[Chemistry][Theory] Artificial Photosynthesis to replenish Oxygen

[MrZayas1]

The problem with space is always that we need resources, and those resources are all here on Earth. In order for humanity to move to become the first known extra-terrestrial inhabitants on another celestial bodies, we have to be able to utilize resources on other planets, or moons. One problem with this is that we have to be on the surface first to get these resources, and we currently do not have the money/budget to sustain or properly build an extra-terrestrial base. We are stuck in LEO, and the problem is: Oxygen (O2). Once oxygen is used up in the human bodies, it is replaced by Carbon Dioxide (CO2), which is routed through the extensive CDRA system on the Destiny module. This gives a slight return on oxygen, but it is not 100%. Eventually, without periodic refueling from Earth, the ISS can run out of oxygen. This can be a significant problem for deep space missions to Mars and other planets in our solar system, and we can't just stop at a gas station to refuel millions of miles from Earth. So what can humans do to counteract this problem? I have listed one below, and the pros and cons of it. Feel free to discuss your own theories as well, and maybe add to mine. Enjoy!

Plants

Pros:

Nice to look at.

Feels like home.

Gives oxygen from photosynthesis.

Cons:

Takes water.

Takes soil.

Needs light.

Possible fixes:

1:Sending unmanned crafts to near solar orbit with some resonance encounters with Earth in order to take advantages of Hydrogen (H) and use them to give space stations supplies of hydrogen that can be used to create water with oxygen. (Maybe you could freeze the two to make rocket fuel?)

2:Shipment of light hydrate gases to orbit for use in separation processes to create water which can be used for hydrogen and oxygen.

3:Some really hot source of energy to separate carbon dioxide into carbon and oxygen. (Nuclear reactor much?)

[Skyler4856]

Apparently electrolysis powered by an average sized nuclear reactor could generate 286,627,588.243 Metric tonnes of oxygen every year.

[MrZayas1]

Yes but where do you get that water from lol thats the biggest question in space science right now

[Bill Phil]

Hmm, maybe Genetically Modified Algae? It could also be a food source.

[Skyler4856]

Yes but where do you get that water from lol thats the biggest question in space science right now

Celestial bodies for one...

Edited December 13, 2014 by Skyler4856

[Bill Phil]

Planetary bodies for one...

Asteroids/comets, really. Landing on a planet and bringing up that much of any resource? Not anytime soon.

[MrZayas1]

Planetary bodies for one...

Well planetary bodies right now are out of the immediate question for resource utilization, we really don't have the infrastructure for a Europa water harvesting plant right now, then again, you could always do such things with a probe which makes me wonder why we haven't yet, but the answer of course, is money and fuel

[Skyler4856]

Asteroids/comets, really. Landing on a planet and bringing up that much of any resource? Not anytime soon.

Probably should have phrased that as "celestial bodies"

[NERVAfan]

Oxygen isn't the biggest problem, as it is pretty light - humans use something like 0.8 kg/day (or 0.63 kg/day depending on who you believe... it's probably pretty variable by activity level, body mass etc. anyway).

Plus it probably wouldn't be too hard to recycle oxygen with some algae.

Water recycling is much more important (and difficult, probably) as much more water is needed (especially when you count in bathing and such).

[MrZayas1]

Oxygen isn't the biggest problem, as it is pretty light - humans use something like 0.8 kg/day (or 0.63 kg/day depending on who you believe... it's probably pretty variable by activity level, body mass etc. anyway).

Plus it probably wouldn't be too hard to recycle oxygen with some algae.

Water recycling is much more important (and difficult, probably) as much more water is needed (especially when you count in bathing and such).

Hmm well in that case the hydrogen receiver close to the sun might work, seeing as oxygen isn't really as much of a problem as I thought it was.

[ZetaX]

Maybe someone wants to explain why making water from solar hydrogen is a good idea and why we presumably can just assume to have enough oxygen¿

Because making water would need oxygen (about 8 times as much, in regard to mass). Additionally, recycling water is pretty trivial if you have some energy to spare for destillation (and being close enough to the sun to collect hydrogen definitely means enough energy).

[Sandworm]

Maybe someone wants to explain why making water from solar hydrogen is a good idea...

It isn't. To collect hydrogen from the sun you have to fly through that hydrogen, slowing you down. The amount of fuel necessary to accelerate the craft, and the harvested hydrogen, to compensate for this drag would be more than the mass of the hydrogen collected. So it's almost certainly easier to just launch it from earth.

