To Terraform or not to Terraform?

[Gawdzilla Sama]

Overly complex.

And, btw, you can reduce the nitrogen in the mix by about 70%. Altitude sickness is a function of low oxygen, not low pressure.

Yeh, but I said that. If you lower the nitrogen, you raise the oxygen.
You would be living in a fire hazard, and it might be harmful long term.
And evaporation from the lungs would be much faster at low pressures, which might make you sick, even if you did drink more.

You don't increase the pressure, you decrease the amount of nitrogen in the atmosphere. This is not an over-oxgenated mix.

[mistermack]

You don't increase the pressure, you decrease the amount of nitrogen in the atmosphere. This is not an over-oxgenated mix.

I'm not with you. If you decrease one component, you raise the others. It has to add up to 100 percent. And I thought the objective was to enrich the oxygen level, to compensate for lower pressures?
The space station would give the best answer, they have the experience and know-how. That would give a good guide as to what humans need long-term.

[mistermack]

I just googled space atmospheres, and got a couple of answers.
(About Nasa Atmosphere)

(Space station on Wikipedia)

The one about Nasa is interesting, it describes some other problems, like emissions from humans and machinery that pollute an enclosed atmosphere.
And the Wikipedia one makes it clear they DO use a pressure of one atmosphere, so they must have a good reason for doing that.
I'm a bit surprised they don't use some reduction in pressure, but it must be a health issue, as the space station has to be very strong to hold one atmosphere inside.
.

[Gawdzilla Sama]

You don't increase the pressure, you decrease the amount of nitrogen in the atmosphere. This is not an over-oxgenated mix.

I'm not with you. If you decrease one component, you raise the others. It has to add up to 100 percent. And I thought the objective was to enrich the oxygen level, to compensate for lower pressures?

What is 100% of 3 psi O2 and 7 psi N2? Every lungful of air has more oxygen in it.

Your first article, I can't find the psi they work under. Your second article is Wiki. Do better.

[mistermack]

Without pressure, even neat oxygen isn't enough :

(Breathing at altitude)

I'm happy with wikipedia. If you think they have it wrong, best you show evidence for that. I wouldn't bet the house on it, if I were you.
.

[Gawdzilla Sama]

Without pressure, even neat oxygen isn't enough :

(Breathing at altitude)

I'm happy with wikipedia. If you think they have it wrong, best you show evidence for that. I wouldn't bet the house on it, if I were you.
.

You just said "not enough is not enough". Gee.

[mistermack]

You just said "not enough is not enough". Gee.

I don't think you really understand what you're debating. There are lots of sites that confirm what wikipedia says, that the ISS uses an air pressure of one atmosphere.
I'll list some more below, but I don't think you're particularly interested in the facts.
I'm very interested myself, that's why I read up on it, not to argue with you, but I'm still happy to share the results.
I find the inflatable pods interesting as a concept, that could well be the way to go, in space, on mars, or even under water, although they would need a lot of added weight under water.

(Link)

(Link)

(Link)

(Link)

[Gawdzilla Sama]

The ISS runs one atmosphere for the convenience of experimenters. The Apollo capsules ran on lower pressure.

And if you inflate an balloon at one atmosphere in 60 fathoms of water, how large will it get?

[mistermack]

The ISS runs one atmosphere for the convenience of experimenters. The Apollo capsules ran on lower pressure.

And if you inflate an balloon at one atmosphere in 60 fathoms of water, how large will it get?

Suddenly you accept the wikipedia figure. Suddenly you're an expert. But "lower pressure" is virtually meaningless.
Apollo missions were time-limited. Health problems of long-term missions weren't a factor. If you think people can live healthily for long periods at significantly lower pressures, you need to make to make your case. It seems NASA disagrees.

As far as an inflatable goes, it would depend on the strength of gravity of the planet, the density of the water, and the stiffness of the inflatable.
You would choose the depth that gave you one bar of pressure when fully inflated.
If the inflatable was strong enough to contain one atmosphere in space, it wouldn't need to be underwater, you could use it on the surface, but it would need to be much stronger, and very durable.

[Gawdzilla Sama]

The ISS runs one atmosphere for the convenience of experimenters. The Apollo capsules ran on lower pressure.

And if you inflate an balloon at one atmosphere in 60 fathoms of water, how large will it get?

Suddenly you accept the wikipedia figure. Suddenly you're an expert. But "lower pressure" is virtually meaningless.
Apollo missions were time-limited. Health problems of long-term missions weren't a factor. If you think people can live healthily for long periods at significantly lower pressures, you need to make to make your case. It seems NASA disagrees.

As far as an inflatable goes, it would depend on the strength of gravity of the planet, the density of the water, and the stiffness of the inflatable.
You would choose the depth that gave you one bar of pressure when fully inflated.
If the inflatable was strong enough to contain one atmosphere in space, it wouldn't need to be underwater, you could use it on the surface, but it would need to be much stronger, and very durable.

I haven't even looked at the Wiki figures, presumptuous one.

[mistermack]

I haven't even looked at the Wiki figures, presumptuous one.

That doesn't surprise me.

[ScholasticSpastic]

And if you inflate an balloon at one atmosphere in 60 fathoms of water, how large will it get?

To answer this question, one would need also to know the temperature of the balloon's environment, the gases used to inflate the balloon, and the masses of the gases (or we can lump the gas and its mass(es) together and express it as moles of gas). Assuming the gases will behave as ideal gases under those temperature and pressure conditions, I can come up with an approximation for you in short order- using the ideal gas equation.

PV=nRT

To solve for the volume of the balloon, rearrange to:
V=(nRT)/P

You've given us only the value for P (pressure). I'll also need n (number of moles) and T (temperature, in degrees Kelvin) to work the problem. V is, of course, volume. R is the gas constant and its value will depend upon the units for V and P. For gases, it's best always to work in degrees K, lest we wind up with negative results for pressure or volume- which cannot, logically, be negative. As K is never negative, it's the only temperature unit that'll work consistently.

We can simplify this problem for you by allowing you to give me a volume at the surface and holding n constant. In this way, you don't have to give me any information aside from an initial volume and temperature and a final temperature for me to crank out a final volume for you. If we assume that the temperature is constant, it becomes even easier: all you need provide is the initial volume.

I can have an answer for you within five minutes of you posting some values and me noticing that they've been posted.

[Gawdzilla Sama]

Empirically, it won't even inflate at one atmosphere. So building aquatic shelters out of balloons is a total fail.

[ScholasticSpastic]

Empirically, it won't even inflate at one atmosphere. So building aquatic shelters out of balloons is a total fail.

Balloons work in such a way that pressure within the balloon is equal to pressure outside the balloon. So yes, balloon environments under the sea would not result in 1-atm living environments by any stretch of the imagination. But they would still have volume- gases are compressible, but not infinitely so. The downside is that, at those pressures, we wouldn't be able to use any of that balloon space.

[Gawdzilla Sama]

Empirically, it won't even inflate at one atmosphere. So building aquatic shelters out of balloons is a total fail.

Balloons work in such a way that pressure within the balloon is equal to pressure outside the balloon. So yes, balloon environments under the sea would not result in 1-atm living environments by any stretch of the imagination. But they would still have volume- gases are compressible, but not infinitely so. The downside is that, at those pressures, we wouldn't be able to use any of that balloon space.

Remember, I said 60 fathoms. 360 feet down. It would not be a pleasant experience if one did get inside that balloon.