Buffer Gasses for Breathing Atmospheres

[penlu]

I was searching for a new buffer gas for use in spacecraft. Nitrogen is not as dense as most of the noble gasses, so I selected those as my targets. My results: the ratio of argon's ratio of expansion to that of nitrogen's was 1.21 (argon's ratio of expansion is 1:840, nitrogen's is 1:694), while argon's density was 1.7 times that of nitrogen. Argon isn't worth it.

I found that neon's ratio of expansion was an incredible 1:1445 and that its density is only 1.49 times that of nitrogen. The upshot of all that is that neon is about one-fourth better in terms of weight than nitrogen. Also, its critical pressure at room temperature is 2756 kPa, compared with 3350 kPa for nitrogen. So, neon is easy to store and weighs less than nitrogen for the same amount of gas. Why don't we use that instead?

Neon is a noble gas, after all. Plus, if there's an electrical short, the crew would have no trouble finding it .

 

[Kaito]

Probably has some adverse effects on our body that we dont even know. Nitrogen is in our atmosphere, so our bodies are used to it. Or maybe Nitrogen is easier to obtain, idk

 

[Linguofreak]

http://en.wikipedia.org/wiki/Breathing_gas

According to that article, neon is fairly expensive. Nitrogren, on the other hand, being a component of normal air, is dirt cheap, and since you probably won't be breathing it under high pressure on a spacecraft, narcosis is not a problem.

I don't think your buffer gas is a big weight concern anyways. Unlike oxygen, it's not used up by breathing, so you can just recycle it. Also, it's entirely possible to use a 100% oxygen atmosphere on a spacecraft. There's no fire risk as long as the pressure isn't too high, and you don't want the pressure to be very high anyways, since that will just be added weight.


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Probably has some adverse effects on our body that we dont even know. Nitrogen is in our atmosphere, so our bodies are used to it. Or maybe Nitrogen is easier to obtain, idk

Well, ironically enough, from what we do know, nitrogen is actually toxic at high pressure, and neon isn't. But since we're dealing with spacecraft, high pressure isn't a concern, and so the only factor is cost. And nitrogen is dirt cheap.

 

[jedidia]

I'd suggest Helium, just for the fun of it... :rofl:*imagine rising pitch towards the end of the sentence*

 

[JamesG]

Helium has been used as carrier gas in deep sea diving for many years, its use is quite well understood.

 

[Linguofreak]

Understood, but not needed for space travel.

 

[JamesG]

But its very light. Actually its not a very good spacecraft gas anyway, it will leak out thru just about any materal. Nice plain old nitrogen is fine.

100% O2 isn't a good idea either. Apollo-1...

 

[Linguofreak]

But its very light. Actually its not a very good spacecraft gas anyway, it will leak out thru just about any materal. Nice plain old nitrogen is fine.

100% O2 isn't a good idea either. Apollo-1...

That was under 16 psi at Earth's surface. The later Apollo flights used N2/O2 on the ground, but bled that mixture out on the way up, and used 5 psi of pure O2 in space. (I've seen one source that said 2 psi, but I find it a bit suspect)

It's the partial pressure of O2 that's a fire risk, so pure oxygen at low pressure is no more of a fire risk than a nitrogen-oxygen mixture at normal pressure. Air at 1 atmosphere is about 3 psi of oxygen and 11.45 psi of nitrogen (with about .3 psi of "other"). So 5 psi of pure oxygen is equivalent to about a 67/33 N2/O2 mixture at one atmosphere. And since lower pressure saves weight (both in atmosphere and in structure), the low pressure pure oxygen environment is better than the high pressure N2/O2 mixture. If you're absolutely phobic about fire, you can use a 40/60 N2/O2 mixture and have the same partial pressure of oxygen as in normal air.

 

[HiPotOk1978]

Neon is a noble gas, after all. Plus, if there's an electrical short, the crew would have no trouble finding it .

I must have laughed at this on and off for like 5 hours