Child's play theoretically. Practicality is a different matter. I think that continuing work on raising the effective temperature of superconductors would be more sensible, especially as it has applications beyond transportation.
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I think that the fact that this guy is proven to deliver on his investments (Space X, Paypal, Tesla) is a sign that if he's willing to mention this as something he's working on, it's likely feasible in a practical sense.