Not to mention the fact that getting close enough to the sun to find say 1000kg of hydrogen on a single orbit would melt most metals.

[ZetaX]

Well, as the second line was supposed to show, that was a rhethorical question to begin with^^

[EzinX]

You do this :

CO2 + 2H2 -> HCO2H + H2O

HCO2H -> CO + H2O

H2O -> 1/2H2 + O2

To summarize : react the C02 gas you isolated from the air (you can remove the C02 by refrigeration or using a regenerative absorber material) with hydrogen gas in the presence of a catalyst. Heat the water/methanoic acid mixture to high temperature. CO will bubble off. Electrolyze the water to hydrogen and oxygen.

That's phase 1. Now, phase 2 :

You need some method to crack CO to straight oxygen. Well, ..... 5000 degree kelvin is required. Ideas?

This process would work fine on Mars, though. So there is that. You can get limitless CO2 from the atmosphere of mars, strip off the oxygen, breathe it, scrub the CO2 from your habitat, recycle half the oxygen back to O2 and vent the rest as CO.

Edited December 14, 2014 by EzinX

[K^2]

Photosynthesis requires water anyhow. And plants are actually very efficient at consuming it. Complex plants do take in more water than they can use and evaporate excess to provide for capilary flow, but that water can easily be recycled in hydroponics. So it's not a problem. All of the water consumed is bound in glucose or its polymers and can be used as a food source. So you aren't actualy loosing anything by using real plants.

The other question is efficiency. It might be possible to build something artificial that's more efficient in terms of space ans weight. But it's hard to beat green algae for that.

[NERVAfan]

Yeah.

I really do not understand why an algae oxygen-recycling system hasn't been flown yet on ISS (or some earlier station for that matter). It could be pretty simple.

[K^2]

They might have some contamination concerns. It's also not exactly light. But a proof of concept could have been done.

[kerbiloid]

A human consumes 1 kg of oxygen per day, 400 kg per year.

Planets crust mostly consists of metal oxides: Mg+O, Al+O, Si+O, Fe+O.

Melting out every ton of a metal gifts a human-year amount of oxygen.

So if you have a large ground base (which is the primary aim of any colonization):

you anyway have an industrial tier,

you anyway mine thousands tons of metal oxides,

you anyway melt out thousands tons of metal,

you anyway get thousands tons of oxygen,

you anyway produce hundreds tons of industrial gaseous waste, especially carbon dioxide.

You have so much oxygen to breathe and so much carbon dioxide to utilize, that all these greenhouses look just ludicrous.

If you have a large orbital base without a ground facility: wait a minute, what for do you have it at all?

(ISS is just an appendix to the on-surface Earth industry.)

If you have ISS or another small three-cabin scientific forpost then chemical/electrical oxygene refinery is:

1) You can just switch it on/off.

2) Predictable: it can't be ill or unhappy, it can't give a bad harvest.

3) Repairable.

4) Scaleable: you may split it to ten mini-modules, and 8 of them will just produce 80% of the whole ten would. But you cant't split your aeroponics in such easy way.

5) If you get a wreck, it's more probable to find some electricity and/or chemical supplies to breathe a little; but it's doubtful that you can keep you greenhouse intact.

6) If you have guests, you can just use reserve refinery and easily increase you oxygen production.

7) No fungi, mildew or yeast will grow on it and then in you lungs (don't forget: any plant and substrate are lovely host for all such bio-feces)

So, I believe, all these "oxygene greenhouses" are just a fiction scenery, and nobody will ever build and use them  except for science or fun.

[lajoswinkler]

Planets crust mostly consists of metal oxides: Mg+O, Al+O, Si+O, Fe+O.

Melting out every ton of a metal gifts a human-year amount of oxygen.

Where would you get energy for all that? Also, a reducer. You need to melt those things first and those are refractory materials.

[kerbiloid]

Where would you get energy for all that? Also, a reducer. You need to melt those things first and those are refractory materials.

Until you have an energy plant, you would just drop supplies, as nowadays.

If you are going to build a large base, you anyway need refine construction materials in-situ. If you already do this, you already have a lot of bonus oxygen.

If your aim is a small scientific station, greenhouse will be their headache, not remedy.

[ZetaX]

So, I believe, all these "oxygene greenhouses" are just a fiction scenery, and nobody will ever build and use them  except for science or fun.

