20-01-2005 19:37									#91
	Support Apolyton buy from Amazon

[QUOTE] Originally posted by Geronimo


this is popular misconception just ask nasa

?

I've already read that. And if you have continued exposure to vacuum, even ignoring the effects of oxygen deprivation, the body gradually (on the order of 5 minutes) suffers massive edema across the entire surface. There is a continued, large pressure differential across the surface of the skin and serious injury is unavoidable.

quote: Mars isn't a vacuum so you could breathe 1KPa oxygen from a tank and safely boost the pressure a bit higher with adustments to a regulator

1kPa oxygen? Gee, thanks, given that the partial pressure of oxygen at the earth's surface is 20kPa and hypoxia follows quickly if the pp falls below 8 kPa or so.

	20-01-2005 19:42									#92
	Inflate your Upload Space

Listen: the human body, to continue functioning at anything other than the lowest level, requires a partial pressure of O2 in the lungs of ~15kPa. There will be serious injury almost immediately if such a pressure is maintained inside the lungs while the exterior pressure is on the order of 1kPa. According to a rough estimate it would be like trying to breathe with a 300kg weight pulling outward on your chest.

Good luck with that. I'll take my hamster ball any day of the week.

	20-01-2005 19:43									#93
	Help yourself to an AD-FREE life

Would probably rip the diaphragm too.

	20-01-2005 19:47									#94
	Support Apolyton, buy Civilization III: Complete

BTW, while we're at daydreaming about Mars, would it be theoritically possible to engineer a lifeform that could survive the pressure and the cold, while feeding off whatever the atmosphere/soil provides?

	20-01-2005 19:49									#95
	Support Apolyton, buy Galactic Civilizations

quote: Originally posted by KrazyHorse Would probably rip the diaphragm too.

Thoughtful of you to consider contraception.

	20-01-2005 19:58									#96
	Support Apolyton

quote: Originally posted by Spiffor BTW, while we're at daydreaming about Mars, would it be theoritically possible to engineer a lifeform that could survive the pressure and the cold, while feeding off whatever the atmosphere/soil provides?

possibly.

I would think that the best bet would be a photosynthetic single-celled organism of some kind (think super-algae).

	20-01-2005 20:09									#97
	Tired of ads?

quote: Originally posted by KrazyHorse I would think that the best bet would be a photosynthetic single-celled organism of some kind (think super-algae).

You need to stop hanging around bars frequented by American Repugs.

	20-01-2005 20:51									#98
	Support Apolyton, buy Alpha Centauri

I have just looked for info about artificial ecosystems (close systems, mind you, not terraformation attempts), and they're surprisingly advenced already. The current MELISSA project of the ESA has an efficiency of about 70%, and a subpart of it, the BIORAT (which only focuses at recycling air) is ready for micro-gravity testing.

While these artificial ecosystems may bring many good things in the civilian area, they are precisely done for Space exploration, especially for a manned mission to Mars that the space agencies believe not to be too far in the future

	20-01-2005 22:21									#99
	Support Apolyton buy from Amazon

quote: Originally posted by Chemical Ollie If you are stationed on a sub (I read between the lines that you are), understanding P and kPa is essential. Most subs will be squezed if P gets above 3000 kPa or something. P is pressure and kPa is the unit it's measured in. Atmospheric pressure at sea level is 100 kPa. Every 10 meters you dive in water adds 1 atmosphere = 100 kPa to the pressure. If I recall right, a modern sub can dive to 300 meters where the pressure is 3000 kPa (I know some can dive deeper, just an example).

not everybody uses kPa to measure pressure. I'm more used to thinking of pressure in mm Hg

	20-01-2005 22:25									#100
	Increase the size of your Attachments

quote: Originally posted by Spiffor I think the reason why they're not thinking outside the box is pressure indeed. If you often scuba-dive, I take it you have the habit of stopping your swim-up at regular intervals (so that your lungs can progressively adapt to the new, lower pressure without exploding). The differences of pressure between deep water and surface are enough to kill you if you don't go progressively enough. And yet, the difference of pressure is faaar inferior to the difference between Earth and Mars. If you get out of a pressurized vehicle and were confront to Mars's tiny pressure, you'd die as surely as if you swam up from the most extremes depths of sea to the durface in one second. If you don't wish to play the bubble-man on Mars, maybe the "outside the box" possibility would be to use your monthes-long trip to progressively adapt the cabin pressure to 1 kPa (Mars's pressure). But I absolutely don't know if the human body could live under this pressure at all, regardless of the transition time.

whoah the difference isn't "faaar" greater. You don't have to dive all that deep to add 1 atmosphere of pressure.

