Well that made for a really fun rabbit hole to start my day. Thanks. https://worldbuilding.stackexchange.com/questions/36667/can-...
A sphere with a 1km diameter has a volume of 680,317,581 cubic yards.
A sphere 1 mile in diameter has a volume of 2,854,543,238 cubic yards.
The driving mass force per those comments seems to be the surface area of the sphere, which grows according to the square, but the lifting power grows by the cube.