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Werfer
2007-Dec-23, 02:32 PM
A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive.

But what would visual accuity be like in a CO2 atmosphere? Would the naked eyeball sting or smart in the Martian atmosphere?

Does the human eyeball require to be in physical contact with external oxygen for its cells to survive long term? Would the astronaut require an oxygenated sealed eyemask?

MaDeR
2007-Dec-23, 02:37 PM
I think that very low pressure is more problematic than lack of oxygen...

grant hutchison
2007-Dec-23, 03:12 PM
A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive.Not so, at least not for long.
A simple face mask would supply oxygen at Martian ambient pressure, which is too low to sustain life. You'd need a tight-fitting mask supplying oxygen at above ambient pressure, which would make it very difficult to breathe out. The higher pressure in your lungs would also interfere with your circulation by compressing your heart, and is high enough to push gas into your circulation or pop your lungs.
And, although the partial pressure of the Martian atmosphere is just high enough at low altitudes to prevent water boiling near its freezing point, it's too low to prevent water boiling at body temperature. Water would boil off from your corneas, water vapour bubbles would form under your skin and in your venous circulation.
It would be pretty much indistinguishable from vacuum exposure.

Edit: But, in answer to your question, the cornea does get a lot of its oxygen by diffusion from the air, because it contains no blood vessels. In a more hospitable oxygen-free atmosphere, I guess you would slough your corneas after prolonged exposure.
The early contact lenses had very low gas permeability, and caused hypoxic corneal damage if you kept them in for too long.

Grant Hutchison

aurora
2007-Dec-23, 06:05 PM
Maybe you'd have to wear something like a scuba diving mask, at a minimum.

Edited to add, I forgot to mention temperature.

Exposed skin would quickly freeze, I assume.

KaiYeves
2007-Dec-23, 06:06 PM
Maybe you'd have to wear something like a scuba diving mask, at a minimum.
Plus, it might be quite cold.

grant hutchison
2007-Dec-23, 06:16 PM
Plus, it might be quite cold.We spoke about this on another "Mars without a spacesuit" thread (http://www.bautforum.com/questions-answers/36151-walking-mars-without-spacesuit.html) a while back, and I rather thoughtlessly said that you'd need Antarctic-type gear. But tony873004 pointed out that I was contradicting something I'd said in the Celestia forum previously, at which point I realized that I agreed more with my former self than my current self. :sad:
So, this previous Grant Hutchison contended that you'd need to insulate your feet from the cold ground, but that the atmosphere was so thin it would not take away much heat by conduction or convection: you'd be effectively surrounded by a pretty good vacuum flask, albeit one that was unsilvered.
Your main surface losses (barring those cold feet) would be by radiation. So it seems like it might not be that difficult to stay warm.

Grant Hutchison

KaiYeves
2007-Dec-23, 06:24 PM
Your main surface losses (barring those cold feet) would be by radiation. So it seems like it might not be that difficult to stay warm.
Okay, so insulated feet and a scuba system would be alright. At least you would not need to wear a weight belt on Mars!

grant hutchison
2007-Dec-23, 06:31 PM
Okay, so insulated feet and a scuba system would be alright.And a pressure suit. Otherwise you can't breathe and you die of vapour embolism.
It's pretty much indistinguishable from the Moon.

Grant Hutchison

KaiYeves
2007-Dec-23, 06:42 PM
And a pressure suit. Otherwise you can't breathe and you die of vapour embolism.
It's pretty much indistinguishable from the Moon.
Check, captain!

joema
2007-Dec-24, 12:43 AM
As Grant said, the surface pressure on Mars is about 0.1 psi, vs Earth's 14.7 psi. Mars is closer to lunar vacuum than any normal earth environment.

A healthy, trained, conditioned mountain climber at the summit of Mt. Everest (29,000 ft) can survive with an oxygen mask. A very few people have summited Everest without oxygen, although the death rate is very high.

In theory using positive-pressure breathing (pure O2 is forced into your lungs, you exert yourself to exhale), survival is possible up to about 50,000 ft. At that altitude, atmospheric pressure is about 1.7 psi, 17 times that on Mars.

