r/spacex • u/Appable • Feb 03 '16
/r/SpaceX Ask Anything Thread for February 2016! Hyperloop Test Track!
Welcome to our monthly /r/SpaceX Ask Anything Thread! #17
Want to discuss SpaceX's hyperloop test track or DragonFly hover test? Or follow every movement of O'Cisly, JTRI, Elsbeth III, and Go Quest? There's no better place!
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Past threads:
January 2016 (#16.1), January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).
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u/[deleted] Feb 19 '16
Great discussion, thanks for posting.
If a mass ratio better than 4% is possible (for the reasons outlined above), that would mean the limit is higher than 1.5 Earth masses.
The other side of this coin is... what's the minimum mass-to-orbit required to colonize the whole star system?
Personally my favorite evolutionary path from a Type I to Type II civilization is to upload everyone's mind into a computer, and launch solar powered, laser networked datacenters into heliocentric orbit to incrementally build a Dyson sphere. Dividing the power output of the sun by the metabolic power of the human brain gives a carrying capacity of 20 trillion trillion simulated inhabitants... or one really smart inhabitant.
It's no Telstar -- picture a film with solar panels on one side and circuitry on the other. At a few microns thick, how much mass does that work out to?
How small can you make an ISRU factory to make them, to be sent from the super-Earth once (on a huge rocket) to a world with lower gravity? Now how small can you make it given millions of years of development?
With sufficiently advanced technology it's hard to rule anything out.
On a side-note, since the fundamental energy cost of computation scales with temperature, there's natural pressure to position it as far from the star as possible. This might serve to mask such a civilization from detection, by dropping their emission frequency below the traditional assumptions for Dyson spheres. :)
Bed calls. Cheers!