughout the 1980s that have continued as late as the 2010s. To date, the Whiskey is the only foreign submarine caught on the surface in Swedish territorial waters.

On October 27, 1981, a Soviet Whiskey class submarine, the U-137, was found grounded on a rock in Swedish territorial waters. The Whiskey was an early Cold War diesel electric submarine, not a nuclear-powered submarine. The Swedish Navy contacted the submarine’s captain, Captain Second Rank A. M. Gushchin, who claimed a navigational error. Captain Gushchin claimed he thought he was 20 miles off the Polish coast when the collision occurred. This claim is rather dubious considering the submarine had transited submerged through a “perilous series of narrow straits infested with rocks and islands” before the grounding. The submarine’s grounding within ten kilometers of the Swedish naval base at Karlskrona while a major naval exercise was being conducted was certainly not just a coincidence brought about by a navigational error. Upon inspection, Swedish officials found no problems with the boat’s navigational equipment and noted its logbook had been altered.

The boat remained grounded for eleven days while the Swedish authorities inspected the submarine and questioned the captain. The Soviet Union responded by sending a flotilla of warships that stayed just outside Swedish waters. The Swedish Prime Minister made a shocking announcement on November 5, 1981, that the submarine was suspected of carrying nuclear weapons. The Swedish government made demands to the Soviets before releasing the submarine. However, weather intervened and Sweden released the submarine before these demands were met. The submarine was exposed to gale force winds and was listing 17 degrees. Swedish authorities were concerned that the boat’s battery acid could spill and cause a fire or release chlorine gas that could kill the crew. Swedish authorities stopped the captain’s interrogation and boat inspection, refloated the boat, and the submarine left on November 6, 1981.

Following this incident, the Swedish government released the Submarine Defense Commission Report in 1983, which detailed the history of foreign submarines intruding into Swedish waters. Prior to the Whiskey incident, and even subsequently, critics had claimed these submarine scares were an excuse to increase the Navy’s budget. The report detailed how foreign submarines entered Swedish waters typically one to two times a year in the 1970s before a dramatic increase during the 1980s. These incursions were concentrated around naval facilities such as coastal defense points, ports, sensor networks, and minefields.

The Report and increased submarine intrusions led to a change in Swedish Rules of Engagement (ROE) applicable to submarine contacts. Prior rules prohibited a commander from firing on an unknown contact without authorization from the civilian leadership. The Swedish Navy was only allowed to make contact with the submarine to identify it and escort it out of Swedish waters. The new ROE allowed the submarine to be fired upon without warning. Initially, warning shots were to be used, either through the employment of depth charges or missiles. The ROE were intended to prevent the damage or destruction of the submarine, but the ROE made a distinction on the location and behavior of the contact. If the submarine was located in Sweden’s outer waters, these are waters beyond the internal archipelago to the 12-mile limit, it would be warned and escorted out. If the submarine was found in internal waters, these are waters of Sweden’s internal archipelago, and refused to leave or proceeded further, it could be treated as hostile and force designed to damage or destroy the submarine could be used.

The Swedish ROE may have contributed to their inability to force submarines to the surface. If they employed depth charges or other devices with an eye toward avoiding damaging the detected submarines, the submarines could simply ignore these attempts. There is evidence that the Swedish ASW may have damaged a submarine. In the summer of 1988, eight pieces of unknown foreign submarine rescue equipment were recovered in the Stockholm archipelago. Similar equipment had been recovered in the 1970s and 80s.

The Swedish Navy continued to deal with foreign submarines intruding into Swedish waters throughout the 1980s. The government stopped providing statistics on these incursions in 1987. Subsequent reports have been vague in their descriptions. This may be to avoid highlighting their inability to stop or deter these incursions.

There is evidence that these incursions did occur. The Swedish Navy noted that these incursions have become more sophisticated with the use of multiple submarines, miniature submarines, and divers. The evidence for these incursions comes from sightings, sonar, and magnetic detection from Swedish sensor networks. There has also been evidence of keel marks and track marks on the sea floor similar to the Norwegian miniature submarine event noted above.

