Ask HN: serious engineering discussion of Hyperloop

There have been several Hyperloop threads already, but the engineering-to-politics-or-simple-ad-hominem ratio has been fairly low. I know HN can support a focused discussion of the engineering feasibility -- let's do it! Any serious engineering topic is fair game, but here are a few to seed the discussion. Citations whenever possible, please. 1. Where, exactly, are the endpoints of the line that is proposed to be buildable for $6B? What additional travel time would be needed to get from downtown SF to downtown LA? 2. Are the proposed pylon costs realistic? Is there precedent for building a comparable elevated structure at a similar cost? 3. Can the necessary accelerations be accomplished without motion sickness? Taking into account various transitions into and out of acceleration at the start and end of the trip, top-up acceleration along the route, turns and grade changes, etc. 4. Can a 30-second capsule spacing be made safe?