[Frankss]

If they mean to run the train in a vacuum or partial vac, the amount of energy it would take to “pump out” a 700 mile tunnel would be fantastic.

[Errant]

the amount of energy it would take to “pump out” a 700 mile tunnel would be fantastic.

It would take 2 large jet engines about 48 hours if my calculations are correct. ;)

[Atlas Sneezed]

If they mean to run the train in a vacuum or partial vac, the amount of energy it would take to “pump out” a 700 mile tunnel would be fantastic.

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And you’d need to have an airlock at each terminal the size of the train, and pump it out for every run.

However, an array of solar panels along the length could maintain the low pressure based on sunshine. Speeds might slow (or propulsion energy increase) during cloudy periods.