The miniature submarines may have also allowed military forces to surreptitiously land on Swedish territory. Between 3 to 6 March 1984, Swedish forces fired at swimmers on the island of Almo. The island was searched and food caches were located. The Swedes have also noted attacks on their “submarine nets, break-ins ashore, to the disruption and destruction of underwater mine lines.” In one case, they were blamed for the theft of a naval mine. Most shockingly, in 1985 fisherman pulled a drowned swimmer up in their nets. The nets had been placed illegally near a naval mine. It is presumed the diver was scouting the mine when he became entangled and drowned. The fisherman did not recover the body and abandoned their nets. When Swedish authorities investigated, the body had been cut out of the net and removed by unknown persons.

Conclusion

This historic submarine incursions remain relevant today, particularly considering heightened tensions from the Russian invasion of Ukraine and the recent application of Finland and Sweden to join the North Atlantic Treaty Organization. Much like the Norwegian fjords, the Swedish archipelago would be an area for these submarines to operate. The reasons for the incursions remain relevant today for any NATO-Russian conflict whether it be to conduct reconnaissance or the insertion of Special Forces. If there is a repeat of one of these Cold War examples such as a stranded submarine like the Whiskey, or more concerning, NATO forces hunting a submarine contact, the consequences could be manifold. First, NATO forces chasing a submarine contact trying to force it to surface might be viewed as an attack on the submarine. The use of explosives to signal a submarine might accidentally damage it or injure the crew. These signals could be misinterpreted as an attack allowing or even requiring a submarine to respond in self-defense. Second, any hostilities in territorial waters directly implicates the collective self-defense clause of Article 5 of the North Atlantic Treaty.

The conduct of Russian submarine espionage in the territorial seas of its neighbors presents one of the greatest challenges to avoiding conflict in the Baltic Sea. These incidents reveal the gap between the law of the sea and the use of force in self-defense against an armed attack. The Nordic coastal states must walk a fine line between protecting their territorial integrity and avoiding escalation of an incident that might quickly spin out of control.

LtCol Brent Stricker, U.S. Marine Corps, serves as the Director for Expeditionary Operations and as a military professor of international law at the Stockton Center for International Law, U.S. Naval War College. The views presented are those of the author and do not necessarily reflect the policy or position of the U.S. Marine Corps, the U.S. Navy, the Naval War College, or the Department of Defense.

Featured Image: Russian Kilo-class submarine in the English Channel. (UK Ministry of Defence photo via Wikimedia Commons)

Culture

Binary Submarine Culture? How the Loss of the USS Thresher Hastened the End of Diesel Submarine Culture

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By Ryan C. Walker

During my short tenure as a submariner in the U.S. Navy, from 2014-2019, I observed the friendly rivalry between sailors who serve on SSN (fast-attack boats), SSGN (frequently shortened to GN boats), and SSBN (Trident boats). Fast-attack sailors like to brag about port calls and joke that sailors on the other vessels are part-time sailors due to the Gold/Blue crew system. For their part, Trident and GN sailors generally have a higher quality of life. They rarely hot-rack, have a more predictable schedule and have more space for crew morale. As much as fast-attack sailors envy these benefits, they know, even if they don’t want to admit, our Trident and GN brethren earn their pay. They do spend extended periods on patrol, have fewer opportunities for port calls, and their time at sea is monotonous. Despite the variations between these subcultures within the submarine fleet, the nuclear culture that stresses safety through rigorous engineering, procedural compliance, and training is still the common bedrock of identity on all platforms.

Previously, two separate cultures existed within the submarine fleet, diesel and nuclear. This article will discuss how the USS Thresher tragedy on April 10, 1963 hastened the end of the binary approach and eventually led to the single bedrock foundation that submarine culture now rests on. The United States Navy’s Submarine Safety (SUBSAFE) Program is written in the blood of the 129 souls who died on the USS Thresher and remain on eternal patrol. Diesel submarine culture, epitomized by the slogan “Diesel Boats Forever,” would be replaced by the cold, calculating, and rigorous nuclear culture design by Hyman G. Rickover. Current proposals to reintroduce diesel submarines in the Navy’s fleet focus on fiscal and operational factors, but the potential risks to its submarine culture should also be considered. This article will examine how the two communities previously interacted as diesel submariners were forced to take on the extra burden of supporting a new technology while that same technology was replacing them. It will further offer that this is not inevitable, but should reintroduction proposals ever gain currency, the conversation on submarine culture should be a major topic by political and military leaders.

