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Space exploration pessimists say that there's nothing to import from space to Earth. So why not begin with doing exactly that?! :-)

It's commonly claimed that the vacuum of space is harder (emptier) than any vacuum created in a lab on Earth. So what about bringing a container to orbit, evacuate it to empty space, seal it and take it home as a perfect vacuum chamber? Would such a thing be in demand?

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    $\begingroup$ The cost of sending a payload into space is too high to justify returning literally nothing back. Earth-generated vacuums are sufficiently cheap and effective. In short, too much cost and too little benefit to justify it. $\endgroup$ – Paul Sep 29 '17 at 17:13
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    $\begingroup$ The container to trap a vacuum from space would definitely weigh a lot, and creating an effective vacuum on earth is much more efficient and cost effective. $\endgroup$ – Paul Sep 29 '17 at 20:32
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    $\begingroup$ If you bring a container into a high orbit and open it to evacuate it, you have to wait very long for a good vacuum. The probabibility for a molecule in the container hitting the walls is much larger than the probability to leave the container by the hole. The area of all walls of the container is much bigger than that of the open hole. You also have to wait for outgasing of the walls of the container. $\endgroup$ – Uwe Sep 30 '17 at 9:08
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    $\begingroup$ Whatever "uncontainer" you use will have walls which will outgas. $\endgroup$ – Dan Sep 30 '17 at 20:12
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    $\begingroup$ @Uwe Suppose you held it upside down and shook it? $\endgroup$ – Steve Ives Oct 1 '17 at 15:11
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There are multiple problems with this idea.

The first and most obvious problem is that the sealed container which has a perfect vacuum inside (seller claims so at least) is not of much use until you can put something inside (experiment, material, ...). And when you do that, you unavoidably get some gas inside with it, which ruins your perfect vacuum.

You could avoid that problem by putting things into the box first and then open it in space. But there is usually hardly any advantage compared to running the whole experiment in space and only bringing back the results (which will often be just immaterial data which you do not need to land softly).

But let's stick to the idea for a while. Let's connect some airlock to the perfect vacuum chamber to put things inside later. This can work... sort of. The problem is that a better vacuum usually means that the pressure is lower by at least an order of magnitude than what we can create on Earth. If your vacuum is not at least an order of magnitude better than the one we have, then usually nobody would care. So, if you can pump down the airlock to your laboratory's ultimate vacuum pressure, and you want to gain at least one additional order of magnitude, the perfect vacuum container needs to have at least ten times the volume of the airlock. And you can only use it that way once. That's not very practical.

Anyway, the real show-stopper is the fact why we can not create a perfect vacuum in laboratories on earth. It turns out that the problem does not lay in the vacuum pumps. The problem is that the container itself ruins the vacuum. You can build an almost perfect vacuum pump, quite similar in effect to connecting an infinitely large container with a perfect vacuum to your experimental chamber. You just need to cool down the chamber wall to a really low temperature (think liquid helium or below). Then any particle hitting this wall just sticks there -- effectively equivalent to the situation when it would continue into an infinitely large empty container.

But such a perfect pump would still not create a perfect vacuum. Every piece of material you use to build your chamber, experiment etc. is continuously outgassing lots of gas ("lots" in terms of an ultra high vacuum where a few thousand particles per cm³ is considered a lot). So the resulting pressure is kind of an equilibrium between outgassing flow and pumping flow. In order to get a better vacuum, you usually need to pump faster, not "better". (And use containers and materials releasing less gas, of course.) And you need to pump out lots of gas (again, "lots" in the terms of an ultra high vacuum, but still a lot compared to the amount of remaining gas present in one moment inside the evacuated chamber), especially for a sustained vacuum. And a container with a perfect vacuum is not a good vacuum pump in these terms.

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  • $\begingroup$ Or you simply use a series of airlocks when introducing test objects into the recovered space vacuum chamber. From best synthetic vacuum to the first space vacuum chamber. Then from there to the next space vacuum chamber and on. Sure, there'll be some dilution, but it would be better than what could be produced artificially. If there are ridiculously sensitive experiments that demand such hard vacuum. Seems to be no lack of ideas. $\endgroup$ – LocalFluff Sep 29 '17 at 20:15
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    $\begingroup$ Series of airlocks won't help much (maybe someone can calculate theoretical maximum, but it will be less than order of magnitude for sure). And all these airlock-separated compartments have to be evacuated to the "space-grade" vacuum, so extra weight etc. But anyway real problem is outgassing, any real vacuum chamber have to be continuously pumped just because of this. $\endgroup$ – Martin Sep 29 '17 at 20:49
  • $\begingroup$ @LocalFluff The vacuum in the series of airlocks would be destroyed by outgassing of the chambers and airlocks. $\endgroup$ – Uwe Sep 29 '17 at 21:16
  • $\begingroup$ So one can't keep a bubble of vacuum in a container, not any better than a pump can maintain it? Then, nothing isn't portable. $\endgroup$ – LocalFluff Sep 29 '17 at 22:22
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    $\begingroup$ @njzk2 the flow of atoms leaving the walls by outgasing is a flow of gases like nitrogen or oxygen, not of atoms of iron, aluminium or titanium. Outgasing will decrease with increasing time. $\endgroup$ – Uwe Oct 1 '17 at 9:21
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According to WP, at the upper end of Earth thermosphere -- that's LEO, somewhere above the orbit of ISS -- the pressure goes to around $1 \times 10^{-7}$ Pa.

This level of vacuum is regularly achieved on Earth, with MBE chambers going down to around $1 \times 10^{-10}$ Pa.

To get a better vacuum you'd need to get quite a bit farther from Earth.

In any case, there's no practical use for "bringing vacuum back". If you bring back a perfectly evacuated chamber of volume $v$ and connect it to your vacuum-requiring-experimental system of equal volume, you only drop the pressure by 50%. To make a significant difference, you'd need to bring back an enormous pressure vessel.

It would make much more sense to send your experimental rig or your MBE or EBL system up into space and do your experiments or production in orbit.

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  • $\begingroup$ If you bring home enough vacuum (if it makes sense to say so), you could dilute the best Earth artificial vacuum by several times in series putting the test article through "collected" space vacuum chambers. If an experiment such as the LIGO gravity wave detector would benefit from more perfect vacuum, it might be easier to bring space down here than LIGO up there. $\endgroup$ – LocalFluff Sep 29 '17 at 20:23
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    $\begingroup$ I’m saying that sending LIGO up is easier than sending a pressure vessel many times larger than LIGO up, bringing it back down, and putting LIGO into it. $\endgroup$ – Russell Borogove Sep 29 '17 at 20:30

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