Every 10 meters you dive adds one atmosphere.

	20-01-2005 22:48									#101
	Support Apolyton buy from Amazon

Well, I'm not an adept of Scuba diving, but I didn't know the divers were used to diving at 1km depth

	20-01-2005 22:49									#102
	Support Apolyton, pre-order Civilization IV

quote: Originally posted by KrazyHorse Listen: the human body, to continue functioning at anything other than the lowest level, requires a partial pressure of O2 in the lungs of ~15kPa. There will be serious injury almost immediately if such a pressure is maintained inside the lungs while the exterior pressure is on the order of 1kPa. According to a rough estimate it would be like trying to breathe with a 300kg weight pulling outward on your chest. Good luck with that. I'll take my hamster ball any day of the week.

You're underestimating the durability of the lungs. The minimum pressure difference required to risk pulmonary barotrauma is about 80 mm Hg .

the 300kg weight analogy doesn't seem right either. The pressure difference experienced by the aorta for example is on the order of 18 kPa and it's hard to imagine it would be equiped to hold back a 300kg weight.

	20-01-2005 22:51									#103
	Increase Your PM Length

quote: Originally posted by Spiffor Well, I'm not an adept of Scuba diving, but I didn't know the divers were used to diving at 1km depth

1km? where did that come from?

	20-01-2005 22:54									#104
	Inflate your Upload Space

quote: Originally posted by Geronimo 1km? where did that come from?

If 10m = 1 extra atm of pressure, you need 1km to have 100 atm of pressure. Which is the difference in magnitude between Earth's and Mars' atmospheres.

	20-01-2005 23:16									#105
	Put an end to popups!

quote: Originally posted by Spiffor If 10m = 1 extra atm of pressure, you need 1km to have 100 atm of pressure. Which is the difference in magnitude between Earth's and Mars' atmospheres.

spiff think twice about that. The difference between earths atmospheric pressure at sea level and a total vacuum will be just one atmosphere. So how could the difference between earth and mars atmosphere be equivalent to a difference of 100 atmospheres?

For physiological considerations it will be absolute change in pressure not relative changes in pressure that are going to matter.

	20-01-2005 23:21									#106
	Avatar Enlargement: We've got the solution

quote: Originally posted by Geronimo spiff think twice about that. The difference between earths atmospheric pressure at sea level and a total vacuum will be just one atmosphere. So how could the difference between earth and mars atmosphere be equivalent to a difference of 100 atmospheres? For physiological considerations it will be absolute change in pressure not relative changes in pressure that are going to matter.

Actually, for physiological considerations the problem is the absolute pressure, period.

Human beings can withstand hyperbaric environments pretty well. At some point you start cutting down on the percent concentration of oxygen in the breathing mix and replacing it with inert gas to avoid oxygen poisoning. The problem with very low pressure is that human beings require at least a certain partial pressure of oxygen in the air they breathe. If the external pressure is much lower than that you can't survive. Period.

	20-01-2005 23:23									#107
	Support Apolyton, buy Galactic Civilizations

So all this bullshit about how well people can go from high pressure to regular atmospheric pressure if they take proper precautions has nothing to do with the problem at hand.

	20-01-2005 23:25									#108
	Support Apolyton, buy Civilization: The Boardgame

C'mon, geronimo: instead of arguing semantics with Spiffor explain to me how you plan to maintain a pressure differential between the lungs and the environment of at least 15 kPa

	20-01-2005 23:43									#109
	Support Apolyton buy from Amazon

quote: Originally posted by KrazyHorse C'mon, geronimo: instead of arguing semantics with Spiffor explain to me how you plan to maintain a pressure differential between the lungs and the environment of at least 15 kPa

15 kPa = 112.5 mm Hg.

the minimum threshold for barotrauma is about 80 mm Hg

Someone who gradually builds up such a pressure difference for several weeks in preperation might conceviably endure the 15kPa difference for a few hours without permanent damage.

	20-01-2005 23:45									#110
	Tired of ads?

quote: It might be possible, as Dan said, to wear a skintight suit which would, by its elasticity, provide sufficient, even pressure across the entire body. No such suit exists, AFAIK. The technical requirements to fit such a suit exactly and to have it provide even pressure under large expansions (such as breathing) are far greater than those required for a simple pressurised suit.

Actually, I can't confirm that this is true. The research on this point is modest, but what is out there seems to suggest that success has to do with fabric choice rather than exotic modifications. Personally, I wonder about the adequacy of the heating and cooling more than the idea of mechanical pressurization.

