>>/45028/
> Australia is an island nation and much of our trade travels through the Indo-Pacific. We have just as much incentive to secure that than the others do, if not more. That's if these nuclear subs will actually deliver that much more performance than a conventional one, it seems that range and the ability to stay underwater without having to come up to charge batteries are the big advantages. The Shortfin Barracuda was supposed to have a range of 33,000 KM when surfaced, it's 6,900km from Adelaide to the Taiwan straight, so they could easily get there and back but only if surfaced, I looked up the ranges of the Collins class that are supposed to be similar.
Modern air-independent subs (mostly diesel-electric combined with batteries) are pretty capable, and they may be even better than nuclear ones in terms of acoustic efficiency, especially when they run on batteries only. Nuclear subs with steam turbine are louder. These subs also much cheaper and easier to maintain than nuclear ones. Only difference is range, but range of modern non-nuclear subs (like German ones) are ok.
> 9,000 nmi (17,000 km; 10,000 mi) at 10 kn (19 km/h; 12 mph) periscope
> 480 nmi (890 km; 550 mi) at 4 kn (7.4 km/h; 4.6 mph) submerged
There is no need to be fully submerged while travelling on long distance, if you doing it in "empty" ocean. Only reason to hide on big depth is situation in hostile waters full with enemy ships/subs/sonar detectors. It isn't USSR-vs-USA in 1980 at North sea, full with sonars, but Pacific/Indian ocean with third-world shitholes as neighbors. They'll never cover ocean with same sensor network.
But anyway, do Australia really need subs that may reach Taiwan quietly? There are no possible conflict for Australia when sub tech would really matter in war. For imaginary conflict with local neighbors like Indonesia even old subs would be ok, especially considering that modern war is about combined arms, not subs. It is hard to imagine situation when AU sub range would be decisive factor in any possible war even in future. Most modern local conflicts are limited operations anyway, and it is hard to imagine real war with subs and convoys like in WW2 in 21st century for Australia. In realistic situation it is wiser to put money in air force as it is much more universal tool.
Direct conflict with China means two options - if it is China vs AU without allies, subs wouldn't matter (but conflict wouldn't happen because Australia already is a Chinese resource supplier that can be forced into anything by economic means). If it is big war with US and others, Australian part also doesn't matter so much.
But for protecting own borders, cheaper subs are perfectly ok. Especially when nuclear tech also brings non-military dangers and eats money. Why having big and costly toy when it doesn't change how do you live?