You may not need them for oxygen, but you need some source of food, and growing vegetables is one of the easier ways to get a sustainable food source. And if you do that you can take the oxygen that comes with it for free. It may even be necessary to use the human CO2 at places where there is no other viable source of CO2 (the moon, space).

[kerbiloid]

You may not need them for oxygen, but you need some source of food, and growing vegetables is one of the easier ways to get a sustainable food source. And if you do that you can take the oxygen that comes with it for free. It may even be necessary to use the human CO2 at places where there is no other viable source of CO2 (the moon, space).

Of course. But plants do not consume every gram of waste which you have feed them.

There is an ecological pyramide, and every next level of it needs ten imes more organics mass existing on the previous.

1 t of carnivore flesh need existing 10 t of herbivore flesh, which needs 100 t of plants flesh, which require 1000 t of soil humus. Not exactly, but you get the idea. You can ride a horse to a water, but you can't force it to drink.

So, for any greenhouse you need tons of organics per human circulating in system. And also you need to move cysterns of ammonia to Mars, of water - to Titan.

And also light sources, heaters, tubes, pumps. It would be a HUGE total mass.

Much easier to grow food where it grows without any interplanetary fertilizer transporting - on Kerbin or Earth, then sublimate it or else and just to send wherever you want.

[Kryten]

Whereas the machinery required to make a ton of metal per person per year is just fine to move about, is it?

[ZetaX]

Of course. But plants do not consume every gram of waste which you have feed them.

There is an ecological pyramide, and every next level of it needs ten imes more organics mass existing on the previous.

1 t of carnivore flesh need existing 10 t of herbivore flesh, which needs 100 t of plants flesh, which require 1000 t of soil humus. Not exactly, but you get the idea. You can ride a horse to a water, but you can't force it to drink.

So, for any greenhouse you need tons of organics per human circulating in system. And also you need to move cysterns of ammonia to Mars, of water - to Titan.

And also light sources, heaters, tubes, pumps. It would be a HUGE total mass.

Much easier to grow food where it grows without any interplanetary fertilizer transporting - on Kerbin or Earth, then sublimate it or else and just to send wherever you want.

There is ongoing and partially successful research on making self-sustaining biodomes including several humans. One of them would suffice.

You would need to make them somehow transportable, i.e. minimizing materials needed for walls, ground (including earth/dirt) and initialisation (you probably can't start with seeds only; but if you can, that sounds optimal). After that, fertilizer will come from the humans and possibly some smaller animals we need to stabilize the ecosystem; and maybe a small amount form chemical machines.

[kerbiloid]

Whereas the machinery required to make a ton of metal per person per year is just fine to move about, is it?

I'm afraid, to build a consistent colony needs much more than one ton per human, as this requires a lot of construction and machinery.

I believe, metallurgy and macjinery manufacturing would be primary aim of all this enterprise: just to bite into the ground and build a hard and protected industrial base equipped with a lot of machines.

Just your car weights about a ton of metal, and imagine that you are building a building on a planet where no other architectural materials except alloys of locally mined metals, restores from oxydes.

Probably, the oxygen would be not the first of you problems.

There is ongoing and partially successful research on making self-sustaining biodomes including several humans. One of them would suffice.

You would need to make them somehow transportable, i.e. minimizing materials needed for walls, ground (including earth/dirt) and initialisation (you probably can't start with seeds only; but if you can, that sounds optimal). After that, fertilizer will come from the humans and possibly some smaller animals we need to stabilize the ecosystem; and maybe a small amount form chemical machines.

In fact, that "biodome" (Biosphere-2) just have shown that you would need to be a sorcerer just to let 7 humans leave in balance with ecology.

Imagine, that they have left one part of their paradise because of plant-louse, or fire, or decompression.

Or imagine their plantation gave a bad harvest just because potato had disliked their fec... fertilizer.

So, to guarantee that they will not starve to death, first of all you must provide them with several times superfluous plantation than they indeed need.

To provide this paradize with fertilizer you will need (say, on Mars) store large ammonia cysterns  to produce nitrates, as by definition this plantation would need much more than all the crew can sh... produce even trying their best.

Why to bother about those puny several hundred kg of crew's "natural product"?

Just bury it at any place on the whole planet.

About what "self-sustained balance" can we say then?

Of course, if/when you build a whole city, and another probleam appears: remove all this biowaste, there will be also greenhouse  just as an easy way to convert bad things into good. But just as a support measure.

And, certainly, greenhouses as a game scenery look nice  as steampunk machines, for example, why not.