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Denis12
2005-Dec-20, 10:00 PM
A friend of mine has told me that you dont need a spacesuit for the planet mars because 'he said' there is an atmosphere. What happens if yoy get out of the marslander unprotected (without) a spacesuit? Greets Denis.

Hamlet
2005-Dec-20, 10:01 PM
A friend of mine has told me that you dont need a spacesuit for the planet mars because 'he said' there is an atmosphere. What happens if yoy get out of the marslander unprotected (without) a spacesuit? Greets Denis.

The Martian atmosphere is less than 1% of the Earth's atmosphere and is made primarily of CO2. You wouldn't last long unprotected on the surface.

grant hutchison
2005-Dec-20, 10:29 PM
You'd certainly need Antarctic-level warm clothing to stop you dying of hypothermia or developing frostbite.
You'd also need some sort of oxygen supply at about one fifth of an atmosphere pressure, which is considerably higher than Mars' atmospheric pressure. A tight-fitting mask could deliver this, but without a pressure suit you'd have hard work breathing out, because of the pressure gradient between your lungs and the Martian atmosphere outside your chest wall. Maybe some sort of elastic chest binder would help.
As I recall, the atmospheric pressure on Mars can be just compatible with liquid water, if the water is close to freezing. That's too low too stop water boiling at body temperature. So without a pressure suit, your eyes and skin would dry out, and gas bubbles would develop in your tissues. You'd develop "vapour locks" in your veins as the water in your blood evaporated. When these got to your heart, they'd stop your circulation.

Grant Hutchison

Lord Jubjub
2005-Dec-20, 11:50 PM
Not too mention an extreme case of the bends. . .though I think general dehydration would kill you first.

redshifter
2005-Dec-20, 11:57 PM
That leads to an interesting follow up question: If you were on Mars with no pressure suit or any other protection, what would kill you first, and how long would you survive? I'd say the lack of air pressure would get you before the lack of oxygen or the cold would, well under 30 seconds.

Van Rijn
2005-Dec-21, 01:33 AM
That leads to an interesting follow up question: If you were on Mars with no pressure suit or any other protection, what would kill you first, and how long would you survive? I'd say the lack of air pressure would get you before the lack of oxygen or the cold would, well under 30 seconds.

You would probably be alive for more than 30 seconds, but you would probably be unconscious inside of 20 seconds. It isn't quite a vacuum, but it is close enough as far as the human body is concerned.

Enzp
2005-Dec-21, 01:35 AM
But other than all that, enjoy the beach.

Ilya
2005-Dec-21, 02:29 AM
That leads to an interesting follow up question: If you were on Mars with no pressure suit or any other protection, what would kill you first, and how long would you survive? I'd say the lack of air pressure would get you before the lack of oxygen or the cold would, well under 30 seconds.
Well, what lack of air pressure does, is your blood dumps oxygen INTO lungs. Which makes you pass out after 15-20 seconds -- much less than you could normally stay conscious while holding your breath. Martian air is close enough to vacuum in that regard.

BTW, it is technically lack of oxygen partial pressure which does that nasty trick. If you breath pure nitrogen at Earth-normal pressure (an industrial accident which happens on rare occasions), you pass out just as fast. It is much more insidious than breathing vacuum because you won't realize anything is wrong until too late.

tony873004
2005-Dec-21, 03:23 AM
You'd certainly need Antarctic-level warm clothing to stop you dying of hypothermia or developing frostbite.
Grant Hutchison

I've heard that you wouldn't, that even a light sweater under your pressure suit would make you sweat once you started exerting energy by walking or lifting or whatever. With the air only 1% as thick as Earth's it has almost no ability to suck the heat out of you through conduction, so you're only going to lose what you radiate. And a good but thin outer layer should be able to reflect much of that back to you.

The exception is your feet which touch the -200 ground. They need to be well insulated for the same reason that people who attend Green Bay Packers games are told to bring styrofoam to stand on.

That's what I've heard anyway. I'd love to know. I hope I get a chance to go there someday :)

joema
2005-Dec-21, 03:27 AM
As previously stated, Mars is so close to a vacuum the question really is "how long could you survive unprotected in a vacuum?"

People don't explode in a vacuum, nor freeze, nor does their blood boil, nor do their eyes pop out. This was proven in a 1966 accident when a NASA technician was accidentally exposed to a near vacuum for 30 sec during a vacuum chamber test. He lost consciousness in about 15 sec, was repressurized in about 30 sec. He recovered with no problems.

You'd remain conscious at least 10 seconds. In a 2001-type scenario where the decompression is voluntary and prepared, and your vehicle (like the Lunar Module) is already at low pressure (Lunar Module was about 4 psi pure O2), you could probably remain conscious somewhat longer. Maybe 20 seconds. The 2001 "open the pod bay doors, Hal" sequence is actually a lot more accurate than Sci-Fi movies showing people exploding.

If recompressed within 60 sec you'd probably have no lingering ill effects.

In 1960 during an ultra-high altitude ballon test, Col. Joe Kittinger was in a near vacuum when his space suit glove failed. His hand was exposed to a vacuum for a long time, it was painful and eventually became very stiff, but he pressed on and continued his mission with one hand in a vacuum. Back on earth he recovered just fine.

http://tinyurl.com/6kkta

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

http://www.sff.net/people/Geoffrey.Landis/vacuum.html

An astronaut breathing pure oxygen would have no problem with the bends. Even if he was breathing an N2/O2 mix before vacuum exposure, he'd be unconscious from asphyxiation long before the bends would kill him.

crosscountry
2005-Dec-21, 06:53 AM
You'd certainly need Antarctic-level warm clothing to stop you dying of hypothermia or developing frostbite.
Grant Hutchison


Actually, it is much colder here in St. Louis than an average high on Mars. I'd be warm enough could I come up with the right pressure suit.


that suit need not be like the Apollo suits, rather it would just need to supply enough pressure that your body wouldn't explode (boil) Tough Spandex would do the job.

crosscountry
2005-Dec-21, 06:55 AM
I've heard that you wouldn't, that even a light sweater under your pressure suit would make you sweat once you started exerting energy by walking or lifting or whatever. With the air only 1% as thick as Earth's it has almost no ability to suck the heat out of you through conduction, so you're only going to lose what you radiate. And a good but thin outer layer should be able to reflect much of that back to you.

The exception is your feet which touch the -200 ground. They need to be well insulated for the same reason that people who attend Green Bay Packers games are told to bring styrofoam to stand on.

That's what I've heard anyway. I'd love to know. I hope I get a chance to go there someday :)


that too. oh, there isn't any -200 F place we would visit. we'd visit the +40F sites.

joema
2005-Dec-21, 07:32 AM
...that suit need not be like the Apollo suits, rather it would just need to supply enough pressure that your body wouldn't explode (boil) Tough Spandex would do the job.
As described above, your body won't explode, nor will your blood boil even if you were stark naked in a vacuum or on the surface of Mars.

The suit would generally need to be similar to the Apollo suits. You'd be in a near vacuum so you'd need a full pressure suit. You don't need the same thermal insulation, but the suit would look and feel very similar to an Apollo suit.

Re spandex, you're probably thinking of an alternative concept called the counter pressure suit. Some research has been done on that, and in theory it can work -- not just on Mars but any vacuum environment. However it's not as well developed. There's nothing special about Mars that makes this type of suit more feasible than a traditional full pressure suit. Here's a research paper (PDF): http://www.dsls.usra.edu/meetings/bio2001/pdf/140p.pdf

Jason Thompson
2005-Dec-21, 11:10 AM
A friend of mine has told me that you dont need a spacesuit for the planet mars because 'he said' there is an atmosphere.

An atmosphere won't do you much good if the pressure is too low, or it is unbreathable. Venus has an atmosphere, as does Titan and even Pluto (sometimes). Technically even the Moon has an atmosphere, although it is so tenous that the Apollo landings actually added a significant proprtion of material to it. Earth remains the only planet with an atmosphere that can support human life, though.

crosscountry
2005-Dec-21, 03:13 PM
As described above, your body won't explode, nor will your blood boil even if you were stark naked in a vacuum or on the surface of Mars.

The suit would generally need to be similar to the Apollo suits. You'd be in a near vacuum so you'd need a full pressure suit. You don't need the same thermal insulation, but the suit would look and feel very similar to an Apollo suit.

Re spandex, you're probably thinking of an alternative concept called the counter pressure suit. Some research has been done on that, and in theory it can work -- not just on Mars but any vacuum environment. However it's not as well developed. There's nothing special about Mars that makes this type of suit more feasible than a traditional full pressure suit. Here's a research paper (PDF): http://www.dsls.usra.edu/meetings/bio2001/pdf/140p.pdf


well. The Apollo suits also had layers of gold and other materials to block the intense solar irradiation. On Mars there will be less sunlight and the atmosphere will protect some from the sun. I suspect that the Apollo suits would be far more protection than what Astronauts would need on Mars.

Of course, they may need them for spacewalking on the way to or back from Mars.


But you have to realize also, Mars has over 2x the surface gravity of the moon. A suit that heavy would be more than cumbersom for anyone wearing it.

phunk
2005-Dec-21, 05:43 PM
Yup, a spacesuit for mars should need less protection than one for the moon, since it's farther from the sun and has at least a little atmosphere to block radiation. Also, I suspect that cooling the suit would be easier since there's atmosphere, so they can get away with a less bulky cooling system than what was used on the moon. I think they would probably be less encumberd than the apollo astronauts were.

joema
2005-Dec-21, 06:50 PM
...The Apollo suits also had layers of gold and other materials to block the intense solar irradiation. On Mars there will be less sunlight and the atmosphere will protect some from the sun. I suspect that the Apollo suits would be far more protection than what Astronauts would need on Mars...
They might not need the same degree of solar protection, but they'd need a full pressure suit that looked very similar to an Apollo suit. They would be similarly encumbered.

There are many full pressure suits in use today where Apollo-style sun and micrometeoroid protection isn't needed. They look and feel similar to a traditional space suit. E.g, the SR-71 full pressure suit:

http://www.wvi.com/~sr71webmaster/psd02.html

It's true that on Mars a more lightweight suite is DESIRABLE. However the question was what would you NEED. The answer is the Martian surface is almost a vacuum -- 0.01 PSI, or 0.0007 of Earth, so you'd need a full pressure suit, which would look very similar to a traditional Apollo suit. There is very little atmosphere to block radiation.

It would need nearly the same type of cooling as an Apollo suit. This is because most of the heat requiring a liquid cooling garment comes from the astronaut's metabolic output, not the external environment.

grant hutchison
2005-Dec-21, 08:23 PM
I've heard that you wouldn't, that even a light sweater under your pressure suit would make you sweat once you started exerting energy by walking or lifting or whateverAh, that's a good point, thanks. You're conductive/convective losses would be very low, both because the atmosphere is thin, but also because it is dry. Damp air has a higher specific heat capacity than dry air.

Grant Hutchison

Disinfo Agent
2005-Dec-21, 08:30 PM
The exception is your feet which touch the -200 ground. They need to be well insulated for the same reason that people who attend Green Bay Packers games are told to bring styrofoam to stand on.Appropriate footwear (http://www.alternative-footwear.co.uk/platform.jpg) might take care of that.

grant hutchison
2005-Dec-21, 08:31 PM
Actually, it is much colder here in St. Louis than an average high on Mars.My bad. If you kept indoors at night and avoided high latitudes, and in the light of tony873004's point about conduction and convection, I'll certainly negotiate down to a light sweater, a pair of thin gloves and a woolly hat!

Grant Hutchison

Disinfo Agent
2005-Dec-21, 08:35 PM
well. The Apollo suits also had layers of gold and other materials to block the intense solar irradiation. On Mars there will be less sunlight and the atmosphere will protect some from the sun. I suspect that the Apollo suits would be far more protection than what Astronauts would need on Mars.Perhaps, but, since the magnetic field of Mars is very weak, you'd probably need protection against cosmic radiation, right?

grant hutchison
2005-Dec-21, 08:42 PM
As described above, your body won't explode, nor will your blood boil even if you were stark naked in a vacuum or on the surface of Mars.Boiling would occur, though your body's certainly tough enough to contain it without exploding.
The vapour pressure of water at body temperature is around 62mbar. Atmospheric pressure on Mars is generally less than 10mbar. Your arterial blood pressure is higher than the vapour pressure of water, so no boiling would happen in your arterial circulation. But the internal pressure in your tissues, capillaries and venous blood would rapidly move into near-equilibrium with the outside pressure, at which point the water content would begin boiling.

Grant Hutchison

Lance
2005-Dec-21, 08:50 PM
Boiling would occur, though your body's certainly tough enough to contain it without exploding.
The vapour pressure of water at body temperature is around 62mbar. Atmospheric pressure on Mars is generally less than 10mbar. Your arterial blood pressure is higher than the vapour pressure of water, so no boiling would happen in your arterial circulation. But the internal pressure in your tissues, capillaries and venous blood would rapidly move into near-equilibrium with the outside pressure, at which point the water content would begin boiling.

Grant Hutchison

Boy!

I sure can't wait for tomorrow's chapter of "Fun Ways to Die"!

Van Rijn
2005-Dec-21, 09:08 PM
Actually, it is much colder here in St. Louis than an average high on Mars. I'd be warm enough could I come up with the right pressure suit.


The top layer of the regolith can get up to around 27C in summer, but that is far from the average high temperature. Surface and atmosphere (thin as it is) temperature are usually much lower than this.



that suit need not be like the Apollo suits, rather it would just need to supply enough pressure that your body wouldn't explode (boil) Tough Spandex would do the job.

You're going to need UV protection at least, and the general radiation protection provided by the Martian atmosphere is limited at best. As for skinsuits, they haven't been perfected yet, but if they are, could be used on Mars or in deep space.

crosscountry
2005-Dec-21, 09:16 PM
Perhaps, but, since the magnetic field of Mars is very weak, you'd probably need protection against cosmic radiation, right?



you and I are bombarded with cosmic rays all the time. Hey are generally so high in energy that they pass strait through the atmosphere and us too.


I'd be more worried about UV light.

Disinfo Agent
2005-Dec-21, 09:29 PM
Which is what I should have written.

galacsi
2005-Dec-21, 10:13 PM
Even if pressure were higher , i am not sure how long the skin can endure an atmosphere of CO2. We breathe also by our skin , it needs oxygen. So a simple respirator is not enough , you need a full pressure suit.

Van Rijn
2005-Dec-21, 10:15 PM
Don't forget about secondaries. A cosmic ray hitting atmosphere or surface will often create secondary particles. The earth's atmosphere is generally thick enough to block most of the secondaries, but the Martian atmosphere isn't. Here's an article you might find interesting:

http://techreports.larc.nasa.gov/ltrs/PDF/1999/mtg/NASA-99-marsw-jww.pdf

The upshot is that our data on Martian surface radiation is still pretty limited, mostly theoretical. For astronauts, total radiation exposure during flight and on the surface have to be considered.

Van Rijn
2005-Dec-21, 10:24 PM
Even if pressure were higher , i am not sure how long the skin can endure an atmosphere of CO2. We breathe also by our skin , it needs oxygen. So a simple respirator is not enough , you need a full pressure suit.

References, please? I was not aware that the skin "breathed." Are you thinking of people getting too hot due to heavy, water-proof protective clothing? That is a temperature control issue.

grant hutchison
2005-Dec-21, 10:26 PM
We breathe also by our skin , it needs oxygen.I think that's just something Ian Fleming made up, for the famous "gold-painted dead girl scene" in Goldfinger. If it were true, you'd die when you went skin-diving, or with a wet-suit.

Grant Hutchison

Lance
2005-Dec-21, 10:28 PM
References, please? I was not aware that the skin "breathed." Are you thinking of people getting too hot due to heavy, water-proof protective clothing? That is a temperature control issue.
I believe MythBusters dispelled this urban legend with their "Gold Painted Adam" and "Silver Painted Kari" episodes.

Of course, simply going under water in a wet suit disproves it pretty quickly too.

Edit:
ToSeeked

joema
2005-Dec-22, 01:48 AM
Boiling would occur, though your body's certainly tough enough to contain it without exploding.
Those are some good points and some good thinking. However I'm not sure that's the case. Here's why:

For one thing the NASA information says blood boiling doesn't occur. Also I've seen a photograph of an astronaut in a vacuum chamber holding a beaker of boiling water at room temperature. He wasn't wearing a pressure suit, but an old capstan-style suit. His skin under the porous garment was exposed to vacuum and he was doing just fine. http://www.astronautix.com/craft/s2pesuit.htm

Even unprotected, I think the counter pressure effect of your skin itself prevents blood boiling, much like a tight water balloon wouldn't boil in a vacuum.

Finally, blood boiling (even in capillaries or venous system) would be a catastrophic ischemic event. It would be like having simultaneous blood clots and strokes throughout your body. Yet the NASA technician exposed to vacuum recovered OK.

Also NASA conducted animal tests where animals including primates were exposed to vacuum for much longer periods. In general they recovered if the exposure was under roughly two minutes. If their body tissues were deprived of oxygen for that period of time through blood boiling, I doubt they'd have recovered:

The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum,
Alfred G. Koestler ed., NASA CR-329 (Nov 1965).

Experimental Animal Decompression to a Near Vacuum Environment, R.W.
Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School
of Aerospace Medicine, Brooks AFB, Texas.

Lord Jubjub
2005-Dec-22, 04:28 AM
The skin does NOT breathe--in any fashion or by any method. THAT is pure myth. It is a continuous complete barrier to any gas or aqueous liquid except under extemely high pressures.

crosscountry
2005-Dec-22, 06:44 AM
The skin does NOT breathe--in any fashion or by any method. THAT is pure myth. It is a continuous complete barrier to any gas or aqueous liquid except under extemely high pressures.

we do sweat to eliminate toxins. No, our skin doesn't breath like our lungs, but a wet suit example doesn't satisfy that argument. Water has oxygen in it.


A better test would be to submerge someone in oil for an extended time. Let's then see if they have adverse effects.

joema
2005-Dec-22, 10:51 AM
we do sweat to eliminate toxins. No, our skin doesn't breath like our lungs, but a wet suit example doesn't satisfy that argument...
Sweat glands are contained WITHIN the skin are don't constitute a pathway THROUGH the skin.

Human skin is waterproof and a complete barrier to most substances.

This is because skin is composed of both lipid and aqueous layers. Most substances are either lipid soluble or water soluble. The skin's lipid layer stops water soluble substances, and the aqueous layer stops lipid soluble substances.

The skin barrier is so effective that it wasn't until the 1980s that transdermal drug delivery systems were developed.

The waterproof nature of skin is obvious since animal skins are used for carrying water and wine. In fact they're even called "waterskins", and "wineskins".

galacsi
2005-Dec-22, 10:57 AM
we do sweat to eliminate toxins. No, our skin doesn't breath like our lungs, but a wet suit example doesn't satisfy that argument. Water has oxygen in it.


A better test would be to submerge someone in oil for an extended time. Let's then see if they have adverse effects.

This test have been done : Feathers and tar , it is a sure death because tar close all the skin pores.

And also if too much of your skin is burn and without modern technology like skin graft with a skin culture , you cannot survive.

Of course we mammalian animals breathe with our lungs , but skin can and need take some oxygen from the air.

galacsi
2005-Dec-22, 11:06 AM
References, please? I was not aware that the skin "breathed." Are you thinking of people getting too hot due to heavy, water-proof protective clothing? That is a temperature control issue.

I did not find true scientific reference on the net , except about frogs and so on. i did find hundreds of references from the cosmetic industry but i dont think it is very interesting.

What i know for sure is if somebody has most of his skin damaged because it is burn or cover with tar or something like that the death is certain. Yet modern medecine can fight that with skin graft.

So an atmosphere of CO2 can be debilitating in the long term even if you breathe oxygen with a mask.

galacsi
2005-Dec-22, 11:10 AM
The skin does NOT breathe--in any fashion or by any method. THAT is pure myth. It is a continuous complete barrier to any gas or aqueous liquid except under extemely high pressures.

Your references ?

Because there is many case of poisoning through the skin. Skin is porous.

Van Rijn
2005-Dec-22, 11:19 AM
This test have been done : Feathers and tar , it is a sure death because tar close all the skin pores.


Please provide the references to those tests and show how they are relevant to this discussion. As said before, there can be a temperature control issue when one can't perspire properly, and it is possible for a person to die due to overheating. It is by no means a "sure death," however. There are also certainly some dangerous chemicals that can be absorbed through the skin. However, there are a number of examples where the skin is not exposed to significant oxygen for long periods of time and does just fine (being in water is one of them, dissolved oxygen is quite limited). And it is a fact that significant research has been done on "skin suit" space suits where the skin is supported mechanically, but is exposed to vacuum through a porous material.



And also if too much of your skin is burn and without modern technology like skin graft with a skin culture , you cannot survive.


True, but not relevant to this discussion. We are talking about the properties of the skin, not what happens when it is lost.



Of course we mammalian animals breathe with our lungs , but skin can and need take some oxygen from the air.


Again, please provide references.

Edited to add:

I saw your response after I submitted this:


I did not find true scientific reference on the net , except about frogs and so on. i did find hundreds of references from the cosmetic industry but i dont think it is very interesting.

Frogs are amphibians, and they certainly do absorb oxygen through their skin. We aren't amphibians. So, no references?


Because there is many case of poisoning through the skin. Skin is porous.

To some chemicals, yes. DMSO is a well known example. Skin is very resistant to absorbing many other chemicals and isn't terribly "porous." In any event, poisoning isn't the issue here. You are stating that the skin cannot go without oxygen, but you haven't shown any evidence for it.

joema
2005-Dec-22, 11:23 AM
Your references ?

