German shipbuilder ThyssenKrupp Marine Systems (TKMS) continues to make progress on the construction of the new Type 218SG submarines for the Republic of Singapore Navy. In recent days, the third submarine in the program, provisionally identified as “Submarine 03,” was spotted sailing through the Kiel Canal (Nord-Ostsee-Kanal) after completing magnetic measurements, heading back toward the company’s facilities in Kiel. The images, taken at the Sehestedt pier, mark another step forward in the testing phase prior to delivery.
The Invincible-class (Type 218SG) submarines form the core of Singapore’s submarine force modernization program. In September 2024, the Republic of Singapore Navy commissioned the first two units of the project — RSS Invincible and RSS Impeccable — both built by TKMS and delivered via cargo ships in July and August of that year. These additions marked the first time Singapore had ever received newly built submarines for its fleet.
Each unit is equipped with an Air-Independent Propulsion (AIP) system, allowing for greater underwater endurance and reduced detectability by radar. They were also designed with accommodations adapted for mixed-gender crews, including separate compartments and ergonomic adjustments tailored to the physical profiles of Singaporean personnel.
The arrival of these new submarines marked the beginning of the replacement of the aging Challenger and Archer-class submarines of Swedish origin, which had been acquired in the 1990s. In November 2024, the Navy officially decommissioned the last two Challenger-class submarines, closing a service cycle of more than two decades. These vessels, originally part of the Swedish Navy’s Sjöormen-class, were incorporated by Singapore between 1995 and 1997 in a deal that included four active units and one additional hull used for spare parts.
In May 2025, Singapore confirmed the purchase of two additional Type 218SG submarines, expanding its planned fleet to six Invincible-class units. The new acquisitions aim to complete the full renewal of the submarine force and strengthen the country’s maritime defense capabilities.
Regarding the contract expansion, ThyssenKrupp Marine Systems CEO Oliver Burkhard emphasized: “The expansion of orders underlines the generally positive situation in the shipbuilding market and provides us with the opportunity to further expand our broad order portfolio. We are also proud that Singapore has once again placed its trust in us, as our cooperation goes far beyond submarine production. We feel deeply connected to the country and contribute to our customer’s security and defense capabilities through our products.”
Each Invincible-class submarine measures 70 meters in length, has a beam of 6.3 meters, and displaces 2,200 tons. The AIP system enables the vessels to remain submerged for extended periods, significantly enhancing their operational stealth.
With the ongoing sea trials of the third submarine, TKMS continues to consolidate progress in one of the most significant naval programs in Southeast Asia. The final two units of the original contract are expected to be delivered by 2028, completing the comprehensive modernization of Singapore’s submarine fleet.
Images for illustrative purposes only.
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