Invincible-class submarine

The Invincible-class submarines, formally classified as the Type 218SG submarines, is a class of conventionally-powered attack submarines, ordered by the Republic of Singapore Navy (RSN) from German-based naval conglomerate ThyssenKrupp Marine Systems (TKMS). The Type 218SG is an extensively-customised derivative of the export-oriented Type 214 submarine, with specific design characteristics drawn from Type 212 submarines. They feature several capabilities, including a substantial level of automation, a significant payload capacity, enhanced underwater endurance and superlative ergonomics. Singapore's Ministry of Defense (MINDEF) ordered a total of four Type 218SG submarines, of which two were ordered in 2013 and two more in 2017, as a replacement to the RSN's existing and submarines. Of the four submarines that were ordered, three have been launched, while the fourth remains under construction. As of July 2023, the first submarine of the class, the Invincible, is being used for the training of the RSN's submariners, while the second, the Impeccable, is scheduled to undergo local sea trials aimed at achieving operationalization. The RSN plans to have all four submarines in active service by 2024. The design of the Type 218SG was jointly created by Defence Science and Technology Agency (DSTA), ThyssenKrupp Marine Systems (TKMS) and the Republic of Singapore Navy (RSN). The design of the submarines is highly customised—conceived to fulfill specific naval requirements of the RSN—including naval operations in littoral waters, guarding sea lines of communication (SLOC), intelligence-gathering (ISTAR) and special operations. The design is believed to be based on the Type 214 export-centric submarine, with design inferences from the Type 212 submarine—both of which were designed by TKMS. The design of the Type 218SG is also believed to have been influenced by the Type 216 submarine concept. The Type 218SG has a length of and a beam of , with an overall displacement of about 2,000 t when surfaced and 2,200 t while submerged.