In the summer of 1975, when space exploration was still ever so young, NASA Ames Research Center and Stanford University put on their thinking caps regarding potential space settlements. That brainstorming summit produced the 1975 NASA Summer Study, which envisioned what life in space might look like. The focus was on orbiting spaceships, and the result was a document called "Space settlements: A design study."
In the forward, then-NASA Administrator James Fletcher called the study a big-picture question for humankind: "To assess the human and economic implications as well as technical feasibility, the participants in this effort have provided us with a vision that will engage our imagination and stretch our minds."
Here, for example, is a cutaway view of ring-shaped "toroidal colonies," exposing the interior. Click on for more illustrations from the study.