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The "Crown of Nobles" Noble Gas Tube Display (2024)

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Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#31

Post by sandworm101 »

hydrogen7800 wrote: post #29
pfdietz wrote: post #2

> [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 wei…

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 sup…

I think it might have taken a larger percentage of high-grade ultrapure xenon, a narrower market than the global bulk supply. A 1% impurity is fine if you are using xenon for welding, not so much if you are firing zenon plasma at a grid carrying a few hundred volts. A little bit of o2 in there and your grid would be rust very quickly.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#32

Post by pfdietz »

sandworm101 wrote: post #31
hydrogen7800 wrote: post #29

Earlier quoted context omitted.

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 sup…

I think it might have taken a larger percentage of high-grade ultrapure xenon, a narrower market than the global bulk supply. A 1% impurity is fine if you are using xenon for welding, not so much if you are firing zenon plasma at a grid carrying a few hundred volts. A little bit of o2 in there and your grid would be rust very quickly.

Does anyone use xenon for welding? Argon, yes, but xenon is five orders of magnitude less common in air.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#33

Post by michaelcampbell »

fhdkweig wrote: post #18
stavros wrote: post #15

Earlier quoted context omitted.

It's amazing that we're getting this now, I don't understand what the prompt was that made the AI take offense at the closed PR, but I also must say, it does have a point. I don't blame the maintainer, though, I think it's a very understandable reaction to close the PR.

If I am understanding it right, the maintainer wants human-readable, human-maintainable code even if it is slower than the AI output. As someone who has to maintain someone else's "clever" code, I have to agree with him.

And there are specific "low impact" easy issues that they want humans to solve, so they can get experience and become better devs.

Having the AI do all the easy grunt work removes that ability.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#34

Post by sandworm101 »

pfdietz wrote: post #32
sandworm101 wrote: post #31

Earlier quoted context omitted.

I think it might have taken a larger percentage of high-grade ultrapure xenon, a narrower market than the global bulk supply. A 1% impurity is fine if you are using xenon for welding, not so much if you are firing zenon plasma at a grid carrying a few hundred volts. A little bit of o2 in there and your grid would be rust very quickly.

Does anyone use xenon for welding? Argon, yes, but xenon is five orders of magnitude less common in air.

You could. It is heavier and so can carry more heat. There may be some specific metal/tool combo where that might be needed.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#35

Post by pfdietz »

sandworm101 wrote: post #34
pfdietz wrote: post #32

Earlier quoted context omitted.

Does anyone use xenon for welding? Argon, yes, but xenon is five orders of magnitude less common in air.

You could. It is heavier and so can carry more heat. There may be some specific metal/tool combo where that might be needed.

Inert gas in welding isn't used to carry heat, it's used as shielding to prevent oxidation, nitridation, and ingress of hydrogen. In any case, the heat capacity of the noble gases are almost identical. What xenon might do is reduce diffusion of heat away from the weld, as its thermal conductivity is just 1/3rd that of argon.

In practice I think a combination of argon and CO2 is typically used for inert gas welding of steel.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#36

Post by skykooler »

pfdietz wrote: post #35
sandworm101 wrote: post #34

Earlier quoted context omitted.

You could. It is heavier and so can carry more heat. There may be some specific metal/tool combo where that might be needed.

Inert gas in welding isn't used to carry heat, it's used as shielding to prevent oxidation, nitridation, and ingress of hydrogen. In any case, the heat capacity of the noble gases are almost identical. What xenon might do is reduce diffusion of heat away from the weld, as its thermal conductivity is just 1/3rd that of argon. In practice I think a combination of argon and CO2 is typically used for inert gas welding of…

It depends on the process. Argon/CO2 is used for MIG welding, while TIG generally uses pure argon. In some situations that justify the expense, helium is used instead as it allows deeper weld penetration.

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#37

Post by bandrami »

pfdietz wrote: post #2

> [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 wei…

Isn't getting nobles to actually ionize pretty energy-intensive though?

Re: The "Crown of Nobles" Noble Gas Tube Display (2024)

#38

Post by pfdietz »

bandrami wrote: post #37
pfdietz wrote: post #2

> [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 wei…

Isn't getting nobles to actually ionize pretty energy-intensive though?

Sure, but one still has a savings if one goes to heavier noble gas elements over the lighter ones. The noble gases are used because they don't contaminate spacecraft surfaces.

About the only place I can think of in a plasma engine where you'd want to use light elements is if the engine is thermal: making a confined plasma, heating it to very high temperature, then expanding it through a magnetic nozzle. There, you'd want to use hydrogen to minimize radiative losses from the hot plasma, especially vs. using a plasma containing partially ionized atoms of higher atomic number elements; these can radiate fiercely.

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