Maximum speed for a modern catapult is 140 kt over the deck edge. What is the speed for the ramp? I read it is 80 kt, is that correct?
I won't comment on the max speed, but the critical moment is when the nose gear attacks the angled deck of the ramp, and the nose gear strut begins to compress immediately. Even when the aircraft starts from the aft launch station, (all the Chinese aircraft appear to launch from the aft station all the time), Full Burner is applied, and when the safety blocks drop, the roll begins, so whether it crosses that transition at 100 knots or 80 knts, it will continue to accelerate to flying speed as it charges up the ramp. That angled ramp allows the aircraft to clear the deck at 100+ knots accelerating in a very high angle of attack....
As that upward momentum begins to dissipate, the aircraft, still in full burner, still at a very high angle of attack, will begin to settle toward the water, particularly if its at a heavier launch weight. That very settling, allows the aircraft to continue to increase lift production and accelerate, when lift production equals aircraft gross weight, the settling will stop, and as the aircraft continues to accelerate it will fly away under its own power......
So the J-15 may launch with more ordinance and less fuel if a buddy tanker is standing by to "top it up"? otherwise its a 50/50 trade off.. Lets be honest, the J-15 will haul a real load off a land based runway, but fill it up with fuel and ordinance, and launch it off CV-16 or CV-17's ramp and its going to be a short ride and a swim.....