21-01-2005 00:17									#121
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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?

I could figure out a formula directly from statistical mechanical considerations but it would be a significant amount of work. I suggest you google it as I'm lazy.

	21-01-2005 00:18									#122
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quote: Originally posted by KrazyHorse Actually, chegitz, the size of the body is the problem.

It's a problem, not the problem. Solar winds have a much bigger impact than body size. Even Pluto has an atmosphere, as well as Io and Titon, all of which are smaller than Mars.

But if we look at the surface features on Mars, one would likely conclude they had a more substantial atmosphere for a longer period of time than ten thousand years, at least one suficient enough for liquid water to exist.

	21-01-2005 00:20									#123
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quote: Originally posted by chegitz guevara But if we look at the surface features on Mars, one would likely conclude they had a more substantial atmosphere for a longer period of time than ten thousand years, at least one suficient enough for liquid water to exist.

Why necessarily liquid water It could have been anything.

	21-01-2005 00:21									#124
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quote: Originally posted by KrazyHorse 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.

no exertion is required, the breathing can occur passively since the tank is at much higher than ambient pressure, both inhalation and exhilation can occur passively.

OTOH, I agree that however long such a low pressure environment might be endured, it will be a very gruelling experience (assuming you don't pass out). Furthermore damage suffered would likey be permanent alveolar damage resembling emphysema.

The blood vessels should deal with the pressure fairly easily but the resulting edema would certainly contribute to making the stay a memorably uncomfortable one.

	21-01-2005 00:24									#125
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quote: Originally posted by KrazyHorse 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.

geysers of sulfuric acid? that certainly makes sense and explains a lot but I didn't know that Venus had been verified to be geothermally active. Do you know when these geysers were discovered?

	21-01-2005 00:24									#126
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Pluto's atmosphere is there solely because the production rate is so high. Pluto's mainly frozen gases, which sublimate rapidly on the sunlit side. There are geysers constantly going on the surface. It loses its atmosphere much quicker than mars does.

Similarly with io . Io has ridiculously active volcanoes.

As for Titan, it's interesting you use that as an example, given that it has no magnetic field of its own and spends much of its time above Saturn's magnetosphere.

EDIT: Titan's dense atmosphere is considered something of a mystery, BTW...

Last edited by KrazyHorse on 21-01-2005 at 00:29

	21-01-2005 00:27									#127
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quote: Originally posted by Geronimo no exertion is required, the breathing can occur passively since the tank is at much higher than ambient pressure, both inhalation and exhilation can occur passively.

How does exhalation occur, praytell? do you have to flip a switch every time you breathe?

	21-01-2005 00:29									#128
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quote: Originally posted by Geronimo geysers of sulfuric acid? that certainly makes sense and explains a lot but I didn't know that Venus had been verified to be geothermally active. Do you know when these geysers were discovered?

I was under the impression that this was the accepted theory. I have no clue if they've been directly observed or not. I'm also a physicist, not a planetary scientist, so this isn't my area of specialty.

	21-01-2005 00:30									#129
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quote: Originally posted by KrazyHorse 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.

Something doesn't seem to compute here. the chest wall is at least as thick relative to it's volume as the walls of the aorta are to their volume.

	21-01-2005 00:34									#130
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quote: Originally posted by KrazyHorse How does exhalation occur, praytell? do you have to flip a switch every time you breathe?

use a regulator (one way inflow and one way outflow valve)! That approach solved exactly the same problem in scuba diving. I think you knew that but just had momentary lapse of understanding.

of course the regulators for scuba are usually designed for a pressure differential only between the tank and the mouthpiece and not an additional differential between ambient and the mouthpiece the principal can be made to work in the same way.

