Did I read it wrong?
"The full-sized ship would also need to have a range of 7,000 miles, support heavy bombers and be torpedo-proof. It was to be over a mile in length, weigh as much as 2.2 million tons and require as many as 26 electric motors to move and steer across the ocean."
That's a crazy target growing out of "cheap to produce aircraft carrier"
Sailing midway all the way!
For starters aircraft carriers face into the wind for takeoff and landing. So that means either engines for maneuvering (noted in the article) or support vessels. Presumably support vessels are vulnerable so not in the picture.
It would sail like a pig ‐ with 90% underwater it'll pretty much go where the current goes. And very slowly.
I imagine the engines would either be small (slow maneuvering) or large (need fuel etc).
Once you need significant fuel you need to store it. Plus of course all the men, and their stores. And a lot of this doesn't like freezing temperatures.
To be useful the thing presumably has to be far from land, presumably closer to the enemy. So the enemy deploys a bunch of anti-aircraft ships to basically follow the thing. Returning aircraft are sitting ducks.
I'm no mechanical engineer, but none of this makes any sense to me at all.
I'm even less an admiral or air marshall but I dont see any tactical or strategic advantage here either.
Not disagreeing with your main points at all, but from a strat/tac point of view, up until later in the war, there was an air gap in the Atlantic where German U-Boats didn't have to worry about a significant air threat from the Allies. A large airfield parked mid-Atlantic might have significantly improved Allied air coverage, and helped reduce the stunningly bad shipping losses they were experiencing.
The US did make some vessels out of concrete because of constraints on steel production. A famous example was a barge in the Pacific (I think at Ulithi?) that was devoted to making ice cream.
"Strength loss for steel is generally accepted to begin at about 300°C and increases rapidly after 400°C. By 550°C steel retains approximately 60% of its room temperature yield strength, and 45% of its stiffness. At high temperatures, steel is also subjected to significant thermal elongation, which may lead to adverse impacts, especially if it is restrained."
At 800 C ("dull cherry red"), the yield strength is down ~90%: https://www.steelconstruction.info/images/9/99/Steel_strengt...
This is talking about short term properties of steel, which would be important in building fires, but creep also increases with temperature.
Most stop as it approaches -50c