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by GeneTraylor
5343 days ago
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>>> Why? We have a whole solar system right on on our front porch <<< This is an honest question, not a rebuttal. How would you get those resources here, or us over there? >>> Water doesn't just get used once and then disappear forever. Now, one could certainly make an argument against (say) sucking water out of the Oglalla Aquifer faster than it gets replenished, but that's a localized problem. We aren't going to "run out of water". Really. <<< Well it would have been labored to add that although it would take a large amount of energy to purify water, or perhaps desalinate our oceans, the loop can be closed. The problem really is that it takes resources to keep that loop closed. I think that all of our issues today boil down to how we convert energy to extract work, if we do manage to make something like fusion work then all of these concerns could be undermined with technology, but how do we get from here to there? |
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There are a number of high-startup-cost, low-running-cost schemes for putting stuff in LEO, and as someone once said, LEO is halfway to anywhere in the solar system, energy-wise. Some possibilities are laser launching, space elevators, launch loops, and electromagnetic guns.
Some of these have much higher startup costs (to be effective for human launching, a gun would have to be very, very long and possibly cost the most of any of these, but shorter ones could launch material at very high acceleration with much less up-front cost), and some of them have awful failure modes (the space elevator could spread destruction in a narrow path wrapped all the way around the earth if it failed in the wrong way, via separation from the counterweight), but they're feasible.
The cheapest ways of getting to orbit, therefore, approach the cost in electricity of the task, which is less than 10 KwH per kilogram, or about $2USD per kilo. A recent flight from coast to coast cost more than that for me.