The space station (to be constructed using rockets with recoverable and reusable ascent stages) would be a toroid structure, with a diameter of ; this built on the concept of a rotating wheel-shaped station introduced in 1929 by Herman Potočnik in his book "The Problem of Space Travel – The Rocket Motor". The space station would spin around a central docking nave to provide artificial gravity, and would be assembled in a two-hour, high-inclination Earth orbit allowing observation of essentially every point on Earth on at least a daily basis. The ultimate purpose of the space station would be to provide an assembly platform for crewed lunar expeditions. More than a decade later, the movie version of would draw heavily on the design concept in its visualization of an orbital space station.