Because there is many case of poisoning through the skin. Skin is porous.
The fact that you're alive to write this shows how effective the skin barrier is. If human skin wasn't a highly effective barrier to most substances, you'd be dead.

As I stated above, the skin barrier is so effective that transdermal drug delivery wasn't developed until the 1980s -- nobody could figure out how to get drugs through the skin.

There are a few substances that have good skin permeability such as Pluronic Lecithin Organogel (PLO) and dimethyl sulfoxide (DMSO). Just because a few substances can penetrate skin doesn't mean it's not a near-universal barrier.

You can find thousands of references on this if you search on "skin barrier function".

PhantomWolf
2005-Dec-22, 01:03 PM
Burns victims tend to dehydrate causing shock because the body excretes ichor from the wounds. The skin keeps water in as well as out, without it we tend to leak. This liquid comes from our blood volume and as that drops we go into shock, the heart beating harder to push the lesser amount of blood about the body, then finally giving out. They are also exposed to disease and other things which can kill a burns victim. It's not because their body can't breathe.

Apart from that the whole exploding, blood boilling thing is a Hollywood myth along with the "instant freeze" ideas.

Lance
2005-Dec-22, 02:28 PM
As I said earlier; the myth of "breathing through the skin" was debunked more that once on MythBusters. You don't breathe through your skin. Not even a little.

I think everyone here is in agreement except possibly the person who first mentioned it.

grant hutchison
2005-Dec-22, 07:58 PM
Those are some good points and some good thinking. However I'm not sure that's the case.Well ...
There is actually a word used to designate the boiling of body fluids at reduced pressures: ebullism. And a term to describe the altitude (19km) at which this occurs on Earth: the Armstrong Line. You can read more about it here (http://www.sff.net/people/geoffrey.landis/ebullism.html) and in the book review here (http://www.physoc.org/publications/pn/archive/article.asp?ARTICLE_ID=204).

There's one medical observation that shows your skin isn't tight enough to stop water boiling. If a person with a chest injury is put on a ventilator, and there's a laceration connecting the lungs to the outside world (a stab wound, say), then the positive pressure of the ventilator will squeeze air into the tissues: the patient swells up to like the old "Michelin man" advertisement, if you remember that. Typical ventilator pressures under these circumstances are about 15mmHg above atmospheric, which shows that your skin isn't tight enough to resist gas bubbles forming under that pressure. The vapour pressure of water at body temperature is much higher: 47 mmHg.

The boiling of venous blood doesn't have to be the rolling boil you see in a pan of water. Blood is full of particles (= blood cells) that might form nucleation points for millions of very small bubbles. Your circulation can tolerate these quite well (in fact, tiny bubbles are sometimes injected into the heart deliberately, to show up aberrant blood flow on an ultrasound scan). So I'm guessing the bubbles start small and build up over a couple of minutes. Repressurization would immediate drive them back into solution, so if they hadn't got to the point of clogging vessels and the heart, full recovery might be expected.
I've no evidence that this is the boiling mechanism that allows survival after brief exposures to low pressure, but it's certainly consistent with the physics, and the physiological changes described in my first link.

I can't explain why your NASA source denies the possibility of boiling, given how well referenced the phenomenon is (including a reference from a NASA publication in my first link). I've certainly seen websites that state "your blood won't boil", but most of them go on to "explain" this by saying that normal blood pressure is higher than 47mmHg. But that's arterial pressure, and it ignores the fact that the pressure in the venous circulation is only 5 to 10mmHg.
Nor can I explain the picture of the man with the boiling water: but I'd love to see some detailed information of the experiment being performed.

Grant Hutchison

galacsi
2005-Dec-22, 10:12 PM
As I said earlier; the myth of "breathing through the skin" was debunked more that once on MythBusters. You don't breathe through your skin. Not even a little.

I think everyone here is in agreement except possibly the person who first mentioned it.

You are right , i disagree.

What i found is :

Skin does breathe.(O2 in , CO2 OUT)
it represent only 1% of lung respiration.
This tiny respiration is indispendable to life.

joema
2005-Dec-22, 10:21 PM
...Armstrong Line...doesn't have to be the rolling boil you see in a pan of water....websites...ignores the fact that the pressure in the venous circulation is only 5 to 10mmHg.
While the Armstrong Line is typically described in popular literature as "the altitude at which blood boils", isn't the technical definition is the altitude at which unpressurized water boils at 98F? But maybe I'm wrong.

The Ebullism paper describes animal experiments where they were exposed to vacuum for 5-7 minutes and as long as their heart continued to beat, they recovered. It would appear physically impossible to fully recover if ischemia happened due to blood "boiling", even if very fine grained. After 5-7 minutes tissue death would have begun at least in some areas, and full recovery would be impossible.

The Ebullism paper also mentions the Kittinger incident. His hand was exposed to essentially a vacuum for over 1.5 HOURS. Yet when he returned to earth, his hand recovered just fine. If vacuum exposure truly causes blood boiling, how could his hand recover? The blood in his hand would have boiled that entire period, disrupting perfusion.

Re statements (not yours) that vacuum ebullism causes gross swelling, this obviously isn't so from the actual experience of Soyuz 11, where the cosmonauts were exposed to a vacuum for several minutes just before reentry. Aside from no respiration and heartbeat, their bodies looked totally normal. I've seen close up pictures of them, and they looked normal -- just like they were sleeping. In fact the recovery crew started CPR, not suspecting the cause. It took a careful investigation to determine what killed them:

http://www.astronautix.com/flights/soyuz11.htm
http://www.factbook.org/wikipedia/en/s/so/soyuz_11.html

So regarding blood "boiling", you have some good points. However some of the above indicates at a minimum, this doesn't happen as commonly perceived. If there is some gas coming out of solution, in a way it's a moot point -- you only have several seconds of consciousness, whether unprotected on Mars, the Moon, or in space. Actual experience indicates this might be 10-15 sec. In the case of rapid decompression it would likely be much less due to barotrauma. In the case of a prepared emergency decompression from a low pressure pure O2 environment (Apollo LM, etc) you'd avoid barotrauma and might have a few more seconds.

Back on the topic subject -- whether on Mars or the moon, you can't survive without either (1) a full pressure suit that looks very similar to shuttle/Apollo astronauts, or (2) an experimental counter pressure suit that looks similar to the tight-fitting capstan suits that fighter pilots wore in the 1950s: http://www.astronautix.com/craft/s2pesuit.htm

It's true more lightweight suits are DESIRABLE for Mars, and there's some active research on enhanced mechanical counter pressure suits (looks roughly like leotards). But the Martian environment doesn't make less protection POSSIBLE, just less cumbersome protection DESIRABLE.

grant hutchison
2005-Dec-22, 10:21 PM
What i found is :

Skin does breathe.(O2 in , CO2 OUT)
it represent only 1% of lung respiration.
This tiny respiration is indispendable to life.
And yet if I give you 1% less oxygen to breathe, and reduce your breathing by 1% so that carbon dioxide builds up (a dose of morphine administered in Denver would more than do the trick), you won't die. You won't even notice. How do you explain that?

Grant Hutchison

archman
2005-Dec-22, 10:28 PM
You are right , i disagree.

What i found is :

Skin does breathe.(O2 in , CO2 OUT)
it represent only 1% of lung respiration.
This tiny respiration is indispendable to life.

Yeah, that's not true. If it were, it would be in the human respiratory system section of basic biology texts. But it's not. I know.

Perhaps you are thinking of some other animal?

joema
2005-Dec-22, 10:39 PM
Skin does breathe.(O2 in , CO2 OUT)...
it represent only 1% of lung respiration....This tiny respiration is indispendable to life...

In addition to what's already been stated, we know skin respiration isn't vital to life for several other reasons:

(1) On two different occasions, the Mythbusters TV show painted a volunteer over their entire body with non-porous paint. The purpose was to examine this exact myth. They didn't die.

(2) Various NASA and military volunteers have been subjected to vacuum conditions while wearing experimental porous space suits. Their skin was exposed to a vacuum beneath the porous fabric, so obviously no skin respiration. They didn't die. Here's a picture (PDF): http://www.dsls.usra.edu/meetings/bio2001/pdf/140p.pdf

(3) Various NASA and aerospace workers have been completely immersed in an inert gas environment (argon, etc) for significant periods while breathing oxygen. Their skin obviously can't transpire oxygen as that atmosphere contains 0% oxygen. They didn't die, nor suffered ill effects.

grant hutchison
2005-Dec-22, 10:47 PM
While the Armstrong Line is typically described in popular literature as "the altitude at which blood boils", isn't the technical definition is the altitude at which unpressurized water boils at 98F? But maybe I'm wrong.You're right, that's how it's calculated. As my link article states, practical physiological considerations make it more of an "Armstrong band."


as long as their heart continued to beat, they recovered. It would appear physically impossible to fully recover if ischemia happened due to blood "boiling", even if very fine grained.You seem to be supposing that ischaemia is an immediate result of gas formation. Blood full of micro-emboli flows very well (there are people walking around with their circulation full of microemboli, from clotting disorders or infections), so I don't see any problems with a brief period of survival during which boiling is on-going and the gas volumes are building up. Remember that arterial pressure is still high enough (until the heart stops) to force some of the gas formed in the veins back into solution during each circulation, and that bubble volume will be reduced more than tenfold by the hydrostatic pressure in the arteries. Only when it gets into the capillaries will it start to re-expand and evolve more gas. So arterial perfusion could continue (for a while) despite significant gas evolution on the venous side of the circuit.


The Ebullism paper also mentions the Kittinger incident. His hand was exposed to essentially a vacuum for over 1.5 HOURS. Yet when he returned to earth, his hand recovered just fine. If vacuum exposure truly causes blood boiling, how could his hand recover? The blood in his hand would have boiled that entire period, disrupting perfusion.The rest of his body was at normal pressure: the gas forming in his veins would be almost immediately returned to an environment in which it recondensed, and very little of his circulation was exposed to gas formation at any given moment. So I'd say his gas load was small, and the arterial supply to has hand contained negligible quantities of gas by the time it had gone around the circulation. His hand would, in fact, be overperfused because the pressure gradient from his heart to his hand was grossly elevated by the vacuum.


Re statements (not yours) that vacuum ebullism causes gross swelling, this obviously isn't so from the actual experience of Soyuz 11, where the cosmonauts were exposed to a vacuum for several minutes just before reentry. Aside from no respiration and heartbeat, their bodies looked totally normal.They'd returned to normal atmospheric pressure. Steam in the tissues isn't going to persist under these circumstances: it'll very quickly condense back into a very small volume of water. Even gross swelling doesn't leave much of an indication behind on the skin once it has resolved: people with the "Michelin man" swelling I described earlier have no visible mark or disruption when the swelling resolves.


If there is some gas coming out of solution, in a way it's a moot point -- you only have several seconds of consciousness, whether unprotected on Mars, the Moon, or in space.For sure. No disagreement from me.

Grant Hutchison

joema
2005-Dec-22, 10:52 PM
...The rest of his body was at normal pressure: the gas forming in his veins would be almost immediately returned to an environment in which it redissolved, and very little of his circulation was exposed to gas formation at any given moment...
My point was his hand was exposed to a vacuum for 1.5 hours. If vacuum exposure causes blood "boiling", why did his hand survive? The blood in it should have been boiling for 1.5 hours, at least on the venous side.

grant hutchison
2005-Dec-22, 11:05 PM
My point was his hand was exposed to a vacuum for 1.5 hours. If vacuum exposure causes blood "boiling", why did his hand survive? The blood in it should have been boiling for 1.5 hours, at least on the venous side.I think I'm maybe not understanding your point, so forgive me if I'm missing something glaringly obvious:
It was boiling at body temperature, so there was no heat insult.
It was boiling for only a very short time (since blood flows quickly through your peripheries and back to your heart), so gas evolution was small and soon reversed, so there was no disruption to the blood itself.
In fact, the blood in the veins in his hand was probably at a rather high pressure (for venous blood, that is), since it was directly connected to veins in his body which were at a pressure equal to (normal venous pressure)+(suit pressure) - I don't know if this would get high enough to completely prevent gas formation, but it would certainly inhibit it.

Grant Hutchison

joema
2005-Dec-22, 11:57 PM
...It was boiling for only a very short time (since blood flows quickly through your peripheries and back to your heart), so gas evolution was small and soon reversed, so there was no disruption to the blood itself...
Maybe I'M missing something. Even though the transit time for bubbles through his hand was short, they'd be continuously replaced with incoming blood that would continuously maintain ebullism on the venous side of his hand's circulation.

Maybe you're saying, yes his hand was continuously experiencing ebullism for 1.5 hr, but it was of less magnitude so maybe that's why he recovered OK.

Re the risk of gaseous microemboli, I'll spare the references, but there are many papers saying this is bad. In fact it's an active research area to reduce gaseous microemboli, especially during heart bypass procedures.

If instead of blood "boiling" like a kettle of water, there's merely microemboli, this would still be bad. Although I agree the subject would likely be long dead before this was a problem.

BTW the research paper on the leotard-like counter pressure suit says it doesn't increase blood pressure. If that's the case, what prevents his blood from "boiling?"

http://www.dsls.usra.edu/meetings/bio2001/pdf/140p.pdf

grant hutchison
2005-Dec-23, 12:38 AM
Maybe you're saying, yes his hand was continuously experiencing ebullism for 1.5 hr, but it was of less magnitude so maybe that's why he recovered OK.More or less: but I don't think recovery from the ebullism was required at all. If a million gas bubbles a few microns across pop into existence, start to grow, but then shrink back to nothing half a second later, I suspect this will have no discernable effect on local blood flow, even if it continues for hours. The difference between the "hand vacuum" situation and the "total body vacuum" situation is that the bubbling blood from the hand is very quickly re-exposed to (arterial pressure)+(suit pressure), and stays in that pressure regimen for a long time before straying back into the hand again (because next time around the same "bit" of blood will go to the head or the leg or the liver or something); whereas if the whole body is exposed to vacuum, the bubbles are briefly exposed to (arterial pressure) only, and then they're back in the venous circulation where they can grow again.


Re the risk of gaseous microemboli, I'll spare the references, but there are many papers saying this is bad. In fact it's an active research area to reduce gaseous microemboli, especially during heart bypass procedures.Sure. But these emboli don't cause sudden death in under 2 minutes from generalized ischaemia, which was what you were worried about when I ventured into the "blood boiling" thing. After a few hours, in some people, they cause subtle degradations in mental status. (The emboli involve chunks of cellular debris and clot, too.)
Just by way of unconnected anecdote, I've heard gaseous venous emboli. With a Doppler ultrasound probe over a neck vein during neurosurgery, you can hear a gentle swoosh as blood flows past the probe (the red cells back-scatter ultrasound, and if you combine the outgoing signal with the Dopplered return signal, the beat frequency is in the audible range). If air bubbles gets into the neck vein (because the surgeon has opened a vein in the brain), the backscatter ramps up, and the swoosh gets scarily loud. But most of these patients suffer no ill-effects, provided you take prompt action.


BTW the research paper on the leotard-like counter pressure suit says it doesn't increase blood pressure. If that's the case, what prevents his blood from "boiling?"Your "blood pressure" is the difference between the pressure inside the vessel and outside the vessel. Under normal circumstances, that's the difference between the vessel pressure and atmospheric pressure: so a venous pressure of 10mmHg is 10mmHg above atmospheric, but is (760+10)mmHg above vacuum (since atmospheric pressure is around 760mmHg).
But if your whole body were exposed to vacuum, then a venous pressure of 10mmHg would be merely 10mmHg above vacuum: water would boil off.

The counter-pressure suit is designed to balance the pressure from breathing gas at 222mmHg: it's squeezing the body all over with (approximately) that pressure. So the venous pressure of 10mmHg is now (222+10)mmHg above vacuum: safely boil-proof.

Grant Hutchison

PhantomWolf
2005-Dec-23, 03:40 AM
There's one medical observation that shows your skin isn't tight enough to stop water boiling. If a person with a chest injury is put on a ventilator, and there's a laceration connecting the lungs to the outside world (a stab wound, say), then the positive pressure of the ventilator will squeeze air into the tissues: the patient swells up to like the old "Michelin man" advertisement, if you remember that. Typical ventilator pressures under these circumstances are about 15mmHg above atmospheric, which shows that your skin isn't tight enough to resist gas bubbles forming under that pressure. The vapour pressure of water at body temperature is much higher: 47 mmHg.

Huh? All this shows is that air can pass through the now perferated lung and into the body cavities. It's got nothing to do with boiling or anything else. The lungs are also very porous to air anyways, if you have a higher pressure of air in your lungs that outside your body you can easily get an embolism. Heck one of my pst flatemates did it when he had an ahasma attack and had to get the bubbles of air on his shoulders pricked to release it. What our lungs do when over pressurized with air has nothing to do with our skin keeping the pressure inside us amnd preventing blood from boil.

joema
2005-Dec-23, 04:01 AM
...Your "blood pressure" is the difference between the pressure inside the vessel and outside the vessel. Under normal circumstances, that's the difference between the vessel pressure and atmospheric pressure...
OK I understand better on all points. Thanks for the detailed reply.

PhantomWolf
2005-Dec-23, 04:34 AM
Your "blood pressure" is the difference between the pressure inside the vessel and outside the vessel. Under normal circumstances, that's the difference between the vessel pressure and atmospheric pressure: so a venous pressure of 10mmHg is 10mmHg above atmospheric, but is (760+10)mmHg above vacuum (since atmospheric pressure is around 760mmHg).

Huh? Unless you are talking about a different type of blood pressure, blood pressure is the force (or pressure) that is applied to the blood vessel walls by the blood being forced abut the body as your heart beats. Systolic pressure is the pressure that is created by the beat of the heart when it forces the blood about the body, while when the heart is at rest, between its beats, you have diastolic pressure.

Lance
2005-Dec-23, 04:46 AM
BBC News | Sci/Tech | Breathe skin, breath out (http://news.bbc.co.uk/hi/english/sci/tech/newsid_285000/285579.stm)


Sci/Tech - Breathe skin, breath out

The first mammal that can breathe through its skin has been discovered. Its unique physiological feat will help future studies of breathing in all mammals.

Jacopo Mortola on how he discovered the marsupial
But the creature that performs this clever trick is a newborn baby only 4mm (0.15 inches) long.

The Julia Creek dunnart is a marsupial mouse from Australia which gives birth to one of the tiniest of newborn mammals in the world. After only 12 days gestation, the pup is delivered to the pouch.

...

"By three weeks, the skin contribution is 50%, which is still an enormous amount if you consider that for other mammals, including humans, the skin contributes zero."

dmccarroll
2005-Dec-23, 05:08 AM
I kind of like the idea of the skin suit. Wear it under a pair of levis and a flannel shirt with a good parka and some mukluks and you would have all the temperature protection you need for those cold martian nights.

joema
2005-Dec-23, 06:39 AM
Huh? Unless you are talking about a different type of blood pressure, blood pressure is the force (or pressure) that is applied to the blood vessel walls by the blood being forced abut the body as your heart beats...
He's essentially describing the difference between gauge and absolute pressure. For more details see: http://en.wikipedia.org/wiki/Gauge_pressure

Blood pressure (whether systolic or diastolic) is typically referenced from local atmospheric pressure, although we rarely think in those terms. Yet whether blood "boils" is determined by absolute pressure, not relative or gauge pressure. That's what Grant was describing.

astromark
2005-Dec-23, 07:32 AM
As is often the case, we have come a long way from the question. To witch I would add. You would die. Unpleasant as it might be to consider, but the environment of no other place can support human life as it does here. End of story. Insufficient pressure, oxygen deprivation, radiation, and the cold, or is that the lack of heat.
No mater, its the end result we don't want to test. Death.

grant hutchison
2005-Dec-23, 12:20 PM
What our lungs do when over pressurized with air has nothing to do with our skin keeping the pressure inside us amnd preventing blood from boil.It's exactly the same thing, in a different guise.
I want to go through the reasoning in detail, so please forgive me if I repeat some stuff you know very well.

Think about what causes the air to leak into your tissues when there's a lung leak: it's the pressure gradient between the air in the lung and the ambient pressure in the tissues: if there's no pressure gradient, gas wouldn't move. The tissues under your skin are usually at about atmospheric pressure (because they're almost in direct contact with the atmosphere).
Your friend developed blebs of gas in his tissues because the pressure in his lungs was driven much higher than atmospheric by coughing, or by the fact that it's very difficult to breathe out during an asthma attack. So he forced gas into his tissues under pressure.
If you're on a ventilator, the same thing can happen if you have a lung leak, because of the pressure the ventilator applies to your lungs.
We know (because we measure and control it) the exact pressure a ventilator generates. So we know that's the pressure in the lungs of a ventilated patient - somewhere around 15mmHg, usually.
If your tissues were tight enough to oppose gas flow down that pressure gradient, ventilated patients with lung leaks wouldn't develop gross air in their tissues. But they do. So we know the tissues are easily forced apart and expand under a pressure of 15mmHg.
The saturated vapour pressure of water at body temperature is 47mmHg. If the pressure outside the tissues is zero (you're in vacuum) then all the water under your skin is trying to flash into gas, pushing with that pressure. The fact that your tissues can't resist 15mmHg of overpressure means we can say that they won't resist 47mmHg overpressure, so gas will form under your skin.

