[V_Terranova_Jr]

Carrier catapults violently accelerate aircraft to the point they are going fast enough to lift their own weight, within the takeoff length on the deck.

You could likely lessen fuel burn of a supersonic aircraft taking off (as you could with a subsonic aircraft) by accelerating it via a catapult of sorts, but you have to do so at acceleration levels tolerable to all passengers, which would make for a long, unwieldy catapult. Release speed is also obviously going to be very subsonic.