Depends on how much atmosphere is leaked back into the tunnel and how much vacuum you need. The former is a much bigger issue with the concept, if it takes a lo

Depends on how much atmosphere is leaked back into the tunnel and how much vacuum you need. The former is a much bigger issue with the concept, if it takes a lot of energy to evacuate the tube once it's not too big of an issue, but ongoing maintenance of the vacuum would be problematic with leaky or damaged seals over the lifetime of the tunnel. Of course, most of the vacuum tube proposals require a vacuum of something like 0.001 atmospheres, which is incredibly problematic as well....