Documenting the Tragedy

The Thresher has an enduring effect on the mentality of the present-day submarine force, forming the basis for many training sessions and case studies. Publications, many from the past decade, reflect the memory of the Thresher is well. Many of these have a general focus, examining how and why the Thresher was lost,1 and how the Thresher disaster can serve as case studies for public affairs, oceanography and naval professionals.2 However, the publications examining how the Thresher disaster inspired changes in submarine culture, shipbuilding design, and SUBSAFE are of particular interest.3 James Geurts’ article in USNI Proceedings discusses how the loss profoundly impacted naval officer’s training, arguing procedures to fully employ the capabilities of nuclear-powered submarines only accelerated in the aftermath, stating the “Navy was still locked into training officers for duty on diesel-electric boats, even though the boats quickly were becoming obsolete.”4 Synthesizing these articles and connecting their arguments shows that the end of the binary submarine culture was a positive change overall.

Rickover, Nuclear Power and SUBSAFE

It is generally accepted that Hyman G. Rickover was the architect of nuclear submarine culture and the driving force for the quicker transition to nuclear culture by promulgating the practices, procedures, mentality and culture of as the standard for all submariners. As Geurts would summarize:

“Despite these demonstrations of superiority, the Navy’s operational thinking carried over from diesel-electric boats to the nuclear submarines. The distinction… was not yet recognized or emphasized during submarine school training. This fundamental failure in thinking contributed to the Thresher disaster, after which the Navy finally met the new reality of nuclear-powered submarines with fresh operational thinking.”5

How the evolution occurred still requires research. A common misperception of the ship’s status at its loss was that it was conducting its first deep dive. Following its commissioning the Thresher had undergone extensive testing, befitting its status as the first of her class. Built in Portsmouth Naval Shipyard in Kittery, ME, the ship completed all its acceptance trials, shakedown availability, and even participated in some fleet exercises.

It came as a complete surprise to all involved when it was lost with all hands, the ship’s former medical officer Arthur L. Rehme shared his experience onboard and that he felt confident in the crew, even sharing the first time they reached a record depth the ship cheered.6 The loss was truly unexpected, it is a testament to contemporary submarines that they were willing to persevere despite the loss. Crew member Ira Goldman, who narrowly avoided death by attending a training school, continued to serve in the submarine fleet, retiring as a Master Chief.7 Rehme did not continue as a submariner, but decided if the men on the Thresher could give their lives in service of their country, he too could continue to serve.8 Their loss served as an inspiration for change, but also an iron determination for those who faced the same risks.

Almost immediately, a Court of Inquiry was organized to discern why the Thresher sank, which canvassed a wide variety of persons. Obvious candidates such as the recently relieved commanding officer (CO), Dean L. Axene and watch standers on the Skylark were involved, but so too were people with only a passing military, technical or familial background. The Court concluded that the Thresher was lost due to flooding casualty from piping in the Engine Room that shorted out vital electrical equipment, a decision that would have consequence for construction, maintenance, and repair of new submarines. This recommendation was influenced by Rickover, who insisted on being interviewed by the Court of Inquiry. Instead of defending the nuclear program, he displayed his shrewd ability to identify problems in a now famous quote:

“I believe the loss of the THRESHER should not be viewed solely as the result of failure of a specific braze, weld, system or component, but rather should be considered a consequence of the philosophy of design, construction and inspection, that has been permitted in our naval shipbuilding programs. I think it is important that we re-evaluate our present practices where, in the desire to make advancements, we may have forsaken the fundamentals of good engineering.”9

It was no accident that he had insisted to be a witness. According to his biographer, Francis Duncan, he thought the testimony “could be an opportunity to show how the technical standards that he had insisted upon should be applied to other work.”10 Rickover came with the intent to promulgate what would become SUBSAFE, offering an immediate solution in the form of nuclear culture.