Grant Hutchison

Edit: to specify "body temperature" for the saturated vapour pressure of water given here

grant hutchison
2005-Dec-23, 12:27 PM
]

Huh? Unless you are talking about a different type of blood pressure, blood pressure is the force (or pressure) that is applied to the blood vessel walls by the blood being forced abut the body as your heart beats...He's essentially describing the difference between gauge and absolute pressure.Exactly, thanks.
When you measure a blood pressure you measure a pressure gradient, between the inside of the vessel and the ambient pressure in the outside world. Your circulation doesn't care what the absolute pressure is, only the relative pressures between different parts of your circulation, because that's what drives the blood around.

Grant Hutchison

Edit: To include PhantomWolf's original text, for clarity

Relmuis
2005-Dec-23, 01:21 PM
As far as I know, the skin doesn't need to take oxygen from the air as long as the blood ciculating through blood vessels in the skin delivers enough oxygen.

But there are two organ pairs in the human body which do take their oxygen directly from the air.

One of them are the lungs. Which means that your lungs might already be damaged before you lose consciousness from hypoxia. (The blood perfusing the lungs has already been depleted of its oxygen.)

The other one are the cornea's of your eyes. Which is why wearing contact lenses may damage them. (No blood vessels enter the cornea, because this would interfere with vision.)

So any mask worn to provide oxygen should cover the eyes.

In a (near-)vacuum, both lungs and cornea's might also be damaged by dehydration, but they wouldn't be safe even in 1 bar of pure argon, or something similar.

grant hutchison
2005-Dec-23, 08:02 PM
OK I understand better on all points. Thanks for the detailed reply.No problem.
But have I convinced you? :)

Grant Hutchison

joema
2005-Dec-23, 09:08 PM
Well I now believe there is some type of ebullism in an unprotected body in a vacuum. But the common description about "blood boiling" seems to convey the wrong idea. In fact many sources graphically describe it as "like a teapot on a stove", etc.

However we may simply not know the specifics. Doppler ultrasound, etc didn't exist when the animal vacuum tests were done, so the data quality isn't like contemporary capability. It was probably mostly observational.

Isn't rapid decompression from a hyperbaric chamber to 1 atm similar? Maybe more contemporary instrumented Navy or Air Force data exists for that. If a test subject was in a hyperbaric chamber at several atmospheres pure O2 and hardware failure caused an instant decompression, wouldn't that cause gas coming out of solution in the bloodstream? How similar is that to going from, say 5 psi pure O2 to vacuum?

To any readers following this: it makes no difference about unprotected survival on Mars. You'd have about 10-15 seconds of consciousness, max, regardless of whether/how your blood was "boiling" or not. Mars is essentially a vacuum environment, similar to the moon or outer space. You can't get by with a parka and oxygen mask.

grant hutchison
2005-Dec-23, 09:45 PM
However we may simply not know the specifics.I'm sure that's correct. My suggestion that the boiling occurs as microbubbles is based only on a chain of supposition and observation:
1) Physics seems to suggest that the evolution of vapour is unavoidable.
2) There is no localized source of heat to drive convection or the local evolution of large bubbles, as happens in a kettle. It seems that the blood should instead fizz simultaneously throughout its volume, like a bottle of champagne being opened.
3) Bubbles general needs nucleation sites to get them started. Blood is full of potential nucleation sites (red blood cells) that are of almost identical size, so again diffuse uniform bubbling seems likely.
4) Experiments show that animals don't experience cardiac arrest in a single circulation time, as they would if big lolloping bubbles were entering the heart from blood at a rolling boil. Again, this suggests that initial bubble formation is small.


Isn't rapid decompression from a hyperbaric chamber to 1 atm similar?It would certainly be interesting to find out how the nitrogen bubbles form: uniform fizz or localized big bubbles. The difference I can see is that there's an endpoint to nitrogen evolution: it'll come out of solution only until the gas reaches a new equilibrium with the dissolved phase. Whereas in vacuum exposure, water will continue to boil until it's all gone: there's certainly the potential to evolve huge volumes of water vapour from the human body. There's also no reason I can think of that would dictate that the rate of gas evolution would be the same in both cases, but perhaps someone might be able to perform a thermodynamic calculation that would allow comparison.
Yep, would be interesting.

Grant Hutchison

joema
2005-Dec-24, 12:13 AM
...interesting to find out how the nitrogen bubbles form: uniform fizz or localized big bubbles. The difference I can see is that there's an endpoint to nitrogen evolution: it'll come out of solution only until the gas reaches a new equilibrium with the dissolved phase. Whereas in vacuum exposure, water will continue to boil until it's all gone...
BTW, I stated pure O2 because that simplifies the situation (avoids nitrogen), and the entire US manned space program before the shuttle used pure O2 (which is still used in space suits).

But you have a good point -- there's a difference between a gas coming out of solution, say when going from 3 atm to 1, vs a vacuum. When going from hyperbaric to 1 atm, the gas evolution stops after a point. In a vacuum it never stops until the fluid is gone.

My guess is the hyperbaric to 1 atm case has been studied with more contemporary technology (ultrasound, ultra-fast MRI, etc), but how closely this correlates to the vacuum case, I don't know. Also a quick NLM search doesn't show any recent papers on that.

However the pure O2 case would rarely be studied. Because of oxygen toxicity, it's almost impossible for a non-astronaut to be exposed to sufficiently high O2 pressure long enough to experience decompression sickness from rapid return to 1 atm. It would require a bizarre situation like being in a pure O2 hyperbaric chamber to just short of oxygen toxicity, then an accident or error causing chamber pressure to quickly drop to about 3 psi pure O2.

Denis12
2005-Dec-24, 12:56 AM
What will really happening with me when i stepping out of a moon or marslander unprotected (without) spacesuit on mars or on the moon,can you explain that from stepping out of the lander until my death. Denis.

Joff
2005-Dec-24, 01:08 AM
Random thoughts on blood boiling:

47mmHg is roughly of 6% atmospheric pressure. Assuming that blood is basically sea water, the pressure would need to be a touch lower to bring the boiling point down to 37C, but we'll keep that margin in reserve for now.

Atmospheric pressure is equivalent to a head of water, under Earth gravity, of 10m. Presumably under Mars surface gravity you would need a head of 10/0.38 = 26m for the same pressure.

Now let's assume that tissue elasticity is going to provide a base pressure of 10mmHg. We then need to find an extra 37mmHg to keep our blood liquid, which is a Mars-water-head of 1.3m. So if you stand on your head, legs straight up, you should have about that much head of liquid above your heart. So we just need to send acrobats of slightly above-average height to Mars and have them live upside-down.

PhantomWolf
2005-Dec-24, 01:39 AM
It's exactly the same thing, in a different guise.

I disagree. With a respirated lung injury or other form of embulism, the air is already a gas and the body has no way of countering that, it can't compress that gas back into a liquid. This means you can't compare this with how a liquid is going to react. Not only that, but when a liquid is bound by a vessel, it doesn't react the same way as it would in the open, and our body's are a vessel. You can't just take the figures for vapourisation in the open and apply it to the internal parts of our body.

You are also ignoring that there are more pressures on the blood that what is on our skin. Our tissues only expand so far and the heart places huge pressures on the blood every heartbeat. Under the way you seem to be going people should drop dead in a vaccum because as soon as their heart beats, they should swell up without the blood going anywhere because there is no pressure. This obviously doesn't happen.

I will give that if they stepped from a N/O mix then they would likely experience the bends, hiowever this is a saturation problem, not a boiling issue. Unlike O2, which is chemiclly bound to the Hemoglobin, N2 is dissolved in the blood. As the pressure drops slightly, the amount of disolved N2 the blood can store decreases and so it becomes super saturated and bubbles out of the solution. This is why it does so until it once more reaches an equilibrium.

I guess since few people would willing volunteeer for such an experiment it would be difficult to check on a person, but perhaps someone here who has access to a vacuum chamber can do a little experiment by filling up a water balloon with water and then putting it in the chamber and seeing what happens when they evacuate it.

joema
2005-Dec-24, 02:10 AM
What will really happening with me when i stepping out of a moon or marslander unprotected (without) spacesuit on mars or on the moon,can you explain that from stepping out of the lander until my death. Denis.
You'd be in tremendous pain, but you'd probably have about 10-15 seconds of consciousness. Presumably the moon or Mars lander would be a low pressure (4-5 psi) pure O2 environment, so there'd be no problem with the bends.

In the reduced gravity, you might be able to run 50 yards on the surface of the moon or Mars before you dropped.

There's only one well documented case of a human in that situation, a NASA worker testing a space suit in a vacuum chamber in 1966. He didn't report any pain, but he remembered the saliva on his tongue boiling just before he passed out.

If it were a planned situation, you'd dial down the pressure to about 2-3 psi before blowing the hatch, which would reduce barotrauma (inner ear shock from sudden pressure drop).

If you've seen the movie 2001: A Space Odyssey there's fairly accurate scene about this. Much more accurate than movies like Total Recall that depict people's eyes bulging out, or other movies that show people exploding in a vacuum.

grant hutchison
2005-Dec-24, 02:27 AM
I disagree. With a respirated lung injury or other form of embulism, the air is already a gas and the body has no way of countering that, it can't compress that gas back into a liquid.But it can simply stop it entering the tissues: if your tissues stretched by only a tiny amount before their internal pressure rose to 15mmHg, then only a tiny amount of air could move from the lungs to the tissue. The massive Michelin swelling would be impossible. It's like the difference between blowing up a balloon (easy) and blowing up an old-fashioned hot water bottle (hard). It is evident from the ventilator example that tissues are easy to blow up with relatively low applied pressure.
Shift to the evaporating liquid: it applies a vapour pressure according to its temperature. If the external pressure is zero, water vapour will push outwards with a pressure of 47mmHg, and the tissues will expand until their internal pressure rises to 47mmHg: because they're easy to blow up, that'll be a big volume change.


Not only that, but when a liquid is bound by a vessel, it doesn't react the same way as it would in the open, and our body's are a vessel.The liquid will evaporate until the vapour pressure over its surface rises high enough to stop any more evaporation. In the open air, that'll happen when the saturated vapour pressure is reached. Or, if the ambient pressure is lower than the saturated vapour pressure, the liquid will boil dry. In an enclosed space, the liquid will evaporate until it has pressurized that space to its saturated vapour pressure. If the space is large, or very distensible, than that may involve the production of a lot of gas. During the time the gas space is filling, the ambient pressure will be below the saturated vapour pressure, and the liquid will be boiling.


You are also ignoring that there are more pressures on the blood that what is on our skin. Our tissues only expand so far and the heart places huge pressures on the blood every heartbeat.I've already dealt with that by pointing out that no boiling will occur in the arterial circulation, because arterial pressure is higher than 47mmHg. Venous pressure is much lower than 47mmHg, however, and the veins are thin-walled and highly distensible.


Under the way you seem to be going people should drop dead in a vaccum because as soon as their heart beats, they should swell up without the blood going anywhere because there is no pressure.No, the arterial blood is well-contained in elastic vessels, won't boil, and will flow to the tissues. As I've said already, your circulatory system doesn't care about the absolute pressure, only the relative pressure between different areas.
Let's say your mean arterial blood pressure is about 90mmHg, and your mean venous blood pressure is 10mmHg. This means your arterial blood is sitting at 90mmHg above atmospheric, and your veins at 10mmHg above atmospheric (=760mmHg). So in absolute terms, your arterial pressure is 760+90=850mmHg, and your venous pressure is 760+10=770mmHg. Blood flows from arteries to veins down that pressure difference of 80mmHg.
I put you in a hyperbaric chamber, and take you up to two atmospheres. I measure your blood pressure: arterial is still 90mmHg above atmospheric, venous is still 10mmHg above atmospheric, flow is still taking place at the same rate down the 80mmHg pressure gradient. But the absolute values are now very different: 1520+90=1610mmHg and 1520+10=1530mmHg.
Now I take you down to vacuum: blood pressure will still (initially!) be 90mmHg arterial and 10mmHg venous above atmospheric (which is now zero), and flow will still occur down the same 80mmHg pressure gradient at the same rate.
(But after a while, as gas builds up in tissues and veins, the venous pressure will rise and the blood flow will tail off. We think your heart may well stop from hypoxaemia before that becomes a problem.)


... but perhaps someone here who has access to a vacuum chamber can do a little experiment by filling up a water balloon with water and then putting it in the chamber and seeing what happens when they evacuate it.It'll depend on the internal pressure of the balloon. If it's above the saturated vapour pressure of the water, the water will stay liquid. If it's below the saturated vapour pressure, the water will boil and evolve gas, distending the balloon until the internal pressure of the balloon rises to match the saturated vapour pressure, or the ballon bursts. You can see the analogies with the human body: the arterial system is a balloon with high internal pressure; the veins and tissues are a balloon with low internal pressure.

Grant Hutchison

fossilnut2
2005-Dec-24, 02:47 AM
You'll need a lot of protection because of radiation. Secondary radiation will blow holes in your DNA. Don't forget that when you get to Mars you'll have been 'zapped' along the way and are going to be 'zapped' on the voyage home. Unless someone comes up with some novel shielding methods nobody will be spending hardly any time, if any, walking around the Martian surface even in a suit. And don't expect much time zipping around in a vehicle on the surface Astronauts will be hunkered in bunkers with radiation shielding.

Radiation exposure is cumulative. It's even questionable at our current understanding of radiation that an astronaut who goes to Mars will be afforded any 'dry runs' to the Moon but will need low exposure to radiation in life before they ever start the trip to Mars.

Van Rijn
2005-Dec-24, 05:32 AM
You'll need a lot of protection because of radiation. Secondary radiation will blow holes in your DNA. Don't forget that when you get to Mars you'll have been 'zapped' along the way and are going to be 'zapped' on the voyage home. Unless someone comes up with some novel shielding methods nobody will be spending hardly any time, if any, walking around the Martian surface even in a suit. And don't expect much time zipping around in a vehicle on the surface Astronauts will be hunkered in bunkers with radiation shielding.


Yes, secondaries are certainly an issue, as I mentioned back here:

http://www.bautforum.com/showpost.php?p=632136&postcount=28

As the NASA article I referenced mentions, we still have more to learn. However, it is a bit much to say that it would be too dangerous to spend any time in a suit. It is an issue, but it isn't that extreme.

The atmosphere provides some protection, and merely placing a habitat next to a good sized hill helps when you aren't out and about. Vehicles can be designed with some radiation protection. It can be managed.

wayneee
2005-Dec-24, 06:00 AM
I found this Article , seems to point to the cause of the mythhttp://debrief.commanderbond.net/index.php?showtopic=16572

PhantomWolf
2005-Dec-24, 07:26 AM
You'll need a lot of protection because of radiation. Secondary radiation will blow holes in your DNA. Don't forget that when you get to Mars you'll have been 'zapped' along the way and are going to be 'zapped' on the voyage home. Unless someone comes up with some novel shielding methods nobody will be spending hardly any time, if any, walking around the Martian surface even in a suit. And don't expect much time zipping around in a vehicle on the surface Astronauts will be hunkered in bunkers with radiation shielding.

I think you are overstating the problem. Okay granted there is a reasonable amount of radiation, (about six months worth on Earth per day on Mars) but only if you are exposed to it. Proton and Electron shielding is not that hard as was shown with Apollo, and secondary radiation from surface strikes is much lower in amount than the initial levels that cause it. Shielding there and back isn't that hard for the standard amounts of Radiation, water and a polymer such as the polyethylene used in the ISS will do that effectively.

Now, a solar flare might be a more dangerous thing. They can throw out 1000x the standard amounts and that'd be a threat, however it is also one that can be planned for. That really just means extra shielding for the ship and habitats.


Radiation exposure is cumulative. It's even questionable at our current understanding of radiation that an astronaut who goes to Mars will be afforded any 'dry runs' to the Moon but will need low exposure to radiation in life before they ever start the trip to Mars.

Radiation isn't cumulative except over short periods. This is because our body regenerates and repairs damage. We aren't like machines that only can take a certain amunt and then fall over, rather by getting away from whatever's dosing us, we can heal and reset to a zero dosage. Between shielding and our healing abilities, there is no reason that Astronauts can survive on Mars remarkably easily, even if they do have to hunker down inside when CME's head their way.

Cylinder
2005-Dec-24, 11:45 AM
It might also be worth noting here that tar-and-feather deaths were caused by burns and rough treatment by whatever mob dispensed the treatment.

Relmuis
2005-Dec-24, 03:06 PM
While thinking about this, it occurred to me that there wouldn't be all that much difference between walking on Mars without a protective suit and doing the same thing on the Moon. Provided that one would be wearing shoes.

On the Moon there would be somewhat more radiation (no atmosphere at all, no magnetic field at all, less distant from the Sun) and more extreme temperatures, which however wouldn't readily communicate themselves to the human body except where it touched something solid.

But the two most immediate threats, on the Moon as on Mars, would be the absence of atmospheric pressure, and the absence of oxygen.

As regards the first threat: any pressure lower than the pressure needed to keep water liquid at 37 degrees centigrade might as well be classified as a clinical vacuum. If blood would boil on the Moon, it would boil on Mars. And if it wouldn't boil on the Moon, it wouldn't boil on Mars.

As regards the second threat: a vacuum might cause hypoxia faster than merely breathing pure nitrogen or argon, because one wouldn't be able to keep air inside the lungs and oxygen might therefore be drawn out of the blood. But of course the blood perfusing the lungs has already lost most of its oxygen, so this might not make much of a difference. Especially as there is no carbon dioxide in a vacuum either, and carbon dioxide expedites the release of oxygen from the blood. (Which helps the transport of oxygen to those tissues where it is most needed, but makes carbon dioxide more dangerous than other non-poisonous gases: CO2 can asphyxiate people even if enough oxygen is still present.)

If this oxygen loss is unimportant, hypoxia would not incapacitate an astronaut before one or two minutes have passed, and would not kill him or her until a few minutes later.

The effects of the pressure loss seem more doubtful. A sudden loss of pressure (a puncture in a balloon-tent causing the tent to blow up), might cause instant death. A large force on the inside of the skin (10 Newtons per square centimeter of skin) is suddenly no longer compensated for by an outside force, and the astronaut pops like a piece of popcorn. Even if the skin would somehow survive, the lungs would rupture, and fill with blood, leaving not enough blood to maintain circulation. Blood starts foaming like champagne, eyes burst open, eardrums shatter, and the remains would be quite unpleasant to look at.

A more gradual loss of pressure might be survivable if one doesn't try to hold one's breath, which would cause the chest to explode. Lungs and eyes start to suffer dehydration damage, compounding the absence of oxygen, and gas bubbles might develop in the venous blood. Even if these bubbles are reabsorbed after returning to the heart, they may by that time have cause blood clots to form, which may cause embolisms throughout the body, which may yet kill the astronaut long after he or she has reached safety. But this, too, would probably take several minutes to kill or incapacitate the astronaut.
(This, however, is a question of luck; a stroke or heart attack might occur within twenty seconds.)

So it seems probable that the astronaut might have a period of one or two minutes to reach safety, but would suffer great and possibly lethal damage during this period. One would not do it for fun, to show off, or to win a bet, but one might do it to save lives, to achieve the purpose of the mission, or to escape from a doomed vessel.

joema
2005-Dec-24, 03:23 PM
As already mentioned several times, there would be little difference in unprotected survival time on the moon vs Mars.

You wouldn't have 2-3 minutes of useful consciousness. It would be about 10-15 seconds. That's certain from previous incidents of human exposure to vacuum.

A sudden decompression would likely cause barotrauma, mainly to the ears. However it wouldn't kill the astronaut or cause him to explode. Many high altitude sudden decompressions have happened to pilots. It's a serious thing, especially at very high altitude, but they don't explode or immediately die.

All the people who walked on the moon so far were breathing a pure oxygen atmosphere at about 5 psi, roughly 1/3 total sea level pressure on earth. The barotrauma and shock from a sudden decompression from 5 psi would be much less than from 14.7 psi.

There would also be no nitrogen bubbling in the blood, but that's probably unimportant since you'd only have 10-15 sec of consciousness.

Relmuis
2005-Dec-24, 04:21 PM
Trained sponge divers and pearl divers could remain submerged (and do their jobs!) for several minutes. A number of five minutes was quoted, though I tend to disbelieve this number.

Sources agree that it was very unhealthy, though. Most of these divers didn't live to see their 40th birthday.

joema
2005-Dec-24, 04:41 PM
Free divers have the air in their lungs. People in a vacuum don't.

Unprotected humans have been exposed to near vacuum conditions during high altitude aircraft decompressions, so we have useful data about time of useful consciousness. It's about 10-15 seconds.

Also the NASA employee in the documented vacuum chamber incident in 1966 stayed conscious for about that period.

All the data we have indicates an unprotected human on the moon or Mars would likewise have about 10-15 seconds of useful consciousness.

grant hutchison
2005-Dec-24, 04:57 PM
But of course the blood perfusing the lungs has already lost most of its oxygen, so this might not make much of a difference.In fact, the haemoglobin in blood returning to the lungs still contains about 75% of its maximum carrying capacity for oxygen. If you can keep a partial pressure of oxygen in your lungs higher than about 40mmHg, that'll prevent this oxygen being lost into the lung gas, and when it recirculates your tissues will still be able to use it. if the partial pressure of oxygen in your lungs is higher than 40mmHg, as it is when you hold your breath, then the venous blood will pick up oxygen, and that will also be delivered to the tissues, prolonging the period before you run out of oxygen.
If your lungs are open to vacuum, then the oxygen will simply pour out, and your arterial oxygen levels will drop very quickly towards zero: hence the prompt unconsciousness.
If you breathe an atmosphere of 100% nitrogen or argon, then oxygen will also leave the venous haemoglobin, but the transfer will stop when the partial pressure of oxygen in the lungs rises towards 40mmHg. Then you breathe that mixture out, breathe more oxygen-free gas in, and the process repeats. So you have a few cycles of breathing before the arterial levels fall disasterously.
I've actually seen someone start in on this process. At a birthday party, years ago, a few people were breathing helium from the party balloons to get the "Donald Duck" voice effect. One guy breathed right out as far as he could, and then breathed in pretty much the whole content of a large balloon, until he could breathe in no more. This shoved the partial pressure of oxygen in his lungs very low, venous blood started to leak oxygen into his lungs instead of pick it up, he went very suddenly very blue indeed and toppled off his chair making a high-pitched "Ooo-ooo-oooh" noise which would have been very funny under other circumstances. He didn't lose consciousness on that single breath, but it was impressively evident that his chances of surviving to get out of, say, a room full of helium would have been very small indeed.