	21-01-2005 00:35									#131
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quote: Originally posted by KrazyHorse Pluto's atmosphere is there solely because the production rate is so high. Pluto's mainly frozen gases, which sublimate rapidly on the sunlit side. There are geysers constantly going on the surface. It loses its atmosphere much quicker than mars does. Similarly with io . Io has ridiculously active volcanoes. As for Titan, it's interesting you use that as an example, given that it has no magnetic field of its own and spends much of its time above Saturn's magnetosphere. EDIT: Titan's dense atmosphere is considered something of a mystery, BTW...

Titan's also very far from the sun, so the solar winds are much weaker there.

As for Pluto bleeding off it's atmosphere much more quickly than Mars, no doubt. The point I'm trying to make is that it would have occured much more quickly if solar winds were as much of an issue there as they are in the inner Solar system.

	21-01-2005 00:39									#132
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Who said anything about thickness?

F = P X A

The aorta has a cross-sectional area of around 1 cm^2 (very rough estimate. The ribcage presents a forward area of something like 0.1 m^2 = 1000 cm^2

to create the lungs were to support a pressure differential of 22 kPa (pp O2 at sea level) they would need to be able to support 22 000 N/m * 0.1 m^2 = 2200 N = 250 kg weight pushing the ribcage outward.

	21-01-2005 00:40									#133
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quote: Originally posted by chegitz guevara Titan's also very far from the sun, so the solar winds are much weaker there. As for Pluto bleeding off it's atmosphere much more quickly than Mars, no doubt. The point I'm trying to make is that it would have occured much more quickly if solar winds were as much of an issue there as they are in the inner Solar system.

i may be showing my ignorance of physics here, but wouldn't the biggest factor of all be the low temperature of the gasses in plutos atmosphere? Isn't the matter of whether the gas escapes just going to be a matter of whether a given gas molecule is moving faster than pluto's escape velocity? And won't that depend directly on the temperature of the gasses?

	21-01-2005 00:41									#134
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quote: Originally posted by Geronimo use a regulator (one way inflow and one way outflow valve)!

I'm aware of that concept. I simply doubt it would work very well when there's a very large standing pressure differential. There's probably a technical solution, but certainly not generally available...

	21-01-2005 00:41									#135
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quote: 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?

Well, the Martian summer would provide a modest growing season, but the low, low pressure means that liquid water can't exist. And that's a real problem for any sort of life.

As for terraforming, I think that the best you could hope for would be a somewhat thicker atmosphere - not suitable for breathing, but enough to limit the temperature flux, allow for some liquid water, and make surface dwellings cheaper to build (because they don't have to withstand a huge difference in pressure).

	21-01-2005 00:42									#136
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That's also correct. That's why, for example, there is very little helium or hydrogen in our atmosphere.

	21-01-2005 00:43									#137
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quote: Originally posted by Sandman As for terraforming, I think that the best you could hope for would be a somewhat thicker atmosphere - not suitable for breathing, but enough to limit the temperature flux, allow for some liquid water, and make surface dwellings cheaper to build (because they don't have to withstand a huge difference in pressure).

I think we could do better than that. Just plow a bunch of comets into Mars, as well as freeing up the oxygen lokced in the crust. It will take a while and require constant replenishing, but we can do it.

	21-01-2005 00:45									#138
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quote: Originally posted by Geronimo i may be showing my ignorance of physics here, but wouldn't the biggest factor of all be the low temperature of the gasses in plutos atmosphere? Isn't the matter of whether the gas escapes just going to be a matter of whether a given gas molecule is moving faster than pluto's escape velocity? And won't that depend directly on the temperature of the gasses?

Not directly; actually as the square root of the temperature.

Plus, Pluto's escape velocity is really damn small. Something like 1000m/s (mars is 5000 and Earth is 11000 or so)

	21-01-2005 00:47									#139
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quote: Originally posted by KrazyHorse Who said anything about thickness? F = P X A The aorta has a cross-sectional area of around 1 cm^2 (very rough estimate. The ribcage presents a forward area of something like 0.1 m^2 = 1000 cm^2 to create the lungs were to support a pressure differential of 22 kPa (pp O2 at sea level) they would need to be able to support 22 000 N/m * 0.1 m^2 = 2200 N = 250 kg weight pushing the ribcage outward.

