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This answer to Why will Starlink satellites use krypton instead of xenon for electric propulsion? says:

I expect they did the math, and found that overall cost was less, even with reduced thrust/watt efficiency, reduced thruster life and increased tankage and solar string mass. The cost of xenon is huge, and supply is very constrained. When NASA builds a craft, they have to stretch their fuel purchase over several years. SpaceX probably can't afford to wait that long or spend that much. They may use xenon for a longer-lived, more slowly deployed second generation satellite.

Question(s):

  1. How much of the world's xenon supply has been used in spaceflight altogether? What's the total kilogramage sent above the karman line?
  2. Is it a lot? Does spaceflight make a dent in the amount of available xenon in the world?
  3. Did it cost a lot? Did NASA take out a mortgage in order to pay for its xenon, "stretch(ing) their fuel purchases over several years"?

Related and sources available in both posts and in comments; good info and links regarding the economics of xenon in spaceflight:

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    $\begingroup$ While still new to matters chemical/physical, and despite my dad's foisting on me all manner of his employer's CANDU promotional materials, I still couldn't fathom why all the world's He hadn't boiled away megamillenia ago. This question may fall into the xkcd "what if" classical poser of what happens when you divide infinity by infinity. He's fallen silent of late. Ergo, +1. $\endgroup$
    – Camille Goudeseune
    Jun 2, 2021 at 3:21
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    $\begingroup$ @Camille There's a fair bit of He in the mantle, about 7% of it's primordial. See physics.stackexchange.com/a/548063/123208 & the attached comment thread. $\endgroup$
    – PM 2Ring
    Jun 2, 2021 at 11:45
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    $\begingroup$ Thank you for saying “kilogramage” and not “poundage”. Metricans of the world, unite :D $\endgroup$
    – user39728
    Jun 3, 2021 at 23:17
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    $\begingroup$ Mars would be terraformed with a thriving civilization by now if we’d switched to metric two centuries ago, my metric calculations suggest. $\endgroup$
    – user39728
    Jun 3, 2021 at 23:27
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    $\begingroup$ There is a simple English word instead of kilogramage : mass $\endgroup$
    – Uwe
    Jun 4, 2021 at 17:02

1 Answer 1

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According to Wikipedia's article about xenon, the gas occurs at 87 ppb (parts per billion) by volume in Earth's atmosphere. Earth's atmosphere weighs 5.15×1018 kg. Dividing this by the density of air (at sea level) gives us 4.207×1018 m3 of air if it were all concentrated at sea level. Multiplying this by the concentration of xenon leaves us with 3.65×1011 m3 of xenon gas. The density of xenon is 5.89 kg/m3, so we end up with 2.15×1012 kg of xenon gas in the air.

This is definitely enough for whatever you want, so what's the issue?

Well, it's still very rare. The only reason there is so much xenon is that there is so much air in general. If you collect 1000000 L of air, you only get 87 mL of xenon gas. This means that it is very slow to manufacture xenon. This probably accounts for its incredible price of 1800 USD per kilogram. It is produced as a byproduct of purifying N2, O2, Ar, and CO2. Krypton is far more common (~1 ppm, over 10x that of xenon), and is produced with similar strategies, so it is a lot cheaper than xenon, at 290 USD per kilogram. SpaceX is launching Starlink very fast, so they can't wait for a suitable xenon supply to show up. Xenon is commonly used only because it has a higher performance.

I had trouble finding exact numbers for the amount of xenon ever launched, but it is probably in the 1000-10000 kg range. The Dawn spacecraft alone used 425 kg of xenon, costing about 765 thousand dollars! Also all-electric propulsion communications satellites in GEO are becoming popular.

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