I have spent a while testing out different ways of making you shoot up super high. I finally came up with one that im sure makes you fly the highest xD.
Please don't make fun of my building skills lol. I just made the structure around the cannon to make it look nicer :P.
The Cannon does need creative mode (without it you will be blown to living death, yes that makes sense).
The cannon is quite easy to reload and just requires some TNT, stone, and a pressure plate. Its already set up in the save file so you can use it instantly after downloading.

Also check out my server. :D ip in the description