Sunday, August 09, 2009
Where would a space habitat be located?I wrote previously on the possibility of making a Ringworld of space colonies which depends on being able to achieve scalable geometric growth in the size of the industry building them, but such scalability should not be a problem. If they can be maintained that far out a mere Ringworld of settlements is barely a start. 10 times further than Pluto is well out into the Inner Oort Cloud containing cometary material, including water & frozen oxygen & nitrogen as well as metals.
...In the long term: Anywhere you like, as long as you're not frequently eclipsed by a planet. You can locate farther from the sun as long as you make your mirrors bigger, and curve them to concentrate the sunlight to make up the difference. How far out can you go? Let's assume no one would want to build a habitat where the mirrors weighed more than the rest of the habitat (a totally arbitrary cut-off point). Earth-like conditions could still be sustained approximately 4 light-days from the sun. That's 10 times the distance of Pluto!
What are the implications for interstellar travel?
Interstellar travel is likely to be done in habitats very similar to what has been described here, and by people who have already been living in space for generations. The major difference is that instead of relying on the sun, they would have to take their power supply with them (probably in the form of antimatter).
Most significantly, space habitats make any solar system a candidate for settlement, not just the ones with Earth-like planets (or indeed any planets at all).
Anybody building there can clearly, if we have fusion to provide power which is an almost certain bet by then, hitch up a comet & using it to provide mass for an ion engine, set out for the next star on the left. At light days out they are 1/400th of the way in distance but in energy terms most of the way. It would take many decades to do it but any settlement that has gone 10 times further than Pluto is unlikely to be worried about separation.
I am not saying this is how it will be done. I don't think it is because there should also be the option of building much faster ships in the Earth Moon system & setting out on a 100 year journey, when it is possible that, within the next 50 years somebody is going to be able to do it at twice the speed doesn't seem likely. Nonetheless it could be done this way with science currently available or near term (fusion) & enough patience. The time limitation however wouldn't be important for sending out unmanned settlements to star systems where people were travelling by some faster system. It would be unlikely that any faster system would be able to compete at moving million ton settlements & mass settlement would go much faster if the first settlements were prepackaged.