There is no stacked mass however. Just a single piece of mass moving up/down that results in linear scaling from height. Edit: reviewed the Terraent slides the

There is no stacked mass however. Just a single piece of mass moving up/down that results in linear scaling from height. Edit: reviewed the Terraent slides they indeed plan to literally drive a mile long train vertically into the ground. In which case the quadratic argument stands. At the cost of significant added complexity. It comes down to drilling cost vs installation/ maintenance cost.