One Small Breath For Man

An anonymous reader writes "The New York Times reports on a new technique that may allow Oxygen to be wrung from the soil on the moon. This may pave the way for a moonbase, and allow permanent habitation on Earth's only natural satellite." From the article: "Lunar soil brought back to Earth is in short supply and highly prized, so Nasa researchers have been using matter with the same composition for its tests. The soil contains about 45 per cent oxygen by weight, but it is mostly 'trapped' in the form of silicon dioxide ... At the moment, all oxygen supplies would have to be brought from Earth, which is so expensive and energy-inefficient that it effectively rules out a permanent Moon base. "

Comments

Re:Can this article be even more pretentios?

[mattmacf]

Read TFA:

To extract oxygen from lunar soil, scientists used a lens-like structure to focus sunlight on to it, heating it to 2,500C.

In Nasa's latest tests, a 12ft-wide dish was used to concentrate the sun's rays on to 100g of a substance similar to Moon soil. After a few hours, one fifth of the substance had turned into oxygen.

Now tell me, how hard was that?

Re:Please pay attention

[1u3hr]

Only the English are inconsistent with their acronyms where they capitalize BBC but not NASA. So much for the cradle of their namesake language.

That modded "informative"? How about "ignorant flamebait"?

The usual UK rule is to preserve caps when you pronounce the letters: (B-B-C) but to use normal case when you pronounce it as syllables. Thus: Nasa, UN, Nato, snafu, UK.

Still not terribly efficient...

[mattmacf]

I'm no chemist either but I did take a high school chem class a few years ago. I'm far from confident in my calculations, so feel free to correct me if I'm egregiously wrong, but AFAICT the amount of energy needed might be a limiting factor. Now, the article gives us two tidbits of information.

In Nasa's latest tests, a 12ft-wide dish was used to concentrate the sun's rays on to 100g of a substance similar to Moon soil. After a few hours, one fifth of the substance had turned into oxygen.

and

The soil contains about 45 per cent oxygen by weight, but it is mostly 'trapped' in the form of silcon dioxide.

Now assuming that one fifth of the 45% of the oxygen in the soil is 100% oxygen, we yield a total of 9g of pure oxygen. A quick trip to Google tells us that oxygen has a molecular weight of (roughly) 16. Therefore, 9g of oxygen translates to 0.5625 moles of pure oxygen. Another check of Google tells us that the volume of oxygen at STP is 17.36 x 10^-6 cubic meters/mole. We finish our Google-sponsored portion of this post by converting to give us 17.36 mL/mol. Multiplying by our previous result (0.5625*17.36) gives us a whopping 9.765 milliliters of oxygen. So how much exactly is that?

We continue our inquiry at the wonderful world of Wikipedia. We learn that the Earth's atmosphere is only 21% oxygen, so our 9.765 mL of pure oxygen effectively becomes 46.5 mL of normal air. Our final reference tells us that the average human breath exchanges 450-500 mL of air.

Putting this all together, we get a notably unimpressive result. The "few hours" that it takes to bake oxygen out of moon sand creates only enough oxygen to support one-tenth of one ordinary resting breath for one average-sized adult male.

I really hope I'm off by an order of magnitude or four, but unless I'm terribly wrong (entirely possible), this technology has a long way to go. The final line of the article does give hope, however: "Alternative methods to extract oxygen from Moon soil are also under investigation, including melting the rocks into a liquid and freeing oxygen with an electric current." Obviously NASA realizes this plan still needs work. Hopefully

Not Quite

[FasterthanaWatch]

The standard molar volume of most any gas is still 22.4 L/mol so 8g of Oxygen would be 5.6L of oxygen. Throwing in a ratio of 25% Oxygen, and we end up with over 20L of air.

Still not sure how you got that other figure, but perhaps it refers to the liquid form.

Re:Not Quite

[DeepStream]

I am a chemist, and the number you have for the molar volume is quite simply wrong (at least at STP). O2 behaves reasonably close to an ideal gas, and does in fact have a molar volume around 24L at STP.

If you think carefully about the numbers you got:
9g to 9.7 mL gives you a density of ~1 g/mL, which is that of water, not that of any gas at atmospheric T/P.

As a previous poster mentioned, you're much closer to getting 50L of breathable air (at 25% O2). While not a very large amount (1 cubic meter is 1000 L), 100g of rock isn't a whole lot either.

The simple fact is that SiO2 is about 50% oxygen by mass, and you can get a LOT more moon rock than you can either liquid O2 or water.