Trying to hold your breath in vacuum (or at very low ambient pressures) to stop this happening might well be counterproductive, though. Since your tissue and blood pressures will equilibrate with the ambient immediately, you'll find yourself trying to hold on to a lung-full of gas at one atmospheric pressure higher than ambient. This is ludicrously higher than your cardiorespiratory system is designed to cope with: I doubt if you'd actually be able to keep your vocal cords or lips closed tightly enough. If you could, the lung capillaries would squash closed, and your heart wouldn't be able to get any blood through the lungs (normal pressure in the pulmonary artery only gets up to 24mmHg, so it's not going to cope well with a pressure of 760mmHg). People who are exposed to high airway pressures also typically blow holes in both lungs and suffer gas emboli into their circulation. (Submariners escaping from depth are therefore told to breathe out continuously as they rise to the surface, to avoid damaging their lungs.)

The astronaut in 2001 would probably have been better off breathing out, too, rather than holding his breath as the actor did in the film.

Grant Hutchison

joema
2005-Dec-24, 09:35 PM
...The astronaut in 2001 would probably have been better off breathing out, too, rather than holding his breath as the actor did in the film...
I just checked my copy of the movie, and it's not totally clear whether he was holding his breath, or just grimacing before blowing the hatch. His eyes were tightly closed. He wasn't shown hyperventilating beforehand. But you're right you'd likely want your mouth opened, not closed like his was.

The entire vacuum scene lasts about 11 sec. before the door closes, so that's roughly consistent with our knowledge about vacuum survival.

The space pod would likely have had low pressure pure O2 cabin environment, similar to the Apollo LM. There are engineering and biomedical reasons for that.

If you were in that situation, you'd dial down the cabin pressure to the lowest momentary survivable level (maybe 2.5 psi) just before blowing the hatch to reduce barotrauma. The movie doesn't specifically depict that, but it shows him pressing several buttons before blowing the hatch, so we could plausibly imagine that.

The scene isn't perfect, but it's the most realistic vacuum survival depiction I recall seeing in any movie. It's certainly much more realistic than movies showing people exploding.

grant hutchison
2005-Dec-24, 09:57 PM
I just checked my copy of the movie, and it's not totally clear whether he was holding his breath, or just grimacing before blowing the hatch.Hmmm. I seem to recollect seeing lips compressed and cheeks bulging during the vacuum-silent sequence as he blew into the airlock. But perhaps my recollection is tainted by having read Arthur C Clarke's writings about the film - Clarke said that Keir Dullea ("Dave Bowman") held his breath, and I guess I've just gone with that thought ever since. (Clarke, of course, pointed out that keeping your mouth open and yawning was probably the better option.)


The scene isn't perfect, but it's the most realistic vacuum survival depiction I recall seeing in any movie.Agreed! I wasn't trying to suggest otherwise.

Grant Hutchison

Denis12
2005-Dec-24, 10:33 PM
How long wil it takes when i step out of the moonlander without spacesuit,when i go die? And i find it very strange that the nasa worker was doing well during his vacuum chamber. And on earth is the mean airpressure 1014 milibar or Hpa (on my barometer at this moment 990 milibar) lower than usual. And how was the pressure (in milibars) in the moonlander before the astronauts get out of it for walking on the moon? And the airpressure in (millibars) in their spacesuits on the time of walking on the moons surface? Denis.

joema
2005-Dec-25, 12:00 AM
If you stepped out of your moon lander with no suit, you'd remain conscious for about 10-15 seconds and be dead without a couple of minutes.

The NASA worker was NOT doing well -- he lost consciousness withing 10-15 seconds was exposed to vacuum for about 30 sec and then recompressed. He did survive with no ill effects.

Both Apollo Lunar Module and all US space suits to present use about 5 psi pure O2, or 344 millibars.

Denis12
2005-Dec-25, 12:54 AM
Is 344 millibar not unhealty low? Why not an near earthpressure of 1000 mb or so?

joema
2005-Dec-25, 03:56 AM
What counts is partial pressure of oxygen. For details see http://en.wikipedia.org/wiki/Partial_pressure

344 millibars of pure oxygen is 5 psi. Earth's atmosphere is 79% nitrogen and 20% oxygen at 14.7 psi (1013 millibars). The partial pressure oxygen at sea level on earth is about 2.94 psi (202 millibars).

Therefore the actual amount of breathing oxygen available to an Apollo astronaut at 5 psi is greater than on earth at sea level.

Pure oxygen at 5 psi (344 millibars) was chosen because it reduces the forces on the cabin structure, avoids decompression sickness (the "bends"), increases survivability during a cabin puncture, avoids lengthy pre-breathing of oxygen before donning a space suit for EVA, and makes space suits usable (a space suit at 14.7 psi would be too rigid to use).

Humans can actually survive for short periods at under 1 psi pure O2. Therefore in a pre-planned emergency unprotected vacuum exposure (like 2001) you'd reduce the pure O2 cabin pressure to 1 psi or below before blowing the hatch. That would greatly reduce the barotrauma shock of sudden pressure drop. http://en.wikipedia.org/wiki/Barotrauma

PhantomWolf
2005-Dec-25, 08:32 AM
Of course the major reason for choosing pure O2 is that you don't have to liquify or compress and then carry around all that annoying 79% N2 that does nothing but hang around in the air. ;)

Van Rijn
2005-Dec-25, 08:54 AM
Both Apollo Lunar Module and all US space suits to present use about 5 psi pure O2, or 344 millibars.

Correction: Apollo era suits during EVA were normally around 3.8 psi. Shuttle era suits are a bit higher at 4.2 psi. Higher pressure makes it harder to work the joints. It would have been very hard to move in an Apollo era suit at 5 psi.

Relmuis
2005-Dec-25, 02:58 PM
In a television programme it was suggested that using pure oxygen presents an increased fire hazard, even if the oxygen pressure doesn't exceed the partial pressure of oxygen on Earth.

This should not be true if the gases in our atmosphere behave approximately like perfect gases.

But if it is true anyway, then a different gas mix with the same partial pressure of oxygen might also present a health hazard. It would not be clear, for example, whether one might survive in 2.8 bars of nitrogen and 0.2 bars of oxygen. And it would not be clear either, whether 0.2 bars of pure oxygen might not damage the lungs.

joema
2005-Dec-25, 05:26 PM
Of course the major reason for choosing pure O2 is that you don't have to liquify or compress and then carry around all that annoying 79% N2 that does nothing but hang around in the air. ;)
That wasn't really the major reason. N2 is inert and not metabolically consumed like O2, so you'd need much less than you'd think.

There were several reasons, but below is a quote from History of Manned Space Flight, by David Baker:

"...systems engineers disliked the complex two-gas atmosphere...an important consideration was...the complexity inherent in a two-gas system. Moreover, with oxygen pressure fixed at a minimum level, the total atmospheric pressure of a two-gas environment would threaten the structural integrity of the pressure vessel. Leak rates would be higher...A basic tenet of spacecraft design...is that simplicity leads to reliability"

So to summarize there were numerous reasons:

- reduced complexity of environmental control system (ECS)
- reduced weight from simplified ECS
- reduced weight from not carrying N2, although total weight savings was modest at 16kg
- avoid need for lengthy prebreath of pure O2 before EVA, necessary to transition to space suit 3.8 psi pure O2 environment. If in a sea level O2/N2 environment, it takes 4 hours of breathing pure O2 before donning a space suit. How'd you like to have a cabin rupture and be unable to don your space suit for four hours?
- reduced weight from thinner cabin walls
- increased safety from a hull puncture due to decreased cabin pressure: Apollo could sustain a 5 inch diameter hull puncture for 2 minutes, which wouldn't be possible with a higher pressure two-gas system
- avoid decompression sickness (the bends) from a sudden pressure drop
- decrease leak rates

After the Apollo 1 fire, NASA adopted a mixed O2/N2 environment while on the pad, but during ascent this gradually changed over to an approx 5 psi pure O2 cabin environment.

The shuttle and ISS use a higher pressure mix-gas environment for several reasons:

- increased confidence in managing the complexity of a two-gas system
- increased confidence in vehicle structural integrity
- decreased fire risk
- avoid the physiological time limits of pure O2, more important for long term missions like the shuttle and ISS. I don't know what the limits are, but you can't breath pure O2 forever (even at reduced pressure) because your body won't tolerate it.

joema
2005-Dec-25, 05:45 PM
In a television programme it was suggested that using pure oxygen presents an increased fire hazard, even if the oxygen pressure doesn't exceed the partial pressure of oxygen on Earth.
That is correct. A pure O2 environment, even at the ppO2 of sea level earth (about 3 psi) is a significant fire risk. That's because nitrogen has a significant fire suppressing effect due to heat conduction from the flame. In a 3 psi pure O2 environment, fire risk is significantly greater.


it would not be clear either, whether 0.2 bars of pure oxygen might not damage the lungs.
0.2 bar (2.9 psi) O2 is about the partial pressure of earth at sea level. You can breath that for long periods (weeks) but there's probably a physiologcal limit for very long periods.

joema
2005-Dec-25, 05:57 PM
Correction: Apollo era suits during EVA were normally around 3.8 psi. Shuttle era suits are a bit higher at 4.2 psi. Higher pressure makes it harder to work the joints. It would have been very hard to move in an Apollo era suit at 5 psi.
That is basically correct, although Apollo suits were not always at 3.8 psi. They were inflated to about 7.3 psi (3.8 psi above a 3.5 psi cabin environment) to check for suit integrity before an EVA. For brief periods they were at 5 psi absolute, and the astronauts (as you said) mentioned it was very hard to move at that pressure.

The Russian Orlan suit operates at 5.8 psi pure O2. It's a semi-rigid design, with flexible arms and legs like American suits, but the torso is rigid.

Van Rijn
2005-Dec-26, 04:43 AM
That is basically correct, although Apollo suits were not always at 3.8 psi.

Yep, that is why I specifically noted that the suits were normally at about 3.8 psi during EVA.:)

tony873004
2005-Dec-27, 07:31 PM
...Your friend developed blebs of gas in his tissues because the pressure in his lungs was driven much higher than atmospheric by coughing
That's interesting. A few years ago I had spontaineous pneumothorax, also referred to as a collapsed lung. A few hours before I first noticed the symptoms, I had a bad case of the hiccups. I asked several doctors if that had anything to do with it and they said no. I was never very confident with their answers. But I could never find anything on the internet confirming my suspicions either. Your quote is the closest I've found, coughing rather than hiccups.

grant hutchison
2005-Dec-27, 07:50 PM
Your quote is the closest I've found, coughing rather than hiccups.I don't know of a connection: when you hiccup the pressure in your lungs goes a little below atmospheric, if anything. But if your pneumothorax was just sitting waiting to happen, with a weak spot on the surface of the lung ready to pop, then maybe any unusual pressure gradient would be the final straw.

Grant Hutchison

tony873004
2005-Dec-27, 10:44 PM
Ah, that's a good point, thanks.
Grant Hutchison
I just realized that I learned that from you on the Celestia forum.



I don't know of a connection.
Grant Hutchison
It's still hard for me to seperate the two in my mind. I always get nervous when I get the hiccups now.

grant hutchison
2005-Dec-27, 10:46 PM
I just realized that I learned that from you on the Celestia forum.Really? Cripes. I wonder why I changed my mind.

Grant Hutchison

Ronald Brak
2006-Oct-12, 09:04 AM
It's true our skin and eyeballs get oxygen from the air. Your cornea aparently requires it and efforts are made to ensure modern contact lenses don't deprive it of oxygen. Obviously the human skin can absorb much oxygen and all other things being equal being deprived of it for a while would probably cause no harm. Whatever amount of oxygen passes through your skin it is it is totally insignificant compared to your moist, squash court in area lungs. Skin is sort of designed not to allow stuff to pass through it. Painting someone can kill them, but just exactly how it kills them I don't know. Too much of some paints may simply be toxic. It is possible that people die because their bodies can't regulate heat when covered in paint.

EDIT: CAN'T! The human skin CAN'T absorb much oxygen. (You wouldn't think leaving out one letter would make such a difference would you?)

crosscountry
2006-Oct-12, 11:33 AM
You'd certainly need Antarctic-level warm clothing to stop you dying of hypothermia or developing frostbite.
You'd also need some sort of oxygen supply at about one fifth of an atmosphere pressure, which is considerably higher than Mars' atmospheric pressure. A tight-fitting mask could deliver this, but without a pressure suit you'd have hard work breathing out, because of the pressure gradient between your lungs and the Martian atmosphere outside your chest wall. Maybe some sort of elastic chest binder would help.
As I recall, the atmospheric pressure on Mars can be just compatible with liquid water, if the water is close to freezing. That's too low too stop water boiling at body temperature. So without a pressure suit, your eyes and skin would dry out, and gas bubbles would develop in your tissues. You'd develop "vapour locks" in your veins as the water in your blood evaporated. When these got to your heart, they'd stop your circulation.

Grant Hutchison


are you sure of that? I may disagree on most parts. Martian temperatures can reach +C during the day time. Hypothermia would be the least of your worries.

You could also contrive some sort of breathing apparatus that would allow you to exhale every few seconds.

And, I've heard different things on the boiling blood. My thought is that your skin is elastic enough to keep the blood from boiling. You would have problems however with dehydration, but over a long time. There just isn't enough atmosphere there to take away your body heat or transfer the water.

grant hutchison
2006-Oct-12, 01:09 PM
are you sure of that? I may disagree on most parts. Martian temperatures can reach +C during the day time. Hypothermia would be the least of your worries.Yeah, as tony873004 reminded me later in the thread, I was wrong about the temperature regulation problem (and had actually posted the correct answer on a different forum myself!) The thin air would mean that normal convective cooling was ineffective, so you might well not need warm clothing. You would need insulated boots, though, since the Martian ground is generally pretty cold.


You could also contrive some sort of breathing apparatus that would allow you to exhale every few seconds.Well, I suggested some sort of chest binder with exactly that in mind. Your problem is that the partial pressure of oxygen required to keep you alive is greater than Martian atmospheric pressure. So you're going to have a greater pressure inside your lungs than outside, and you need some mechanism to deal with that. Otherwise your lungs will be forced up to maximum capacity and will stick there, despite your best efforts to breathe out into your (tight fitting!) facemask. if you cycle between your air supply and an expiratory opportunity to lower pressure, then it'll be like intermittently breathing from a pressure hose. I can tell you from personal experience that breathing from a supply that's set 0.03 bar above ambient is unpleasant and difficult, and you're going to need something like 0.2 bar in this setting if you breathe pure oxygen.


And, I've heard different things on the boiling blood. My thought is that your skin is elastic enough to keep the blood from boiling.That turns out not to be so, with the evidence also discussed on the thread. Pretty low air pressures can force air into your tissues if you have a lung injury, despite the elasticity of your tissues. The same skin elastic pressures are what would resist water evaporating: if the skin elastic pressures are demonstrably overcome by one source of pressure, they'll be overcome by another of similar magnitude.


There just isn't enough atmosphere there to take away your body heat or transfer the water.Yes indeed, with regard to heat, which was what I forgot in my original post. Not so for water, since the water doesn't care what other gases (if any) are present: it'll evaporate until the environmental partial pressure of water rises to match its vapour pressure. Partial pressure of water on Mars is much lower than we encounter in the dryest desert on Earth, so I'd stand by my suggestion that you'd get pretty brisk drying of exposed moist surfaces, though I wouldn't commit to a timescale. Such a continuous water loss would also have significance for maintaining body temperature, hence my hedge that you "might well not" need warm clothing.

Grant Hutchison

joema
2006-Oct-12, 02:01 PM
...You could also contrive some sort of breathing apparatus that would allow you to exhale every few seconds...
And, I've heard different things on the boiling blood. My thought is that your skin is elastic enough to keep the blood from boiling. You would have problems however with dehydration, but over a long time...
As described earlier in this thread, Mars is essentially a vacuum --0.01 PSI, or 0.0007 of Earth. From an atmospheric pressure standpoint, it's nearly like standing on the moon.

In that environment, no mask-type breathing apparatus will allow survival, even briefly. You're above the "Armstrong Limit", which is a pressure altitude of about 62,000 feet. That's why SR-71 pilots wore full pressure suits. A cabin pressure loss above 62,000 feet would be deadly, even if breathing pressure-fed pure oxygen via a mask.

http://en.wikipedia.org/wiki/Armstrong%27s_Line

Wearing a pressure-fed pure oxygen mask on Mars, you'd probably be unconscious within 30 seconds. Your skin would contain gross swelling, but is insufficient to prevent ebullism (gas bubbles forming in blood) in the venous system.

The bubbles would probably reduce or dissappear in the arterial system. Whatever the physiological result from that ebullism, it's probably a moot point -- you'd be unconscious within about 30 sec, even if breathing pure O2. You'd have to wear either a traditional Apollo-type pressure suit, or a 1950's-style capstan partial pressure suit: http://en.wikipedia.org/wiki/Image:Joe_Walker_X-1E.jpg, or an updated version called the Space Activity Suit: http://en.wikipedia.org/wiki/Space_activity_suit.

Either by gas pressure or mechanical counter-pressure, your skin must be pressurized on Mars (or the Moon), no matter what gas mixture or pressure you're breathing.

DaveC426913
2006-Oct-12, 02:41 PM
As I said earlier; the myth of "breathing through the skin" was debunked more that once on MythBusters. You don't breathe through your skin. Not even a little.


Because Lord knows, Mythbusters is the pinnacle of scientific rigor. :eh:

joema
2006-Oct-12, 03:04 PM
Because Lord knows, Mythbusters is the pinnacle of scientific rigor. :eh:
Since the counter-position that total skin painting causes asphyxiation comes mainly from "Goldfinger" (a fictional movie), yes it's scientifically rigorous by comparison.

crosscountry
2006-Oct-12, 03:37 PM
As described earlier in this thread, Mars is essentially a vacuum --0.01 PSI, or 0.0007 of Earth. From an atmospheric pressure standpoint, it's nearly like standing on the moon.

In that environment, no mask-type breathing apparatus will allow survival, even briefly. You're above the "Armstrong Limit", which is a pressure altitude of about 62,000 feet. That's why SR-71 pilots wore full pressure suits. A cabin pressure loss above 62,000 feet would be deadly, even if breathing pressure-fed pure oxygen via a mask.

http://en.wikipedia.org/wiki/Armstrong%27s_Line

Wearing a pressure-fed pure oxygen mask on Mars, you'd probably be unconscious within 30 seconds. Your skin would contain gross swelling, but is insufficient to prevent ebullism (gas bubbles forming in blood) in the venous system.

The bubbles would probably reduce or dissappear in the arterial system. Whatever the physiological result from that ebullism, it's probably a moot point -- you'd be unconscious within about 30 sec, even if breathing pure O2. You'd have to wear either a traditional Apollo-type pressure suit, or a 1950's-style capstan partial pressure suit: http://en.wikipedia.org/wiki/Image:Joe_Walker_X-1E.jpg, or an updated version called the Space Activity Suit: http://en.wikipedia.org/wiki/Space_activity_suit.

Either by gas pressure or mechanical counter-pressure, your skin must be pressurized on Mars (or the Moon), no matter what gas mixture or pressure you're breathing.

I think we've all forgotten here that it isn't one instant that we take to go from Earth pressure to Martian pressure. The Astronauts would have months to acclimate and drop down to maybe 3PSI that was used by the men who landed on the moon. Of course the pressure is still much greater than that of Mars, but it greatly reduces the effects and lengthens exposure time possible.

-----------
Recall everyone that the Apollo Astronauts wore very large heavy suits. This was mostly to protect them from the sun - not the lack of pressure. that can be overcome much more easily than the large suits.

Also, the suits were so large because the astronauts would be unable to cool themselves - so each suit had a built in Air Contitioner - NOT a heater. I seem to recall that several complained of overheating in their books.

My thoughts are that we have better materials now to protect from solar rays and also lighter ways to make space suits. A Martian suit weighing just 5 or 10 kilograms in not unimaginable. The air tank would of course be more.

What it all comes down to, IMO, is available air. It would be very difficult to obtain enough Martian atmosphere to fill a tank of breathable air. That might take days. In the mean time the men and women would have to wait. Unless they could carry portable CO2 scrubbers and make O2 from their own exhaust.

Ronald Brak
2006-Oct-12, 03:46 PM
Since the counter-position that total skin painting causes asphyxiation comes mainly from "Goldfinger" (a fictional movie), yes it's scientifically rigorous by comparison.

