A few questions:

What kind of pressure exists in the vacuum of space? 0 psig? Positive Pressure? Negitive Pressure? What would gauge pressure read for psi.?

What kind of pressure exists inside current spacecraft? psi? Atmospheres?

What mixture of gasses are used for breathing inside current spacecraft?

What mixture of gasses are used during spacewalks? How is this supplied?

Thanks

Lamphater,
The Q&A forum might work better to get answers to your questions.


As far as your first question, in most of space, the pressure would be essentially 0 psi. Depending on exactly where you were (for example, how close to a planet with an atmosphere, on in the solar wind from the sun) and how precise your gauge was, you might get readings of 10^-11 to 10^-20 Pascal.
One reference

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Swift,

Thanks for the reply and the link. This answers one of my questions.
I am sorry if I posted in the wrong spot. My questions relate to humans living in space and I was unsure as to where to place it. Perhaps Q&A will give better results.

Hi, You are currently breathing at 14.7 lbs per squre inch. Luxury.
Building a pressure vessle that will hold that much pressure is indeed difficult.
You notice the differnce when you are at mile high in Colorado.
Space is difficult.
Best regards,
Dan

I understand atmospheric pressure on earth.
I was wondering about the pressure inside current space craft?
I was also wondering about the mixture of breathing gasses inside the spacecraft and during spacewalks.

Building a pressure vessel that will hold 1 ATA is not difficult.
We currently have human occupied pressure vessels here on earth that can handle 50x that.

In addition:
What you are feeling at high elevations on earth is a lower o2 level.

true, but there is less of every other gas as you go up higher, too, which means less pressure on you.

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True, I understand this well.
Less O2 because of less pressure, less of other gasses because of less pressure. Less 02 is what is "noticed" along with perhaps a slight adjustment in the nasal cavity.

There are other problems you may notice due to long exposure at high altitudes directly related to lower gas pressure but I really am interested in my original questions and would like to get back on topic.

from the wiki on the IIS located at http://en.wikipedia.org/wiki/Interna..._Space_Station

from the wiki on space suits located at http://en.wikipedia.org/wiki/Spacesu...ating_pressure
wikipedia is a pretty cool place.

You're kidding, right? Scuba tanks hold 3,000 psi...

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I believe pretty much everything these days (ISS, Shuttle, Soyuz, Shenzhou) normally keep around sea level pressure.

Oxygen/Nitrogen.

Oxygen. Suits are kept at lower pressure than the spacecraft to make it easier to flex joints (limbs, hands).

Oxygen tank or hose.

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For general background on space life support, see http://www.projectrho.com/rocket/rocket3g.html

Think he meant one big enough to live in.

You have to consider pressure and area. On submarines, we have high pressure compressed air at pressures well beyond 3000 lbs. How big are the lines that carry it? Hmmm.......less than a 1/4 inch. Area ,son, I say area.
That's what it's all about,ya see? (Foghorn Leghorn lecturing on engineering).
Making a strong enough pressure vessel "To Live In" , is quite an engineering chore. And it has to be LIGHT ENOUGH,See? LIGHT WEIGHT. It is the very essence of aviation engineering and especially Aerospace engineering.
The bigger something gets under pressure, the more it wants to disintegrate.
Yes, you can make it stronger, but....can you boost it into space?
Can you move it some place besides LEO? Ha! Can you "Land" it somewhere????????? Now you have set for yourself a genuine problem.
And this one isn't going away any time soon.
Dan
PS: Oh....by the way: A space craft in a vaccuum has the equivalent of 30 lbs. per square inch as compared with the same vessel on Earth.
Now you've heard..............the rest of the story.
Good day.

While it's true the stress goes up as the tube radius increases for any given pressure and wall thickness, the university I attended had some rather large high-pressure tanks used to supply air for the mach wind tunnel. I don't recall the exact pressure, but I do recall it was in the thousands.

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Using Wikipedia and Wolfram Alpha I get for the cold/warm neutral interstellar medium somewhere in the range of 10^-19 atmospheres of pressure. (A few times 10^-14 Pascals.) Give or take a few...

