[MrForbes]

It can be very dangerous to make a mechanism that is capable of launching a ball that high, so you would need to go to a lot of extra trouble to make sure your design is safe. As I see it, the danger is not with actually launching the ball...the danger is that someone could have their bodily parts in the way of the mechanism when the ball is NOT in it, and it could give them a severe blow.

We figured out a way to use an air powered catapult that moves slowly if there is no ball on it, but with a ball in place, it is able to launch the ball quickly.

This is not an easy thing to design....so if you go this route, you really need to think about it carefully. We are using restrictor valves to keep the cylinders from filling quickly, and using an arm on top of the ball to hold it down, and the ball holds the catapult arm down. The system can only build up pressure when the ball is in place, and launching the ball uses up all this pressure.