The shift may have happened over time as nuclear-trained officers with no experience on diesel submarines became the norm. The influence of the Rickover-designed training program is still evident from the admirals he trained down to junior officers learning the principles for the first time. The expectations established for nuclear trained enlisted personnel would also be expected in the forward compartment, or “cone.” While there is still a strong divide between “nukes” and “coners,” both groups have the mindset of engineering indoctrinated through training and qualifications. The disaster itself acted as a catalyst for change, alongside the Scorpion, to implement Rickoverian philosophy in the submarine fleet.

SUBSAFE is among the crowning administrative and engineering achievements of the USN. It became such a successful quality assurance program that other organizations looked to it for inspiration on their own programs. In the aftermath of the Challenger disaster, NASA was recommended to look “to two Navy submarine programs that have “strived for accident-free performance and have, by and large, achieved it – the Submarine Flooding Prevention and Recovery (SUBSAFE) and Naval Nuclear Propulsion (Naval Reactors) programs.”11 SUBSAFE is a body of practices that became a mindset and an essential building block of culture for the present submarine culture. It was no longer, as Geurts had stated succinctly, a diesel dominated fleet, but a nuclear fleet first and foremost, as reflected by Navy recruitment and informational topics by the period.12

The Origin of Diesel Boat Forever Culture: Diesels Boats Perform an Essential Transitional Duty

The delays in nuclear submarine construction and their lengthier overhaul periods, relative to diesel boats, would prove to have long-term consequences that are still present today. The immediate effect was to increase the costs and time periods construction and overhaul would consume. As a result, operational commitments often fell to diesel submarines as they took on the missions of the nuclear submarines stuck in overhaul. Even in the present day, overruns in cost and time are frequent and accounted for but are merited in the name of safety. Diesel boats would serve an important purpose during the early implementation of SUBSAFE in new construction, holding the line, but frequently forgotten in the public Cold War narrative of nuclear boats that seemed to get the attention as the future.

The Submarine Force Library and Museum archives carry the development of this culture epitomized by the Diesel Boat Forever (DBF) pin. The DBF pin was created by the crew of the USS Barbel, with an enlisted sailor Leon Figurido drawing it for a contest and adopted by the command, conflicting accounts offer 1967-1971 as the period they were made.13 The pin was explicitly designed as the answer to the Polaris Patrol Pin and inspired by the Submarine Combat Patrol Pin. Two bare chested mermaids clasping hands while laying over a submarine silhouette with the immortal acronym, “DBF” surrounded by holes for stars. According to Meagher, the former commanding officer (CO) who approved the project, John Renard, confirmed instead of receiving a star for each patrol, DBF pins would receive a star “each time a diesel boat you served on had to get underway for a broke-down nuke.”14 There was still a surprising amount of buy-in from diesel sailors in higher chains of command. The pin was unofficially condoned to the point that the CO of the Tigrone held a ceremony awarding RADM Oliver H. Perry jr., who had previously served on diesel boats.15 Smith in his interview with Adams also remarked other memorabilia, such as Red DBF Jackets were a part of the culture and sold out as soon as they were back from their deployment, reflecting an appeal for a new identity formed in the shadow of the new nuclear submarine culture.16

Unsurprisingly, this was greeted coolly by nuclear submariners. The animosity was shared, where Smith recalled fights that broke out “between the ‘nukes and the reds’ when they wore their jackets ashore.”17 This further indicates the budding nuclear culture was prideful enough to take offence at the “other” fleet. To fully illustrate the diesel culture of the submarine fleet, look no further than the 1996 film, Down Periscope. The film follows an unconventional Submarine Officer LCDR Dodge taking command of the decrepit diesel submarine, the USS Stingray. Manned by what can only be politely described as the dregs of the Navy, the Stingray crew embraces this mentality, performing unorthodox tactics and techniques throughout the film. The director elected to utilize a retired enginemen named Stanton, as the chief engineer. It is from him we hear the clear signaling of intent of the film when he yells at the climax of the film, “This is what I live for! DBF!”18

