New idea for Mechanical CounterPressure suit

SpaceNut · 2014-01-10 22:53:11

The ISS decompression time might be appropiate.

http://www.nasa.gov/pdf/686338main_AP_E … ession.pdf

http://www.nasa.gov/pdf/686339main_AP_S … ession.pdf

There must be others....

Quaoar · 2014-01-12 14:39:23

SpaceNut wrote:

The ISS decompression time might be appropiate.
http://www.nasa.gov/pdf/686338main_AP_E … ession.pdf
http://www.nasa.gov/pdf/686339main_AP_S … ession.pdf
There must be others....

How can a MCP suit apply a contropressure against male genitals?

RobertDyck · 2014-01-12 17:03:10

Quaoar wrote:

How can a MCP suit apply a contropressure against male genitals?

Plastic bag filled with liquid silicone. Elastic fabric of your shorts is stronger than a woman's corset, so you really really want to even that out. The bag of liquid does do that. You also need a narrow bag along the crack of your butt, and the trough of your lumbo-dorsal spine. That's a medical term: "lumbar" is the small of your back, "dorsal" is your back.

Dr. Paul Webb made the first MCP suit in 1967. He has video of a test subject wearing the suit in a vacuum chamber, decompressed to equivalent of 50,000 feet. His first paper was written in December 1967, published in the April 1968 issue of the Journal of Space Medicine. He got a contract from NASA, improved it. He tested his second suit in a vacuum chamber equivalent to hard vacuum of space. His NASA contractor report was dated November 1972. The idea of "bags of liquid" comes from those papers. So it's been tested, it works.

SpaceNut · 2014-01-12 20:29:56

Suit up for Skinsuit

The Space Medicine Office of ESA’s European Astronaut Centre is managing a project that could help astronauts overcome back problems in space, simply by wearing a high-tech tight-fitting ‘skinsuit’.
The Skinsuit is a tailor-made overall with a bi-directional weave specially designed to counteract the lack of gravity by squeezing the body from the shoulders to the feet with a similar force to that felt on Earth.

Void · 2014-01-13 06:49:37

I have a few questions in my mind on this topic.

When you are purging the Nitrogen from the human blood to do an EVA, is that done in 1 bar pure Oxygen?

Also yesterday I stumbled on a article where they said CT scans of persons breathing pure oxygen like that causes many undesired medical effects, such as capilaries of some organs squeezing shut, so that they those sections of the body are Oxygen deprived. The solution that they found was to use a mix of 95% Oxygen and 5% CO2. This was all on the topic of resussitation of a human, but it might relate to space activities. Does anyone have an awareness of this?

Finally, I remember the notion of a partial pressure suit which would be used on Mars, if there was some greater pressure than there is. So that the Helmet would be pressurized but the hands could be open to air. Obviously this cannot be done on the existing Mars, but I am wondering if you can have a greater pressure than 20-25% in the pressurized helmet, and still use the 20-25% counterpressure suit for the rest of the body. Does that have bad effects?

Last edited by Void (2014-01-13 06:50:30)

GW Johnson · 2014-01-13 10:39:17

Regarding Void's last question just above: yep, the pressure applied to the rest of the body needs to match the gas pressure in the lungs. It doesn't have to be perfect if protection is only needed for a few minutes. That's what got done with the pressure breathing rigs and early partial-pressure suits of the 1940's and 1950's.

Exceed the time, around 10 to 30 minutes, and the water in the blood gets forced into the tissues (that's called edema, and the under-compressed parts swell up hugely). Plus, blood tends to pool in undercompressed parts, and you faint. Fix that, and you can use this idea to walk around in deep space. In a suit that is far, far less restrictive than any full pressure suit we have ever flown.

Paul Webb's elastic spacesuit of the late 1960's was a redesign of the partial pressure suit idea with compression by a porous elastic fabric, instead of an inelastic fabric tensioned by inflated capstans. He got much more even compression distributed over the body that way.

The remaining difficulty is adjusting the distribution of fabric tensions to achieve an even effective pressure inside the body. It doesn't have to be perfect, but Webb found you need to get the extremities compressed to about 160 mm Hg if the gas breathing pressure was the 190 mm Hg that he used. You have to trade off even compression design against difficulty donning such tight garments.

The final test in 1972 was 30 minutes in a vacuum chamber pedalling a bicycle ergonometer, at a pressure equivalent to 87,000 feet. The body doesn't know that from the vacuum of space. The zero O2 deathpoint is around 60,000 feet, where even a pure O2 breathing gas is completely displace by the water vapor at body temperature inside wet lungs. No cooling system was required, the test subject simply sweated through his 6 or 7 layers of pantyhose material, directly into vacuum. The whole rig (helmet, O2 backpack, and clothing) was only 85 pounds. The backpack was an O2-rebreather with CO2 absorber, and make-up O2 from a LOX bottle.

