In article .com,
wrote:
By halving the diameter of the sphere to 50m, you
quarter the mass of shell that needs to be launched
at once. The mass of air drops 1/8th that of
a 100m sphere, too.

Shell mass drops to 1/8 too, actually. 1/4 of the surface area, plus it
only needs to be half as thick to hold the same pressure.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |