I don't think energy for air pumps is anywhere near the biggest problem for Hyperloop. There are other far hairier engineering challenges. That said, the effici

I don't think energy for air pumps is anywhere near the biggest problem for Hyperloop. There are other far hairier engineering challenges. That said, the efficiency of pumps is not at all linear with air pressure - 100 Pa is significantly better than near vacuum. The other misconception here is the assumption that the entire length needs to be maintained at 100 Pa. This is not necessary. Having a pressure gradient is fine because it isn't going fast near the terminals anyway.