Mass of the Atmosphere

More difficult to supply could be the mass for the atmosphere. The structure's volume is 3.5 x 10¹⁸ m³, which would require 2 x 10¹⁸ kg of atmosphere if evenly distributed, but it is not necessary to supply that full mass of atmosphere. The pseudogravity of the station's rotation will collect the bulk of the atmosphere close to the outer perimeter. >From [10] one can derive a simple model of atmospheric density of

(5)

where r is any radius of interest within the cylinder, r0 is the atmospheric density at the outer radius, and p0 is the atmospheric pressure at the outer radius. Integrating along r through the cylinder and spherical endcaps gives a total required mass of only 7.2 x 10¹⁶ kg, or roughly 3% of what would be required to fill the cylinder uniformly. Near 36 km above the surface, the atmosphere will fall to only 1% of the surface density. Thus, each square meter of surface requires a roughly comparable mass of atmosphere above it, whether that surface is in a very large open space station as described here, or on the surface of Earth with real gravity.