[HN Gopher] Starlink plans to use mercury propellant, 100s tons ...
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       Starlink plans to use mercury propellant, 100s tons expected to
       enter atmosphere
        
       Author : throwaway2048
       Score  : 12 points
       Date   : 2022-03-28 22:11 UTC (51 minutes ago)
        
 (HTM) web link (twitter.com)
 (TXT) w3m dump (twitter.com)
        
       | Gravityloss wrote:
       | Mercury is actually a very old electric thruster propellant.
       | 
       | Xenon is a later invention, revealed in public only after the
       | fall of the soviet union.
        
       | perihelions wrote:
       | This thread gives no evidence that SpaceX plans (or had ever
       | planned) to use mercury as an ion propellant. I don't think the
       | "Starlink plans" part of the title is justifiable. The "100s of
       | tons expected..." also looks counterfactual.
       | 
       | Starlink thrusters use krypton,
       | 
       | https://en.wikipedia.org/wiki/Starlink
        
       | aluminum96 wrote:
       | What is the impact of "hundreds of tons" divided over the world's
       | surface area? It of course sounds like a lot, but the Earth is
       | also quite large, so it's hard to know if these are trace
       | amounts, or large enough to have real health impacts.
        
         | wmf wrote:
         | AFAIK burning coal releases mercury and radioisotopes into the
         | atmosphere in addition to the CO2 and particulates that people
         | worry about but somehow we haven't banned coal.
        
           | paulryanrogers wrote:
           | Coal, much like alcohol and tobacco, is basically
           | grandfathered in. If it were newly considered as an energy
           | source with all the externalities we know now then it's
           | unlikely we'd use it so widely.
        
           | lgats wrote:
           | EPA estimates 50 tons a year from US coal plants. [1] Around
           | 8.5% of global coal consumption is from the US [2], so a
           | ballpark estimate would be 588 tons/year globally from coal.
           | I would guess this estimate is a bit low as there are EPA
           | standards to limit mercury emission by coal plants [3]. Top
           | coal consumers like India and China are likely to have less
           | mercury emission regulations, but I don't have a source for
           | that. US coal varies in mercury content by up to 3x [1] so
           | global mercury emissions are likely to be highly dependent on
           | coal sources.
           | 
           | [1] https://pubs.usgs.gov/fs/fs095-01/fs095-01.html#:~:text=E
           | PA%....
           | 
           | [2] https://www.worldometers.info/coal/coal-consumption-by-
           | count...
           | 
           | [3] https://www.epa.gov/mats/cleaner-power-plants
        
       | matheweis wrote:
       | This is an extremely editorialized title.
       | 
       | The thread is about a law firm that got a un resolution passed to
       | ban the use of mercury as a satellite propellant, on the basis of
       | a company that used it in their thrusters, that was in the
       | process of selling the tech to spacex.
       | 
       | What it doesn't say:
       | 
       | * whether spacex bought it or not
       | 
       | * whether spacex ever used it or not
       | 
       | * whether spacex still plans to use it or not
       | 
       | ... and if I'm reading it right, it sounds like the resolution
       | was passed, which ought to mean that spacex doesn't plan to use
       | it, because that'd be a violation of un treaty.
        
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       (page generated 2022-03-28 23:02 UTC)