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> put them in high orbit so they do useful things in local night, limiting you to a small total count planet-wide Geostationary orbit is a circle over the equa

• ben_w 5y ago
  I think you’ve misunderstood the problem I’m describing, so I’ll see if I can rephrase. The limit is not how many physically fit in geostationary orbit — I agree that’s fine — it’s that if more than one such system is in your sky (Edit: that is, above your horizon) then you need to care what happens if all the different ones in your sky (above your horizon) target your location at the same time. >> put them in a low orbit [...] worry about multiple orbit-to-ground beams being directed at the same spot That ellipsis is combining different scenarios.
  • T-A 5y ago
    > you need to care what happens if all the different ones in your sky (above your horizon) target your location at the same time No, you don't need to, because they don't need to. >>> put them in a low orbit [...] worry about multiple orbit-to-ground beams being directed at the same spot >> >> That ellipsis is combining different scenarios. Only if you insist that "about half a dozen giant ground-station for half a dozen giant beams" is the limit for what can be put in geostationary orbit, which you now seem to acknowledge is not true.
    • ben_w 5y ago
      I don’t understand how you can assert what you’re asserting, especially as you appear to be claiming to read my mind despite the paragraph break you cut with the ellipsis. Hypothetical scenario: 1000 satellites evenly arranged around geostationary orbit, each beaming 1 GW to a ground station. Now hackers point all the ones visible to NYC at NYC. How do you guarantee this does not happen? I can only think of two options: (1) small number of big satellites (down side being centralisation); (2) low orbit (downside being no nighttime power because they’re now in shade at local night). I say you must not allow this hypothetical to happen. This is a safely limit, and it never has anything to do with the volume of the orbit. It is still a limit.
      • T-A 5y ago
        > Now hackers point all the ones visible to NYC at NYC. What you just did there is called moving the goalposts. The discussion up to that sentence was about constraints imposed by orbital geometry. You claimed incorrectly that the "limited" space available in geostationary orbit would allow "up to about half a dozen giant ground-station for half a dozen giant beams", concluded that it would therefore be necessary to use LEO instead (it's not), and (again incorrectly) jumped to the conclusion that this would necessarily imply multiple beams on the same target. Neither you nor anybody else said anything about sabotage. > This is a safely limit, and it never has anything to do with the volume of the orbit. Actually you just threw away your original argument and made up a whole new one. > How do you guarantee this does not happen? I don't. I also don't guarantee that terrorists won't fly airliners into skyscrapers or put a nuclear device in a container and ship it to New York's harbor. Yet we keep building skyscrapers, flying airliners and shipping containers across the world, despite the obvious risks, because the advantages of doing so outweigh those risks. The specific risk in question is not even all that hard to mitigate, especially when you're dealing with large stations in geostationary orbit, each targeting a limited set of fixed locations (which would be dedicated receiver arrays, not cities). You put fail-safes on station which are hardwired to track antenna orientation and shut down the beam if it strays from its target. Now all your hypothetical hackers can do is interrupt the beam until you regain control, which is irritating but nothing new: https://en.wikipedia.org/wiki/Ukraine_power_grid_hack https://en.wikipedia.org/wiki/Ukraine_power_grid_hack