I put more serious effort on subs:
-Collins 20000 km range, 60 days.
-Scorpene 8500 nm range, 45-50 days.
-S80 similar diesel range to Scorpene plus Aip, 50-60 days.
Range in general, surface, snorkel, just to get an approx. idea.
If Ran wanted to have overglobe sub intelligence capacity it couldnt do it with size given to Collins anyway, because those 6000 or 7000 kms more kms of range, and those 10 or 15 more days it is not that much if you want to have an independent mission far away, how far, let´s say an interesting intelligence scenario, the north coast of Russia, imagine Ran agrees with Usa to cooperate knowing Russian fleet or sub activities and facilities in Russia´s north coast. Then we see in the map as 12000 kms of coast, divide in two sectors, which end in the coast of Norway, where we have an interesting refuelling zone of 2000 squared kms, and the other sector ends in Alaska where there is another 2000 squared kms zone to refuel, just below the Alaskan corner. If Ran deploys a sub to the 6000 kms Russian coast sector, that ends in Alaska, they can be kept permanently patrolling and listening in that sector provided they refuel and change crew easily discretly in those 2000 squared kms, the crew can be sent by airplane to Alaska where picked up by the refueller ship.
A good ship to refuel the subs would be in the 10000 t. size with:
-4000 t. of fuel for own use and autonomy and to refuel the subs.
-place for supplies.
-even for weapons or sonoboyes for the sub to deploy them round interesting facilites.
-giving an endurance of like 45000 kms and give the refuel to the sub.
-dress up of cargo ship, ie no showing the pipes for the refuel etc..
-with 4 hidden 20 mm basic optronic Ciws able to shot down missiles, modern Ciws tech.
-manned by 50 sailors (it´s a simple ship).
-these data are making the half of the newest Spanish fleet refueller ship.
This ship can reach in:
-2 weeks the refuelling zone for the Ran sub controlling the east 6000 kms russian coast sector.
-3-4 weeks the refuelling zone in front of Norwegian coast.
All is much simpler if the zones to gain intelligence are Chinese, Indian or East Pacific Russian coast, in these the 2000 kms refuelling zone is just like a week or 2 for the refuelling ship from Australia, and so the sub can continue quickly and shortly to the action zone with new crew, just like being away 2 or 3 days to refuel safely in the middle of nowhere.
So having this refuelling ships refief the Ran from looking at bigger and more expensive and more risky subs, with any sub the Ran will have they will be able to gain intelligence in any part of the world, in peace times, and also in wartimes because those 2000 squared kms touch waters that are either allied to Australia waters, or are in the middle of the ocean where hundreds of ships have routes, or are national of some country waters which are very difficult to control for any 3rd nation involved in any conflict. And take into account that the contact between the sub and the refueller ship is going to be just a few hours, to refuell, supplies, crew and etc. In a few hours both are gone.
Edit: and even houseport the refueller ship in any port in the world and send both crews (ship and new crew for sub) by airplane to take the ship and go to the contact point. In this case in Irish port for being refuelling each 30-45-60 days the sub in the 2000 squared kms zone in fron of Norway.
