Its totally feasible. It is ridiculous to think we can't create such a thing in an economically feasible way. I am not saying every part of Musk's original design was the best possible approach. No first design ever is. I personally think using maglev in air reduced tunnels is the way to go (which is what is currently being developed). But the whole idea is both brilliant, and frankly obvious. In fact it was already being developed decades ago to some degree. The suppression of (or possibly stealing of?) the technology was likely done by the DS.