You need some sort of liquid or gel packs to fill all the body surface concavities, or they don't get compressed correctly. There's genitals, small of the back, women's breasts, armpits, and back of the knees.

I find it appalling that all this was working experimentally in 1972, and again in recent years once again at MIT, but all at low funding and academic-research priorities. This thing should have been flying by now.

The MIT work (Dava Newman) uses anisotropic fabric tensions to achieve compression effects with less donning difficulty. That's the oriented fiber thing she has been using.

GW

Last edited by GW Johnson (2014-01-13 10:44:38)

Void · 2014-01-13 11:18:03

Thanks for expaining that.

I found the 95% O2 + 5% CO2 article again.

http://www.scientificamerican.com/artic … mage-brain

Of course this applies to stroke victims, but I would think that it might also apply to space activities as well.

Do you know how long a person can be exposed to a 200-250 mb Oxygen dominated mix and not have health issues?

"Those brain areas which influence the hypothalamus, when you give 100 percent oxygen, they turn on like crazy," Harper says. "They begin driving the hypothalamus very hard." The action triggers the gland to flood the blood with catecholamines: hormones (such as adrenaline and norepinephrine) and neurotransmitters, like dopamine, all of which feed into the pathway that controls contraction of the heart muscle. This chemical dump disrupts the heart rate, causing a reduction in blood flow and, hence, less oxygen being delivered to cells.
The good news: researchers discovered that the negative effects can be avoided if the oxygen is mixed with as little as 5 percent carbon dioxide before being administered. The combo neither triggered significant changes in any of the aforementioned brain regions nor disturbed the hypothalamus.

Maybe the above problem is solved just by having a lower pressure?

Last edited by Void (2014-01-13 11:20:41)

GW Johnson · 2014-01-13 14:02:53

I'm no medical person. But I do know from my days as a scuba diver that 1 atm partial pressure of oxygen induces convulsions in about half the people exposed to it, and 2 atm partial pressure O2 is lethal to all exposed to it. I'm simply guessing that it's a partial-pressure / osmosis thing across the membranes in the lung alveoli. These data are for sea level atmospheric pressure, and some very lethal experiences trying to breathe pure oxygen when underwater, plus some really bad experiences with compressed air hard hat divers between about 170 to 300 feet down. No one has ever lived for more than a few minutes on compressed air more than 300 feet down. Convulsions and death are fairly fast at those conditions.

The article cited would seem to indicate that 0.9 to 0.95 atm partial pressure O2 is mostly OK. Assuming the Sci Am-cited experiments took place near sea level, that would be 0.95 atm O2 plus 0.05 atm CO2 added to 1.00 atm atmospheric pressure.

I didn't notice where the experiments were run. But if near 500 feet where the atm is 0.9644 atm in pressure, that would be 0.9162 atm O2 and 0.0482 atm CO2. If done in Denver a mile up, atmospheric is 0.8321 atm, and at 95-5 split, the O2 would be 0.7905 atm and the CO2 would be 0.0416 atm. So the partial pressures depend upon where you run the experiments, as well as what the gas volume percentages are.

So the 0.95 atm partial pressure of O2 being a max safe value makes a lot of sense as a rule-of-thumb. Composition (like having the 5% CO2) no doubt complicates the picture. Just to be safe, I'd guess nearer 0.9 atm than 0.95. And even then not for chronic long-term exposures.

The NASA spacesuit standard is near 0.33 atm pure O2, for a partial pressure of O2 of 0.33 atm. You only really need around 20 to 25% of an atmosphere's worth of O2 to be quite healthy in a spacesuit. So, we're talking partial pressures between around 0.2 to 0.33 atm inside the suit. That would be fine indeed for long EVA's, etc. I'm not so sure about exposures over a very long tern, say weeks-to-months, even years. That's a completely different issue than immediate brain damage from too rich an O2 partial pressure. I know next-to-nothing about chronic exposure effects.

You medical types need to offset those gas composition data by the vapor pressure of water at body temperature, if you want to check osmotic diffusion numbers inside the lungs. That process works on the difference in effective partial pressures of each constituent you check. That water vapor offset gets you a better estimate of the oxygen partial pressure inside the actual wet lung alveoli spaces. That water vapor pressure is right at 0.062 atm. So an astronaut inside a suit with 0.33 atm pure O2 would have something closer to 0.268 atm partial pressure oxygen and 0.062 atm partial pressure water vapor, inside his lungs. That reduced PP of O2 in the lung is what actually drives osmosis of O2 across the membranes into the blood.

Fortunately, most rigs have a really good CO2 absorber, so that gas remains a far smaller trace in the breathing gas than the water. But, if you deliberately put CO2 in the breathing gas mix, then you sharply reduce the rate at which it can leave the blood across the lung membranes.

