McKendree cylinder

A McKendree cylinder is a scaled-up version of the O'Neill cylinder. It is a space habitat originally proposed by NASA engineer Tom McKendree. As with other space habitat designs, the cylinder would spin to produce artificial gravity by way of centrifugal force. It would use carbon nanotubes instead of steel, allowing the habitat to be built much larger. In the original proposal, the habitat would consist of a cylinder approximately 460 km (290 mi) in radius and 4600 km (2900 mi) in length, containing 13 million square kilometers (5.1 million square miles) of living space, nearly as much land area as that of Russia.

Because it is a cylindrical region of space that is in a state of dynamic equilibrium, the gravitational force is balanced by the centripetal force caused by the rotation of the cylinder. McKendree then suggested that it could serve as a model for the structure of spiral galaxies, with the cylinder representing the disk of the galaxy and the central black hole at the axis of the cylinder representing the galactic bulge.