An Alternate Design

The previous design the atmospheric density at the zero-g center of the colony is virtually zero. This does not support the secondary goal of allowing shirt-sleeve zero g activities [13]. Both [10] and [12] state lower pressure limits for manned habitation is 1/2 atmosphere. If one sets the design goal of 1 atmospheric pressure at the outer radius (101,350 Pa), and 1/2 atmosphere at the center, this gives a design radius of 11,700 m. This can be achieved with the 50% safety factor by titanium, rotating as an empty shell to simulate one g at the outer radius. An aluminum structure would have a 16 % safety factor, and the safety factor for steel for this structure would be 39 %. While all three materials could survive as empty rotating shells, they could not also hold the requisite atmosphere. The MNT material of diamond satisfies this application, including holding the atmosphere and the internal station furnishings, with a shell thickness of 4 cm. Adding the additional design goal of 5 kg/m² thick structural material yields a 3,783 % safety factor for diamond.