That's because the driving pressure in the blood is low, acting against an increasing "backpressure" resisting its diffusion back out into the breathing gas. Plus, at too high a concentration, it upsets the body chemistry and kills you.

I have no numbers for that, but 4% CO2 in the polluted air was the usual "deathpoint" rule-of-thumb in submarine rescue accidents. Air in that scenario also has a lot less than 21% oxygen, so it's medically far more complicated than I really understand.

GW

Last edited by GW Johnson (2014-01-13 14:16:08)

Void · 2014-01-13 14:54:50

Thanks for the reply.

I have my own notions of a device to access the Martian environment, which would have some greater strengths than a CounterPressure Suit or a bag suit, but it also would be inferior in some ways. Still thinking it out. It would be more suitable for some tasks. Would borrow some from each I suppose, just as the CounterPressure suit borrows the helmet.

Long durations in a low pressure environment might be the situation. I guess if it were ever made, users would figure out just how long can be tollerated.

Terraformer · 2014-01-13 16:43:39

GW, you will probably want to check out the minimal martian terraformed atmospheres thread. Midoshi has some interesting figures on CO2 toxicity and adaptation. Sheep have managed to adapt to 120mb partial pressure CO2. That's probably to do with how the body deals with CO2, dissolving it as carbonic acid in the blood rather than binding it to anything. As long as the body has time to sort out it's buffering, it can deal quite well.

GW Johnson · 2014-01-14 10:45:53

Thanks, Terraformer, I'll see if I can find it. I vaguely remember Midoshi had some figures about that.

GW

RGClark · 2014-11-30 09:13:27

GW Johnson wrote:

I'm no medical person. But I do know from my days as a scuba diver that 1 atm partial pressure of oxygen induces convulsions in about half the people exposed to it, and 2 atm partial pressure O2 is lethal to all exposed to it. I'm simply guessing that it's a partial-pressure / osmosis thing across the membranes in the lung alveoli. These data are for sea level atmospheric pressure, and some very lethal experiences trying to breathe pure oxygen when underwater, plus some really bad experiences with compressed air hard hat divers between about 170 to 300 feet down. No one has ever lived for more than a few minutes on compressed air more than 300 feet down. Convulsions and death are fairly fast at those conditions.
...
GW

Weird Crystal Can Absorb All The Oxygen In A Room -- And Then Release It Later.
Popular Science
This could potentially make fuel cells, space travel, and scuba diving a lot more efficient.
http://www.popsci.com/article/science/w … m9tRRgO.30

Bob Clark

RGClark · 2014-12-02 03:11:16

RGClark wrote:

GW Johnson wrote:
I'm no medical person. But I do know from my days as a scuba diver that 1 atm partial pressure of oxygen induces convulsions in about half the people exposed to it, and 2 atm partial pressure O2 is lethal to all exposed to it. I'm simply guessing that it's a partial-pressure / osmosis thing across the membranes in the lung alveoli. These data are for sea level atmospheric pressure, and some very lethal experiences trying to breathe pure oxygen when underwater, plus some really bad experiences with compressed air hard hat divers between about 170 to 300 feet down. No one has ever lived for more than a few minutes on compressed air more than 300 feet down. Convulsions and death are fairly fast at those conditions.
...
GW
Weird Crystal Can Absorb All The Oxygen In A Room -- And Then Release It Later.
Popular Science
This could potentially make fuel cells, space travel, and scuba diving a lot more efficient.
http://www.popsci.com/article/science/w … m9tRRgO.30

The Martian atmosphere contains a small percentage of oxygen:

Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars

While this is a low percentage, it's a much higher percentage than that of CO2 in the Earth's atmosphere on which all plant life on Earth is dependent, and therefore on which all animal life is also dependent.

Because of the presence of free O2 in Mars atmosphere, conceivably you could have unlimited spacesuit time on Mars with the oxygen drawn from the surrounding atmosphere. However, the amount of O2 on Mars is so small you would need a fan to draw in more atmosphere. How much air flow would there have to be to get the required amount of breathable oxygen for a person?

Bob Clark

Last edited by RGClark (2014-12-02 03:12:10)

Antius · 2014-12-02 06:41:16

The Martian atmosphere contains a small percentage of oxygen:
Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars
While this is a low percentage, it's a much higher percentage than that of CO2 in the Earth's atmosphere on which all plant life on Earth is dependent, and therefore on which all animal life is also dependent.
Because of the presence of free O2 in Mars atmosphere, conceivably you could have unlimited spacesuit time on Mars with the oxygen drawn from the surrounding atmosphere. However, the amount of O2 on Mars is so small you would need a fan to draw in more atmosphere. How much air flow would there have to be to get the required amount of breathable oxygen for a person?
Bob Clark

Going off topic significantly - Martian air appears to contain both a combustible gas (CO) and an oxidiser (O2). Looking at the phase diagram for CO2 reveals that the triple point is about -58C and 7bar pressure. This is close to Martian daytime temperatures and significantly above nightime temps. With this is mind, it should be possible to compress Martian air, remove liquid CO2 and then burn what's left in a gas turbine. The energy needed to compress the CO2 can mostly be recovered in the expander.

