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Would it be possible on the outer planets to use water vapour instead of Nitrogen for the bulk of the atmosphere? That would eliminate the problem of finding nitrogen and it would heat the planets surface to (hopefully) the level where the Water Vapor wouldn't turn back into ice.
Use what is abundant and build to last
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You suggest to breathe say dozens of miliBars of H2O. Under what temperarure?
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The normal temp. of air.
Use what is abundant and build to last
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Absolutely not possible. There is a limit to the amount of water vapor in the air, which is proportional to the temperature of the air. Its generally calculated via either the Goff-Gratch or Arden Buck equations. Though I have always looked it up in a table whenever it was necessary. Water vapor exists because water (or ice) is constantly in a state of equilbrium with its enviroment. A small amount of it constantly being evaporated/subliminated away while a similar (but smaller) proportion condenses back to water/ice.
However while the amount of water vapor in the atmosphere may be signifigant for a number of calculations (as is the rate of evaporation/sublimination of water/ice) it is no where near enough to produce a breathable atmosphere. Were talking kPa here. To produce a "breathable" atmosphere of water vapor you would have to raise the temperature above its boiling point, 100*C. Obviously we would have a hard time surviving in such an atmosphere, even if it was breathable. Which it probably wouldn't be, as the human bodies lower ambient temperature would probably result in the water condensing inside our lungs, drownding us. So you would be in the interesting situation of being able to be both roasted and drowned to death at the same time! What fun!
He who refuses to do arithmetic is doomed to talk nonsense.
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Austin, I'm not so sure it's "absolutely not possible". Perhaps you can clarify your statement.
What would happen if you had a hermetic dome, then brought in x tons of water ice, then used a vacuum pump to suck out nearly all the gases, then raised the temperature enough to melt the water ice? Wouldn't that produce an environment where the bulk of gas is water vapor?
For example, if the dome had 1Pa pressure from other gases (0.01millibar), the sublimation point of water ice would be (according to one phase diagram I found) approx. 220K. So heating the x tons of water ice to shirtsleeve temperature would produce x tons of water vapor as the predominant atmosphere of the dome.
Then, pump in some oxygen, and the original poster's question was, would it be feasible to breathe a mixture of say, 80% H20 and 20% O2? Or would we, I dunno, drown or something? Or would the two combine into H2O2 and bleach all our hair?
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Austin, I'm not so sure it's "absolutely not possible". Perhaps you can clarify your statement.
What would happen if you had a hermetic dome, then brought in x tons of water ice, then used a vacuum pump to suck out nearly all the gases, then raised the temperature enough to melt the water ice? Wouldn't that produce an environment where the bulk of gas is water vapor?
For example, if the dome had 1Pa pressure from other gases (0.01millibar), the sublimation point of water ice would be (according to one phase diagram I found) approx. 220K. So heating the x tons of water ice to shirtsleeve temperature would produce x tons of water vapor as the predominant atmosphere of the dome.
Then, pump in some oxygen, and the original poster's question was, would it be feasible to breathe a mixture of say, 80% H20 and 20% O2? Or would we, I dunno, drown or something? Or would the two combine into H2O2 and bleach all our hair?
As you apparently know the melting and boiling points of ice/water is dependent on the pressure it is under. So if you lower the pressure the water is under, the temperature it boils/subliminates at will decrease as well. So if you evacuate the atmosphere in a room containing alot of ice, you could possibly expect more of it to turn into vapor. However, if you decrease the pressure in the chamber by evacuating a portion of it (ie, removing the air, while keeping the volume constent) the temperature will also decrease, causing it to freeze again. In the end you will end up with relatively little water vapor and ice, as water exists in a fairly narrow temperature band and ice freezes readily.
But actually that is irrelevant to this discussion, as no matter the process you arrive at it at, you must in the end deal with an environment that is survivable by humans. That means something close to 1 atm and 32*C. At these temperatures and pressures the properties of water are fairly constrained. Only a tiny fraction of it can exist as water vapor (about 35 mm HG) and the rest must be plain water. If you started at different conditions the mix will reach equilibrium as you try (but fail) to bring it to human surviable mixtures.
He who refuses to do arithmetic is doomed to talk nonsense.
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So to put it concisely, if an area was pumped 100% full of water vapor and there was nothing else in the area, the gaseous H2O would automatically condense until only 35mmhg remained gaseous? No matter the ratios of H20/available volume? It would always gravitate, in any volume available, to 35mmhg of gas and the rest as water?
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So to put it concisely, if an area was pumped 100% full of water vapor and there was nothing else in the area, the gaseous H2O would automatically condense until only 35mmhg remained gaseous? No matter the ratios of H20/available volume? It would always gravitate, in any volume available, to 35mmhg of gas and the rest as water?
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So how much of the atmosphere can be H2O to produce a feedback of heat to keep the water as a gas? Would the temp. be survivable by humans?
Use what is abundant and build to last
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So to put it concisely, if an area was pumped 100% full of water vapor and there was nothing else in the area, the gaseous H2O would automatically condense until only 35mmhg remained gaseous? No matter the ratios of H20/available volume? It would always gravitate, in any volume available, to 35mmhg of gas and the rest as water?
Well not totally. Water vapor pressure does vary with both temperature and pressure (or possibly more precisely with the waters boiling point). As the temperature of water increases (or the pressure decreases) the vapor pressure increases until the water boils. In fact that is exactly what a liquids boiling point is, the point at which the waters vapor pressure equals the atmospheric pressure.
However, as I said previously this is quite irrelevent to the situation at hand. While waters vapor pressure maybe be somewhat variable at certain extremes, in a human livable atmosphere it is constrained to fairly small percentage of the air. The chart Karov posted is quite correct. If you want to have an atmosphere that people can survive in (ie something like 1 atm and 32*C), water will HAVE to be in the form that chart dictates. If you start with some exotic mixture of water vapor and bring it to human survivable atmosphere, you will simply fail to bring it to a breathable mix. The temperature will either have to be to high or the pressure to low.
In a human breathable atmosphere water vapor will always gravitate to its saturation limit for those conditions (which is always a small, but significant percentage). If you had more than this amount of water it would simply condense away. And if you had say a 100% water vapor atmosphere, you would not be able to bring this mixture to human livable conditions in any case. Look at the phase chart, if you want water vapor in large quantities, it lists the conditions it can exists at.
So how much of the atmosphere can be H2O to produce a feedback of heat to keep the water as a gas? Would the temp. be survivable by humans?
I'm not sure what you are trying to ask here, but water vapor pressures in a human survivable atmosphere are quite constrained. A quick google will give you a calculator or a chart. More then this percentage are you get condensation, like dew. To have more than this percentage (or partial pressure) of water vapor in the air, you have to heat the water/surrounding atmosphere. And to get and keep it at a significant percentage you have to raise it near waters boiling point, which is obviously not survivable.
If you just say boil some water without raising the atmosphere temperature, you won't get any kind of "feedback" the water will just condense back out of the air someplace else.
He who refuses to do arithmetic is doomed to talk nonsense.
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Would it be possible on the outer planets to use water vapour instead of Nitrogen for the bulk of the atmosphere? That would eliminate the problem of finding nitrogen and it would heat the planets surface to (hopefully) the level where the Water Vapor wouldn't turn back into ice.
I think that you don't have an idea about air humidity.Humans will suffocate with more than 90 perc. humidity.I once breathed air with 85 perc. humidity and it was hell.And I get a severe and painful mold invection of both of my ears.
And even at 100 perc. humidity you have just a few percents of it in the air.
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