This Gun Could Reach Space https://www.youtube.com/watch?v=W4EMf_MTXVc
https://interestingengineering.com/science/jules-vernes-space-gun
The Space_gun started out as just another science fiction concept.
https://interestingengineering.com/innovation/space-cannon-hypersonic-speeds
https://newatlas.com/space/greenlaunch-space-cannon-gas-launch/