No need for nuclear reactors or solar panels, Mars appears to have its own 'fossil fuel' stored within its atmosphere.

RGClark · 2014-12-02 14:12:19

Antius wrote:

The Martian atmosphere contains a small percentage of oxygen:
Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars
While this is a low percentage, it's a much higher percentage than that of CO2 in the Earth's atmosphere on which all plant life on Earth is dependent, and therefore on which all animal life is also dependent.
Because of the presence of free O2 in Mars atmosphere, conceivably you could have unlimited spacesuit time on Mars with the oxygen drawn from the surrounding atmosphere. However, the amount of O2 on Mars is so small you would need a fan to draw in more atmosphere. How much air flow would there have to be to get the required amount of breathable oxygen for a person?
Bob Clark
Going off topic significantly - Martian air appears to contain both a combustible gas (CO) and an oxidiser (O2). Looking at the phase diagram for CO2 reveals that the triple point is about -58C and 7bar pressure. This is close to Martian daytime temperatures and significantly above nightime temps. With this is mind, it should be possible to compress Martian air, remove liquid CO2 and then burn what's left in a gas turbine. The energy needed to compress the CO2 can mostly be recovered in the expander.
No need for nuclear reactors or solar panels, Mars appears to have its own 'fossil fuel' stored within its atmosphere.

Interesting idea. Anyone know the stoichiometric ratio between CO and O2? How much energy could you get out of the reaction?

For Earth's atmosphere the combustible elements of hydrogen and methane are in much smaller proportions than is CO on Mars so you couldn't get useful amounts of energy this way on Earth:

Bob Clark

RobertDyck · 2014-12-02 15:32:04

I notice total trace gas for Earth is listed as 0.037680%, but CO2 alone is 0.04%. If you take trace gas and subtract everything but CO2, that works out to 0.034989%. That's more in line with what I've read elsewhere. So CO2 in that chart has a rounding error.

According to this NASA webpage, Earth's atmosphere has

Surface pressure: 1014 mb
Surface density: 1.217 kg/m3
Scale height: 8.5 km
Total mass of atmosphere: 5.1 x 1018 kg
Total mass of hydrosphere: 1.4 x 1021 kg
Average temperature: 288 K (15 C)
Diurnal temperature range: 283 K to 293 K (10 to 20 C)
Wind speeds: 0 to 100 m/s
Mean molecular weight: 28.97 g/mole
Atmospheric composition (by volume, dry air):
Major : 78.08% Nitrogen (N2), 20.95% Oxygen (O2),
Minor (ppm): Argon (Ar) - 9340; Carbon Dioxide (CO2) - 400
Neon (Ne) - 18.18; Helium (He) - 5.24; CH4 - 1.7
Krypton (Kr) - 1.14; Hydrogen (H2) - 0.55
Numbers do not add up to exactly 100% due to roundoff and uncertainty
Water is highly variable, typically makes up about 1%

I keep thinking: where's the Xenon? According to Wikipedia, Earth's atmosphere has 87±1 parts per billion.

Void · 2014-12-02 17:50:05

If there actually is a energy benefit from the atmosphere of Mars (Oxygen & CO), then if it could be applied to a spacesuit that would be wonderful.

However, I choose to start with the low hanging fruit first.

Stationary machines trying to get energy from the atmosphere would be a start. CO and Oxygen, perhaps.

But I also look other ways.

http://phys.org/news/2014-11-protons-fu … pects.html

The above technique wants a moist atmosphere to produce Hydrogen, and they have not proved that they can get it yet. However, I recall one of our persons here suggests a plastic greenhouse that does not block UV. That would be good. a moist greenhouse that produces Hydrogen that could be harvested by the means suggested in the above link. Perhaps organisms would grow under a translucent sand layer at the top of the soil, to provide another useful purpose. (Shielded by the sand from UV). Or, perhaps a plastic layer inside the greenhouse to provide protection from the UV, but letting the volume above it be exposed to UV.

I also wonder if the salt pans of the temperate areas allow for collection of Oxygen and CO by electroplating.

And I wonder if organisms in such an environment get a salt reduced drink of water each night/day when the freeze thaw cycle is in action? Could they live off of Oxygen and CO?

As for suits, if possible, then I would first hope to power fuel cells from the atmosphere, and then upon greater technological achievements, perhaps Oxygen for the person in the suit. But that would be the end game.

