Elon Musk have change the car industry with Tesla, and projects like Hyper loop and SpaceX often reach the news. But in this interview he talks about how he want to change the way we build tunnels for cars by changing the tools and the requirements for the tunnel. It is interesting to see how he adress a problem and how he step-by-step working towards a solution. Look at the interview about 3D tunnels and the future for Elon Musk.
You drop the diameter by a factor of two and the cross-sectional area by a factor of four, and the tunneling cost scales with the cross-sectional area. So that’s roughly a half-order of magnitude improvement right there. Then tunneling machines currently tunnel for half the time, then they stop, and then the rest of the time is putting in reinforcements for the tunnel wall. So if you design the machine instead to do continuous tunneling and reinforcing, that will give you a factor of two improvement. Combine that and that’s a factor of eight.