Hi Obi Wan, I wonder, what's your opinion what's the smallest and cheapest practical CATOBAR carrier? Let's take Italian Cavour-class carrier- could they have made it as CATOBAR, able to operate say F-18 and E-2, without significantly higher costs or enlargement of the ship?
I dabbled with this very thought myself a few years ago, there are two sides to the question I believe. Could a ship of that size successfully launch and recover CATOBAR aircraft? And would it be able to carry enough aircraft to make the job worthwhile. On the second point it is worth noting that nations that built the smallest carriers they could in the 70s and 80s are building bigger now, for exactly this reason.
Back to the first point, my own gut feeling is to bottom line for a viable CATOBAR Carrier is probably around 30,000 tonnes, and about 800ft long, which would equate to an angled deck of around 550-600ft:
In these two illustrations the first being the basic Cavour design and the second being my own take on a CTOL variant, consequences of the change are immediately apparent: in order to accommodate the angled deck, the island superstructure had to be shortened somewhat, but this is compensated for by building a starboard sponson beneath the 'Alaska Highway' outboard of the island (as was done with HMS Hermes in 64-66), so that compartments lost with a smaller island are simply relocated lower down. This starboard extension also helps to balance out the new portside sponson for the angled deck itself. If the Cats are steam powered, then a dedicated steam generating plant is needed as this design like most modern warships is Gas Turbine powered. If EMALS are used, then extra electricity generating capacity will be needed, which means more demand for internal space somewhere in the ship (possible answered as in the CVFs, by putting GTs in the Sponsons under the flight deck level. More engines require more crew and... well now you see the beginning of the growth spiral.
And we haven't even got to the size of the air group yet. When planning any warship, the requirements start with the mission, not the size. Define your mission, define the types and numbers of aircraft needed to execute that mission (eg how many fighters are needed to maintain CAP over the fleet, Do you want dedicated strike aircraft of a separate type or will their mission be amalgamated into the same type as your AD). AEW is a must, fixed wing or rotary? ASW is a minimum requirement, so six to nine helos at least even on CATOBAR Carriers. That 30,000tonne hull is starting to feel very cramped now isn't it?
If all you want is a basic capability, say 12 fighter bombers, 3-4 AEW and six ASW then you're probably still ok at this size. For a relatively small extra outlay you can buy a much bigger hull though (assuming the same weapon and sensor fit, and mostly the same power plant) as the ship steel is probably the cheapest part of the design. This is why the CVFs are pushing 70,000tonnes even though their basic air group is about the size I outlined above. They can soak up a lot more aircraft when needed and still be run economically in peacetime. There are many more factors that influence the design, but my bottom line is yes, a 30,000 tonne CATOBAR Carrier is feasible. If you can afford one, you can afford something a bit bigger too...
This discussion really belongs in the Aircraft Carriers III thread, I'd be grateful if one of the Mods could move it over.