RGClark · 2014-12-04 07:01:51

Antius wrote:

The Martian atmosphere contains a small percentage of oxygen:
Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars
While this is a low percentage, it's a much higher percentage than that of CO2 in the Earth's atmosphere on which all plant life on Earth is dependent, and therefore on which all animal life is also dependent.
Because of the presence of free O2 in Mars atmosphere, conceivably you could have unlimited spacesuit time on Mars with the oxygen drawn from the surrounding atmosphere. However, the amount of O2 on Mars is so small you would need a fan to draw in more atmosphere. How much air flow would there have to be to get the required amount of breathable oxygen for a person?
Bob Clark
Going off topic significantly - Martian air appears to contain both a combustible gas (CO) and an oxidiser (O2). Looking at the phase diagram for CO2 reveals that the triple point is about -58C and 7bar pressure. This is close to Martian daytime temperatures and significantly above nightime temps. With this is mind, it should be possible to compress Martian air, remove liquid CO2 and then burn what's left in a gas turbine. The energy needed to compress the CO2 can mostly be recovered in the expander.
No need for nuclear reactors or solar panels, Mars appears to have its own 'fossil fuel' stored within its atmosphere.

Don't we also need to know the temperatures at which CO and O2 become liquified? They might be mixed in with the liquid CO2 rather than existing as separate gases, though probably as liquids we could still separate all of them by centrifuge.

Bob Clark

Impaler · 2014-12-08 21:05:37

It seems certain people have an unduly positive opinion of Mechanical Counter Pressure suits and need to be reminded of their short-comings.

Their are only fragments of a complete suit currently and very very optimistic goals for what a final suit would look like so all such goals must be viewed sceptically. But just to be generous I'll address the shortcomings that are inherent IN the optimistic goal, the things that will be a problem even if all the most ambitious goals were reached.

1) Don/Doff time, this has always been the Achilles heel of the concept due to the tightness of the materials against the body. Their are ideas about the 'lines of non-extension' being some how relaxed by a memory-shape material but the general spandex material still needs to be tight creating a minimum time expenditure. How short the time might ultimately be is very hard to determine now, any assistance needed to get into or out of the suit is a huge operational liability.

2) Evaporative cooling, this is often touted as an advantage but it comes at a huge cost.

2a) First the physiological sweating capability of the astronaut becomes a limiting factor for cooling, this means things like heat-stroke are now very likely if the individual becomes dehydrated and stops sweating. Systems that capture sweat and cool the astronaut by other means aim to minimize sweating and will cool the astronaut regardless of their sweat production, this means they both reduce the likely-hood of heat-stroke AND apply the correct cure should it occur. Astronaut over-exertion has been a very common occurrence in EVA's and will likely continue to occur just as they do on the surface of the Earth.

2b) More water will need to be carried to rehydrate the astronaut and all the water expended in sweating will be lost into the Martian atmosphere and be on ongoing logistical cost to the base/vehicle from which EVA is done, water is by far the most precious material on Mars so using it here would be wasteful compared with assets like electricity or compressed atmosphere, which will cool you easily by just expansion. Water is also bulky so EVA from a long-range rover vehicle will be a large mass requirement for the vehicle to carry, when water is exhausted EVA activity must stop. Again a sweat (and exhaled water) capturing system is superior because it will provide endless drinking water to the astronaut and result in virtually no water losses for EVA.

2c) Evaporation also continually contaminates the surrounding environment with water vapor making the search for native Martian water (and life) highly problematic, the astronauts simplest tool for detecting a sub-surface ice deposit, a simple humidity sensor is now useless because he continually detects his own sweat rather then the native Martian humidity, remember the native humidity is in PPM so the sweat output of a human swamps the native environment by orders of magnitude, it may even be great enough to drive away the bulk atmosphere and create a bubble of pure water vapor around the astronaut.

2d) The efficiency of evaporation for cooling on Mars is subject to huge variation, Martian pressure and temperature are all varying a good deal through the day/night cycle (during daytime we must also shed the heat of the sun which is significant) and through the Martian seasons, finally their is highly variable wind. If any of these conditions slow the rate of evaporation below what is needed keep an astronaut cool then large no-go times and places may exist for the MCP. Also if the astronaut HAS built up a sweat in and on the suit and conditions change to one of excessive cooling their is no way to turn off the cooling and hypothermia may result even if sweating stops. More study of the actual rates of cooling that can be achieved and to what degree it can be controlled are needed, this paper seems to go into some of the math on how to calculate evaporative cooling rates on Mars but the math is beyond my ability http://www.geo.brown.edu/geocourses/geo … ht2002.pdf, the summary as best as I can understand it finds that the W/m^2 cooling rate would be lower on Mars then on Earth due in large parts to reduced convective cooling.

