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Keeping mass in orbit about a point requires absolutely no energy. That is because energy is force times distance (with times being a dot product), and the force you apply is always at right angles to the motion.

It is a good thing that this is true, else the Earth could not manage to go around the Sun indefinitely!

Therefore the energy to keep a system like this going is entirely what is needed to replace various incidental losses like friction. With maglev technology there some electromagnetic drag, but the bulk of losses are air friction.

There is no way to keep a train like you describe going against air friction at 1200 mph. If you eliminated air friction, it would be very doable.

What if the entire loop was in motion? Picture a maglev train 1200km long. There is no "front" to the train, it's a loop, so air is not being compressed as it whizzes along at 1200kmph. Most of the space inside the train could be void, which could be filled with passenger cars as needed.

Would that eliminate enough of the air resistance to be feasible? Is a 1200km long contiguous structure feasible?

I am fairly sure it would not help. If you're rubbing past air at that speed, you'll have pretty serious friction issues.

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