Our Best Look At Taiwan’s First Homegrown Submarine

Taiwan’s first domestically made submarine, named Hai Kun, is now in the water and about to commence its first at-sea trials.

byThomas Newdick|
Taiwan photo
CSBC Corporation


With Taiwan’s first domestically made submarine seen entering the water for the first time and about to start at-sea trials, observers have had their best chance to look at the boat in more detail, revealing some intriguing — and advanced — aspects. The Hai Kun (SS-711), which was launched in the southern port city of Kaohsiung last September, as you can read about here, is a diesel-electric design, part of eight planned hulls that are set to revamp Taiwan’s desperately aging submarine force.

New photos of the Hai Kun emerged today, as the boat was being moved from the shipyard where it was constructed to a floating dock and then finally into the water to begin at-sea trials. According to earlier reports, the submarine should go to sea for acceptance trials in late April and be delivered before the end of the year, although there are signs that this process could be delayed.

It should be recalled that there were previous suggestions that the overall quality of the finish on the boat may not be to the highest level, especially around the sail. The latest imagery doesn’t exactly refute those suggestions, but it’s important also to remember the rapid pace at which the first-of-class submarine was completed.

With that in mind, Matus Smutny, a submarine warfare analyst, and a features contributor to The War Zone, has identified some of the key features of the Hai Kun that we can see in these images.

via Matus Smutny

Looking at the forward part of the hull, we can see the six apertures concealing the 533mm torpedo tubes, which constitute the main armament of the Hai Kun. As well as Mk 48 heavyweight torpedoes, these tubes can accommodate Harpoon anti-ship missiles, and potentially also sea mines.

Also in this part of the submarine is the cylindrical array sonar (CAS), the primary part of the boat’s acoustic sensor suite. Comprising an arrangement of hydrophones in a circle around the hull’s cross-section, this provides a panoramic view of any surrounding contacts.

Sticking out prominently from the top of the hull, well forward of the sail, is the mast-like arrangement of the acoustic intercept/ranging array. This is used to localize, process, and display intercepted active sonar transmissions and any acoustic transient events. The system provides the bearing, range, and speed of the signal source. It can also be used to monitor weapons and countermeasures deployed by the submarine itself, as well as underwater communications and the boat’s own noise level.

Moving further down the hull, we see evidence of the passive ranging sonar (PRS), which is located higher up the hull, and, further down, the scabbed-on flank sonar array. Having the flank sonar projecting further out than the rest of the hull optimizes its acoustic ‘decoupling’ from the submarine itself, improving its contact classification capabilities.

Unlike some other submarines, there is no evidence that the Hai Kun is also fitted with a towed sonar array — thanks to the distance between this type of sensor and the hull, acoustic decoupling can be further improved.

An intriguing large aperture in the side of the hull indicates the transition between the double hull and the single hull. This feature is also found in the Dutch Walrus class, which heavily influenced the Taiwanese design. Essentially, the forward and after sections of the submarine incorporate a double hull, while the pressure hull in the center (which includes the crew accommodation) is a single hull, to provide more internal space, resulting in a slightly different overall diameter. While this makes practical sense, it could also generate additional noise.

A small set of ports set into the side of the hull are used to deploy torpedo countermeasures. You can read all about how modern torpedo decoys work in our previous in-depth feature on the subject.

At the rear of the boat, we can see the X-shaped rudder and tail fin arrangement, as well as a fairly standard propeller, a bladed type, without a signature-reducing vortex attenuator, as found on the German Type 212 class, for example.

There are so far no reports of the rumored air-independent propulsion (AIP) system, which would significantly increase the time the submarine can stay submerged and make it harder to detect. However, there could still be space reserved for this in the future, in the same way that some of the Spanish Navy Isaac Peral class boats are receiving AIP systems during extensive overhauls.

While we have previously seen the Hai Kun under construction, as well as draped with patriotic banners on the occasion of its launch, what is not immediately clear is the full extent of foreign involvement in making this submarine a reality.

An interesting time-lapse video shows the construction of the Hai Kun:

With a reported cost of $1.54 billion, the submarine was built by Taiwan’s China Shipbuilding Corporation (CSBC Corp.), but, in addition to the aforementioned weapons, other critical mission systems are provided by Lockheed Martin. At least six other countries have also reportedly provided help, including the United Kingdom.

The Hai Kun submarine during its unveiling ceremony at the CSBC Corp. shipbuilding company in Kaohsiung on September 28, 2023. Photo by SAM YEH/AFP via Getty Images

The fact that Taiwan embarked, in 2014, on a program to build its own submarines is a story in its own right, and also something that we have discussed before. Essentially, however, pressure from Beijing played a significant role in closing off opportunities for Taiwan to buy foreign-made submarines, after looking closely at various options from the United States and Italy.

Meanwhile, Beijing has continued building up an impressive underwater fleet of its own, meaning that the submarine fleet of the People’s Liberation Army Navy (PLAN) has become a particular concern for Taiwan.

With a PLAN submarine fleet numbering at least 60 boats, and with the production of different designs continuing at a rapid pace, Taiwan will never be able to challenge China in terms of submarine numbers. In terms of capabilities, too, China is clearly at the forefront, with powerful nuclear-powered attack submarines, nuclear-powered ballistic missile submarines, increasingly innovative conventionally powered designs, and uncrewed surface vessels and underwater vehicles (USVs and UUVs).

A Type 094 Jin class ballistic missile submarine of the Chinese People’s Liberation Army Navy (PLAN). MARK SCHIEFELBEIN/AFP via Getty Images

There remains some debate about the true value of Taiwan’s submarine program, although it has remained a cornerstone of military plans as defense spending continues to rise.

Taiwanese officials have boldly stated that the new submarines are a “strategic deterrent,” that could maintain a “lifeline” to the Pacific in times of crisis, such as a Chinese naval blockade.

In response to claims like these, China’s state-run Global Times media outlet has said that the Taiwanese submarine strategy shows that the island is “daydreaming” and that China “has already constructed a multidimensional anti-submarine network all around the island.”

Modern diesel-electric submarines can play a valuable military role, especially in terms of ‘asymmetric’ warfare. In this way, even a small fleet of these boats could be used to ambush Chinese vessels or potentially launch special operations raids. Their shallow-water proficiency could also see them venture further afield, into the so-called ‘first island chain,’ where they could disrupt PLAN activities in major chokepoints like the Bashi Channel and the Miyako Strait. This, however, presupposes that the Taiwanese subs could last this long in a conflict, especially as the PLAN's already substantial anti-submarine warfare capabilities continue to improve.

A Pentagon graphic showing the geographic boundaries of the First and Second Island Chains. U.S. Department of Defense

More importantly, however, the Hai Kun class represents a huge improvement over the decrepit submarine fleet that currently serves the Republic of China Navy (ROCN). As you can read more about here, this comprises a pair of Hai Lung class boats, built in the Netherlands in the mid-1980s but subject to a mid-life upgrade that began in 2016.

Two ancient Hai Shih class boats, which were originally built as Tench class and Balao class submarines during World War II, very likely no longer go to sea at all.

However successful the Hai Kun class proves to be, these boats will always be outnumbered and, in some instances, outclassed by China’s fast-growing underwater armada. The start of trials of the first of these submarines, however, does demonstrate the huge advances made by Taiwan’s shipbuilding industry, and its military in general, albeit still heavily reliant on foreign help.

With thanks to Matus Smutny, who you can follow here on X.

Contact the author: thomas@thewarzone.com