2e) Evaporation requires that liquid water from the astronauts skin permeate through the suit to manifest as water on or in the surface of the suit from which the evaporation takes place, the suit is cooled and then the suit cools the astronaut by direct conduction. Water permeable and water wikiing materials are no problem as we use such materials commonly in sporting and outdoor-wear applications here on Earth, but the set up requires the astronauts skin to be in contact with the concentrated residue of sweating. This residue would rapidly become a salty, slimy, smelly bacteria filled film in contact with the skin leading to discomfort and if allowed to dry inside the suit it may interfere with future wiking not to mention cause all kinds of odor. Meanwhile the outside of the suit is also manifesting moisture on/in it's surface, while this moisture might initially be pure water it would immediately be contaminated by dust and promote the creation of a 'crust' of whetted and then dried dust. Alternatively instant contact-freezing may occur when the moistened suit comes in contact with extremely cold regolith during a trip or fall, this could be much like touching your tongue to a steel pole in winter. Thus the MCP suit looks to be messy both inside and out. While it may be easier to wash this must be weighed against the higher need for cleaning.

3) Jock-discomfort, it is unsurprising that the newest MCP suit prototypes from MIT are only available for females, the difficulty in applying pressure mechanically to male genitalia are quite bad. Some kind of foam cup is going to be needed and this will have chaffing and range of motion issues.

4) Mandatory super-customized tailoring and total lack of interchangeability or modular fixing. The customized creation of a suit is not an insurmountable problem, indeed the Russians do it for their launch suits and NASA dose a bit of it too. But conventional suits made of modular pieces will offer much more operational flexibility to combine pieces to make a suit that fits any crew member. A MCP suit is monolithic and can't be exchanged between two people unless they are near twins. The modular suit can also be repaired by replacing individual worn-out or damaged sections, the MCP is basically junk once any part of it becomes degraded or damaged. Lastly the MCP suits fit is so exacting that normal changes in body fat or muscle mass may compromise the fit, if we send people to Mars with suits that fit initially, their is significant risk that they won't fit well enough after nearly 2 years.

5) Bodily orifices not on the head are ignored by the MCP suit. As gross as it is to think about a spacesuit has an adult diaper in it, MCP suits basically pretend that these orifices don't exist and bodily functions don't happen, when in reality the application of pressure mechanically to the skin is going to make stuff want to come out of these orifices more not less because were squeezing the body and not plugging the holes with air pressure. Urine collection is going to make the jock problem even more tricky, though catheterization might be a solution. Unless the crew on on a liquid-diet as was done in Apollo the solid waste problem has to be dealt with too and that means a diaper which will likely interferer with mobility in such a tight fitting suit.

RobertDyck · 2014-12-08 23:46:22

Dr. Paul Webb's original paper. Submitted for publication in December 1967; published in the Journal of Aerospace Medicine, April 1968 issue.
Space Activity Suit

Paul Webb and James Annis received funding from NASA to futher develop their suit. Conctractor report from November 1971.
NASA CR-1892 - Development of a Space Activity Suit

The second paper is a more advanced suit. The first paper includes pictures of a test subject wearing the suit in a vacuum chamber, equivalent to 50,000 feet. The suit in the second paper was designed for hard vacuum. The second one included the air bladder vest.

Last edited by RobertDyck (2014-12-08 23:47:37)

RobertDyck · 2014-12-09 11:33:08

I find it interesting that you report only female suits are currently available from MIT. Dr. Dava Newman is the researcher at MIT. She is continuing work on MCP. Dr. Paul Webb, Dr. Allen Hargens, and Dr. Mitchell Clapp have all retired. Actually, Dr. Webb is in his 80s; I hope he hasn't passed yet. But my point is suits designed by them were for men, suits designed by Dava are for women.

Dr. Paul Webb used a plastic bag filled with liquid silicone. Yea, the same silicone used for breast implants. Pressed against the male genitalia. I'll let you have fun with that. But it worked very well to spread the force evenly. So underwear (jockey shorts), then silicone liquid bag, then the MCP layer (tight spandex pants, tighter than a woman's girdle). The silicone filled bag would have a "finger" that extended around the crack of the ass, then up the trough of the lumbo-dorsal spine. You only need it up the small of your back, because the air bladder vest protects your back.

Spacesuits have been custom tailored to the astronaut since Mercury. Shuttle introduces standard glove sizes, but suits themselves were still custom made. I think you could make MCP with "standard" part sizes like Shuttle suits. Remember the thorax and upper abdomen is covered by an air bladder vest, so some change in weight and muscle mass in chest muscles, back, and stomach can be accommodated by air in the bladder.