The absolute limit without a pressure suit or equivalent is the "Armstrong Line", (about 62,000 ft): http://en.wikipedia.org/wiki/Armstrong_Limit At that altitude atmospheric pressure is the same as vapor pressure of water at 98.6F. IOW fluids in the unprotected human body will boil.

Pressure at 62,000 ft is about 0.9 psi, or 9 times that of Mars. That explains why survival on Mars requires a pressure suit.

djellison
2007-Dec-24, 03:36 PM
A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive.

Could a man survive at 100,000 ft on Earth with just an Oxygen mask?

(clue - it's not 'yes')

Doug

MentalAvenger
2007-Dec-26, 05:26 AM
Could a man survive at 100,000 ft on Earth with just an Oxygen mask?
(clue - it's not 'yes')
DougOk, I guess the answer is maybe. Maybe it depends upon the oxygen mask. Maybe it depends on what he is wearing. If it is a mask such as those that drop down in a commercial airliner, no. If the guy is at 100,000, we might be able to assume he is not naked. (or is he? :) ) May we assume if he is at 100,000 feet he is not wearing street clothes? IMO, he wouldn’t need a space suit, or even a pilots pressure suit. A simple spandex body suit should do it.

Neverfly
2007-Dec-26, 05:35 AM
Ok, I guess the answer is maybe. Maybe it depends upon the oxygen mask. Maybe it depends on what he is wearing. If it is a mask such as those that drop down in a commercial airliner, no. If the guy is at 100,000, we might be able to assume he is not naked. (or is he? :) ) May we assume if he is at 100,000 feet he is not wearing street clothes? IMO, he wouldn’t need a space suit, or even a pilots pressure suit. A simple spandex body suit should do it.

Not necessarily

Even at 100,000 feet, I wouldn't be caught dead in spandex:neutral:

MentalAvenger
2007-Dec-26, 06:27 AM
I don’t think this was supposed to be a fashion discussion. :)

man on the moon
2007-Dec-26, 09:40 AM
Not necessarily

Even at 100,000 feet, I wouldn't be caught dead in spandex:neutral:

Somehow I think you would be.. Assuming you started out with it of course (and that was all you started out with, over clothes not counting). :p ;)

I like Kim Stanley Robinson's series personally, though I am not of a level to know if EVERYTHING in it is possible. He had the Mars-o-nauts outside in a runner/athletic version of a high altitude pilots suit with a whole lot more technology involved. I got the impression that between the layers of cloth/whatever was a carbon nano-tube full body version of a chinese finger trip. So not a pilot suit, but thin, pressurized and not terribly insulated all the same. Also, they had helmets or masks of some sort to keep their faces intact.

djellison
2007-Dec-26, 12:11 PM
Maybe it depends on what he is wearing.

The OP said

"A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive. "

The only valid response to that is that no, he couldn't. No point exercising semantics on this - the OP was assuming something that's simply not true.

Doug

grant hutchison
2007-Dec-26, 01:41 PM
A simple spandex body suit should do it.The "simple spandex body suit" is a myth, unfortunately.
To let you breathe a high enough oxygen pressure to keep you alive, it would have to compress your entire body at that pressure. The pressure involved is about the same as your normal arterial pressure. This makes the business of getting in an out of the suit hazardous and complicated. It also requires quite exquisite tailoring to your body surface.
We had some discussion about this on a previous thread (http://www.bautforum.com/questions-answers/36151-walking-mars-without-spacesuit.html).

Van Rijn provided a good link to a NASA technical document, describing development work on such a compression suit:
http://chapters.marssociety.org/winnipeg/sas/DevelopmentOfASpaceActivitySuit.pdf

I summarized some of the key points in that study as follows:
Raised lung pressure, if not properly matched by external compression, causes circulatory collapse (p4)
150mmHg is seen as a minimum working pressure for health (p10)
Matching pressure to oppose this working pressure must be applied over the whole body (p11)
Breathing can't be supported by a simple elastic garment alone, but needs an additional mechanism to maintain constant pressure during the large volume excursions of the chest (p10)
Trunk zippers are almost impossible to close at working pressures over 45mmHg (p22)
These garments (as designed in this study) are not loose-fitting indoors: they're elastic garments that maintain their high compression even at one atmosphere ambient (p57)
This constant high level of compression creates problems during donning and doffing, requiring the wearer to breathe from a stepwise increasing overpressure source while the garment is progressively assembled around him (p67)
This complicates donning and doffing: assistance is needed and it took 45 minutes to suit up; impressively, only seven minutes for doffing, however (p67)

