Beginning in the early 1990s, the RWN began to consider the development or procurement of a replacement class of submarine for the Type 209-based Menace
-class, which had first entered service in the mid-1970s. Numerous studies were undertaken over the following years trying to decide what capabilities were required, whether it should be an off-the-shelf, altered or completely new design, and whether it should be built in Westralia or overseas. Particular attention was payed towards Australia's new Collins
-class submarines coming into service, and the numerous problems that program had faced, especially considering that the RWN's requirements were similar to that of the RAN.
By 1997, it had been decided that a new design was to be pursued, but designed and manufactured by an experienced shipbuilder overseas (despite Westralia's experience in shipbuilding, it had not built submarines before and was wary of experiencing the troubles that befell Australia with the Collins
-class). Preliminary tenders for the new design were examined from Kockums, HDW, Marconi Marine (VSEL) and DCN International, with Kockums (after 1999 a part of HDW) being declared the winner, primarily because of the success of the new Gotland
and its experience with AIP, which was offered in the design. Despite the conflicts involving the Swedish Defense Materiel Administration and Kockums new German owners, the Westralian submarine design was agreed to be built using Kockums expertise but in the HDW yard in Kiel.
Construction on the new class of submarines, christened the Sentinel
-class (to follow the RWN (and RN) tradition of somewhat overly-dramatic submarine names), began in early-2000, with the first boat (Sentinel
) being delivered in late-2005. This was followed by Severe
in 2006, Seeker
in 2008, and finally Serious
Displacement: 2900/3200 tonnes
Speed: 10kts surfaced, 20kts submerged
Endurance: 25 days submerged on AIP, 75 days total
Complement: 42, with room for 10 more trainees or other personnel
Armament: MK48 ADCAP Mod 7 (CBASS), UGM-84G Sub-Harpoon, fired via six 533mm torpedo tubes