Day old thread but I can't resist 8) The basic ideas are sound as you say but there is a huge difference between basic ideas and practical reality. I doubt an

Day old thread but I can't resist 8) The basic ideas are sound as you say but there is a huge difference between basic ideas and practical reality. I doubt anyone has looked into the localized stability of say 240m^3 chunks of a volcano's structure. That's the size of a flat of 10x10x2.4m. This thing is a termite mound scaled up to human size and is absolutely terrifying to me. How would it deal with say an earthquake? I mentioned resonance as the curse of Civ Eng earlier and this thing is absolutely huge - who can predict what weird oscillations might occur due to wind loadings and counter them? Do you engineer it for a 1 in 100 year or 1 in 10000 year event? Given climate change, do we even know what a 1 in 10000 year event even is any more? You may have heard about a fire in a tower block in London recently. The Grenfell tower disaster (amongst many others) show that whilst we are capable of building huge structures, economics and base stupidity will strike. That was a few 100 people of which 80 odd died. This beast would house up to 1,000,000 people. I am pessimistic because we have plenty of history to look at and this thing is too big to fail, yet we are unable to do the basics yet. Grenfell should not have happened and neither should many other tower block disasters. The floor plan of this thing is 36km^2 who knows what weird effects might happen in a building that covers that area. It would be a right bugger to discover that you really should have put say huge rubber washers into each joint to damp vibrations afterwards. Heck, 6km is enough to have to worry about the earth's curvature. This is God, (sorry, $DEITY) sized engineering. Try and hold an image in your mind of a 36km^2, 4km high space frame with cells of say 20x10x2.4, pin joint all elements. Reduce the structure to lines. Now bend and twist it. My mental model wobbles like a https://en.wikipedia.org/wiki/Blancmange https://en.wikipedia.org/wiki/Blancmange but some of the loads will be absolutely huge and I can't be arsed to quantify them: I know. Try perturbing say one corner and watch it propagate. Capability is not the same as responsibility.