	20-01-2005 23:50									#111
	Avatar Enlargement: We've got the solution

KH, do you know a way to calculate how much atmosphere a body with Mars's gravity could hold before it would start leaking off into space at an appreciable rate?

	20-01-2005 23:54									#112
	Support Apolyton, buy Civilization: The Boardgame

quote: My second question is could we make a habitat for the day traveller to sleep in so that he can extend his stay. Once again using items that are commercially available or at least relatively cheap.

Taking a **** would be a problem. Other than that, you could probably eat liquid food that is heated and pressurized using a mechanical pressure cozy, just like the skintight suit.

Area heating might be a problem (like in a tent), although you might be able to work up a ground heat pump in some fashion.

	20-01-2005 23:56									#113
	Support Apolyton, buy Call to Power 2

quote: Originally posted by Geronimo You're underestimating the durability of the lungs. The minimum pressure difference required to risk pulmonary barotrauma is about 80 mm Hg .

80 mm Hg = 10 kPa

So we're 50% above that at least

That assumes the minimum oxygen level for survival and that we're operating in a 100% oxygen atmosphere.

quote: the 300kg weight analogy doesn't seem right either. The pressure difference experienced by the aorta for example is on the order of 18 kPa and it's hard to imagine it would be equiped to hold back a 300kg weight.

My god. Force = pressure X area

The chest has a much larger area than the cross-section of the aorta. probably by a factor of 1000 or so. Thus for an equivalent pressure differential the chest experiences a force 1000 times greater.

	20-01-2005 23:59									#114
	Support Apolyton buy from Amazon

quote: Originally posted by Geronimo KH, do you know a way to calculate how much atmosphere a body with Mars's gravity could hold before it would start leaking off into space at an appreciable rate?

IIRC the lifetime for an atmosphere comparable to the Earth's would be on the order of 10 000 years. Can't recall exactly.

	20-01-2005 23:59									#115
	Got spare money?

quote: Originally posted by Geronimo KH, do you know a way to calculate how much atmosphere a body with Mars's gravity could hold before it would start leaking off into space at an appreciable rate?

It's not the size of the body that's the problem. It's that Mars doesn't have a molten core, which would generate a magnetic field around the planet, which would deflect solar particles and keep them from blowing away the atmosphere. Consider that Venus has an atmospheric pressure 900 times that of Earth.

	21-01-2005 00:03									#116
	Tired of ads?

Mars does have at least a partially-molten core.

	21-01-2005 00:07									#117
	Support Apolyton, buy Galactic Civilizations

quote: Originally posted by Geronimo Someone who gradually builds up such a pressure difference for several weeks in preperation might conceviably endure the 15kPa difference for a few hours without permanent damage.

I truly doubt it. You're welcome to try, though.

Might be possible for a couple of minutes. Not for an hour.

Assuming everything went perfectly you're still exerting yourself heavily to breathe in a strong pressure diffential with very very little oxygen while your lung tissue is slowly being ripped, your blood vessels are becoming badly swollen etc.

You're 50% above the safe limit of pressure differential at best. That's not very bright.

	21-01-2005 00:12									#118
	Full PM-box? Change here!

quote: Originally posted by chegitz guevara It's not the size of the body that's the problem. It's that Mars doesn't have a molten core, which would generate a magnetic field around the planet, which would deflect solar particles and keep them from blowing away the atmosphere. Consider that Venus has an atmospheric pressure 900 times that of Earth.

Actually, chegitz, the size of the body is the problem. Mars would lose its atmospher something like 100 times faster than the Earth does if they had equivalent surface pressures (these are rough figures and I'm quoting them from a source I read something like 10 years ago, so they might be off).

So in addition to the fact that the Earth retains its atmosphere much better than Mars does, there is also the replenishment issue (the Earth replenishes its atmosphere at a much higher rate than Mars does too).

The difference between Venus and the Earth is solely due to the supply issue (there are geysers of sulfur dioxide etc. constantly being pumped out from the surface of venus at an incredible rate). Between the Earth and Mars it's due to both supply and loss.

As for the magnetic field slowing loss, it might have an effect, but the basic issue is one of diffusion. The smaller the potential well you trap the gas particles in the faster they escape.

	21-01-2005 00:14									#119
	Enter the AD-FREE zone

quote: Originally posted by DanS Mars does have at least a partially-molten core.

But it doesn't spin, which is what generates the magentic field.

	21-01-2005 00:16									#120
	Support Apolyton, buy Civilization III: Complete

Make up your mind about why there is no magnetic field.