Hi Ryan, thanks a lot for taking the time and leaving your thoughts, I appreciate it! I agree that extremely resilient and self-sustaining disaster shelters might offer similar benefits from an X-risk perspective. I didn't go all to deep into that topic because I feel there aren't the same incentives (and excitement) around building shelters on earth compared to starting settlements away from earth. At least, I am unaware of designated X-risk shelters being built specifically to save humanity in the event of a catastrophe (an exception might be the Svalbard Seed Vault or some of the military nuclear bunkers, or maybe nuclear submarines). On the other hand, there are multiple efforts currently aimed at starting a space settlement, and the concept is much more embedded into the popular awareness. I think there is an inherent attractiveness of spreading "outwards" as opposed to going "inwards". To put it romantically: there seems to be more potential for human development in the reaches of space than below the earth. HOWEVER I totally agree with you that it would certainly be smart to prepare (x-risk) shelters on earth for many reasons! Are you aware of any projects currently pursuing this?