I think people have been dropping dead from being painted for a long time. Back in the middle ages actors apparently died from it. Just why they died I don't know. It could have been from toxins absorbed through the skin, or possibly something to do with controlling body heat. After all, just how do you go about sweating after you've been painted?

joema
2006-Oct-12, 04:12 PM
I think we've all forgotten here that it isn't one instant that we take to go from Earth pressure to Martian pressure. The Astronauts would have months to acclimate and drop down to maybe 3PSI that was used by the men who landed on the moon. Of course the pressure is still much greater than that of Mars, but it greatly reduces the effects and lengthens exposure time possible...
It actually makes little difference. As you'd expect this area of human physiology has been closely studied by NASA and the military, and the data is well understood. E.g, scroll down and see the first graph on this page, which shows survivability for acclimatized and unacclimatized individuals to low pressure environments:

http://www.projectrho.com/rocket/rocket3g.html

With weeks of acclimatization, a hardy individual might climb Mount Everest with no oxygen, but it makes little difference if he's standing in a vacuum (which the surface of Mars essentially is).

The only way a low-pressure O2 environment might help is in a 2001-type "Open the pod bay doors, Hal", scenario (sudden cabin pressure loss). If you're in a 14.7 psi environment, sudden pressure loss could knock you out instantly from barotrauma. In a 3 psi pure O2 environment (which you could dial down to 1 psi before blowing the hatch), barotrauma would be much less a factor.

But whether entering a space vacuum unprotected, or standing on the surface of Mars unprotected, having an O2 mask would make little difference. Whether acclimatized or not would make little difference. In all cases you'd be unconscious within 30 sec at the outside unless wearing a pressure suit of some type.

crosscountry
2006-Oct-12, 05:07 PM
what about constriction suits that applied pressure, up to normal atmospheric if you like, evenly over the entire body? I've seen women wear blue jeans that tight.

joema
2006-Oct-12, 05:53 PM
what about constriction suits that applied pressure, up to normal atmospheric if you like, evenly over the entire body?.I've seen women wear blue jeans that tight.
That's what the above-mentioned mechanical counter-pressure suits are. However it takes more than tight jeans. The garment must be specifically designed to evenly distribute the right amount of pressure evenly across the body.

But whether a traditional full pressure atmospheric suit, or a mechanical counter-pressure suit, you must have one or the other to survive on Mars, which is essentially a vacuum. An oxygen mask, parka and sun shade are not sufficient. You'd be unconscious within 30 sec. It would make little difference whether you previously acclimated to a 3.5 psi pure O2 environment.

crosscountry
2006-Oct-13, 01:58 PM
I guess I imagine a spandex type suit that would exert enough pressure to aid with respiration and keep our blood healthy. All we need is pressure - it doesn't matter how we get it.

If this were possible travelling on Mars would be a lot easier and heat transfer would probably be no problem.

ZaphodBeeblebrox
2006-Oct-13, 02:48 PM
I guess I imagine a spandex type suit that would exert enough pressure to aid with respiration and keep our blood healthy. All we need is pressure - it doesn't matter how we get it.

If this were possible travelling on Mars would be a lot easier and heat transfer would probably be no problem.
Yeah ...

And, No More Worries, About Snagging your Spacesuit on a Rock ...

If it RIPS, Juust Throw on Another Layer!

antoniseb
2006-Oct-13, 02:53 PM
You'll need to work out how to deal with natural cavities such as underarms.

ZaphodBeeblebrox
2006-Oct-13, 03:52 PM
You'll need to work out how to deal with natural cavities such as underarms.
Not to Mention, The Backs of The Elbows and Knees ...

The WORST Though, Wiill Be The Small of The Back ...

The Solution However, Is Fairly Straightforward in Any Case, Inflatable Sacs Wiill Fill The Hollows of The Body and Proviide for Fairly Even Pressure All Around!

:dance:

crosscountry
2006-Oct-13, 05:28 PM
yep, and it could look like this
http://www.spandexwear.com/buffet/buf023-1.jpg

HAHA

or more like a wetsuithttp://www.onlinescubalessons.com/store/images/hotskin.jpe

Ronald Brak
2006-Oct-14, 01:44 AM
In Japan they have plenty of weird squishy stuff that would probably do the job you want. They make toys and pillows and stuff out of it.

ZaphodBeeblebrox
2006-Oct-14, 02:32 AM
In Japan they have plenty of weird squishy stuff that would probably do the job you want. They make toys and pillows and stuff out of it.
Yeah ...

That Fabric Would Work ...

And, By The Tiime we Actually Go to MARS, it'll Be Even Better!

:dance:

crosscountry
2006-Oct-14, 02:44 AM
is there any reason to think it wouldn't work? Maybe solar radiation, but mars is farther than the moon and has some atmosphere to decrease UVB

Ronald Brak
2006-Oct-14, 02:53 AM
Radiation is a big problem. If marsnauts aren't exposed to higher than normal levels of radiation on the trip there (and back) they could afford to walk around in light space suits for quite a while, provided they had decent shelter while not on excursions.

Van Rijn
2006-Oct-14, 06:17 AM
is there any reason to think it wouldn't work? Maybe solar radiation, but mars is farther than the moon and has some atmosphere to decrease UVB

Skinsuits have long been in fiction and there has been serious research on it. Dealing with voids and changing weight or body shape are key issues. Another is that you want to keep helmet/lung air pressure as low as possible. With a skinsuit, your own skin provides cooling, and you have to limit evaporation to the vacuum. You would likely wear a protective (but not airtight) coverall for UV protection. On Mars, the atmosphere provides some radiation protection. Not as much as earth, but it isn't clear that fancy rad. protective suits would help much.

crosscountry
2006-Oct-14, 06:22 AM
Skinsuits have long been in fiction and there has been serious research on it. Dealing with voids and changing weight or body shape are key issues. Another is that you want to keep helmet/lung air pressure as low as possible. With a skinsuit, your own skin provides cooling, and you have to limit evaporation to the vacuum. You would likely wear a protective (but not airtight) coverall for UV protection. On Mars, the atmosphere provides some radiation protection. Not as much as earth, but it isn't clear that fancy rad. protective suits would help much.


Right. I'm not claiming to have invented the idea. Actually the book Red Mars is where I first learned of it. It just seems inevitable that we could do something like that.

Ronald Brak
2006-Oct-14, 06:35 AM
Right. I'm not claiming to have invented the idea. Actually the book Red Mars is where I first learned of it. It just seems inevitable that we could do something like that.

Red mars? I think that's the book where they describe giant suspension bridges constructed out of material stronger than diamond. Then later on someone falls down and manages to cut a hole in their spacesuit. I guess they must have made the spacesuit out of squishy Japanese toy stuff instead of that harder than diamond stuff. Not good thinking.

Radrook
2006-Oct-14, 06:47 AM
They say a picture speaks louder than a thousand words?
Want to know what happens if you are exposed to the Martian atmosphere without a Spacesuit? See the ending part of the film Total Recall where Arnold and his lady friend find themselves in precisely that enviable situation. I guarantee that seeing their facial contortions will discourage any attempt to try it.

Omicron Persei 8
2006-Oct-14, 09:22 AM
They say a picture speaks louder than a thousand words?
Want to know what happens if you are exposed to the Martian atmosphere without a Spacesuit? See the ending part of the film Total Recall where Arnold and his lady friend find themselves in precisely that enviable situation. I guarantee that seeing their facial contortions will discourage any attempt to try it.

But we know that wouldn't happen....

grant hutchison
2006-Oct-14, 12:59 PM
A skinsuit would have to be tight: not just uncomfortably tight, but cut-off-the-circulation-to-your-arms-and-legs tight if you wore it indoors. It would also have to be tight enough to suffocate you if you didn't breathe from a pressurized source that matched the compressive effect being generated.
This is because the skinsuit has to everywhere match the over-pressure generated by the gas source you're breathing from (otherwise there will be unphysiological pressure gradients within your blood vessels, and blood won't flow properly). If we assume a fifth of an atmosphere of oxygen to be required, that's a pressure of 150mmHg: higher than my systolic blood pressure. Even if we drive our astronauts to acclimatize to half that partial pressure of oxygen (about the level at which permanent human habitation becomes impossible on Earth), that's 75mmHg: still higher than my diastolic blood pressure.
So I'd suggest that a skinsuit of the kind proposed would be quite a dangerous bit of kit, difficult (and life-and-limb threatening) to put on and take off, and difficult to move around in.


Grant Hutchison

crosscountry
2006-Oct-14, 07:26 PM
A skinsuit would have to be tight: not just uncomfortably tight, but cut-off-the-circulation-to-your-arms-and-legs tight if you wore it indoors. It would also have to be tight enough to suffocate you if you didn't breathe from a pressurized source that matched the compressive effect being generated.
This is because the skinsuit has to everywhere match the over-pressure generated by the gas source you're breathing from (otherwise there will be unphysiological pressure gradients within your blood vessels, and blood won't flow properly). If we assume a fifth of an atmosphere of oxygen to be required, that's a pressure of 150mmHg: higher than my systolic blood pressure. Even if we drive our astronauts to acclimatize to half that partial pressure of oxygen (about the level at which permanent human habitation becomes impossible on Earth), that's 75mmHg: still higher than my diastolic blood pressure.
So I'd suggest that a skinsuit of the kind proposed would be quite a dangerous bit of kit, difficult (and life-and-limb threatening) to put on and take off, and difficult to move around in.


Grant Hutchison

you're not serious are you? It would have to be no tighter than the air you breath.

grant hutchison
2006-Oct-14, 07:41 PM
you're not serious are you? It would have to be no tighter than the air you breath.Very serious.
The gas you would be breathing, assuming you're breathing a fifth of an atmosphere of pure oxygen (the equivalent of sea level on Earth), is 150mmHg above the ambient pressure on Mars. So if your chest isn't squeezed at that pressure, you wouldn't be able to breathe out. And if your limbs aren't squeezed at that pressure, blood can't return to the heart. If I pressurized your lungs to even 30mmHg above ambient in a standing position, you'd pass out because of lack of blood returning to your heart, and might well pop one or both lungs.
You need a partial pressure of oxygen of 150mmHg to drive the chemical reaction between oxygen and haemoglobin that allows oxygen to be delivered to your tissues in normal quantities. So you'll die very quickly indeed if you try to breathe oxygen at Martian ambient pressure, or the few mmHg above ambient you can generate with a simple stretchy suit of the kind shown in your pictures.

In effect, you'd have gas in your lungs with the pressure and density of Earth's atmosphere (or at least the oxygen component of Earth's atmosphere), pushing your chest wall outwards and compressing your heart and major blood vessels. Meanwhile you've just got the wisp of Martian atmosphere outside your body pushing inwards. The skinsuit has to make up the difference between those two pressures: it has to squeeze you hard enough to raise the ambient pressure inside your body to match the pressure in your lungs. Do that, and your breathing and circulation will work normally; fall short of that, and you'll struggle to breathe and keep your blood circulating.

Grant Hutchison

grant hutchison
2006-Oct-14, 10:11 PM
Another way to see how this works is to realize that your absorption of oxygen depends on the absolute pressure (relative to vacuum), whereas your circulatory system works on gauge pressure (relative to ambient).
So as long as all the bits of your circulation are subject to the same ambient pressure, it'll carry on working normally. That's why being in a pressure chamber doesn't affect your blood pressure (which is measured relative to ambient).
However, if your blood is to absorb oxygen effectively from your lungs, the lungs must be pressurized to some minimum absolute pressure. Since your lungs are full of blood vessels, and since your heart is pretty much surrounded by lung tissue, a big and important chunk of your circulation "sees" this applied pressure in the lungs; and that immediately leads to a requirement for the rest of your circulation (and hence your whole body) to be pressurized to match the pressure in the chest cavity. Hence the requirement for a very tight skinsuit.

Grant Hutchison

crosscountry
2006-Oct-15, 01:11 AM
so, what you're really saying is, if we can make a suit that mimics atmospheric pressure on earth, or 1/5 of that then humans can walk on mars without a full Lunar suit of the past.

grant hutchison
2006-Oct-15, 01:54 AM
so, what you're really saying is, if we can make a suit that mimics atmospheric pressure on earth, or 1/5 of that then humans can walk on mars without a full Lunar suit of the past.I'm saying that's one thing that's required.
We'd need to think, too, about the thermal properties of whatever material was used in such a suit, as well as how it would cope with radiation.

But producing a stretching "skinsuit" that allows free movement while maintaining an even pressure across the whole surface of your body at 150mmHg is something of a technological challenge, I think. Even more so if you want to get in and out of it safely and easily.
Just imagine wearing a suit that's tight enough to cut off the circulation to your limbs if you wore it in an Earth-like environment. Now bend your elbow. What sort of pressure is going to be generated against the bone at the tip of your elbow, where the suit stretches and tightens? What's going to happen on the inside of your elbow, where the suit flexes and slackens? For this suit to be safe, and to give you mobility, these pressures should change very little while you flex your elbow through 120 degrees or more. It's tricky.

Grant Hutchison

Van Rijn
2006-Oct-15, 02:03 AM
I'm saying that's one thing that's required.
We'd need to think, too, about the thermal properties of whatever material was used in such a suit, as well as how it would cope with radiation.


What thermal and radiation coping issues are you thinking of for the mateiral?



But producing a stretching "skinsuit" that allows free movement while maintaining an even pressure across the whole surface of your body at 150mmHg is something of a technological challenge, I think. Even more so if you want to get in and out of it safely and easily.
Just imagine wearing a suit that's tight enough to cut off the circulation to your limbs if you wore it in an Earth-like environment. Now bend your elbow. What sort of pressure is going to be generated against the bone at the tip of your elbow, where the suit stretches and tightens? What's going to happen on the inside of your elbow, where the suit flexes and slackens? For this suit to be safe, and to give you mobility, these pressures should change very little while you flex your elbow through 120 degrees or more. It's tricky.

Grant Hutchison

This page has a short discussion on that:

http://www.physorg.com/news10683.html

Liang notes that MIT research has already demonstrated that mechanically applied pressure successfully protects humans against exposure to a vacuum. The main challenge now is to ensure that such pressure can be maintained uniformly across the skin, a task that is particularly difficult around joints. Success will likely require advances in two promising areas: mastery of active materials such as “Shape Memory Polymers,” and exploitation of so-called “lines of non-extension” on the human body.

Shape memory polymers are materials that can revert back to specialized shapes when an electric current or other stimulus is applied. They could ensure that pressure stays constant even when the skin is distorted. Lines of non-extension are lines along the human body which do not stretch even when the body is moving. They can be exploited to create a “skeleton” of strong, non-elastic material that does not inhibit movement.

I would note that the suit doesn't need to exert heavy constriction as much as resist expansion of body tissue. I don't see why a properly designed suit would cut off circulation under normal pressure.

publius
2006-Oct-15, 02:18 AM
Grant,

Based on some of the wild things I've been reading about some Pentagon and DoD ideas, such a near magic skin suit might be possible (the cost of course will probably make $500 hammers look like a bargain, I'm sure).

They're looking at basically a designer "exoskeleton" for humans using all sorts of wild nanotechnology. First of all make the suit bullet proof. Let it remain as flexible as possible, a second skin, until a hard object tries to hit it. The nanofibers respond as the bullet makes contact and becomes harder than kevlar and stops the bullet. They're working on that now, and it's not impossible, just may take a while to get the details worked out.

Now, let the exoskeleton help your muscles, sort of a power steering type of thing. You start to move, and a control system notices and streches and stiffens various nanofibers to act sort of like a hydraulic ram helping you do work. So, do feats of amazing strength, leap tall objects in a single bound, etc, etc.

All that would require some serious CPU power, and they're considering the soldier of the future will have wads of CPU power in small packages strapped to his body. Now, network all the CPUs of the men in a squad to platoon sized unit together, and have a very powerful distributed network that can solve complex dynamical problems in a hearbeat. Say like directing a "smart bullet" to a moving target. They'll have head gear that can track their eyeballs and determine exactly where they're looking. Apache attack choppers have that technology built in the pilot's helmet now.

The rifles will be wired right into the that network, and can be made to fire a bullet wherever any member of that squad or platoon unit eyes happen to be looking. Add a little drone other eyes and ears looking at the larger picture, which links the info to that local units processors, and you can have a soldier fire a gun at a small target he can't even see and have it guided right to the target, whether moving or not.

That sounds like scifi, but from I've read, this kind of thing is being actively worked on. I'm sure a second skin type of pressure suit behavior would just be a matter of tweaking things a bit.

-Richard

eburacum45
2006-Oct-15, 02:21 AM
From reading this thread I am imagining a suit made of some hi-tech smart material, perhaps a derivative of shape memory polymers; it squeezes down on your entire body with one fifth of a bar of pressure while you breathe pure oxygen from a pressurised helmet.
Bend your arms, legs, fingers, and the suit accomodates to your movement by contracting or expanding along certain specific 'lines of extension' or whatever. Tricky bit this; the suit probably need sensors to read the movements of your muscles and a load of processing power to convert that information into active shape changing.
Hmm; increase the strength of the suit's shapechanging properties and it could become a powered exoskeleton of sorts.
Or...
give it the wrong software and it would walk away across the Martian landscape with you struggling inside it...

It certainly is a lot more complex than just spandex.

grant hutchison
2006-Oct-15, 02:28 AM
What thermal and radiation coping issues are you thinking of for the mateiral?Any suit material brings with it its own thermal behaviour, which we have to factor into the interaction between a human body and Mars' thin, cold atmosphere and cold soil. We also need to know how we plan to deal with a solar flare. Good forecasting and readily available shelter? Or working through it? I'm not portraying these as show-stoppers, just responding to crosscountry's "... what you're really saying is ... humans can walk on mars ...". That wasn't what I was really saying. :)


I would note that the suit doesn't need to exert heavy constriction as much as resist expansion of body tissue. I don't see why a properly designed suit would cut off circulation under normal pressure.So it fits the skin surface of the astronaut precisely indoors, but constrains it forcibly in the Mars environment?
That'd work, but there's the fierce response of pressure to volume changes in liquids and solids to contend with. You wouldn't want to try to get into such a suit after a heavy meal or after you'd gained a kilo, after you'd bruised a knuckle or been to the gym. And there's still the matter of breathing in, when any increase in body volume is strongly resisted. Any slight mismatch in volume and shape would lead to either the cutting off of circulation when donning the garment, or sudden changes in circulatory pressure when entering the Martian environment. It's tricky.

Grant Hutchison

grant hutchison
2006-Oct-15, 02:35 AM
I'm sure a second skin type of pressure suit behavior would just be a matter of tweaking things a bit.Fair enough. All I've ever been saying is:
1) It's tricky.
2) It's not spandex.

To which I would now add:
3) You guys go first. I'll watch. :)

Grant Hutchison

Ronald Brak
2006-Oct-15, 02:39 AM
Science fiction 101:

Step into an airlock on mars, put on your helmet and make with the Leonardo position. A brand new skin suit is extruded onto your body by a rather advanced machine and tailored to your body at this particular instant. The material is very smart and deforms smoothly at the joints and can even deal with the swelling of muscels due to exercise or the abdomen due to water intake. It of course changes colour to help regulate body temperature as well as allowing you to sweat. When you are done with your excursion the material is stripped off you and recycled.

Skinsuit (TM) probably won't be ready anytime soon however.

publius
2006-Oct-15, 03:00 AM
Science fiction 101:

Skinsuit (TM) probably won't be ready anytime soon however.

Ronald,

The military will have it sooner than you might guess (at great expense). Probably only the elites will get it first.

Imagine a Navy SEAL team with such exoskeletons. Imagine it looks rather insectoid, with helmets with big insect looking eyes. :) They can run at 60MPH or better, jump 30' or more in the air, with the strength of 10 gorillas.

They come like lightning and start mowing you down before you know what's happenning, breaking and crashing through things with impossible strength. You're off to the side and out of their direct initial assault. You manage to get off a shot at one. But his suit just makes the bullet bounce right off, and maybe knocks him back a little. He's back on his feet in a second.

And then their little Doppler radar unit immediately recognizes a hostile projectile was fired, and instantly calculates the location it came from using all the data each team member's suit is continually reading. They have a fix, and the system immediately relays the information to a grenade launcher somewhere and fires that right at you all within a second or two of your firing that shot.

-Richard

Ronald Brak
2006-Oct-15, 03:09 AM
Imagine a Navy SEAL team with such exoskeletons. Imagine it looks rather insectoid, with helmets with big insect looking eyes. They can run at 60MPH or better, jump 30' or more in the air, with the strength of 10 gorillas.

That's all we need. More stuff to make hoax believers think we're being visited by aliens.

publius
2006-Oct-15, 03:21 AM
That's all we need. More stuff to make hoax believers think we're being visited by aliens.

We won't have to worry about that because I doubt anyone who saw that in action would be alive to tell about it. :)

-Richard

Van Rijn
2006-Oct-15, 04:03 AM
Any suit material brings with it its own thermal behaviour, which we have to factor into the interaction between a human body and Mars' thin, cold atmosphere and cold soil. We also need to know how we plan to deal with a solar flare. Good forecasting and readily available shelter? Or working through it? I'm not portraying these as show-stoppers, just responding to crosscountry's "... what you're really saying is ... humans can walk on mars ...". That wasn't what I was really saying. :)


I think the primary issue in thermal regulation would be controlling skin evaporation (very efficient heat loss). The atmosphere is too thin to carry much heat. In any skinsuit concept I've seen, there would always be coveralls for environmental protection, and obviously, boots.

Given the atmosphere, radiation wouldn't be as big an issue as on the moon or deep space, but skinsuit, hardsuit or conventional space suit, you probably don't want astronauts in an exposed location during a solar flare.



