It might be remotely practical but it certainly isn't rocket science. Romans used catapults for goodness sake. If its a thesis why aren't you doing it scientifically & directing the airflow over the wings of a thethered vehicle to provide the lift and then blow it from behind. You'd generate less g's for one thing & wouldn't have to worry about piston speeds & such. But like they say "If there's a hard way to do the job somebody will find it." ■

This query is well outside Bulk-online remit and the domain of basic engineering. Obviously, the machine must be accelerated above stalling speed and the mechanics is straightforward. It would seem probably that a conventional air cylinder would have to work through a stroke multiplier to keep the cylinder to a reasonable length and piston speed. I would work backwords from the chosen accelerating force to determine the runway length and then select a cylinder and mechanism to suit if the figures are acceptable. ■