Remember that I posited factors that I think makes large-scale lunar settlements feasible. One is the lava tubes replacing a lot of heavy construction. The other is to half-heartedly take Elon Musk sort of at his word, that if he thinks he can send people and their possessions to Mars for $200,000, he might be able to pull it off much closer to home.

I suspect Musk may have picked that figure because to an American it's the average price of a home, and he wanted to evoke the image of liquidating your Earthly homestead, piling your possessions into his version of a Conestoga wagon, and schleppng it all out to the new frontier. Again humoring Musk's logic, being able to do that for real as close the Moon would, I really believe, unleash a stampede of people whose net worth neatly fits into Musk's scenario.

Maybe Musk is blowing smoke. I keep throwing in caveats there are two lower stories to my house of cards.

Not sure how a comparison to the shuttle in 2001 (or any spacecraft) is relevant. The lava tube provides an enormous volume for free. Why be cramped?

I overlooked one practical obstacle, the length of the tube. That's an enormous distance over which to maintain pressure. You'd want to install pressure doors every kilometer or so, and that's a big engineering job in its own right. I'd build a tunnel/airlock on the floor, then collapse the roof on top of it. But that's around 30 airlocks in the cited lava tube. No small job. I envision stepwise development as each new section is sealed off and pressurized.

I'm a space groupie at heart, I guess, if you carefully define the term. I certainly don't knee-jerk endorse any damn thing to do with space flight. Nor do I worship NASA (though I remain respectful of its accomplishments). I get misty-eyed a bit over the faithful Soyuz capsule. No hero worship for Elon Musk, whose plans are most likely to lead to a gated community on Mars for the 0.01%...they don't deserve terraforming, and I've come to see it as a bad idea anyway--space habitats, hollow asteroids, and lava tubes make more sense. The SR-71 still makes my heart soar. Images from all those trusty robots never ceases to amaze and delight me.

So sure, I'm a space groupie, of a certain kind, and always will be.