12-12-2017, 12:05 PM | #111 | |
Join Date: Jan 2014
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
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Another reason why Earth is a superior source of Nitrogen (at least for Mars and Venus). You can forget all the work about building and fueling rockets like this and use solar sails to tug your Nitrogen around. |
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12-12-2017, 02:18 PM | #112 |
Join Date: Feb 2016
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
Earth is the last place you want to use for Martian nitrogen and Venus has plenty of nitrogen (four times as much as Earth). The problem is that it is much harder to get off the surface of the Earth than to get off the surface of Titan. Even though Titan is very far away, high impulse drives allow nitrogen from Titan for a fifth the cost of nitrogen from Earth. In addition, solar sails such for moving stuff around, as their low acceleration means that you will spend years traveling per AU.
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12-12-2017, 06:03 PM | #113 |
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Join Date: Mar 2012
Location: far from the ocean
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
Earth's gravity well is one of those pieces of nature that seems designed to mock us. Its just small enough that we can use chemical rockets to get things into orbit, if we use multiple stages and live with 90% of our weight being thrown away. Space elevators require materials that might just barely be possible. And so forth. If you get much smaller, transport gets a lot cheaper and a lot more efficient. Interplanetary travel does make sense... if you have people outside of earth-sized gravity wells. Though at that point it might not be interplanetary travel.
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12-19-2017, 12:07 AM | #114 | |
Join Date: Feb 2007
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
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Seriously, there's a reason why SF in the old days used to tend to assume that interplanetary travel would be a post-20C thing, it needs energy sources and densities to do it well that are hard to achieve with near-term tech. Chemical rocketry is adequate for a bare-bones unmanned program, but not much more.
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12-19-2017, 08:03 AM | #115 | |
Join Date: Jun 2005
Location: Lawrence, KS
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
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12-19-2017, 09:00 PM | #116 | |
Join Date: Feb 2007
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Re: Does Interstellar Trade Make Sense For Realistic Science Fiction?
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Heinlein used to propose that nuclear rockets would eventually made SSTO and escape from the ground, but he usually showed that coming later. Not always, as you note. All the way back in the 30s, Jack Williamson's old space opera The Legion of Space turned on the invention of the geodyne drive which made interplanetary (and eventually interstellar) flight practical. He posited the earliest flights being made using fission rockets, but portrayed them as bulky and inefficient and uneconomical.
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