So it fits the skin surface of the astronaut precisely indoors, but constrains it forcibly in the Mars environment?
That'd work, but there's the fierce response of pressure to volume changes in liquids and solids to contend with. You wouldn't want to try to get into such a suit after a heavy meal or after you'd gained a kilo, after you'd bruised a knuckle or been to the gym. And there's still the matter of breathing in, when any increase in body volume is strongly resisted. Any slight mismatch in volume and shape would lead to either the cutting off of circulation when donning the garment, or sudden changes in circulatory pressure when entering the Martian environment. It's tricky.


Sure, changes in body shape is one of the key issues, and barring smart materials, a skinsuit would need to be custom fitted, but I don't see any reason a suit must be overly constrictive in pressure. Also, I can think of some fairly low tech methods to reduce the issue, such as "expanders" (flexible removable frames) at strategic points to reduce constriction when needed.

crosscountry
2006-Oct-15, 08:45 AM
So it fits the skin surface of the astronaut precisely indoors, but constrains it forcibly in the Mars environment?
That'd work, but there's the fierce response of pressure to volume changes in liquids and solids to contend with. You wouldn't want to try to get into such a suit after a heavy meal or after you'd gained a kilo, after you'd bruised a knuckle or been to the gym. And there's still the matter of breathing in, when any increase in body volume is strongly resisted. Any slight mismatch in volume and shape would lead to either the cutting off of circulation when donning the garment, or sudden changes in circulatory pressure when entering the Martian environment. It's tricky.

Grant Hutchison

This is where our opinions differ the most. I believe that I can breath at atmospheric pressure on earth, more easily at 1/5 of that.

You seem to believe that it would be impossible for someone to breath with a suit reproducing that 1/5.

The tricky part to me is convincing you that a suit reproducing atmospheric or the like would feel the same, concerning ability to breath, as you and I feel right now on earth.

This suit need not be rigid. The term Exo Skeleton has no place in this discussion unless we want it to morph. A strong enough, tight enough, spandex like material would work. Of course it would have to be water proof and protect from the sun. IMO we already have material that does most of that. Ever worn a wet suit? Can you still breath while wearing one?

astromark
2006-Oct-15, 08:52 AM
Stop being ridiculous. This is just an extension of the nano technology leap that may not actually ever happen. Polymer space suits that change as needs dictate may be possible. I would be willing to claim that it will never happen this century. My negative view is heightened by the fact that as a child I was led to believe that we would be living on the moon by now. That robots would be running all the factories. That space travel would be the norm by now., and I would have as much leisure time as I wanted. Yea right !
Yes there are some assembly lines that are largely robotic but, generally it has failed to replace manual work as we were led to believe it would. We haven't been back on the Moon since the Apollo program was canceled (was that 1974).
This rush to develop only happens when we are at war. Or under the direct threat of it. The only other time this rule has been bent was to beat the Russians to the Moon. NASA is not about to dump its pressurized space suit program in the hope of nano tech., skin suit. Not for a long while yet. . Unless. . . some body discovers some thing we need in the asteroid field.
Its all about the money. Not our technology

Van Rijn
2006-Oct-15, 11:51 AM
Stop being ridiculous. This is just an extension of the nano technology leap that may not actually ever happen.


Eh, no. An advanced nanotech based suit would be far more sophisticated than conventional skinsuit concepts. Experimental skinsuits have been developed, though they have problems. Practical suits would likely require active hardware of some type around joints and other locations, but not advanced nanotech. I'm sure a useable skinsuit could be made with today's technology if it was considered important enough. The question is if it would be worth it. I'm not convinced a skinsuit would be all around better than other suit designs.



Polymer space suits that change as needs dictate may be possible. I would be willing to claim that it will never happen this century. My negative view is heightened by the fact that as a child I was led to believe that we would be living on the moon by now. That robots would be running all the factories. That space travel would be the norm by now., and I would have as much leisure time as I wanted. Yea right !
Yes there are some assembly lines that are largely robotic but, generally it has failed to replace manual work as we were led to believe it would. We haven't been back on the Moon since the Apollo program was canceled (was that 1974).


And in both cases, it has more to do with political and economic reality than technological feasability.

greenfeather
2006-Oct-15, 12:17 PM
Red mars? I think that's the book where they describe giant suspension bridges constructed out of material stronger than diamond. Then later on someone falls down and manages to cut a hole in their spacesuit. I guess they must have made the spacesuit out of squishy Japanese toy stuff instead of that harder than diamond stuff. Not good thinking.

I'm struggling thru the Mars trilogy. I'm curious about their "tent" fabric too. They seem to have created some sort of transparent "tent" fabric that can cover entire cities, so the settlement of Mars becomes a reality. These things must be incredibly strong yet flexible, they seem to blow up like huge baloons.

Would that be feasible for Mars colonies?

grant hutchison
2006-Oct-15, 12:29 PM
This is where our opinions differ the most. I believe that I can breath at atmospheric pressure on earth, more easily at 1/5 of that.

You seem to believe that it would be impossible for someone to breath with a suit reproducing that 1/5.No, I'm saying you need a suit that compresses your chest by one fifth of an atmosphere over ambient, throughout the whole respiratory cycle, if you are to breathe a proper partial pressure of oxygen (from a pressurized helmet) while outdoors on Mars. Then you'll have 0.2 atmosphere in your lungs, and 0.2 atmosphere compressing your body (suit + negligible ambient pressure).

But wear that suit indoors, in a one-atmosphere environment, while trying to breathe ambient air, and you won't be able to breathe: because there will be one atmosphere pressure inside your chest and 1.2 atmospheres pressure outside your chest (suit+ambient). So you'll need to breathe a pressurized air source indoors while you have the suit on. So how do you get the suit on and off easily and safely?
This is why, ages ago on this thread, I suggested some kind of tighten-able chest band would be required, so that the compression could be started only when you went outside.
But since people are now invoking smart, computer controlled materials, the problem can be dismissed with a bit of handwaving: the computer will slacken the suit indoors and tighten it outdoors.


Ever worn a wet suit? Can you still breath while wearing one?Of course. It's designed to apply minimal pressure when correctly worn. It generates nowhere near the pressure required to let you breathe on Mars, and yet it's still difficult to get on and off.

Ever tried to breathe through a long pipe to the surface while submerged 2m below the water?
That's what breathing ambient air indoors while wearing our hypothetical Martian spandex suit would feel like. And that's why (or at least one reason why) diving masks have short snorkels: because the water pressure stops you breathing through anything much longer.

Grant Hutchison

Ronald Brak
2006-Oct-15, 02:54 PM
I'm struggling thru the Mars trilogy. I'm curious about their "tent" fabric too. They seem to have created some sort of transparent "tent" fabric that can cover entire cities, so the settlement of Mars becomes a reality. These things must be incredibly strong yet flexible, they seem to blow up like huge baloons.

Would that be feasible for Mars colonies?

I suppose so, but in the books they solved the radiation problem with advanced medicine. Without that a tent wouldn't provide enough protection unless it was pretty thick. But I guess one earth atmosphere on mars could hold up a fairly thick tent however. I suppose you could even try to maintain a high humidity inside to provide some extra radiation protection.

crosscountry
2006-Oct-15, 09:21 PM
No, I'm saying you need a suit that compresses your chest by one fifth of an atmosphere over ambient, throughout the whole respiratory cycle, if you are to breathe a proper partial pressure of oxygen (from a pressurized helmet) while outdoors on Mars. Then you'll have 0.2 atmosphere in your lungs, and 0.2 atmosphere compressing your body (suit + negligible ambient pressure).

But wear that suit indoors, in a one-atmosphere environment, while trying to breathe ambient air, and you won't be able to breathe: because there will be one atmosphere pressure inside your chest and 1.2 atmospheres pressure outside your chest (suit+ambient). So you'll need to breathe a pressurized air source indoors while you have the suit on. So how do you get the suit on and off easily and safely?
This is why, ages ago on this thread, I suggested some kind of tighten-able chest band would be required, so that the compression could be started only when you went outside.
But since people are now invoking smart, computer controlled materials, the problem can be dismissed with a bit of handwaving: the computer will slacken the suit indoors and tighten it outdoors.

Of course. It's designed to apply minimal pressure when correctly worn. It generates nowhere near the pressure required to let you breathe on Mars, and yet it's still difficult to get on and off.

Ever tried to breathe through a long pipe to the surface while submerged 2m below the water?
That's what breathing ambient air indoors while wearing our hypothetical Martian spandex suit would feel like. And that's why (or at least one reason why) diving masks have short snorkels: because the water pressure stops you breathing through anything much longer.

Grant Hutchison

You know, that makes sense. I wasn't even thinking about inside problems. But that's not the goal - the goal is to walk on the surface of Mars.

Of course there would be air locks on any settlement. Depressurizing the entire facility would be wasteful. I suppose that would be the time and place to take the suit off.

grant hutchison
2006-Oct-15, 10:28 PM
I suppose that would be the time and place to take the suit off.Sure. But given the tight fit of this suit, there's likely to be some moderate period of time during which you have the helmet off (or at least depressurized) but don't have the suit fully off. I'd hate to be under the time pressure of not being able to breathe while getting out of a very tight-fitting suit. Similar problems with donning.

So this suit has to be able to generate biologically significant pressures (ie, pressures that can kill you, or part of you, if they're misapplied) in a very controlled and controllable way. It has to be more complicated than the simple, spandex thing one pops in and out of in SF stories.

Grant Hutchison

Jeff Root
2006-Oct-15, 11:10 PM
But wear that suit indoors, in a one-atmosphere environment,
while trying to breathe ambient air, and you won't be able to
breathe: because there will be one atmosphere pressure inside
your chest and 1.2 atmospheres pressure outside your chest
(suit+ambient).
What makes you think that the pressure of the suit and the
pressure of atmosphere would add together?



So this suit has to be able to generate biologically significant
pressures (ie, pressures that can kill you, or part of you, if
they're misapplied)
How does the pressure of the suit compare to the pressure of my
weight on my butt while sitting in a chair? How long can I sit
before my bottom dies?

-- Jeff, in Minneapolis

publius
2006-Oct-15, 11:45 PM
What makes you think that the pressure of the suit and the
pressure of atmosphere would add together?


How does the pressure of the suit compare to the pressure of my
weight on my butt while sitting in a chair? How long can I sit
before my bottom dies?

-- Jeff, in Minneapolis


Let's see, I just sat on the bathroom scale in a chair. It registered about 140lbs. I weight about 170lbs total. My two hands cover my hind in about the same footprint as it applies to the chair. My hands are roughly 6" x 3 - 4", and we'll call that 20 square inches of are. 140/20 = 7 psi applied to my read end. ETA; that's for one hand, *sigh*, that's 40 square inches total for 3.5psi.

Why that's almost 1/4 atm, no? Now, let me sit on *your chest* while you try to breathe. Hang over the side of something, say the side of a pickup bed and put all your weight on your chest and note how hard it is to breathe.

-Richard

grant hutchison
2006-Oct-16, 12:07 AM
What makes you think that the pressure of the suit and the pressure of atmosphere would add together?They're independent sources of pressure, acting on the same surface area. What makes you think they wouldn't?


How does the pressure of the suit compare to the pressure of my weight on my butt while sitting in a chair?Depends on your weight, and the area of your butt/chair interface. One atmosphere is ~105 N.m-2, making a fifth of an atmosphere the equivalent of ~2000 kg sitting on a square metre. If your torso, head and arms weight 50kg, then you'd need a bottom maybe 15cm square to get the same effect. Perching on one buttock on a soft chair, or sitting normally on a hard chair, might give you the desired effect (assuming you consider it desirable).

How long can I sit before my bottom dies?The answer is generally a small number of minutes before you get tissue changes, a couple of hours before you get tissue death. People who can't move will start a pressure sore in that time frame. I know a paraplegic doctor who has an electronic alarm that reminds him to shift position regularly while he's in his chair.

The body is actually quite ingeniously designed to keep arteries on the flexor surfaces of your joints, where they're largely protected from areas of pressure when the body is at rest: that way the distal limb retains perfusion even if there's local tissue compression. The main artery in your leg spirals from the front of your leg at the groin to the back of your leg at the knee, for instance, so you can sit or kneel without your feet going white. Clever, eh? :)

Grant Hutchison

grant hutchison
2006-Oct-16, 12:15 AM
Why that's almost 1/4 atm, no? Now, let me sit on *your chest* while you try to breathe.We'd need to crowd in a couple more Richards, too, since parts of your chest are escaping compression, and your abdomen is at present uncompressed. A lot of the volume change associated with breathing is generated by diaphragmatic movement, so abdominal compression is a significant player in this, too.

Grant Hutchison

Van Rijn
2006-Oct-16, 01:28 AM
I'm still reading through it (it's long!), but if you are interested in this subject, here is a PDF I highly recommend reading:

http://chapters.marssociety.org/winnipeg/sas/DevelopmentOfASpaceActivitySuit.pdf

This was actual work done at NASA. They had people in a suit in a vacuum chamber for as long as three hours at a time. The suits had multiple layers, each adding compression, with a number of zippers. To help breathing, they used a "breathing bladder" system. It's obvious improvement was needed, but that certainly doesn't look impossible.

PhantomWolf
2006-Oct-16, 02:15 AM
Imagine a Navy SEAL team with such exoskeletons. Imagine it looks rather insectoid, with helmets with big insect looking eyes. They can run at 60MPH or better, jump 30' or more in the air, with the strength of 10 gorillas.

They come like lightning and start mowing you down before you know what's happenning, breaking and crashing through things with impossible strength. You're off to the side and out of their direct initial assault. You manage to get off a shot at one. But his suit just makes the bullet bounce right off, and maybe knocks him back a little. He's back on his feet in a second.

I tried, but the knowledge that SEAL teams are nothing like this in RL and it's just a Hollywood fantasy having them ruishing in and wiping out an entire base, keeps getting in the way. Sorry.


The primary mission of the SEAL Teams is intelligence gathering; absolute stealth and silence is required under such circumstances. Most SEAL assignments are carried out without a single word ever being uttered... or a single shot being fired.

publius
2006-Oct-16, 02:37 AM
PW,

Hee-hee. But that Hollywood image doesn't hurt them in the minds of any potential enemies does it?

And if any shots did have to be fired, I would not want to be on the receiving end of it. One team certainly couldn't take out something the size of a base, but smaller targets are something else. I saw a documentary on Discovery or TLC or somewhere, showing SEAL training exercises. The part about carrying the telephone pole is true.

Then the good part was an exercise where a SEAL team was to take over an enemy boat. It was a mock war game type drill with some other bunch playing the crew of the boat, and they had cameras mounted everywhere so they could review the action.

Well, that team did indeed descend on that boat like lightning, "killing" all the crew and taking over the boat before that crew knew what happened.

-Richard

crosscountry
2006-Oct-16, 12:50 PM
Sure. But given the tight fit of this suit, there's likely to be some moderate period of time during which you have the helmet off (or at least depressurized) but don't have the suit fully off. I'd hate to be under the time pressure of not being able to breathe while getting out of a very tight-fitting suit. Similar problems with donning.

So this suit has to be able to generate biologically significant pressures (ie, pressures that can kill you, or part of you, if they're misapplied) in a very controlled and controllable way. It has to be more complicated than the simple, spandex thing one pops in and out of in SF stories.

Grant Hutchison


the strap idea works. what about a simple zipper?

grant hutchison
2006-Oct-16, 01:59 PM
the strap idea works. what about a simple zipper?Depends how cool you are about dying because of a jammed (or popped) zipper, I guess. :)
It's going to be under considerable tension when zipped. Think of the tightest jeans you ever got into, or helped someone else get into. Multiply by ten.

Grant Hutchison

crosscountry
2006-Oct-16, 04:57 PM
only when you're inside. ;)

I'd carry a knife too, JIC

grant hutchison
2006-Oct-16, 05:45 PM
only when you're inside. ;)All the time, since the tension is what's keeping you alive outdoors.
The zipper pops when you're outside, your chest inflates and won't deflate. How far can you run on one (big) lungful of air?

Grant Hutchison

Van Rijn
2006-Oct-17, 02:28 AM
Depends how cool you are about dying because of a jammed (or popped) zipper, I guess. :)
It's going to be under considerable tension when zipped. Think of the tightest jeans you ever got into, or helped someone else get into. Multiply by ten.

Grant Hutchison
First, zippers are important on conventional space suits, so I don't see your point. Second, as stated before, there is no reason for the clothing to force extreme compression, only to limit expansion. Third, the actual experimental suits used multiple layers, not a single layer. That turned out to be far more practical, and safer.

Van Rijn
2006-Oct-17, 02:30 AM
All the time, since the tension is what's keeping you alive outdoors.
The zipper pops when you're outside, your chest inflates and won't deflate. How far can you run on one (big) lungful of air?

Grant Hutchison

I'd suggest you read up on the use of the breathing bladder in the SAS suit design.

crosscountry
2006-Oct-17, 07:32 AM
All the time, since the tension is what's keeping you alive outdoors.
The zipper pops when you're outside, your chest inflates and won't deflate. How far can you run on one (big) lungful of air?

Grant Hutchison



you're just a naysayer

As you read from Van Rjin the suit need not compress just guard against expansion. it could be loose until you walked outside. of course then your personal volume would go up slightly.

grant hutchison
2006-Oct-17, 10:34 AM
First, zippers are important on conventional space suits, so I don't see your point.Are the zippers on conventional suits responsible for holding them together against their internal pressure?

Second, as stated before, there is no reason for the clothing to force extreme compression, only to limit expansion.The expansion will exert 150mmHg on the suit, if that's the pressure of the gas being breathed. The suit has to shove back.

Third, the actual experimental suits used multiple layers, not a single layer. That turned out to be far more practical, and safer.I don't doubt that the experimental suits are well designed and up to the safety standards of experimental designs. My argument here is simply against the idea that we're going to come up with some simple spandex item with a big zip on the front that'll do all the tricks. This seemed to be crosscounty's original take on the problem, and I've just been trying to point out the design constrains that make producing one of these things a hard task.

I'd suggest you read up on the use of the breathing bladder in the SAS suit design.Again, you're confirming my only two points, which I've already posted clearly:It's tricky and it's not spandex (http://www.bautforum.com/showpost.php?p=845698&postcount=135).


you're just a naysayer:) Naysayers sometimes turn out to be right.
But I actually agree with Van Rijn, that the technical challenges could be overcome if we had the will and the money, but I'm not sure there would be advantages in safety, mobility or ease of use over conventional suits.

Grant Hutchison

grant hutchison
2006-Oct-17, 05:14 PM
I'm still reading through it (it's long!), but if you are interested in this subject, here is a PDF I highly recommend reading:

http://chapters.marssociety.org/winnipeg/sas/DevelopmentOfASpaceActivitySuit.pdf

It's certainly interesting reading: thanks Van Rijn. Good to see how the various problems have been dealt with, and which were easy (breathing compensation) and which were hard (suit donning).
It also confirms everything I've been talking about in this thread:

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)

Now, I've no doubt that further research and improved technology could massively improve the efficiency of these things, making them both easier to get in and out of and less complex in their multilayer construction. I am certainly not naysaying that possibility.
But I am right (and this report bears me out in detail) when I claim that matters are considerably more complicated than putting on a simple stretchy fabric suit and an oxygen mask, and then stepping out on to Mars.

Grant Hutchison

RHAMX
2006-Oct-18, 03:02 PM
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.
Currently the “Mark III, Zero prebreath suit” is the most likely candidate for the return to the Moon or a trip to Mars. It offers higher working pressure (8 to 9 psi) with very little impact on mobility. It is far superior to the Apollo A7Lb in mobility and durability. One has to remember that the Apollo suits where a compromise in suit design, they had three different jobs to do and had to be engineered to do all three, instead of optimized for one. Also, in addition to the already mentioned benefits of higher cabin pressure to a lower one, at lower pressures, cooling of equipment is a problem. For example fans need to be bigger to move the thinner atmosphere and are also noisier. So a higher cabin pressure is desirable for many reasons. Thus a suit that can operate at a higher pressure is also desirable.
Cheers.

crosscountry
2006-Oct-18, 03:50 PM
good info.

grant hutchison
2006-Oct-18, 04:37 PM
Yes, thanks, RHAMX.

Grant Hutchison

Ruslan_Sharipov
2014-Oct-03, 08:28 PM
Hi Folks!
Probably no pressure suit is needed at all. There are many sources which say that a human cannot survive under the abrupt exposure to vacuum. What would happen if the exposure is not abrupt? Can a regularly clothed human survive in a vacuum chamber if we gradually lower the air pressure in the chamber to vacuum values for several hours of decompression and if he has a breathing mask with pure oxygen covering his eyes, nose, mouth and ears? The oxigen pressure in the mask is kept at the level of 1/10 of normal atmospheric air pressure in the end of decompression hours. The exhaled carbon dioxide is removed from the mask e.g. by using an outbreathing valve and CO2 absorbing substances. Do you know if experiments like this have ever been carried out?

grant hutchison
2014-Oct-04, 02:00 PM
Hi Folks!
Probably no pressure suit is needed at all. There are many sources which say that a human cannot survive under the abrupt exposure to vacuum. What would happen if the exposure is not abrupt? Can a regularly clothed human survive in a vacuum chamber if we gradually lower the air pressure in the chamber to vacuum values for several hours of decompression and if he has a breathing mask with pure oxygen covering his eyes, nose, mouth and ears? The oxigen pressure in the mask is kept at the level of 1/10 of normal atmospheric air pressure in the end of decompression hours. The exhaled carbon dioxide is removed from the mask e.g. by using an outbreathing valve and CO2 absorbing substances. Do you know if experiments like this have ever been carried out?Wow, old thread.
That won't work, for reasons already described in the thread.
As your tissues fall below the vapour pressure of water at body temperature, bubbles of water vapour will form in your tissues and blood, blocking capillaries and eventually forming a compressible volume in you heart that will stop your circulation.
Even if that weren't a problem, a tenth of an atmosphere of oxygen (which isn't much oxygen) is still a tenth of an atmosphere higher than the vacuum pressure which will be ambient throughout your tissues. So your lungs would be at a tenth of an atmosphere higher pressure than your circulation - that's comparable to your diastolic blood pressure and an order of magnitude higher than the pressure in your veins. So the pressure in your lungs alone would be sufficient to shut down your circulation.

