sibeen said:
dv said:
sibeen said:
I think some of you should be reconsidering your stance on this. I have vivid memories of a thread on the SSSF called the Very Long Cylinder, or VLC for short, where it was comprehensively proved by the originating poster, whose name I have forgotten, that all you really need to do is put a cap on the top of the cylinder.
I remember a thread of that kind, but the original poster had the wrong end of the stick completely.
Are you sure?
scratches head
I thought he had overturned established science and convinced us all.
I definitely don’t remember the original. But my memory is imperfect, and this would have been back at a time when I was considering undersea desalination using the strategy that it requires less energy to pump 10 tons of fresh water from the sea to the land than pump 100 tons of salt water from the sea to the land.
mollwollfumble said:
The Rev Dodgson said:
> Before heating, the column of air inside the tube is in almost exactly the same state as the column outside the tube. After heating, the centre of mass moves up the tube a bit, but by the time you get to geostationary orbit level surely it would still be almost a perfect vacuum?
> Ya. It has to be pushed up from below, can’t be sucked from above.
> OK, there is no obvious problem pumping it up using an external energy source, other than the technical impossibilities of a continuous loaded tube up to geostationary orbit of course.
> Couldn’t enough oxygen be extracted from the various ice deposits near the south pole of the Moon?
> I think almost anything would be better than this, even extracting oxygen from rocks.
Agree with you all. Almost. Moon ice is too precious a resource to be used in this way, but yes, oxygen from rocks is the best strategy.
On the pure technical impossibility side, I’m beginning to think that a better strategy would be to dip the cold finger, cooler than 58 Kelvin, directly into the Earth’s upper atmosphere, some 80 to 90 km up where the atmosphere’s temperature is 200 Kelvin, and then when enough has been collected as solid haul it up then repeat. It can’t be collected as liquid because the pressure is so low that it would immediately evaporate.
This seems analogous to mining oil by freezing it subsurface and then lifting it on a conveyor belt – ridiculous – but it’s not a good analogy because liquid oil is less dense than the surrounding rocks whereas gaseous air is more dense than the surrounding vacuum.
> I watched a documentary about the huge volume of methane on a planet within earth’s solar system recently and while the methane could replace our earth energy resources’ needs many times over the viability of transporting the methane for use on earth simply wasn’t there.
Hold on! Transporting the methane to Earth is ridiculous. But transporting it to the Moon or Mars would make much more economic sense. Methane is food, or rather, it’s easily converted into food. Take the Moon for example, oxygen is easily extracted from rock but both hydrogen and carbon are rare. Yes I know there is some of both, a little ice and a little carbon in rocks, but both are very precious resources. To me it makes sense to transport methane, not water, to the Moon and Mars because hydrogen is rare in both places but oxygen is common as rock.