3 ms·

Turns out -- no, it permanently escapes to space with the help of the solar wind

by dmitrygr 6mo ago

stvltvs 6mo ago
Even if it didn't, collecting it seems wildly expensive.
- subscribed 6mo ago
  Or free if we managed to run solar powered sails (or so) skirting the very top and autonomously sending the harvest down.
  - krisoft 6mo ago
    If by “free” you mean “very very expensive” then i agree with you. It would cost a fortune to even just attempt a pilot project proving feasability. Then we would need to send up regular replacements to the “sending the harvest down” hardware at the minimum. Just imagining the cost of a tank which can be launched into space, autonomously dock with the collector sails, then deorbit and land makes my head spin. And then doing that at scale, paying people to launch it, paying people to operate the system. It could be free if we imagine some crazy advances in autonomous self-replicating spacecrafts. But by then we live in the post-scarcity diamond age probably.
    - subscribed 6mo ago
      I meant some semi permanent harvesters (which would cost a fortune to build and deploy). Sending the harvest down could maybe happen inside plastic containers built in place, made with the abundant sunlight, some Co2 and water (not sure if there's CO2 this high though. In retrospect we'd need also some metals to print some sort of the antenna reflecting radar frequencies (for the ground stations tracking them on the approach)? And with the hundreds of small containers (carefully balanced so they don't smash in the ground but slowly rain onto the area) maybe it'd be easier. I don't know. I think it's hard sci-fi, achievable within our lifetimes :)
zozbot234 6mo ago
The overall amount of helium in the atmosphere is still more than enough for the foreseeable future, and it could be extracted (albeit at high energy cost) by augmenting existing air separation units (ASU's). Of course natural gas wells currently provide an easier to extract source, seeing as the concentration there is way higher.
- deleted 6mo ago
  [deleted]
- nradov 6mo ago
  Helium is only 5ppm in the atmosphere. Extracting useful quantities of it that way will probably never be economically viable. In other words, if for some reason we can no longer get helium from natural gas wells then it will be cheaper to just let patients die instead of doing cryogenic distillation of helium from the atmosphere to run MRI machines.
  - zozbot234 6mo ago
    We are already separating out the majority elements from air via ASU plants, so we should compare the abundance of helium in what is left from typical extraction. And that looks quite technically viable, if obviously uneconomic at present.
    - ted_dunning 6mo ago
      This is a very good point. Oxygen, nitrogen, CO2 and argon make up 99.94% of the atmosphere. The remaining 0.06% has 5ppm is nearly 1% helium. That's up 200x from the original concentration and is well above the 0.3% that is sometimes quoted as the limit for economic extraction of helium (and well below the 7% of some natural gas). Furthermore, the leftover gas is also already cold. It is absolutely true that 85K isn't very close to the boiling point of helium, it is a lot closer than starting at the temperature of gas at the well head. The gotcha is almost certainly going to be that an ASU probably doesn't liquify most of the gas it takes in. That means that the exhaust gas will only be slightly enhanced.
dguest 6mo ago
Space is at the top of the atmosphere right? That place is full of stars producing helium by the teragram. GP ain't wrong, but the phrasing implied we'd have it closer by than it actually is.
- nomel 6mo ago
  No, they're entirely incorrect because they used the word "near". There is no practically usable helium near the top of the atmosphere. But, I'm also confident they were making a silly joke.
  - DoctorOetker 6mo ago
    Is this graph wrong? http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmosphere-composition-all.png http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos...
    - dguest 6mo ago
      I'd believe it. Wikipedia has a similar one [1] but it shows a bit more hydrogen than helium at higher elevation. Awesome graph! Worth stating that the increase in the relative fraction of He isn't so much because there's a lot of He out there as because there's a lot less of everything else. Overall density falls off roughly exponentially but lighter elements have a longer tail. So once you get out to a few earth radii quite a bit of what you see might be ionized helium but that doesn't mean you can do much with it. [1]: https://en.wikipedia.org/wiki/File:Chemical_composition_of_atmosphere_accordig_to_altitude.png https://en.wikipedia.org/wiki/File:Chemical_composition_of_a...
    - nomel 6mo ago
      > There is no practically usable helium near the top of the atmosphere. The context of this discussion and the fourth word in that sentence is important. Something existing isn't the same as something being practically available. That graph isn't wrong, percentage wise, but it's missing both density an cost per liter that makes it relevant to this discussion.
DoctorOetker 6mo ago
http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmosphere-composition-all.png http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos... the density is low though observe that where Helium becomes a significant percentage, there is also Hydrogen and (monoatomic) Oxygen. if one were driven by purism or vanity for stoichiometric exactness, then at a height of 1000 km theres 2 Hydrogens per Oxygen atom, so this could be reacted to water, and the energy used to power compression of the Helium, the water would freeze. without this vanity, helium becomes a significant fraction at much lower heights... and thus higher densities. The energy to compress becomes nearly insignificant at low pressures. if humanity ever builds space elevators, this will be one of many benefits of having space elevators.