Hi, Yes, a very nice tunnel. And it weighed...........how much? And it moved
where ? And it was boosted how far and at how many gees ?
About the best heavy duty pressure vessel we have launched into near orbit is the main engine tanks of the Space Shuttle. Boost the a little bit more and you have the makings of a darn good envelope. Gotta clean it and build something inside....but... I bet Werner Von Braun would like the idea.
Best regards,
Dan

The last I heard pressure in low Earth obit is about one millionth PSI About because most gauges don't measure that low = read zero, so pressure must be inferred from how many particles per minute hit a target of perhaps one square inch and estimates of their speed, complicated by the target moving almost 18,000 miles per hour, with respect to Earth's surface.
The pressure in the space shuttle drops to about 10 psi with the oxygen enriched from 21% to about 25% in orbit. About the same for ISS. Mir was lower pressure: about 7 psi with oxygen enrichment at about 50%. Lower pressure is possible, and is used for EVA = extravehicular activities = space suits, but water vapor is low, and causes chapped lips, condensation and other problems.
psig = pounds per square inch with a gauge can read as much as negative 15 psi in a vacuum container at sea level, but this this terminology is rarely used in orbit or even for high flying aircraft so we could say there is no such thing as negative pressure.
I don't think any humans have been subjected to 100 atmospheres. 50X maybe. The container would be very costly, but I suppose a few have been built that would just barely hold one human. 100 atmospheres would be fatal unless approached gradually over many hours, and even more hours to return to one atmosphere even breathing helium or hydrogen instead of nitrogen. Apparently helium and hydrogen are less likely to produce bubbles in the tiny capillaries, which causes bends. Some of the above is guessing, so please correct where I am wrong. Neil

I would like to thank everyone for all the excellent responses and answers.

So my understanding now:

Pressure in space? 0 psi generally.
Pressure in current spacecraft? 1 ATA or 14.7 psi
Breathing mix in spacecraft? Air or basic NeO2
Breathing mix in spacesuit? O2 with higher Partial Pressure because of lower suit pressure of around 7 psi

I now wonder how Co2 is scrubbed and if gasses are reclaimed?
Gasses obviously are taken onboard compressed, but I wonder if cylinders are similar to ones used on Earth?

Makes me wonder how the space station is re-supplied or Mir?

Helium and Hydrogen off gas at a faster rate than nitrogen. Leaving less saturated inert gas in the body when decompressing.

Subjecting humans to 60x atmospheric pressure is about the limit.
Many have been built that can hold 4, 6, or 12 persons.
100x is out of the question. It makes little difference how fast a human aproches said pressure but decompression can take weeks not hours.

These Saturation Systems, as they are called, are used every day in the underwater construction business. And yes quite costly; for every man in the can you can add $1,000,000.00 in consruction cost.

This I know about, hence my interest in living in space.

Well as I understand it the current scubbers in space craft are something use something like lithium hydroxide. As CO2 passes over the lithium hydroxide the result is Lithium Carbonate and Water. You could then use electrolysis to reclaim the Oxygen at that point. I believe the Lithium Carbonate can be transformed back into Lithium Hydroxide but you need to use the same amount of water to do so. I don't know if there is any pure electrolysis method of scrubbing CO2 directly

That's a bit high, unless there's been something new. US EVA suits are about 4.3 psi, I think the Russian Orlon is about 5.8 psi.

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Ne is neon which could be used, but I don't think neon is ever used for breathing. N is nitrogen.
I agree, 7 psi in a space suit would make movement difficult. Wickipedia says 4.7 psi. If 4.3 psi is correct, that accounts for the astronaught wareing the suit for a while before the EVA to get most of the nitrogen out of the lungs and suit. 100% oxygen may be close, but not correct as there needs to be some water vapor. The 5.3 KPa (40torr) of carbon dioxide seems way high, even for the maximum allowed. The 6.3 KPa (47 torr) of water vapor likely exceeds 100% relative humidity, so that number is also suspicious. 6.89 KPa per psi agrees with my calculator. Pa must be new terminology as it is not in my 1976 conversion tables. One torr = one millimeter of mercury. If you guys can invent a few thousand new units of measurements, we can confuse everyone with an IQ under 150. Neil

Resupplying Mir would be quite the challenge, it being burned up and all Resupply for ISS is done by carrying stuff on the Shuttle, and with unmanned freighters like Progress and ATV. I don't know how much cargo capacity Soyuz has, besides 3 astronauts. Progress was used with Mir too. Not sure if this is what you were looking for as answer, or maybe something more specific about consumables.

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Yes I know Mir is gone... I meant in the past..and ISS now.

I was wondering about gas as a consumable..and re-supply of cylinders.

Sorry If I was less than clear.

Yes... 4.7psi..........I can see where I mis-read. My mistake.

Thanks again for all the great responses and answers.

Funny Thing:

When reading one of the links posted above about C02 scubbers on ISS I learned the system is inside a Russian Modual. The funny thing is it was launched by a rocket with a Pizza Hut advertisement on it.

Excellent Response; I was thinking of He02 and deep diving when I wrote that. I do think Neon has been tested once and abandoned for some reason.
Maybe cost. I could be wrong.

I think you are correct.....I am reading about Russian systems aboard ISS.

Thank You for the help.

In thinking:

If a person is at 14.7 on air, then does a space walk at 4.7 on 02. Decompression sickness would result. Time must be spent breathing 02 only before a spacewalk.