See the Australian government owned ABC News article dated May 27, 2021.
PETE COMMENT
This ABC article is an Australian Government "we are pressuring Naval Group to speed up" beatup - for public consumption.
1. So called "interim subs" take a minimum of 7 years to plan and build (and even then by the politically impossible Build Overseas route). Then you need a plan to retain them for 20-30 more years or hope for a buyer (all very expensive and risky).
2. Interim is only quicker if Australia is buying large second hand subs (a la the Upholder/Victoria "solution" - a sad UK/Canadian failure.)
3. And besides, whatever happened to Australia's mid-life upgrade intention? This carries the odd name "life of type extension (LOTE)"). The LOTE interim solution should keep some Collins subs operational all the way from 2029 to 2050.
Some in the Australian Navy are looking at a modified (presumably very enlarged) TKMS Type 214. TKMS could call it the 4,500 tonne Type 216 again (history repeating itself?)
Also see H I Sutton's accurate doubts that Australia is bucking its LARGE 3,000 to 4,700 tonne submaine trend in contemplating a small 1,800 tonne Type 214 interim sub.
I also note that the 214 explicitly features air independent propulsion (AIP) - designed for short range missions - eg. for navies with such missions as sitting on the seafloor 100km from their main base. Examples are:
- Israel's AIP 212/214 2,200 tonne Dolphin 2 (nuclear missile armed) variants. These seafloor sit just outside their Haifa, Israel, main base.
and
- South Korea's (seafloor sit in the Yellow Sea and Sea of Japan) locally made 1,800 tonne 214 variants).
A 214 can be seen as a Type 209 with a 300 tonne AIP plug. .
AIP is something Australia has always seen as counter-productive for Australia's long (all the way from Fleet Base West (Rockingham) to the Malacca Strait? round trip) mission profile. An AIP's LOx and Hydrogen containers represent a dead weight for long range missions - particularly when the LOx and Hydrogen propellants are used up.
Furthermore (lets assume) in terms of Aus sub discretion risks we are generally talking "Indonesia-peacetime" as well as surveilling/tailing surface ships and subs transiting the Malacca Strait.
In contrast if Aus subs needed to stay on station in vastly more dangerous Chinese waters (anywhere near China's Hainan SSBN Base, Port of Hong Kong or Shanghai or the Taiwan Strait?) then AIP might be a good idea.