A bit ironic to politely decline helping with the Hyperloop only after criticizing the Hyperloop. Acting as a critic helps Musk in his noble quest. I have enjo

A bit ironic to politely decline helping with the Hyperloop only after criticizing the Hyperloop. Acting as a critic helps Musk in his noble quest. I have enjoyed the Hyperloop discussion as a thought experiment, and I appreciate that Musk is willing to throw around crazy ideas that challenge conventional thinking. Regarding thermal expansion, the change in length must be dissipated through the curves and changes in vertical alignment. The hyperloop is mostly straight, not perfectly. Oil and gas pipelines are almost perfectly straight, thus needing an expansion bend. The Hyperloop changes bearing frequently. Being mostly straight is a major item to overlook, as any pylon near any change in direction will have to deal with thermal expansion, not the end tubes. A 20 mile arc with a 20 mile radius will absorb a significant change in tube length with only modest pylon deflection. Musk's pylons could handle the strain with smart structural engineering. At a glance, I would design the pylons to pivot on a hinge portion with pretensioned steel and (viscous fluid) dampers to control vibration, letting the tubes push the pylons to modestly reduce or increase the curve radii. The major difference in Musk's design is that the tube would need to be periodically anchored in various dimensions to discourage the end-station movement and force the tubes to use the pylons' flex rather than snaking the whole length of tube.