I imagine they will be able to hold 250 kg if the weight were evenly distributed over the surface of the thoracic cavity. Certainly the ribs could contain such an evenly distributed weight.

	21-01-2005 00:59									#140
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I think they could too. For a very brief period. How long before **** starts to rip around the edges though? Have you ever had a 70 kg person sit on your chest? Not too comfortable, huh? What about 3 of them?

I'm not claiming there will be sudde, catastrophic failure of the structural integrity of the ribcage. But you have to imagine that the connective tissue wasn't built with such forces in mind. Things will definitely not hold out very well. How long before you're coughing out blood?

	21-01-2005 01:01									#141
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quote: Originally posted by KrazyHorse I think they could too. For a very brief period. How long before **** starts to rip around the edges though? Have you ever had a 70 kg person sit on your chest? Not too comfortable, huh? What about 3 of them?

I'd be freaking out and panicking.

	21-01-2005 01:03									#142
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I'd be safe and sound in my hamster ball.

	21-01-2005 01:07									#143
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And all of you idiots who thought you could breathe outside could kiss my ass for all I'd care.

	21-01-2005 01:12									#144
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quote: Originally posted by KrazyHorse And all of you idiots who thought you could breathe outside could kiss my ass for all I'd care.

whoah, what about when you see us frantically imploring you to let us in the hamster ball to relieve the unbearable pain of exposure to the unforgiving martian elements? Surely you would show some compassion in the face of such desperation?

	21-01-2005 01:15									#145
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Pffft. If I let you in then there might not be enoough cookies for me.

	21-01-2005 01:16									#146
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You probably didn't even remember to bring cookies.

	21-01-2005 01:23									#147
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What if we brought martian low pressure beer?

	27-01-2005 06:46									#148
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Appropos of this thread, although I think they're making this unnecessarily high tech...