As for water. I thought of that. But current spacesuits spray water on an evaporator. Astronauts wear an underwear body stocking with plastic tubes sewn in. The plastic tubes carry cool water to cool the body. That water is circulated through a heat exchanger in the PLSS backpack. The heat exchanger has an aluminum heat sink, which is where the other water is sprayed. It's allowed to evaporate into the vacuum of space. So current suits consume water for cooling. An MCP suit also consumes water for cooling, but the cooling system is the body's own regulatory system. The human body can do it better. When you aren't hot, the rate of sweating decreases.

Dr. Webb measured "insensible perspiration". That's sweat due to vacuum, even when you aren't hot. When the astronaut is hot, perspiration is regulated to maintain body heat. But insensible perspiration is the minimum. He calculated that heat loss due to insensible perspiration was lower than heat gain while at rest. So in the vacuum of space, this isn't a problem. Remember, he originally intended his MCP suit for the Moon. Mars has atmosphere, its pressure is very low but extant. That changes calculations for insensible perspiration. And Mars is cold. You may have to be careful about thermal insulation for a suit on Mars.

Furthermore, any Mars suit has to deal with atmosphere. Pressure is low, but enough for convection. Suits until now have used layers of aluminized Mylar as radiant heat reflectors, separated with a loose weave netting to separate the layers. This uses the vacuum of space to act as a thermos bottle, aka Dewar flask. But pressure on Mars is enough that the aluminum in those layers would act as a heat sink, causing more cooling than heat retention. Something else is needed for Mars. Whether for an MCP suit or a conventional air bag suit, thermal insulation on Mars has to be different. I have suggested Thinsulate, the thermal insulation of Ski pants and Ski jackets.

Antius · 2014-12-09 16:20:17

MCP suits certainly have their cons, but you overstate the matter.

Impaler wrote:

It seems certain people have an unduly positive opinion of Mechanical Counter Pressure suits and need to be reminded of their short-comings.
Their are only fragments of a complete suit currently and very very optimistic goals for what a final suit would look like so all such goals must be viewed sceptically. But just to be generous I'll address the shortcomings that are inherent IN the optimistic goal, the things that will be a problem even if all the most ambitious goals were reached.
1) Don/Doff time, this has always been the Achilles heel of the concept due to the tightness of the materials against the body. Their are ideas about the 'lines of non-extension' being some how relaxed by a memory-shape material but the general spandex material still needs to be tight creating a minimum time expenditure. How short the time might ultimately be is very hard to determine now, any assistance needed to get into or out of the suit is a huge operational liability.

Not sure why this would be the case. We are talking about elasticated under-garments sufficient to exert a 2-3PSI pressure on the skin. It would take a bit of extra time no doubt as we are putting on an extra layer of clothing, but sensibly we are talking a few minutes, not hours. How long does it take a woman to put on a pair of tights? Does it take a lot more time putting on a tight sweater as opposed to a loose jumper?

Impaler wrote:

2) Evaporative cooling, this is often touted as an advantage but it comes at a huge cost.
2a) First the physiological sweating capability of the astronaut becomes a limiting factor for cooling, this means things like heat-stroke are now very likely if the individual becomes dehydrated and stops sweating. Systems that capture sweat and cool the astronaut by other means aim to minimize sweating and will cool the astronaut regardless of their sweat production, this means they both reduce the likely-hood of heat-stroke AND apply the correct cure should it occur. Astronaut over-exertion has been a very common occurrence in EVA's and will likely continue to occur just as they do on the surface of the Earth.

True, but this is no more of a problem on Mars than it would be on the surface of the Earth. And with low external pressures, sweating would be a lot more efficient at removing heat. In any event, we came up with an innovation here on Earth that solved these problems centuries ago. It is called clothing. You can put more of it on if you get too cold and take it off if you get too hot. You can even provide fine tuning by zipping and unzipping your jacket or unbuttoning your overalls. On Mars, at -60C, keeping warm is likely to be a bigger problem. This is especially true for toes and fingers, which have poorer circulation and will lose heat by conduction during walking / handling. A good pair of thermal socks and gloves would be a necessity. A good pair of leather boots with thick soles. But I don’t see why the solution need be any more complex than that.

Impaler wrote:

2b) More water will need to be carried to rehydrate the astronaut and all the water expended in sweating will be lost into the Martian atmosphere and be on ongoing logistical cost to the base/vehicle from which EVA is done, water is by far the most precious material on Mars so using it here would be wasteful compared with assets like electricity or compressed atmosphere, which will cool you easily by just expansion. Water is also bulky so EVA from a long-range rover vehicle will be a large mass requirement for the vehicle to carry, when water is exhausted EVA activity must stop. Again a sweat (and exhaled water) capturing system is superior because it will provide endless drinking water to the astronaut and result in virtually no water losses for EVA.

