Recently someone from navy either three star or four star officer claimed that if EMALS used, EMALS alone will force IN to go for nuclear propulsion.
It'd have to be nuclear. Remember, the US EMALs system:
Could not be retrofitted onto a Nimtiz Class Carrier - which have two A4W nuclear reactors putting out 100MWs of power:
That wasn't enough power for an EMALs system and the necessary overhead for emergency power.
USS Gerald Ford:
Has two A1B reactors each capable of putting out 300MWs, which gives Ford enough power to launch a fully loaded F/A-18 or F-35 like this:
Nimitz, a nuclear powered carrier didn't have enough power for an EMALs system. No conventional carrier will either. The IN's EMALs equipped carrier will need nuclear power too.
I don't know why nuclear is needed for EMALS
^^^
There's your answer. The high power requirements of the EMALs system, and the power requirements of the rest of the ship, for lighting, emergency power, plumbing, waste processing, elevators... and on and on, means nuclear is the way to go, and not all nuclear capable ships have the necessary power output either.
Nimitz didn't, but Ford does.
I don't understand, what is wrong with Nuclear and Catobar ?
Nothing is wrong with CATOBAR. But an EMALs system puts less stress on an aircraft during take off and thus improves maintenance costs and turn around.
It also launches aircraft faster allowing for a higher sortie rate and can support aircraft with higher weight then a steam catapult:
The Electromagnetic Aircraft Launch System (EMALS) is more efficient, smaller, lighter, more powerful, and easier to control. Increased control means that EMALS will be able to launch both heavier and lighter aircraft than the steam catapult. Also, the use of a controlled force will reduce the stress on airframes, resulting in less maintenance and a longer lifetime for the airframe. The power limitations for the Nimitz class make the installation of the recently developed EMALS impossible.
USS Gerald Ford is also replacing the arrestor cable recovery method with high-power magnets, which again, will cut down of wear and improve maintenance turn around and costs:
This is replacing the Mk 7:
CATOBAR is fine, but for the trade off on greater development and ship cost and the necessity for more efficient reactors with greater power output, but less cost in ship maintenance as it's cheaper to maintain, an EMALs system is more efficient and capable then CATOBAR.