A structure to "wall out" the atmosphere would be pretty heavy, and if it existed putting launcher on top would be easier. https://en.m.wikipedia.org/wiki/Sp

A structure to "wall out" the atmosphere would be pretty heavy, and if it existed putting launcher on top would be easier. https://en.m.wikipedia.org/wiki/Space_fountain https://en.m.wikipedia.org/wiki/Space_fountain of around 20km of height, is rather close to this idea.