A few months ago, I made this comment. It deserves more elaboration, so I decided to write an entire webpage about it.
The bulk of the webpage talks about O’Neill Cylinders and includes questions and answers from Claude relating to them. The page also includes thoughts and commentary relating to space travel and the book, Futurist Fantasies. The page ends with a list of easier goals and baby steps that should be accomplished before attempting space colonization.
The price of Mars colonization is equal to the price of first full self-replicating nanorobot. Anything before it is waste of resources. And such nanobot will likely be created by advance AI.