While never in doubt due to the subject of this film, the true intent of the film was illuminated in this moment. This pithy aphorism epitomizes the romanticized diesel sailor; a mythos that has not disappeared in the nuclear navy. The final, romanticized aspect of the film is fleshed out when Dodge rejects his promotion to command a new, nuclear powered Seawolf class submarine, opting instead to stay with the barely seaworthy, antiquated, hopelessly outmatched Stingray.19 In many respects, its origins lie in the hero worship of WWII submariners who did not need procedures and the high attention to safety paid in the modern Navy yet still brought the fight to the enemy and performed admirably. It is spoken in the same vein spoken by resentful sailors from the age of sail who viewed their younger generations in the age of steam as soft, jibing them comments such as “once the navy had wooden ships and men of iron; now it has iron ships and wooden men.”20 There is no doubt in anyone’s mind who has read the accounts from diesel sailors that it was an undoubtedly difficult life.21 Nuclear submarine crews are lucky by comparison, but submarine duty is rightfully still considered to be difficult in the present day.

For all intents and purposes, there were two distinct cultures within the submarine fleet, but principally from 1963-73, as diesel submarines were replaced. Throughout the 1970s Meagher recalled “scores of career electricians and engineman were forced to “surface” as there was no room for them on Rickover’s boats.”22 Smith agrees they knew that they were a “dying breed,” but also adds “we’re damn proud to be diesel boat sailors.”23 Eventually, the unofficial pin was banned, and midshipmen were kept from diesel boats from 1973 onward, with some rumors stating it was due to concerns midshipman were being indoctrinated into diesel culture.24 This was part of the transition to a nuclear dominant force as the tragedies of the Thresher and Scorpion helped accelerate it. Diesel submarines are an important part of submarine heritage that is talked about today. The last combat ready diesel submarines, Barbel, Blueback and Bonefish, were decommissioned between 1988-90, meaning the operational capacity of the submarine force has been exclusively nuclear for over thirty years and had been dominated by nuclear trained officers for decades before.25

Proposals to Adopt Diesel Boats in the Present Day

Thus, the expectations for all sailors, both in engineering and non-engineering realms, are dictated by the principles instilled in them by Rickover’s nuclear program. The USS Thresher disaster was the defining moment for both the submarine fleet and the U.S. Navy itself. It was decided in the immediate aftermath to pursue an ambitious program that would touch all aspects of submarine culture, in construction, maintenance, overhaul, training, and operations. It would make the trends set forth by Hyman G. Rickover the norm, not the exception. The Thresher disaster was the moment the US Navy reinvented itself to embrace the mentality to become the force it is today.

Despite the success of the nuclear force, discussions on adopting the diesel submarine have resurfaced. Proposals such as the award-winning essay written for USNI Proceedings by Ensigns Michael Walker and Austin Krusz are frequently published. “The U.S. Navy would do well to consider augmenting its current submarine force with quiet, inexpensive, and highly capable diesel-electric submarine.”26 The argument is based on the increasing capability of the diesel submarines, the high cost of maintaining nuclear submarines, and the merit of increased operational flexibility. These proposals have merit and are popular outside of naval professionals, the citations of Walker and Krusz reflect the wide scope of popular interest.27

A discussion not mentioned is a potential return to the binary culture separating diesel submarine crews and nuclear submarine crews. DBF culture formed as a resentful reaction to the nuclear submarine crews for simultaneously giving them a greater portion of work and threatening their role in the Cold War. SUBSAFE can be bedrock of identity for a potential diesel submarine culture in the USN, but the cultivation of such a culture must be carefully managed and planned. Diesel submariners require a different mindset, and it is likely they will create some of their own norms; the question must be asked: does the Navy want this outcome? Or does it value the ability of career submariners to move between platforms with similar cultures and mindsets without having to worry about what their previous hull had been?

Nor will there be any insight seen in foreign markets in terms of safety. There have been several high-profile diesel submarine disasters in recent years. The KRI Nanggala 402 in 2021, the ARA San Juan in 2017, and the PLAN Ming 361 in 2003 are among the most recent and well known. It would be a mistake to assume nuclear submarines in other nations are immune to this either. Conversely, no US submarines built using the rigorous requirements in SUBSAFE have been lost to any disaster. The safety record is impressive and is due to more than the processes and procedures, but the culture of the crews manning the boars. Submarine Officers, with the exception of the supply officer, are engineers first and the mindset instilled in them would be instilled in their crews and stands as the legacy of the Thresher disaster and SUBSAFE programs.

