When hyperloop was first mentioned I considered the criteria required and worked on a matching result. I came up with something that deviates from later info b

When hyperloop was first mentioned I considered the criteria required and worked on a matching result. I came up with something that deviates from later info by nevertheless I came up with something that matched. Working on the principle that the speeds and efficiency mentioned means it has to avoid the friction of travelling through a medium. Since he had said "not a vac tunnel" I set my mind considering how the problem could be solved without relying on a vacuum. I figured, 'why not move the medium as well?'. Making a tube train travelling in a fluid medium would be interesting. Make the inner surface of the tube a hydrophobic surface. Use solar power along the length of the tube to accelerate the liquid. The speed would increase until the energy lost through friction with the sides reached equilibrium of the solar acceleration. If you can reduce the surface friction sufficiently, extremely high speeds should be possible. Comparing against the checklist you did, a Hydrophobic torus full of high speed liquid gets a fair number of hits. The same aspect applies of energy storage as kinetic. It's a better match for 'ground based' but The same ground based aspect means it would get in the way. Building the liquid filled thing would be much easier, possibly implementable at smaller scales initially. Mostly I think this just goes to show the interesting ideas you can come up with when given a set of constraints and a goal. I seem to vaguely recall a Mike Abrash anecdote about VGA fifos that applies here too. I think I'd be a bit disappointed if it is a Lofstrom loop(but that's what it likely is) unless there is some significant innovation extending the idea. It's just like a vac tunnel with cool inertial skyhooks.