Grant Hutchison

Ruslan_Sharipov
2014-Oct-05, 03:37 AM
So the pressure in your lungs alone would be sufficient to shut down your circulation. Oscillating pressure in the breathing mask could be a solution. Like in pulmonary ventilation machines used in surgery. Anyway actual experiments could clarify things better than just speculations. Do you know any?

Walking in vacuum is an urgent need for manned space colonizing. So the problem should be solved even by using an artificial blood pump in addition to the regular heart.

swampyankee
2014-Oct-05, 10:36 AM
Hi Folks!
Probably no pressure suit is needed at all. There are many sources which say that a human cannot survive under the abrupt exposure to vacuum. What would happen if the exposure is not abrupt? Can a regularly clothed human survive in a vacuum chamber if we gradually lower the air pressure in the chamber to vacuum values for several hours of decompression and if he has a breathing mask with pure oxygen covering his eyes, nose, mouth and ears? The oxigen pressure in the mask is kept at the level of 1/10 of normal atmospheric air pressure in the end of decompression hours. The exhaled carbon dioxide is removed from the mask e.g. by using an outbreathing valve and CO2 absorbing substances. Do you know if experiments like this have ever been carried out?

At some altitude or equivalent pressure, a human cannot get enough oxygen to function. They found this out, largely the hard way, in WWII when air combat was attempted at 45,000 ft or so.

grant hutchison
2014-Oct-05, 09:15 PM
Oscillating pressure in the breathing mask could be a solution. Like in pulmonary ventilation machines used in surgery.Unfortunately, that won't work. You'll still have a tenth of an atmosphere higher pressure in the lungs than in the circulation.


Anyway actual experiments could clarify things better than just speculations. Do you know any?I know what happens to people who are exposed to lung pressures equal to their blood pressures - that sort of thing occasionally happens because of mechanical failures or operator errors with mechanical ventilators. The result is unsurvivable, unless very quickly rectified.
Because of that problem alone, you can't take a human body down to extremely low pressures in the way you imagine.

Grant Hutchison

Jens
2014-Oct-06, 01:32 AM
Walking in vacuum is an urgent need for manned space colonizing. So the problem should be solved even by using an artificial blood pump in addition to the regular heart.

But we do have a solution: pressurized space suits. As long as they work well, why would we want to do something invasive like an artificial blood pump, even if it could be made to work? Plus, you still need protection from radiation, so you're going to have to have a suit anyways.

Ruslan_Sharipov
2014-Oct-06, 07:36 AM
I know what happens to people who are exposed to lung pressures equal to their blood pressures - that sort of thing occasionally happens because of mechanical failures or operator errors with mechanical ventilators. Well, what is the regular pressure increment in normally operating surgical ventilators?
But we do have a solution: pressurized space suits. Pressurized space suits are bulky and awkward for working and even for walking. Space colonizing means to live permanently in vacuum, not in narrow air barrels like present space vessels.
Why would we want to do something invasive like an artificial blood pump? This is a temporary compromise. The ultimate solution is to genetically form organs replacing heart and lungs and letting us to live in vacuum. Here I would like to discuss options to adapt human lungs and heart to stay in vacuum for long time though using an oxygen mask. Otherwise, if it is absolutely impossible, one can try artificial blood pumping along with spraying oxygen directly into blood in the form of tiny bubbles. Lungs and breathing mask in this case would be used for removing CO2 and preventing water loss through eyes, mouth and nose.

grant hutchison
2014-Oct-06, 11:31 AM
Well, what is the regular pressure increment in normally operating surgical ventilators?Typically peaking at 15mmHg. That's for a short part of the ventilator cycle, and is the pressure measured at the ventilator, not the patient's lungs. If you hold that pressure so that the lungs are continuously exposed to a pressure gradient of 15mmHg, the patient's blood pressure will fall, because this is higher than the normal pressure in the veins bringing blood back to the heart. (Since the heart and great veins run through the chest cavity, they are readily compressed by the lungs.)
For comparison, a tenth of an atmosphere of oxygen is 76mmHg. Normal blood pressure 120mmHg / 80mmHg.

Grant Hutchison

NEOWatcher
2014-Oct-06, 12:22 PM
The ultimate solution is to genetically form organs replacing heart and lungs and letting us to live in vacuum. Here I would like to discuss options to adapt human lungs and heart to stay in vacuum for long time though using an oxygen mask.
But; the problem is not limited there.
It's going to affect the entire circulatory system and how the cells interact with the blood.


Otherwise, if it is absolutely impossible, one can try artificial blood pumping along with spraying oxygen directly into blood in the form of tiny bubbles.
Tiny bubbles is the worse thing you can do.

I suggest you read up on decompression sickness.

Ruslan_Sharipov
2014-Oct-06, 03:30 PM
If you hold that pressure so that the lungs are continuously exposed to a pressure gradient of 15 mmHg, the patient's blood pressure will fall, because this is higher than the normal pressure in the veins bringing blood back to the heart (since the heart and great veins run through the chest cavity, they are readily compressed by the lungs).

Saying these words you assume that the pressure in the chest cavity and in the body in whole would be equal to the ambient pressure, which is zero in vacuum. However, the water vapor pressure at human body temperature 36.6°C is about 47 mmHg. The blood pressure in veins cannot be less than this value. At the expense of reflexive blood vessels constriction it could be even higher (some extra water drinking during the decompression could help to keep this pressure high). For the absolute values of the arterial pressure then we have at least 80+47=127 mmHg and 120+47=167 mmHg. So we can surely keep the pressure in the oxigen mask at the level not less than 47 mmHg and pulsing up to 47+15=53 mmHg synchronously with breathing.


But; the problem is not limited there. It's going to affect the entire circulatory system and how the cells interact with the blood.

OK. It's the matter of complexity only. This should be done for space colonizing.


Tiny bubbles is the worse thing you can do. I suggest you read up on decompression sickness.

Tiny bubbles of oxigen are different from air bubbles and nitrogen bubbles. In venous blood they will be absorbed immediately in reaction with hemoglobin.

NEOWatcher
2014-Oct-06, 04:20 PM
Tiny bubbles of oxigen are different from air bubbles and nitrogen bubbles. In venous blood they will be absorbed immediately in reaction with hemoglobin.
Different, but still potentially dangerous (http://www.nature.com/news/rabbits-kept-alive-by-oxygen-injections-1.10899).

But these methods can be dangerous, because the free oxygen gas can accumulate into larger bubbles and form potentially lethal blockages called pulmonary embolisms.

grant hutchison
2014-Oct-06, 04:23 PM
Saying these words you assume that the pressure in the chest cavity and in the body in whole would be equal to the ambient pressure, which is zero in vacuum. However, the water vapor pressure at human body temperature 36.6°C is about 47 mmHg. The blood pressure in veins cannot be less than this value. At the expense of reflexive blood vessels constriction it could be even higher (some extra water drinking during the decompression could help to keep this pressure high). For the absolute values of the arterial pressure then we have at least 80+47=127 mmHg and 120+47=167 mmHg. So we can surely keep the pressure in the oxigen mask at the level not less than 47 mmHg and pulsing up to 47+15=53 mmHg synchronously with breathing. Well, since you brought it up ...
That 47mmHg of water vapour is also unavoidably present in the lungs, by evaporation from the large gas exchanging surface area, so your tenth of an atmosphere of oxygen is necessarily sitting on top of that (along with 40mmHg of carbon dioxide that is being breathed out). So the minimum pressure in the lungs is 47+40+76 = 163mmHg. This is a catastrophically non-physiological pressure, and it will stop your heart working and blow a hole in your lungs.
You're also confusing absolute pressure with gauge pressure (a common problem throughout this thread, IIRC). The saturated vapour pressure of water at body temperature is 47mmHg absolute. The physiological pressure in the veins is 5-10mmHg gauge. At one atmosphere ambient, that's 765-770mmHg absolute, which is fine to stop water converting to gas in the tissues. Take the ambient pressure down below about 40mmHg, and the absolute pressure in the veins falls below the saturated vapour pressure of water, and gas starts to form in the veins. The tissues of the human body are incapable of generating the internal pressure to prevent this. So water gas will return to the heart and stop it functioning.

An ambient pressure of 47mmHg is called the Armstrong Limit (named after an aerospace medicine specialist called Harry Armstrong), and it's an absolute limit on human survival, because it's the point at which a lot of your body starts to evaporate. Long before the Armstrong Limit you reach the problems with gas exchange I've been describing.

Grant Hutchison

NEOWatcher
2014-Oct-06, 04:27 PM
OK. It's the matter of complexity only.
Non-trivial.
Even if you can keep the bubbles down in the heart and other organs, and extend this to the technology of the circulatory system. Then how do you control all the individual cells from having the issue?

Ruslan_Sharipov
2014-Oct-06, 05:58 PM
The tissues of the human body are incapable of generating the internal pressure to prevent this. So water gas will return to the heart and stop it functioning. The best way to test it is to take a part of animal vein, fill it with water and firmly tie both its ends by a thread, thus making somewhat like a sausage. Then to place this sausage into the vacuum chamber and see if it will explode due to water vapor in it.
Even if you can keep the bubbles down in the heart and other organs, and extend this to the technology of the circulatory system. Then how do you control all the individual cells from having the issue? Remember Joe Kittinger's hand mentioned above. It was in vacuum for a long time, but its cells were not damaged.

grant hutchison
2014-Oct-07, 12:00 AM
Anyone interested in what actually happens to the amount of oxygen in your blood when you breathe different concentrations of oxygen at different ambient pressures needs to be able to use the Alveolar Gas Equation (AGE).
There is a simple version that gives wrong results when high concentrations of oxygen are breathed. A nice review appeared in the Royal College of Anaesthetists' Continuing Education Journal (http://ceaccp.oxfordjournals.org/content/4/1/24.full) - the full equation appears in the last section entitled "Refining the AGE". This is mathematically equivalent to the version of the full equation given by GlobalRPh (http://www.globalrph.com/martin_4_most2.htm#Alveolar%20Gas%20Equation), and to the wilfully complicated version on Wikipedia (http://en.wikipedia.org/wiki/Alveolar_gas_equation).

What the equation does is take the amount of dry oxygen and carrier gas you breathe in, and dilute it with the saturated vapour pressure of water at body temperature - an inevitable consequence of the large moist surface area of the lungs. Then it mixes in the quantity of carbon dioxide you're breathing out (which of course also occupies space in the lungs). Then there's a little jigger factor because the volume of carbon dioxide you breathe out is usually less than the volume of oxygen you breathe in, so you suck in a little extra breathing gas because of that difference - that gets important if you are breathing high concentrations of oxygen.
That gives you the partial pressure of oxygen in your lungs, which in a perfect world would equal the partial pressure in your circulation.

So if you are breathing low pressures of oxygen, the humidity and carbon dioxide occupy almost all the available space in the lungs. You have to hyperventilate to blow off carbon dioxide to make enough space in your lungs to get oxygen in in sufficient quantities to stay alive. We've actually measured and/or estimated the level of oxygen you can get into your lungs on the top of Everest. There's a nice page about that here (http://www.lakesidepress.com/pulmonary/MtEverest/bloodgases.htm).
The important thing to notice is that, high on Everest, people need to reduce their carbon dioxide levels to about a quarter of normal to get just enough oxygen to survive. The measured and calculated levels of oxygen are about 25mmHg - a sixth of the normal oxygen partial pressure in the arteries, and indeed well below what is normally present in the "waste" blood coming back from the tissues in your veins! It's astonishing that people can stay alive at that level, and no surprise that they die if they stay there too long. And they get this marginal survival by hyperventilating very hard indeed. These carbon dioxide partial pressures of about 10mmHg can only be achieved with massive effort and distress, and many people are simply incapable of generating such low carbon dioxide levels - indeed, none of us can do it without a period of physiological adaptation lasting for days.

So what happens if you breathe a tenth of an atmosphere of pure oxygen? Hyperventilating to maximum, with a PaCO2 of 7.5mmHg, you end up with an alveolar PO2 of 22mmHg - a bit worse than on Everest.
Now imagine that the pressure around the outside of your chest has been reduced to zero (forget the other disastrous physiological consequences of this for the moment). You now have to hyperventilate as hard as anyone has ever managed to hyperventilate while breathing out against a tenth-of-an-atmosphere pressure gradient. In effect, to stay alive you have to blow up a very tight balloon with every breath you take (about forty gasping breaths a minute, in this scenario).

Grant Hutchison

grant hutchison
2014-Oct-07, 06:32 PM
The best way to test it is to take a part of animal vein, fill it with water and firmly tie both its ends by a thread, thus making somewhat like a sausage. Then to place this sausage into the vacuum chamber and see if it will explode due to water vapor in it.That's just wishful thinking, I'm afraid. It only tells you the pressure a large vein can withstand at its elastic limit. We already know that's well in excess of 150mmHg, because large veins are used as arterial grafts on a daily basis. "Exploding" isn't the problem. The problem is evolving gas in the circulation. Since veins are capacitance vessels, they expand very readily below their elastic limit - like blowing up a collapsed plastic carrier bag, rather than a balloon. They can easily double or treble in volume without generating significant internal pressure. So your veins can fill with dangerous amounts of gas without "exploding".


Remember Joe Kittinger's hand mentioned above. It was in vacuum for a long time, but its cells were not damaged.The rest of his suit was pressurized, so any water vapour bubbles evolved in the veins of the hand were promptly repressurized before they reached his heart. On the arterial side, his hand was initially exposed to an arterial pressure hugely higher than tissue pressure, and so swelled to twice its normal size, at which point it was physically constrained by the material of his (unpressurized) glove. From there on, his problem was one of high tissue pressure. He had a painful oedematous hand with reduced blood flow. Every day, people routinely undergo complete loss of limb blood flow for a couple of hours without suffering tissue damage (many orthopaedic operations are carried out under tourniquet), so there's no surprise that his hand survived, and returned to normal function when the swelling had gone down three hours later.

Grant Hutchison

Jens
2014-Oct-07, 11:07 PM
Perhaps this should be a new thread, but it's just a simple question: is there a layer of air between the skin and the spacesuit, or is it like a wetsuit that basically hugs against the skin?

grant hutchison
2014-Oct-07, 11:18 PM
Perhaps this should be a new thread, but it's just a simple question: is there a layer of air between the skin and the spacesuit, or is it like a wetsuit that basically hugs against the skin?Are you talking about conventional spacesuits (which have a layer of air) or the experimental Mechanical Counter Pressure suits discussed on this thread (which need to exclude air spaces)?

Grant Hutchison

Jens
2014-Oct-07, 11:22 PM
Thanks Grant, your question basically answered my question. So both are basically possible.

grant hutchison
2014-Oct-07, 11:36 PM
Thanks Grant, your question basically answered my question. So both are basically possible.The second method, using mechanical counterpressure, is tricky to deliver in practice, though I seemed to become remarkably unpopular on this thread for pointing out the problems.

Van Rijn gave a link to a large pdf in post #153 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=846068#post846068)

I summarized the list of problems described in that report in post #164 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=847317#post847317)

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)

RHAMX gave the perspective of someone who has been involved in MCP suits in post #165 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=847974#post847974)

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.
Grant Hutchison

Ruslan_Sharipov
2014-Oct-08, 12:45 AM
That's just wishful thinking, I'm afraid. ... They (veins) can easily double or treble in volume without generating significant internal pressure. So your veins can fill with dangerous amounts of gas (vapor) without "exploding".Probably injection of extra water (saline) could be a solution. Then veins and capillars will be filled up to their elastic limit thus producing some inner pressure. Probably the same is true for other tissues. In this case a human in a vacuum would look like a wineskin with water. If he manages to survive in vacuum for several days or weeks (under assumption that lungs problems are solved somehow), this could become a physiological norm and his body would generate extra amount of blood/lymph in place of injected water.

Van Rijn
2014-Oct-08, 07:23 AM
Probably injection of extra water (saline) could be a solution. Then veins and capillars will be filled up to their elastic limit thus producing some inner pressure. Probably the same is true for other tissues. In this case a human in a vacuum would look like a wineskin with water. If he manages to survive in vacuum for several days or weeks (under assumption that lungs problems are solved somehow), this could become a physiological norm and his body would generate extra amount of blood/lymph in place of injected water.

A human would die in minutes, perhaps less. However you go about it, the human body is going to need some sort of space suit for survival in a vacuum. You'd have to rather dramatically reengineer the body for it to be otherwise. A better direction is to improve spacesuits, which will undoubtedly happen as we work more in space.

Van Rijn
2014-Oct-08, 07:36 AM
I'll add too: Another direction would be to use robotics and telerobotics for many tasks, such as construction, while humans stay in safer and more comfortable habitats. (Of course, we already use them for exploration.) There's only so much a suit can do to protect against radiation, dust would be a big problem on the Moon, Mars, and likely asteroids as well (move around a surface, and it will almost certainly kick up dust that won't settle quickly). Dust can be dangerous if brought back into a habitat, and it can damage suits (in later Lunar EVAs, there was significant air loss through the pressure bladder zippers, for instance). There could be other hazardous chemicals too that could be a problem if brought back into a habitat. It's also harder to make a closed cycle suit than habitat, which could lose precious resources.

grant hutchison
2014-Oct-08, 10:10 AM
Probably injection of extra water (saline) could be a solution. Then veins and capillars will be filled up to their elastic limit thus producing some inner pressure.That's a good way to kill someone. People go into crashing heart failure with fluid overload much less than what you suggest. Those venous pressures would overdistend the heart, so that its valves became ineffective. They would also cause massive fluid leak from the capillaries, filling the patient's tissues with fluid. Their airway would obstruct. Their liver would become distended and stop working. Once the heart valves became ineffective, left heart failure would also occur, and they would drown in pulmonary oedema.

Grant Hutchison

Jens
2014-Oct-08, 11:01 AM
The second method, using mechanical counterpressure, is tricky to deliver in practice, though I seemed to become remarkably unpopular on this thread for pointing out the problems.


I know that happens and I always find it weird that it does. You'd think that people would be grateful for somebody taking the time to point out the physical difficulties they will confront, but people sometimes take it like, "keep your filthy hands off my pie in the sky," to mix some metaphors.

The post about the difficulties with mechanical counter-pressure was fun reading.

grant hutchison
2014-Oct-08, 03:50 PM
I know that happens and I always find it weird that it does.I think in this case there was a real level of incredulity that something so apparently simple could actually be so complicated and dangerous to life and limb.
People in daily life have absolutely no reason to think about the magnitudes of the gas and liquid pressures that keep them alive, and how these pressures interact. There's no ready frame of reference for them. Intuition tells them that their bodies are solid and robust and can tolerate an atmosphere of pressure without noticing. So being told that a fifth of an atmosphere can kill or disable you in multiple different ways is quite startling, I guess.
And because I've spent the last thirty years exploring the parameter space of physiological pressures on an almost daily basis, I think it's also easy for me to forget how unprepared people are for various analogies and lines of argument that seem second nature to me.

Grant Hutchison

crosscountry
2014-Oct-08, 04:06 PM
... I think it's also easy for me to forget how unprepared people are for various analogies and lines of argument that seem second nature to me.

Grant Hutchison


This is a true statement for all experts in all fields.

Ruslan_Sharipov
2014-Oct-08, 06:03 PM
However you go about it, the human body is going to need some sort of space suit for survival in a vacuum. You'd have to rather dramatically reengineer the body for it to be otherwise.Please, tell us your proposal, what kind of reengineering we need and how soon it can be done.
Another direction would be to use robotics and telerobotics for many tasks, such as construction, while humans stay in safer and more comfortable habitats. Living in comfortable but narrow air barrels is not a life. Insisting on that, you mean that manned space colonization is impossible at all.
There's only so much a suit can do to protect against radiation, dust would be a big problem on the Moon, Mars, and likely asteroids as well. Let's dont discuss dust and radiation since vacuum is the main issue.
Since veins are capacitance vessels, they expand very readily below their elastic limit - like blowing up a collapsed plastic carrier bag, rather than a balloon.You describe veins as very loose vessels. Then how can they lift blood from our feet and legs to our heart?
Those venous pressures would overdistend the heart, so that its valves became ineffective. Standing upside down (http://yoginitiff.files.wordpress.com/2014/09/headstandyoga.jpg), we experience the pressure of about 1/10 of the reglar atmospheric pressure (i.e.76 mmHg) in the veins coming to our heart. While for removing vapor from our veins in vacuum we need only 47 mmHg in them. Please, explain these two numbers.

grant hutchison
2014-Oct-08, 06:53 PM
You describe veins as very loose vessels. Then how can they lift blood from our feet and legs to our heart?They have valves in them. The collapsible, low pressure veins are intermittently compressed by the leg muscles, and blood is pumped back to the "central compartment" (abdomen and thorax). Take away the muscle pump (by standing very still for a long time) and blood stops coming back from your legs, and you faint. That's why guardsmen are taught to intermittently contract their leg muscles while on parade.


