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What are some techniques/ways to provide enough oxygen for some manned mission that would last, say, years?

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I mean some arbitrary mission departing from earth to infinity and beyond... No particular destination, just in the opposite direction from the sun, and for a very, very long time. The passengers would remain inside the space ship, which would continue to wonder away from the earth indefinitely...

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Providing sufficient oxygen for a long journey is not the challenge. If you have enough to meet the demands for a week, you have enough to meet the demands forever. Oxygen is not destroyed or created in respiration Animals (people) take in oxygen where there are two atoms joined together and exhale Carbon Dioxide where there are is a carbon between the two oxygen atoms. On earth plants take in Carbon Dioxide keep the carbon, and release oxygen.

The challenge is two fold.

  1. Having enough oxygen to replace any that escapes from your vehicle

  2. Having enough energy to power the recyling system, which can be mechanical or biological.

See related questions

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    $\begingroup$ You are giving the impression that all of the oxygen breathed in ends up in CO2. It does not. It also ends up in water and many waste products. To recycle all of the oxygen would take a much more involved approach than just splitting CO2. Your statement on plants is not complete: plants take in carbon dioxide and water and sunlight, and release oxygen and store sugars. Even that statement is oversimplified. Recovering all of the oxygen breathed is a huge challenge. It's not just about preventing escape and providing energy. Those in fact are the two easiest to solve. $\endgroup$ – Mark Adler Nov 24 '13 at 20:39
  • $\begingroup$ @MarkAdler completely agree. some of that is addressed in links in the answer. But the totality of the complexities is beyond the scope of a single answer and beyond what (I believed) the OP was looking for. $\endgroup$ – James Jenkins Nov 25 '13 at 11:30
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Sure. Just replicate the ecosystems of the Earth and the power source of the Sun sufficiently to provide a closed cycle. The Earth and Sun are such a spaceship.

You can buy such closed systems (Sun not included) with plants, animals and bacteria.

ecosphere

They are called "ecospheres". They work thusly:

eco cycle

If you really want something "indefinite", biological systems are self-replicating, self-repairing, and will even evolve over time to better meet your needs if you cull the populations that don't meet your needs.

As for replicating the Sun if you're far from any star, that would require nuclear power in any practical system of long duration. You could use existing fission systems, or, we can hope, future fusion systems. And bring enough fuel. You could in theory collect interstellar hydrogen, but that is not likely to be practical. Truly "indefinite" is not possible, and is limited by the fuel you can bring or find. The same is true of our Sun.

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  • $\begingroup$ Cool. So about how much space would something like that take up so that it's big enough to generate enough oxygen for one human per "cycle" (day/hour/etc)? $\endgroup$ – rodrigo-silveira Nov 24 '13 at 5:19
  • $\begingroup$ Not known. A human-occupied ecosphere was attempted twice, but failed. $\endgroup$ – Mark Adler Nov 24 '13 at 5:41
  • $\begingroup$ You might want to add that to your answer, as this is a massively complex way to generate oxygen and a currently unsolved problem for anything larger than a toy. $\endgroup$ – Hobbes Nov 24 '13 at 17:11
  • $\begingroup$ For continuing "to wander away from the Earth indefinitely", it is currently the only solution that would recycle all waste products (not just CO2) and allow for a truly closed system that could work indefinitely. I would go so far as to claim the the eventual solution for generation ships will be the product of bioengineering (including genetic engineering), not chemical engineering. Bioengineered solutions reproduce themselves, providing their own maintenance. Chemical engineering plants are generally not self-reproducing or self-repairing. $\endgroup$ – Mark Adler Nov 24 '13 at 17:18
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    $\begingroup$ @Amber: by the way, your comment implies that the Earth biome is pointless, since the Sun will eventually run out of nuclear fuel. I would not contest that conclusion. :-) $\endgroup$ – Mark Adler Nov 24 '13 at 21:40

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