Taiwan has conducted a series of shallow-water submerged tests of its indigenous submarine prototype over the past two weeks, marking a key step towards potential navy delivery as early as June.
The Hai Kun, or Narwhal, is part of the island’s Indigenous Defence Submarine programme, a project widely seen as central to its efforts to boost asymmetric naval capabilities amid increasing military pressure from Beijing.
Surface navigation tests began last year, with undersea trials and weapons testing originally slated for completion between September and October ahead of navy delivery in November.
That schedule was not met, prompting opposition lawmakers to freeze NT$1.8 billion (US$56 million) in funding for follow-on submarines. The funding is part of a broader NT$284 billion programme to build seven additional subs.
The budget would remain frozen until the prototype completed sea trials, opposition lawmakers said.
In the face of growing political pressure, CSBC Corp, Taiwan – which built the prototype – conducted the first submerged test on January 29.
Three more shallow-water submerged tests have followed since then, and CSBC released its first official video of all four on Sunday.
The footage documented the full sequence from departure and submergence to resurfacing and return to port.
The submarine was shown operating at periscope depth, conducting rudder control and mast deployment tests.
The video also featured first-ever footage of the launch of an acoustic decoy system developed by the National Chung-Shan Institute of Science and Technology, Taiwan’s main weapons developer.
In a statement, CSBC said the tests were carried out in accordance with established procedures. It described the trials as “part of an incremental testing process that would continue with system calibration and further submerged testing once safety evaluations were completed.”
Testing would “proceed step by step, with safety and quality requirements taking priority before delivery”, it said.
CSBC officials were cautious when asked about the delivery timeline, noting that all required testing must be completed before a final delivery date could be confirmed.
However, based on current progress, outside estimates of a June delivery target were “generally within a reasonable range”, they said.
Defence ministry spokesman Sun Li-fang said submarines “play a critical role in escort missions, intercepting hostile fleets and providing deterrence”.
He said that two of Taiwan’s four submarines in service were mainly used for training because of their age, while the other two were also ageing despite upgrades.
“This highlights the importance of the submarine programme in meeting operational requirements.”
Analysts said the latest tests marked an important technical milestone but cautioned that several stages remained before delivery.
Military expert Chi Tung-yun, who observed the tests, said submarine testing was an inherently complex process. “Performance varies at different depths because of changes in temperature, propulsion speed and power consumption.”
“Testing must therefore examine the operation of all onboard systems under varying depths and speeds,” he said. “The full range of test objectives cannot be completed in just a few dives.”
Stealth remained the most critical characteristic of a submarine, Chi noted.
“Extremely low acoustic signatures are required. Testing must therefore verify whether hull welding quality and structural behaviour under [intense] underwater pressure produce detectable noise or vibration, making such trials essential for validating overall performance.”
Su Tzu-yun, a senior analyst at the government-funded Institute for National Defence and Security Research, said the successful launch of the acoustic decoy system showed progress after earlier foreign procurement efforts failed.
“The footage showing diminishing light levels also suggested the submarine had exceeded the planned 50-metre (164-foot) test depth,” he added.
Chen Kuo-ming, editor of the Taipei-based magazine Defence International, said submerged trials this year would focus on verifying dive depth, stability and pressure tolerance before moving to evaluation testing.
“This includes endurance trials, underwater noise assessment and system integration. Combat evaluation, including torpedo firing tests, would only take place after those stages were completed,” he said.
Military analyst Wu Ming-chieh described the submerged trials as a critical step towards practical underwater operation.
“Testing depth would increase gradually from snorkel depth to deeper operational levels,” he said, adding that safety, propulsion performance, structural integrity and pressure resistance remained the priorities during this stage.
Integration challenges were more complex because many components had been sourced from multiple foreign markets, Wu said.
This made “system integration more demanding” than in places with long-established submarine-building industries.
Regarding the budget freeze, opposition lawmakers said they supported strengthening defence capabilities but stressed the need for continued legislative oversight.
Lin Pei-hsiang, from the main opposition party Kuomintang (KMT), said funding related to the programme could be “gradually unfrozen if progress continued smoothly, but any decision would require further internal discussion and review of the project’s status”.
Another KMT legislator, Wu Tsung-hsien, rejected accusations that the opposition opposed defence development.
“Lawmakers have the responsibility to ensure defence budgets are properly used,” he argued.
Defence minister Wellington Koo Li-hsiung has said the funds will not be used until the Hai Kun completes all sea trials. He has also noted that contractual penalties would apply if delivery deadlines were missed, while urging the navy and CSBC to speed up testing.
With shallow-water tests completed, analysts said the next phase would involve deeper dives and system integration testing. The results will determine whether the Hai Kun can meet its planned delivery schedule and eventually enter service.
Beijing views Taiwan as part of China to be reunified by force if necessary and has intensified military threats against the island since the pro-independence Democratic Progressive Party came to power in 2016 and rejected the one-China principle.
Most countries – including the United States, Taiwan’s main weapons supplier – do not recognise the self-ruled island as an independent state, though Washington is opposed to any attempt to take it by force and remains committed to supplying arms for it to defend itself. -- SOUTH CHINA MORNING POST
