I've thought about it and I believe this is the most likely solution. The vehicle would remain aerodynamically subsonic, but could attain supersonic speeds as t

I've thought about it and I believe this is the most likely solution. The vehicle would remain aerodynamically subsonic, but could attain supersonic speeds as the air in the tunnel speeds up. This would also allow vehicles to follow one another without too much separation. Turbo fans can be used to keep the air moving throughout the loop. If enough vehicles are running at full speed, the system will always be "pressurized" as the vehicles themselves will accelerate the air in the loop. Passenger/cargo loading would occur outside the loop (a fork) and would be brought up to speed by the power rail and inserted into the loop. EDIT - It appears jacquesmattheij agrees with us: http://jacquesmattheij.com/elon-musk-and-the-hyperloop http://jacquesmattheij.com/elon-musk-and-the-hyperloop