launching ship borne fixed wing aircraft

First of all: A happy new Christian Year everybody, and the expectation of a happy Chinese new year in a month time.
I promised to open a thread on this subject a few weeks ago but for long didn't have the time even to follow my favorite threads. This is about the past and future of the several ways of launching winged aircraft.

First a consideration of the ski ramp. There are two different ways:

For single engine aircraft, V/STOL or STOVL, the aircraft runs up the slope and leaves at the top at some 80 mph with a considerable contribution of engine thrust ( the Harrier turns down its fan and core exhausts 40 degrees). If during this procedure the engine fails the pilot leaves his office using his personal elevator.

For a multi engine aircraft the situation is different. Multi engine aircraft have such notions as decision speed and balanced runway length. These do not apply to ski ramp ships. When the ship retracts the wheel chocks there is no going back. So the assumption is that the critical engine fails at the moment the moment the wheel chocks are retracted and the aircraft will accelerate to the top of the ski ramp achieving about 60% of the speed it would have without engine failure, and fly off - dropping any external stores say two seconds after leaving the ramp - flying a curved trajectory at reduced lift to reduce induced drag - and accelerate to a safe flying speed and not drop into the sea. The case for engine failure is the governing case for determining the maximum allowable take off weight.

Now let's look at the ski ramp with EM cats.
An EM cat is a kind of linear motor and these were proposed half a century ago for the support and propulsion of trains: maglev as in Shanghai. Such linear motors can be curved in the horizontal as well as the vertical plane. We are only interested in the second.
If we assume that the J-15 now leaves the ramp at the same speed as an aircraft launched by a cat from a USN carrier ( I think it is less ) then a cat providing 60% of that speed while providing the same acceleration can be 36% of length of USN cat. If the EM is designed to provide the same acceleration whether an engine failed or not that will be the length of the cat. That means that the distance from the aft end of the deck to the aft end of the cats will be larger in a Liaoning with cats than the corresponding distance in a USN super carrier by some twenty meters. This will materially increase the deck area were neither cat nor trap operation interfere with the spotting of aircraft. And this reduces the respotting necessary and the work load of the deck crew.

I think it likely that the two carriers said to be building in China will be fitted with such cats. I see confirmation in a news item in Marine Forum a few weeks ago that the Russian Navy has delayed the start of the reconstruction of Adm K by four years. It may be that they decided the ship was not as dated as they earlier thought or that Putin spent all his spare cash at rescuing Ukraine from the clutches of Brussels but it seems more likely that during the reconstruction China will be in a position to provide cats after building four in the new carriers and at least two in land based facilities and two in a replacement bow section for Liaoning. Indeed they might be using the same design for a new bow section for Adm K.

Let's look at USN following suit, would that make sense? I think not. The advantage on a USN super carrier is not large and the costs and time of reconstruction considerable. Ninety years of experience would not have been thrown away but a lot of new tricks would have to be learned. On the 40k flattops in addition there are serious political objections. And all that after compromising F-35A and -C for the unfortunate -B and think of the Not Invented Here syndrome.