Standing upside down (http://yoginitiff.files.wordpress.com/2014/09/headstandyoga.jpg), we experience the pressure of about 1/10 of the reglar atmospheric pressure (i.e.76 mmHg) in the veins coming to our heart. While for removing vapor from our veins in vacuum we need only 47 mmHg in them. Please, explain these two numbers.Your first number is incorrect, because you are assuming that there is a continuous fluid column all the way from the heart to the soles of the feet, giving a head of pressure of about a metre of water, which is about 77mmHg. But veins are collapsible, and all the veins in the legs and pelvis of the inverted woman in your picture have collapsed. Blood is cascading back through these collapsed veins like water running down a drain pipe, not like a continuous column of fluid, so the only head of pressure established is within the great vessels of her abdomen and thorax.
It's very easy to demonstrate this on yourself. Hang your hand low, grip your forearm tightly, and pump your hand until the veins stand up. Now let go of your forearm, and slowly raise your outstretch arm to the horizontal position and then beyond. Somewhere about ten degrees of elevation, you'll see your hand veins suddenly collapse - you've moved them above the level of the continuous fluid column in your chest, and your arm has quickly emptied into the central compartment.

When I was a medical student, I was taught to examine the jugular venous pulse, with my patient sitting propped up at forty-five degrees. In this posture, if the patient has normal central venous pressure, the upper limit of uncollapsed veins lies part-way up the internal jugular vein in the neck - the vein is distended in the lower neck, collapsed in the upper neck. The demarcation line oscillates slightly with the cardiac cycle, and can be used to help diagnose some abnormalities of cardiac function. Typically this pulsation appears only a few centimetres above the level of the heart, reflecting the low pressure in the venous system. That's why we have to lie the patient back a little - if they sit completely upright, all the veins in their neck collapse, and the jugular venous pulsation disappears into the root of the neck.

Grant Hutchison

Jens
2014-Oct-08, 10:37 PM
Living in comfortable but narrow air barrels is not a life. Insisting on that, you mean that manned space colonization is impossible at all.

I don't really see why. I spend most of my time in my living room and office room, and travel between them in a metal subway car. The time I spend exposed on the surface is probably just an hour a day. Mostly we use machines to do outside work for us even on earth, so if the barrels are made relatively spacious and comfortable, I don't see that it would be such a big problem. People live on ships and rarely go outdoors, particularly in submarines...

Ruslan_Sharipov
2014-Oct-09, 06:05 PM
Dear Dr. Grant Hutchison,

Thank you for your explanations in the post #196 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=2247555#post2247555). They are reasonable. I will learn them and possibly will ask some questions. Looking forward, my proposal is to discuss how to reconstruct the human body in order to let him live in vacuum. Saying "to reconstruct", I mean surgical reconstruction rather than genetic one.

grant hutchison
2014-Oct-09, 06:21 PM
Rereading the old part of this thread made me go looking for the original NASA vacuum-exposure experiments on animals. These used to be available online, but NASA seems to have taken them down, so it would require an interlibrary loan to get hold of them now. I'm guessing NASA don't want to be publicly associated with these any more - I do recall a description of a dog "swelling up like a goatskin bag", or words to that effect.
So I dug out the Second Edition of the Bioastronautic Data Book (Parker & West, 1973), which summarizes the animal data in the course of generalizing to humans. It's worth quoting a large chunk for anyone who wants to know what actually happens when a mammal is exposed to vacuum:
Some degree of consciousness will probably be retained for 9 to 11 seconds. In rapid sequence thereafter, paralysis will be followed by generalized convulsions and paralysis once again. During this time, water vapor will form rapidly in the soft tissues and somewhat less rapidly in the venous blood. This evolution of vapor will cause marked swelling of the body to perhaps as much as twice its normal volume unless it is restrained by a pressure suit. Heart rate may rise initially but will fall rapidly thereafter. Arterial blood pressure will also fall over a period of 30 to 60 seconds, while venous pressure rises due to distension of the venous system by gas and vapor. Venous pressure will meet or exceed arterial pressure within 1 minute. There will be virtually no effective circulation of blood. After an initial rush of gas from the lungs during decompression, gas and water vapor will continue to flow outward through the airways. This continual evaporation of water will cool the mouth and nose to near-freezing temperatures; the remainder of the body will become cooled, but more slowly.

Cooke and Bancroft (1966) report occasional deaths in animals due to fibrillation of the heart during the first minute of exposure to near-vacuum conditions. Ordinarily, however, survival was the rule if recompression occurred within about 90 seconds. The hearts in these studies tolerated even repeated decompression well (Cooke & Bancroft, 1966), although it is by no means certain that the human heart will be as tolerant. Once heart action ceased, death was inevitable, despite attempts at resuscitation. During recompression, as the absolute pressure exceeded about 50mmHg (1 psia) a dramatic reduction in swelling was demonstrated. Breathing usually began spontaneously, the time being dependent on the duration of exposure at minimum pressure. Heart rate and blood pressure rose to fairly high levels, the gradually returned toward normal. There was suggestive evidence in the Cooke and Bancroft studies that denitrogenation prior to exposure, and recompression with 100 percent oxygen, both improved recovery time and decreased mortality. Neurological problems, including blindness and other defects of vision, were common after exposures, but usually disappeared fairly rapidly.

ETA: The "dramatic reduction in swelling" at 50mmHg is of course due to the recondensation of water as the ambient pressure rises about its SVP at body temperature.

Grant Hutchison

grant hutchison
2014-Oct-09, 06:25 PM
Dear Dr. Grant Hutchison,

Thank you for your explanations in the post #196 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=2247555#post2247555).You're welcome. Thanks for saying thanks.

Grant Hutchison

neilzero
2014-Oct-09, 08:26 PM
There seems to be general agreement that you might die even if your buddy (in a space suit) got you back in the air lock 60 seconds after you stepped out. How about we cheat on the conditions: Naked except for shoes and a prosthesis that dissolves the optimum amount of oxygen and water (To offset dehydration/You probably cannot swallow water) in your blood and enough mirrors reflecting sun light on your skin to keep your skin at a desirable temperature. Your lungs would likely exhale enough carbon dioxide and more than the desired amount of water vapor plus perhaps half of the oxygen that the prosthesis dissolved in your blood. So the remaining problems would be dehydrated eye balls, and making the transition from 300 millibars pressure to about 3 millibars ambient pressure. I'm guessing, some of the experts are wrong. The inside of your body is still be at almost 300 millibars, so your blood won't boil, near term, except from wounds. Edit: I read some more of this thread. Possibly we also need tiny pumps to move fluids and vapors from places where they will be excess to places in the body to where they are insufficient. Yes the prosthesis approach may get very complicated.
I'm guessing sun block solves the ultra violet problem for the first hour and alpha, beta, and gamma are not a serious problem until the second hour of exposure. Can the solar mirrors have filters that minimize the reflected alpha, beta gamma, as well as the ultraviolet? I suspect thin mirrors reflect very little gamma, nor neutrons.

grant hutchison
2014-Oct-09, 08:39 PM
So the remaining problems would be dehydrated eye balls, and making the transition from 300 millibars pressure to about 3 millibars ambient pressure. I'm guessing.So just the "swelling to twice your normal size and dying of venous gas embolism within 90 seconds" problems remaining. Oh, and the "continuous evaporative cooling freezing your upper airway" problem.

Grant Hutchison

cjameshuff
2014-Oct-09, 08:39 PM
There seems to be general agreement that you might die even if your buddy (in a space suit) got you back in the air lock 60 seconds after you stepped out. How about we cheat on the conditions: Naked except for shoes and a prosthesis that dissolved the optimum amount of oxygen and water (To offset dehydration/You probably cannot swallow water) in your blood and enough mirrors reflecting sun light on your skin to keep your skin at a desirable temperature. Your lungs would likely exhale enough carbon dioxide and more than the desired amount of water vapor plus perhaps half of the oxygen that the prosthesis dissolved in your blood. So the remaining problems would be dehydrated eye balls, and making the transition from 300 millibars pressure to about 3 millibars ambient pressure. I'm guessing.

Your guesses are wrong. There's no need for guessing, actual research has been done. As has been stated already in this thread, the veins will fill with water vapor, the body will bloat, and blood circulation will effectively stop. Without circulation, oxygenating the blood is impossible and you will not live long enough for temperature or dehydration to be a problem.

Jens
2014-Oct-09, 10:37 PM
Looking forward, my proposal is to discuss how to reconstruct the human body in order to let him live in vacuum. Saying "to reconstruct", I mean surgical reconstruction rather than genetic one.

OK, if you want to think of that, then basically you want to reconstruct the person so they are self-pressurized and can have access to a supply of oxygen. I suppose the most feasible way would be to implant the person inside an exoskeleton with a replaceable oxygen pack and a transparent membrane to allow you to see outside. You could also have a cooling mechanism to prevent you from overheating.

grant hutchison
2014-Oct-09, 11:03 PM
OK, if you want to think of that, then basically you want to reconstruct the person so they are self-pressurized and can have access to a supply of oxygen. I suppose the most feasible way would be to implant the person inside an exoskeleton with a replaceable oxygen pack and a transparent membrane to allow you to see outside. You could also have a cooling mechanism to prevent you from overheating.:D

Grant Hutchison

neilzero
2014-Oct-10, 01:24 AM
I likely read most of the tread in 2006, but posted today after reading only page one. Some of page one seems to be debunked on later pages. A small amount of additional sunlight, likely makes naked skin the optimum temperature since convection heat loss is near zero at that low ambient pressure. Yes significant evaporation of water in the lungs would likely produce a small amount of frost in the upper airway, but that is unlikely to prove near term fatal, if the oxygen is dissolved in the blood with a prosthesis.
It was not suggested that the animals suffered more than minor blood leakage in the animal lungs, even though the pressure decrease was lots more than the 297 millibars that I suggested.
It does not appear that the vein pressure would drop quickly to 47 mm of hg, and the evaporation would likely prevent any lower pressure for minutes, if not hours. Some posters think only mm size bubbles would form, which would not cavitate the heart, and the heart muscle likely uses arterial blood at higher pressure, so heart muscle failure would likely be delayed minutes, if not hours. Page one talked about alive for minutes rather than long term. Several posters described animal tests where the animals were exposed to vacuum for several minutes and survived. There was no suggestion of swelling to double size, but perhaps the animals survived swelling to double size of some small portions of their body tissue. Extremity temperatures are more typically 27c degrees instead of 37c, so blood boiling in the extremities is less likely.

Ruslan_Sharipov
2014-Oct-10, 04:51 AM
And because I've spent the last thirty years exploring the parameter space of physiological pressures on an almost daily basis...Dear Grant Hutchison,

Are you a professional resercher? For what organization do you work? Have you got a vacuum chamber and can you perform your own experiments with animals in vacuum chamber?

Van Rijn
2014-Oct-10, 06:11 AM
OK, if you want to think of that, then basically you want to reconstruct the person so they are self-pressurized and can have access to a supply of oxygen. I suppose the most feasible way would be to implant the person inside an exoskeleton with a replaceable oxygen pack and a transparent membrane to allow you to see outside. You could also have a cooling mechanism to prevent you from overheating.

Pretty much what I was going to say - if they're still to be biological, they'd need something like a spacesuit, natural or artificial.

Van Rijn
2014-Oct-10, 06:16 AM
Dear Grant Hutchison,

Are you a professional resercher? For what organization do you work? Have you got a vacuum chamber and can you perform your own experiments with animals in vacuum chamber?

He's a doctor, and from past experience, also well enough informed about many issues outside of medicine - to the point of sometimes making me feel a bit ignorant on areas I thought I knew well, and I like to think I know at least a few things.

If you're still trying to challenge what people here are telling you, may I suggest doing a little research yourself on what has been said first?

grant hutchison
2014-Oct-10, 07:11 AM
I likely read most of the tread in 2006, but posted today after reading only page one. Some of page one seems to be debunked on later pages. A small amount of additional sunlight, likely makes naked skin the optimum temperature since convection heat loss is near zero at that low ambient pressure. Yes significant evaporation of water in the lungs would likely produce a small amount of frost in the upper airway, but that is unlikely to prove near term fatal, if the oxygen is dissolved in the blood with a prosthesis.
It was not suggested that the animals suffered more than minor blood leakage in the animal lungs, even though the pressure decrease was lots more than the 297 millibars that I suggested.
It does not appear that the vein pressure would drop quickly to 47 mm of hg, and the evaporation would likely prevent any lower pressure for minutes, if not hours. Some posters think only mm size bubbles would form, which would not cavitate the heart, and the heart muscle likely uses arterial blood at higher pressure, so heart muscle failure would likely be delayed minutes, if not hours. Page one talked about alive for minutes rather than long term. Several posters described animal tests where the animals were exposed to vacuum for several minutes and survived. There was no suggestion of swelling to double size, but perhaps the animals survived swelling to double size of some small portions of their body tissue. Extremity temperatures are more typically 27c degrees instead of 37c, so blood boiling in the extremities is less likely.This is all incorrect. The experiments have been done, we know what happens.
See my transcription in post #199 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=2247735#post2247735).

Grant Hutchison

grant hutchison
2014-Oct-10, 07:41 AM
Dear Grant Hutchison,

Are you a professional resercher? For what organization do you work? Have you got a vacuum chamber and can you perform your own experiments with animals in vacuum chamber?I'm a clinician. The nature of my work means I spend my days measuring, interpreting and adjusting physiological (and non-physiological!) pressures - ventilator settings, gas mixtures, invasive monitoring of arterial and venous pressures. Back in the day, we used to float catheters into the pulmonary artery, too, but nowadays we use largely indirect measures of left heart function. I deal with sick people whose hearts and lungs are failing in a variety of ways.
Once you've done that for thirty years, you acquire an understanding of the parameter space of physiological gas and liquid pressures - what will work, what will kill people, and how everything connects to everything else through the physics of the cardiorespiratory systems.

Grant Hutchison

crosscountry
2014-Oct-10, 09:38 PM
OK, if you want to think of that, then basically you want to reconstruct the person so they are self-pressurized and can have access to a supply of oxygen. I suppose the most feasible way would be to implant the person inside an exoskeleton with a replaceable oxygen pack and a transparent membrane to allow you to see outside. You could also have a cooling mechanism to prevent you from overheating.

:whistle:

Ruslan_Sharipov
2014-Oct-11, 06:18 PM
Dear Grant Hutchison!

Below I have quoted your explanations from your post #196 (http://cosmoquest.org/forum/showthread.php?36151-Walking-on-mars-with-or-without-spacesuit&p=2247555#post2247555).


... if the patient has normal central venous pressure, the upper limit of uncollapsed veins lies part-way up the internal jugular vein in the neck - the vein is distended in the lower neck, collapsed in the upper neck.

It's very easy to demonstrate this on yourself. ... Somewhere about ten degrees of elevation, you'll see your hand veins suddenly collapse - you've moved them above the level of the continuous fluid column in your chest, and your arm has quickly emptied into the central compartment.

I understood that the continuous blood column in the chest veins of a normally standing or normally sitting human is 15-20 cm higher than his heart level. The pressure of 15-20 cm of blood column, is it that very pressure that pushes blood into the heart during diastole? And another question. Where is the bottom of the continuous blood column of the veins in central compartment of our body? There must be several valves preventing the leakage of this blood column down and outside the sentral compartment. And there must be some pressure that acts (probably in some restricted time intervals) against the blood column of the central compartment of our body and opens these several valves. What is the origin of this pulsating vein pressure? Is it due to the heart systole? What is its peak value?

grant hutchison
2014-Oct-11, 10:20 PM
I understood that the continuous blood column in the chest veins of a normally standing or normally sitting human is 15-20 cm higher than his heart level. The pressure of 15-20 cm of blood column, is it that very pressure that pushes blood into the heart during diastole?15-20cm is high. Somewhere around 5-10cm is normal.
Yes, the right atrium fills because the pressure in the great veins is greater than in the atrium. Towards the end of ventricular diastole, the atrium contracts to push more blood into the ventricle. When the atrium relaxes and the valve between ventricle and atrium closes, the atrial pressure is at zero or even subatmospheric pressure. (The pressure in the thorax is subatmospheric when you breathe in.)


And another question. Where is the bottom of the continuous blood column of the veins in central compartment of our body? There must be several valves preventing the leakage of this blood column down and outside the sentral compartment.The anatomy of venous valves is a bit variable, but it wouldn't be unreasonable to think of the entrance to the pelvis being protected by valves, whereas the large veins inside the pelvis and abdomen are generally valveless.


And there must be some pressure that acts (probably in some restricted time intervals) against the blood column of the central compartment of our body and opens these several valves. What is the origin of this pulsating vein pressure? Is it due to the heart systole? What is its peak value?I've mentioned one source already - the muscle pump in the legs. The other source is the thoracoabdominal pump. When you breathe in, your diaphragm descends and your abdominal contents are compressed, while the pressure in your chest drops below atmospheric. Since valves prevent backflow out of the abdomen, blood moves into the chest and right atrium. When you breathe out, the reducing pressure in the abdomen allows the pelvic valves to open and add more blood to the central compartment.
The total pressure cycle in the central veins is normally quite small - three or four centimetres of water between atrial contraction and atrial relaxation, with an extra excursion due to the breathing cycle, of comparable magnitude.

Grant Hutchison

Ruslan_Sharipov
2014-Oct-13, 03:37 AM
Well, under such a loose pressure cycle, how central veins provide the same circulation volume as in arteries? How do they prevent the blood outflow that could empty the heart in diastole?

grant hutchison
2014-Oct-13, 12:42 PM
Well, under such a loose pressure cycle, how central veins provide the same circulation volume as in arteries? How do they prevent the blood outflow that could empty the heart in diastole?It's an adaptive system. The veins contain about 80% of your circulating blood, although that's a highly variable figure, so they have a lot of fluid to play with. If the venous return to your heart falls, the stroke volume of your next heartbeat falls. This is sensed by baroreceptors in the aortic arch and carotid, and feeds back to the sympathetic nervous system, which starts to constrict venules and increase tone in the small amount of muscle in the vein walls. This pushes the volume of the central compartment back up again.
This is turning into a tutorial about normal physiology, which you can easily find in a textbook.

Grant Hutchison

BigDon
2014-Oct-16, 03:12 PM
This might be a good place to ask this as it seems sort of related to the subject.

Dr. Hutchison, Mr. Sharipov

You ever have one of those days where you and you friends were dinking with something you shouldn't have been and accidently sucked all the air out of the room?

That happened to me once. When I was in the Navy.

What I'd like to ask about was the way it felt when my chest bulged. It wasn't like you would imagine it feeling. I would have thought you would feel the pressure high across the widest part of your pectorals when actually it felt like some ghostly person was pushing hard on the back of my sternum, with their hand not centered, but low, so most of the palm was below the xyphoid process. Very, very distinctive.

So was that just my upper digestive system bulging or was that my lungs coming together and forward?

(The door failed, rather violently I might add, thus preventing a five casualty industrial accident.)

grant hutchison
2014-Oct-16, 05:05 PM
Don, I read that four times and I have absolutely no idea what you're talking about. :)

Grant Hutchison

Hornblower
2014-Oct-16, 05:53 PM
Don, I read that four times and I have absolutely no idea what you're talking about. :)

Grant HutchisonMy best guess is some sort of powerful pump creating a partial vacuum in a battened-down compartment aboard a ship, perhaps related to damage control. Perhaps his sensation was caused by his stomach bulging against the abdominal wall. Just a guess.

Jeff Root
2014-Oct-17, 12:17 PM
My guesses are that you had a coughing fit after you got
back to normal pressure, and that the door blew inward,
toward you, not away.

-- Jeff, in Minneapolis

BigDon
2014-Oct-17, 02:47 PM
Hornblower had the right of it.

Though not a DC pump. One of the "carburetor" vents for a main engine formed our overhead in our shop. We had an access hatch open and the door to the passage shut when it came online at an unexpected time. We were all in the inner room when the hatch blew in. The hatch had only one dog partially latched instead of all eight. It wasn't even a water tight room and that vent still sucked a steel hatch open!

Anti-blast louvers inside the vent give it the structure it needs to draw that kind of suction without collapsing itself.

grant hutchison
2014-Oct-17, 03:47 PM
Hornblower had the right of it.

Though not a DC pump. One of the "carburetor" vents for a main engine formed our overhead in our shop. We had an access hatch open and the door to the passage shut when it came online at an unexpected time. We were all in the inner room when the hatch blew in. The hatch had only one dog partially latched instead of all eight. It wasn't even a water tight room and that vent still sucked a steel hatch open!

Anti-blast louvers inside the vent give it the structure it needs to draw that kind of suction without collapsing itself.OK. Sounds like your gastric air bubble expanding.
Anything to do with your lungs you'd feel in your neck and central chest, the same sensation as you feel if you try hard to breathe out while keeping your vocal cords closed - doing a bench press or straining at an unwieldy stool, for instance.

Grant Hutchison

BigDon
2014-Oct-17, 04:18 PM
OK. Sounds like your gastric air bubble expanding.
Anything to do with your lungs you'd feel in your neck and central chest, the same sensation as you feel if you try hard to breathe out while keeping your vocal cords closed - doing a bench press or straining at an unwieldy stool, for instance.

Grant Hutchison
Bold mine.

Six years ago I *used* to benchpress over twice my body weight. Three sets of thirty in a fortyfive minute daily work out. I think I know what you mean then. :)

grant hutchison
2014-Oct-17, 04:31 PM
Bold mine.

Six years ago I *used* to benchpress over twice my body weight. Three sets of thirty in a fortyfive minute daily work out. I think I know what you mean then. :)I thought you probably would. But I just slipped in the constipation reference for completeness. :lol:

Grant Hutchison