Ryan C. Walker served in the USN from 2014-2019, as an enlisted Fire Control Technician aboard the USS Springfield (SSN-761). Honorably discharged in December of 2019; he graduated Summa Cum Laude from Southern New Hampshire University with a BA in Military History. He is currently a MA Candidate at the University of Portsmouth, where he studies Naval History and hopes to pursue further studies after graduation. His current research focus is on early submarine culture (1900-1940), early development of Groton as a Naval-Capital Town, and British private men-of-war in the North Atlantic. He currently resides in lovely Groton, CT.

Endnotes

1. See: Norman Polmar, The death of the USS Thresher: The story behind history’s deadliest submarine disaster. (Guilford: Rowman & Littlefield, 2004); James B. Bryant “Declassify the Thresher Data,” Proceedings, Vol. 144, (July 2018). https://www.usni.org/magazines/proceedings/2018/july/declassify-thresher-data; Jim Bryant, “What Did the Thresher Disaster Court of Inquiry Find?” Proceedings, Vol. 147, (August 2021), https://www.usni.org/magazines/proceedings/2021/august/what-did-thresher-disaster-court-inquiry-find; Dan Rather, “The Legacy of the Thresher,” CBS Reports, Television Film Media digitized on YouTube, originally aired March 4, 1964. Accessed April 22, 2022, https://www.youtube.com/watch?v=8aZ4udTMlZI

2. See: Robert J. Hurley “Bathymetric Data from the Search for USS” Thresher”.” The International Hydrographic Review (1964); Frank A. Andrews “Search Operations in the Thresher Area 1964 Section I.” Naval Engineers Journal 77, no. 4 (1965): 549-561; Joseph William Stierman jr., “Public relations aspects of a major disaster: a case study of the loss of USS Thresher.” MA Dissertation, Boston University, 1964.

3. See: James R. Geurts, “Reflections on the Loss of the Thresher,” Proceedings, Vol. 146, (October 2020), https://www.usni.org/magazines/proceedings/2020/october/reflections-loss-thresher; Michael Jabaley, “The Pillars of Submarine Safety,” Proceedings, Vol. 140, (June 2014), https://www.usni.org/magazines/proceedings/2014/june/pillars-submarine-safety; Joseph F. Yurso, “Unraveling the Thresher’s Story,” Proceedings, Vol. 143, (October 2017), https://www.usni.org/magazines/proceedings/2017/october/unraveling-threshers-story

4. James R. Geurts, “Reflections on the Loss of the Thresher,” Proceedings, Vol. 146, (October 2020), https://www.usni.org/magazines/proceedings/2020/october/reflections-loss-thresher

5. Geurts, “Reflections,” Proceedings

6. Arthur L. Rehme Collection, (AFC/2001/001/37677), Veterans History Project, American Folklife Center, Library of Congress, accessed April 24, 2022. https://memory.loc.gov/diglib/vhp/bib/loc.natlib.afc2001001.37677

7. Jennifer McDermott, “50 years later, Thresher veteran still grieves loss of shipmates at sea,” The Day, Waterford, April 5, 2013, 12:52PM, https://www.theday.com/article/20130405/NWS09/304059935

8. Arthur L. Rehme Collection, (AFC/2001/001/37677), Veterans History Project, American Folklife Center, Library of Congress, accessed April, 24 2022. https://memory.loc.gov/diglib/vhp/bib/loc.natlib.afc2001001.37677

9. Francis Duncan. Rickover: The struggle for excellence. (Lexington: Plunkett Lake Press, 2001). 85

10. Francis Duncan, Rickover, 81

11. Malina Brown. “Navy group to observe NASA’s return-to-flight activity: COLUMBIA ACCIDENT REPORT CITES SUB PROGRAMS AS MODEL FOR NASA.” Inside the Navy 16, no. 35 (2003): 12-13. Accessed December 8, 2020. http://www.jstor.org/stable/24830339.12-13

