:duel
The Collins is an essentially rare boat type. It is the largest conventional submarine in the world, and among a few that attempt to fill the roles of a nuclear hunter killer submarine while running on non-nuclear propulsion and power source. It's a design that no other country in the world uses, or even uses something similar- it spends a lot of cash in maintaince (some 330 million dollars per annum as of 2008) and a lot of time in drydock.
So far the discussion has leaned towards bigger boats, potentially conventional clones of nuclear subs such as the astute. However i fear as the boats get bigger the problems with running them off diesel engines will only mount- even nextgen conventional engines can not be an adequate solution for boats that will be far larger than any other conventional subs in existence.
At the end of the day though the gravest threat to the current plan isn't the boat itself but the people to crew it. the navy faces manpower shortages attempting to crew the 6 subs they have now. unless something changes drastically they'll have no more luck in 15 years time attempting to crew 12.
The other major problem is it depends a lot on technology which may be obsolete by the time it comes into service (not technologically obsolete but rather politically obsolete) replaced by nuclear fusion. While nuclear fusion is unlikely to have the benefits of Diesel-electric, smaller size, less noise and cheaper price (which considering we aren't really utilising this in the first place is largely inconsequential) it will viably replace the nuclear fission reactor by the 2040s or so (if the ITER is anything to judge by)- and since it carries none of the political quagmire that fission has).Australia could use it to power the long range, long endurance, large boats that appear to be what many people here are considering.
I apologise if i overshot myself in my previous post. I have no where near as much experience as some members of this forum.
hwell