Turns out -- no, it permanently escapes to space with the help of the solar wind

stvltvs 6mo ago

Even if it didn't, collecting it seems wildly expensive.

subscribed 6mo ago
Or free if we managed to run solar powered sails (or so) skirting the very top and autonomously sending the harvest down.
- krisoft 6mo ago
  If by “free” you mean “very very expensive” then i agree with you. It would cost a fortune to even just attempt a pilot project proving feasability. Then we would need to send up regular replacements to the “sending the harvest down” hardware at the minimum. Just imagining the cost of a tank which can be launched into space, autonomously dock with the collector sails, then deorbit and land makes my head spin. And then doing that at scale, paying people to launch it, paying people to operate the system. It could be free if we imagine some crazy advances in autonomous self-replicating spacecrafts. But by then we live in the post-scarcity diamond age probably.
  - subscribed 6mo ago
    I meant some semi permanent harvesters (which would cost a fortune to build and deploy). Sending the harvest down could maybe happen inside plastic containers built in place, made with the abundant sunlight, some Co2 and water (not sure if there's CO2 this high though. In retrospect we'd need also some metals to print some sort of the antenna reflecting radar frequencies (for the ground stations tracking them on the approach)? And with the hundreds of small containers (carefully balanced so they don't smash in the ground but slowly rain onto the area) maybe it'd be easier. I don't know. I think it's hard sci-fi, achievable within our lifetimes :)

zozbot234 6mo ago

The overall amount of helium in the atmosphere is still more than enough for the foreseeable future, and it could be extracted (albeit at high energy cost) by augmenting existing air separation units (ASU's). Of course natural gas wells currently provide an easier to extract source, seeing as the concentration there is way higher.

deleted 6mo ago
[deleted]
nradov 6mo ago
Helium is only 5ppm in the atmosphere. Extracting useful quantities of it that way will probably never be economically viable. In other words, if for some reason we can no longer get helium from natural gas wells then it will be cheaper to just let patients die instead of doing cryogenic distillation of helium from the atmosphere to run MRI machines.
- zozbot234 6mo ago
  We are already separating out the majority elements from air via ASU plants, so we should compare the abundance of helium in what is left from typical extraction. And that looks quite technically viable, if obviously uneconomic at present.
  - ted_dunning 6mo ago
    This is a very good point. Oxygen, nitrogen, CO2 and argon make up 99.94% of the atmosphere. The remaining 0.06% has 5ppm is nearly 1% helium. That's up 200x from the original concentration and is well above the 0.3% that is sometimes quoted as the limit for economic extraction of helium (and well below the 7% of some natural gas). Furthermore, the leftover gas is also already cold. It is absolutely true that 85K isn't very close to the boiling point of helium, it is a lot closer than starting at the temperature of gas at the well head. The gotcha is almost certainly going to be that an ASU probably doesn't liquify most of the gas it takes in. That means that the exhaust gas will only be slightly enhanced.

dguest 6mo ago

Space is at the top of the atmosphere right? That place is full of stars producing helium by the teragram. GP ain't wrong, but the phrasing implied we'd have it closer by than it actually is.

nomel 6mo ago
No, they're entirely incorrect because they used the word "near". There is no practically usable helium near the top of the atmosphere. But, I'm also confident they were making a silly joke.
- DoctorOetker 6mo ago
  Is this graph wrong? http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmosphere-composition-all.png http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos...
  - dguest 6mo ago
    I'd believe it. Wikipedia has a similar one [1] but it shows a bit more hydrogen than helium at higher elevation. Awesome graph! Worth stating that the increase in the relative fraction of He isn't so much because there's a lot of He out there as because there's a lot less of everything else. Overall density falls off roughly exponentially but lighter elements have a longer tail. So once you get out to a few earth radii quite a bit of what you see might be ionized helium but that doesn't mean you can do much with it. [1]: https://en.wikipedia.org/wiki/File:Chemical_composition_of_atmosphere_accordig_to_altitude.png https://en.wikipedia.org/wiki/File:Chemical_composition_of_a...
  - nomel 6mo ago
    > There is no practically usable helium near the top of the atmosphere. The context of this discussion and the fourth word in that sentence is important. Something existing isn't the same as something being practically available. That graph isn't wrong, percentage wise, but it's missing both density an cost per liter that makes it relevant to this discussion.

DoctorOetker 6mo ago

http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmosphere-composition-all.png http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos... the density is low though observe that where Helium becomes a significant percentage, there is also Hydrogen and (monoatomic) Oxygen. if one were driven by purism or vanity for stoichiometric exactness, then at a height of 1000 km theres 2 Hydrogens per Oxygen atom, so this could be reacted to water, and the energy used to power compression of the Helium, the water would freeze. without this vanity, helium becomes a significant fraction at much lower heights... and thus higher densities. The energy to compress becomes nearly insignificant at low pressures. if humanity ever builds space elevators, this will be one of many benefits of having space elevators.