> [xenon is] great for in-space propulsion because it’s fairly heavy (so you get more ooomph per atom)
More specifically, for a given exhaust velocity and grid spacing, the space charge limited thrust density (thrust/area) of an ion engine scales as the square of the mass/charge ratio of the ions. So you really want heavy singly charged ions. This is completely unlike thermal rockets, where you want low molecular weight exhaust gases.
Plasma engines that accelerate a quasi-neutral plasma aren't subject to space charge limits, but even there heavy ions help because they reduce the energy used in ionizing the propellant per unit propellant mass.
BepiColombo [0] uses 581 kg of Xe gas for its electric propulsion. I remember reading at the time this was being built that it consumed a measurable portion of the global xenon production for that year. This post reminded me to look that up, and it seems to be only ~1% of the ~50 tons, which is quite a bit less than I remember but still quite significant for a single application to use a non-trivial amount of the supply.
With Radon it might even be conceivably possible (not sure how hard it is to get and if any restrictions apply because of its radioactivity), and it would work for a few years, because it has a half-life of 3.825 days (EDIT: this is of course complete nonsense, the "." is a decimal point, so it will only work for a few days). In the quantities needed for a gas tube (and as long as it stays in the tube!), I guess it should also be relatively safe, but I'm not an expert. Apparently it produces red light when used in a tube. Oganesson however has a half-life of 0.7 ms, so, aside from how expensive it would be to synthesize enough of it, it's doesn't stay around long enough for any experiments...
I purchased one of the Lumora gas displays and it works well. Simple enough to build yourself (laser cut, 3d print) if you have the gas filled tubes. Fun to have my kids guess what color a gas will glow.
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[ 4.3 ms ] story [ 36.5 ms ] threadMore specifically, for a given exhaust velocity and grid spacing, the space charge limited thrust density (thrust/area) of an ion engine scales as the square of the mass/charge ratio of the ions. So you really want heavy singly charged ions. This is completely unlike thermal rockets, where you want low molecular weight exhaust gases.
Plasma engines that accelerate a quasi-neutral plasma aren't subject to space charge limits, but even there heavy ions help because they reduce the energy used in ionizing the propellant per unit propellant mass.
[0]https://sci.esa.int/web/bepicolombo/-/60642-bepicolombo-mtm-...
With Radon it might even be conceivably possible (not sure how hard it is to get and if any restrictions apply because of its radioactivity), and it would work for a few years, because it has a half-life of 3.825 days (EDIT: this is of course complete nonsense, the "." is a decimal point, so it will only work for a few days). In the quantities needed for a gas tube (and as long as it stays in the tube!), I guess it should also be relatively safe, but I'm not an expert. Apparently it produces red light when used in a tube. Oganesson however has a half-life of 0.7 ms, so, aside from how expensive it would be to synthesize enough of it, it's doesn't stay around long enough for any experiments...
https://en.wikipedia.org/wiki/Radon
https://en.wikipedia.org/wiki/Oganesson
People have be filling it with different gasses to get different colors.
https://www.youtube.com/watch?v=iXqbCmTt1Yg
https://www.aliexpress.com/item/1005007446864488.html
I'll get my coat