Great read on a fascinating and very current subject. It is exciting to think of our future where these hurdles may be overcome and interplanetary travel may become a real thing for humans. A NASA engineer who gave a talk at our Civil Air Patrol Squadron brought up another big issue which is our insufficient current propulsion systems. Moving people, equipment, soil, etc... means moving mass. The more we transport, the more mass. Current hurdles are getting there fast enough to limit radiation exposure during the journey. Radiation shielding for the craft must be considered, but at the cost of even more mass. Fuel to increase the speed means more mass. Getting all of this free of Earth's gravity is currently a huge stumbling point that will require better, more efficient propulsion systems than we currently have, even if we stage materials in space to be picked up and then moved during a second stage journey. All possible, but not yet a reality. We're counting on Musk to help solve some of these challenges in physics.