Additional notes: My main theory before the announcement was that the concept used a fast-speed-of-sound, low-density STP hydrogen tube and maglev rather than slow-speed-of-sound air tube, or an expensive-to-seal vacuum tube. An STP hydrogen tube hovercraft levitation model still seems pretty damn attractive to me, especially with a sealing liquid buffer of some sort - it cancels out the problem of water-vacuum interface, and in water, flammable seals, as well.