Tunnels will be required on Mars to shield from radiation. Getting a head start on the technology while on Earth only makes sense. Pretty much everything he pla

Tunnels will be required on Mars to shield from radiation. Getting a head start on the technology while on Earth only makes sense. Pretty much everything he plans is in perspective of having a dual use: will it be needed on Mars - SpaceX's true goal? I hate to say the word but, it's all about synergies.