quote: High-Tech Spacesuits Eyed for ‘Extreme Exploration’ By Leonard David Senior Space Writer posted: 26 January 2005 06:43 am ET CAMBRIDGE, Mass. -- Future explorers on the Moon and Mars could be outfitted in lightweight, high-tech spacesuits that offer far more flexibility than the bulky suits that have been used for spacewalks in the 1960s. Research is under way at the Massachusetts Institute of Technology (MIT) on a Bio-Suit System that incorporates a suit designed to augment a person’s biological skin by providing mechanical counter-pressure. The “epidermis” of such a second skin could be applied in spray-on fashion in the form of an organic, biodegradable layer. This coating would protect an astronaut conducting a spacewalk in extremely dusty planetary environments. Incorporated into that second skin would be electrically actuated artificial muscle fibers to enhance human strength and stamina. The Bio-Suit System could embody communications equipment, biosensors, computers, even climbing gear for spacewalks or what NASA calls an Extra Vehicular Activity (EVA). “When we get back to the Moon and on Mars, we’re not going there to stay in a habitat,” said Dava Newman, professor in the Department of Aeronautics and Astronautics and Engineering Systems here at MIT. “EVA becomes … a primary function,” she said. Newman is leading the Bio-Suit System work, assisted by researchers Kristen Bethke, Christopher Carr, Nicole Jordan, and Liang Sim in the Department of Aeronautics and Astronautics and Engineering Systems. The study is multi-pronged and is intended to better calibrate astronaut performance, explore improvements to current spacesuit designs and generate novel ideas for a new generation of space exploration suits. The NASA Institute for Advanced Concepts, headquartered in Atlanta, is sponsoring the Bio-Suit System effort. “We need to shrink-wrap the astronaut,” Newman said. “It would be like wearing a second skin.” The Bio-Suit System, Newman said, would provide life support through mechanical counter pressure where pressure is applied to the entire body through a tight-fitting suit with a pressurized helmet for the head. Ongoing research is targeted at understanding, simulating, and predicting capabilities of suited astronauts in a variety of scenarios — be they performing simple motions or more complex movement, such as overhead or cross-body reach, stepping up, or trudging across an exotic landscape. The scenario envisioned by Newman and her associates is an astronaut first donning his or her customized elastic Bio-Suit layer. Then a hard torso shell would be slipped on, sealed via couplings located at the hips. A portable life support system is then attached mechanically to the hard torso shell and provides gas counter pressure. Gas pressure would flow freely into the wearer’s helmet and down tubes on the bio-suit layer to the gloves and boots. Newman said that the spacesuits of today are very limited in terms of mobility. In addition, the current weight or mass of EVA suits is another limiting factor. “In the microgravity environment those limitations are not show-stoppers. But for an advanced exploration spacesuit for the Moon or Mars, unlimited mobility and a very low mass spacesuit are paramount,” Newman told SPACE.com . There are several advances in technology that Newman and her MIT colleagues consider key in turning their work into a practical, suitable suit for human space explorers. “We’re looking into cutting edge materials, development and modeling capabilities to turn our Bio-Suit concepts in to working prototypes implementing mechanical counter-pressure,” Newman advised. Newman said Bio-Suit relies on advances in fabrication and application of open cell foam, smart materials like advanced “muscle wire” technologies, and electrospinlacing. “All of these have seen vast improvements in the last few years,” she said. The MIT group has investigated unique modeling techniques, such as taking 3D laser scans of a person. Then, using mathematical modeling and mechanics techniques, a “stress-strain field calculation” is performed for the entire human body. “The modeling allows us to prescribe a minimum energy suit that literally could be ‘painted on’ to provide maximum mobility for extreme exploration required on the Moon or Mars,” Newman said. Lightweight and easy to don and doff, the bio-suit layer would be custom fitted to each astronaut — made possible by a laser scanning/electrospinlacing process. That method stems from work at the U.S. Army Soldier Systems Center in Natick, Mass. where researchers there are tapping into science and technology for 21st century combat uniforms, as well as police officer garb able to thwart chemical or biological agents. In addition, the MIT Bio-Suit System team is working with Midé Technology Corp. of Medford, Mass. to adopt such items as micro-actuators and smart (active) materials in their designs. Among other collaborations, Bio-Suit System researchers are also drawing upon the Institute for Soldier Nanotechnologies, an interdepartmental research center at MIT. The ultimate goal of that institute is to create a 21st century battlesuit that combines high-tech capabilities with light weight and comfort. “The roadmap that the president and NASA have established involves spiral development and multiple destinations and operating environments over a relatively short period of time. With the very real budget pressures we will all face, I think the most critical element for success will be the early creation of an effective, modular EVA system architecture,” said Edward Hodgson, a Technical Fellow at Hamilton Sundstrand Space Systems International in Windsor Locks, Conn. Hodgson said an evolutionary approach will permit changes in response to altering mission needs, and also to infuse new technology as it develops with a minimum of system level redesign and recertification. Hodgson has also received support from the NASA Institute for Advanced Concepts to study a “Chameleon Suit.” The name reflects the fact that walls of the suit change in response to variations in the environment or in the wearer’s need for cooling. The ultimate goal of this concept is a symbiotic interaction of astronaut and spacesuit like that between humans and terrestrial plants in which the astronaut’s waste carbon dioxide and water vapor are converted back into respirable oxygen in the suit walls using environmental energy sources. Technologies under study, Hodgson noted, include shape change polymers and electro-emissive materials to modify heat transfer characteristics of the spacesuit skin so it is similar to that found in natural biological systems.

	27-01-2005 06:54									#149
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Wow

	27-01-2005 07:10									#150
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I don't know, Dan. Providing uniform eleastic pressure across a wide range of motions is not a simple exercise. I'm not surprised that they're looking at exotic solutions.