12. Periscope Films, “1965 U.S. NAVY NUCLEAR SUBMARINE RECRUITING FILM ‘ADVENTURE IN INNER SPACE’ 82444.” Accessed June 26, 2022, https://www.youtube.com/watch?v=RdgIqhf6FOY; Periscope Films, “U.S. NAVY NUCLEAR SUBMARINES MISSIONS, CHARACTERISTICS AND BACKGROUND 74802,” Accessed June 26, 2022, https://www.youtube.com/watch?v=d9ftfhiUMzY

13. Cindy Adams. “Barracks COB favors fossil fuels: ‘Diesel boats are forever,” The Day, November 14, 1980, Newspaper Clipping, Submarine Force Library and Museum, Submarine Archives, Uniforms & Insignia Collection; Stu Taylor, “The following story is about the origin of the DIESEL BOATS FOREVER emblem.” Submarine Force Library and Museum, Submarine Archives, Uniforms & Insignia Collection; Patrick Meagher. “THE DBF PIN.” Accessed May 22, 2022, http://www.submarinesailor.com/history/dbfpin/dbfpin.asp

14. Patrick Meagher. “THE DBF PIN.” Accessed May 22, 2022, http://www.submarinesailor.com/history/dbfpin/dbfpin.asp

15. Meagher, “DBF PIN,” Website

16. Cindy Adams. “Barracks COB favors fossil fuels: ‘Diesel boats are forever,” The Day, November 14, 1980, Newspaper Clipping, Submarine Force Library and Museum, Submarine Archives, Uniforms & Insignia Collection

17. Adams, “Barracks COB,” Newspaper Clipping.

18. Down Periscope, Directed by David S. Ward, (20th Century Fox, 1996), 1:19:00.

19. Down Periscope, 1:24:00 to 1:26:00

20. Baynham, H. W. F. “A SEAMAN IN HMS LEANDER, 1863–66.” The Mariner’s Mirror 51, no. 4 (1965), https://www.tandfonline.com/doi/abs/10.1080/00253359.1965.10657847?journalCode=rmir20, 343

21. Mark K. Roberts, SUB: an oral history of US Navy submarines. (New York: Berkley Caliber, 2007); Paul Stillwell. Submarine Stories: Recollections from the Diesel Boats. (Annapolis: Naval Institute Press, 2013); Claude C. Conner, Nothing Friendly in the Vicinity: My Patrols on the submarine USS Guardfish during WWII. (Annapolis: Naval Institute Press, 1999).

22. Meagher, “DBF PIN,” Website

23. Adams, “Barracks COB,” Newspaper Clipping.

24. Meagher, “DBF PIN,” Website

25. Honorable mention to the Darter and the Dolphin, both used for auxiliary purposes as well, decommissioned in 1990 and 2007 respectively.

26. Ensigns Walker & Krusz. “There’s a Case for Diesels.” Proceedings, Vol 144, (June 2018). Accessed August 25, 2021. https://www.usni.org/magazines/proceedings/2018/june/theres-case-diesels

27. See: James Holmes, Doug Bandow, and Robert E. Kelly, “One Way the U.S. Navy Could Take on China: Diesel Submarines,” The National Interest, 17 March 2017; Jonathan O’Callaghan, “Death of the Nuclear Submarine? Huge Diesel-Electric Vessel Could Replace Other Subs Thanks to Its Stealth and Efficiency,” Daily Mail Online, 4 November 2014; Sebastien Roblin, James Holmes, Doug Bandow, and Robert E. Kelly, “Did Sweden Make America’s Nuclear Submarines Obsolete?” The National Interest, 30 December 2016; Vego Milan, “The Right Submarine for Lurking in the Littorals,” U.S. Naval Institute Proceedings, 137, no. 6, June 2010, www.usni.org/magazines/proceedings/2010-06/right-submarine-lurking-littorals.

Featured Image: Port bow aerial view of USS Thresher, taken while the submarine was underway on 30 April 1961. (Photographed by J.L. Snell. Official U.S. Navy Photograph, from the collections of the Naval History and Heritage Command)