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We have resources at home!

• mlindner 4y ago
  We do! And for a long while most of the resources will come from Earth. However you can't keep doing that forever as the costs will grow to an unsustainable level. If you could magic up a civilization on Mars today, it'd exponentially cheaper to launch materials from Mars to elsewhere in the solar system than to launch those same materials from Earth. Similarly it'd be cheaper to dig those materials out of the ground for use on Mars than it would be for them to be used directly on Mars. Counterintuitively, it's cheaper to launch materials from Mars to Earth's Moon than it is to launch them from Earth's surface to the Moon.
• mlindner 4y ago
  One note on the "exponentiality" in the other comment. Getting from Earth's surface to the moon (without staging) requires a rocket that is approximately 99% fuel by mass (calculated using rocket equation and engine performance of a high quality engine). That leaves you with very little margin for building a rocket's structure which means it needs to be built extremely carefully with little room for error. Also in order to get reasonable payloads, you need to make rockets of tremendous sizes in order to get reasonably sized payloads to locations. On the other hand a rocket that flies from Mars surface too Earth's moon only needs to be 90% fuel which is a lot easier to do with modern materials. This also means that you can carry significantly more payload as your total mass. With some napkin math, this allows you to launch, with the same rocket, from the surface of Mars to Earth's moon a payload 10 times bigger than if you launched it from Earth. The penalty you pay getting stuff out of Earth's gravity well is just simply huge.