Maybe I don't know enough about physics or thermodynamics, but this portion puzzled me: > Here, I’m showing the pipe sitting on the pillars at the low temperat

Maybe I don't know enough about physics or thermodynamics, but this portion puzzled me: > Here, I’m showing the pipe sitting on the pillars at the low temperature. The lines and arrows above the pipe are where it expands to at the high temperature. > Now add 100′ of pipe and another piller to either end. How much movement do the dampers in these new end pillars have to accomodate? Just ¾″? No. They have to accommodate 1½″ because their lengths change ¾″ and their “starting points,” so to speak, also change ¾″. I won't pretend to understand what Musk was proposing, but for the sake of argument, can't you simply allow the ends of each portion of pipe to expand into each other, thus creating a net change of 0? All you'd need is a tongue-in-groove connection with a small gap of .75". For sealing the connection, just line the tongue with rubber, and for aerodynamics, just line the resultant gap with a thin strip of material.