Then a spacesuit designer provided some current information:
Hi there. If I may add something here. I am involved in the development of spacesuits, and have (over the past 15 years) seen many claims of this and that as the solution to the bulky spacesuit. There are too many problems in spacesuit design, which seem simple at first glance, or to the armchair engineer, that are actually very difficult to solve. If, and this is a big if, you can solve the numerous problems faced by mechanical counter pressure suits, practical MCP spacesuits are at best a very long way off.
Here are just some of the issues with this type of suit:
One, custom fit required, modern CNC cutting and measuring can do this in the cutting and patterning of the garment, but sewing is still by hand fed machine and the same experianced person can sew two pieces of fabric, the same way and they will react differently. Currently there is not a material or technique that I am aware of that can be “sprayed on” as a solution for this problem. Advancements in materials seldom lead to revolutionary breakthroughs in product invention. They do, generally after many years, offer an improved product. Then to new products.
Two, the hollows of the body. Forget elbows and knees, how about areas like your crotch, you still have to walk remember. Keep in mind, any small area that doesn’t receive the correct counter pressure will be affected like sticking a vacuum cleaner on you skin, after a while you have a big “hickey” and then the skin is very tender and sore. I think you get the picture:o
Three, donning and doffing in an emergency, or donning or doffing in any case? Very difficult with a suit tight enough to do you any good. Getting a suit on in a hurry is a big consideration.
Four, Sores on the body, or "hot spots" from small excesses of pressure in one area of the body. Rest your body on a fold of fabric or a bump for anytime and your skin and under tissue get sore and stays sore for a long time. I have been a diver for many years and a wet suit worn on the surface for a long time can get uncomfortable, and it doesn’t have anywhere near the amount of squeeze needed.
So perhaps in the next 50 years we may see something in this are that is a better trade off than a full atmospheric pressure suit, but there are a bunch of things, beyond a cool new material that would need to be solved. I have seen many of the "new skin suits" and they don't address many of the above problems, in fact I have some of my own ideas that I am experimenting with for a mechanical counter pressure suit, but some same problems will be there even if my system works. So you have to weigh the trade offs of those problems verses the problems of a full pressure suit.Grant Hutchison

joema
2007-Dec-26, 04:19 PM
Ok, I guess the answer is maybe. Maybe it depends upon the oxygen mask...A simple spandex body suit should do it.
It doesn't depend on the type of oxygen mask. You can't survive at 100,000 ft no matter what type of oxygen mask -- even one that forces pure O2 into your lungs at pressure.

You also can't survive with a simple spandex body suit.

It's theoretically possible a highly sophisticated counter-pressure suit could allow survival -- however that is NOT a simple spandex body suit.

E.g, a medical compression stocking (say for varicose veins) might be 20-30 mm Hg pressure (0.38 - 0.58 psi).

A class III compression garment (the tightest kind) is about 40-50 mm Hg (0.77 - 0.97 psi). It is VERY tight and quickly becomes uncomfortable. Also they are only available for small areas, like a sock.

By contrast about 150 mm Hg (2.9 psi) is needed for survival on Mars -- over the entire body.

That's why NASA doesn't buy spandex leotards from an athletic supplier and use those.

While an approximate description of a counter-pressure suit might be "sort of like a spandex suit", in fact the required pressure is MUCH higher. This means all the issues of doffing/donning, pinching, maintaining uniform pressure during movement, etc. are vastly harder.

Imagine you're on Mars, wearing the tightest available commercial spandex suit. You have a positive-pressure O2 regulator (you work to exhale, upon relaxation it forces O2 into your lungs).

You'd nonetheless be dead from ebullism within a few minutes: http://en.wikipedia.org/wiki/Ebullism.

Separately, I wonder how long you could survive on Mars with an old-style military "capstan" counter-pressure suit? http://www.astronautix.com/craft/s2pesuit.htm

MentalAvenger
2007-Dec-26, 05:41 PM
The OP said

"A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive. "

The only valid response to that is that no, he couldn't. I wasn’t responding to the OP, I was responding directly to your question.