I love that style of illustration. Something about the sharpness of the lines, contrasted with the non-specificity of the details... there are no bolts, or girders, or practical considerations beyond the broad sweep of "a toroidal living space", but the line work is fine, and detailed. I'm not sure how something can be so precise and so general at the same time. Love it.

When I worked for NASA, the hallways were full of this type of conceptual space art, spanning all the way back to the 60's.

My understanding is that NASA had artists working with the scientists. A scientist would come up with a general idea - like a toroidal living space - and speak to the artist about what that might look like. The artist would create the illustration, and it would be used as a tool by the scientists to discuss the practical details. A product visualization, literally.

I have no idea if that is true, or not. Just something I heard from someone when I worked there. But it is a beautiful thought, and it jibes with my understanding of how other scientists work (Pauli, Pauling, Feynman, etc, all had models they played with to visualize if a concept "looked right".)

I've seen these pictures before and I remember trekking into the basement stacks of a remote library at my university to find this book by O'Neill.

One thing that strikes me about the artistic depictions is how verdant the landscapes are. These colonies aren't depicted as futuristic technological marvels but as natural or agricultural oases in the heavens, surrounding "idyllic" suburbia. In one picture there are even kids playing in a stream, surrounded by lush vegetation. It's an interesting choice.

On the same site: Space Settlements: A Design Study and Space Resources and Space Settlements.

... and also a Stewart Brand thing