True. We are trading lower complexity against an extra logistical cost. But you overstate the matter. Complete evaporation of 1kg of water removes 2MJ of heat – 2000 Cal. So an astronaut burning 200Cal per hour on Mars EVA will need to drink an extra 70ml of water – just over half a litre for an 8 hour shift. Not ideal, but it doesn’t exactly break the bank. On the moon, it is a different story. We would need some means of capturing and condensing the water vapour, probably using a polymer over garment and a small compressor.

Impaler wrote:

2c) Evaporation also continually contaminates the surrounding environment with water vapor making the search for native Martian water (and life) highly problematic, the astronauts simplest tool for detecting a sub-surface ice deposit, a simple humidity sensor is now useless because he continually detects his own sweat rather then the native Martian humidity, remember the native humidity is in PPM so the sweat output of a human swamps the native environment by orders of magnitude, it may even be great enough to drive away the bulk atmosphere and create a bubble of pure water vapor around the astronaut.

True I guess. But there are other ways of detecting water. Somehow, I doubt that this will be a big issue.

Impaler wrote:

2d) The efficiency of evaporation for cooling on Mars is subject to huge variation, Martian pressure and temperature are all varying a good deal through the day/night cycle (during daytime we must also shed the heat of the sun which is significant) and through the Martian seasons, finally their is highly variable wind. If any of these conditions slow the rate of evaporation below what is needed keep an astronaut cool then large no-go times and places may exist for the MCP. Also if the astronaut HAS built up a sweat in and on the suit and conditions change to one of excessive cooling their is no way to turn off the cooling and hypothermia may result even if sweating stops. More study of the actual rates of cooling that can be achieved and to what degree it can be controlled are needed, this paper seems to go into some of the math on how to calculate evaporative cooling rates on Mars but the math is beyond my ability http://www.geo.brown.edu/geocourses/geo … ht2002.pdf, the summary as best as I can understand it finds that the W/m^2 cooling rate would be lower on Mars then on Earth due in large parts to reduced convective cooling.

Evaporation of 1kg of water removes 2000Cal of heat. At body temperature, it evaporates quite rapidly at Martian pressures. On Mars, atmospheric pressure is substantially below the vapour pressure of water at human body temperature. This is the case everywhere, all the time. As for sunlight heating, how is this any more of a problem than on Earth? You get warmer, you sweat more. The human body self regulates.

Impaler wrote:

2e) Evaporation requires that liquid water from the astronauts skin permeate through the suit to manifest as water on or in the surface of the suit from which the evaporation takes place, the suit is cooled and then the suit cools the astronaut by direct conduction. Water permeable and water wikiing materials are no problem as we use such materials commonly in sporting and outdoor-wear applications here on Earth, but the set up requires the astronauts skin to be in contact with the concentrated residue of sweating. This residue would rapidly become a salty, slimy, smelly bacteria filled film in contact with the skin leading to discomfort and if allowed to dry inside the suit it may interfere with future wiking not to mention cause all kinds of odor. Meanwhile the outside of the suit is also manifesting moisture on/in it's surface, while this moisture might initially be pure water it would immediately be contaminated by dust and promote the creation of a 'crust' of whetted and then dried dust. Alternatively instant contact-freezing may occur when the moistened suit comes in contact with extremely cold regolith during a trip or fall, this could be much like touching your tongue to a steel pole in winter. Thus the MCP suit looks to be messy both inside and out. While it may be easier to wash this must be weighed against the higher need for cleaning.

Sweating makes you smelly wherever you are. And if you are exerting yourself in a space suit, you will sweat, whether it is a pressure suit or MCP suit. Why do you suggest that it would be especially bad in an MCP suit? Under vacuum conditions prevalent on Mars, water and ice rapidly sublime. The body heat conducted through the suit will increase this effect. And skin would rapidly dry – indeed sublimation would be more rapid and efficient in a vacuum. It doesn’t make any sense to me why this ‘odour’ problem would be worse in an MCP suit on Mars, than it would be here on Earth in normal clothing, where the sweat does not evaporate quickly.

Impaler wrote:

3) Jock-discomfort, it is unsurprising that the newest MCP suit prototypes from MIT are only available for females, the difficulty in applying pressure mechanically to male genitalia are quite bad. Some kind of foam cup is going to be needed and this will have chaffing and range of motion issues.

Again, a relatively minor design issue. This could be solved by adding a butyl rubber lining to a pair of elasticated biking shorts. They would then trap enough air to maintain counter pressure.

Impaler wrote:

4) Mandatory super-customized tailoring and total lack of interchangeability or modular fixing. The customized creation of a suit is not an insurmountable problem, indeed the Russians do it for their launch suits and NASA dose a bit of it too. But conventional suits made of modular pieces will offer much more operational flexibility to combine pieces to make a suit that fits any crew member. A MCP suit is monolithic and can't be exchanged between two people unless they are near twins. The modular suit can also be repaired by replacing individual worn-out or damaged sections, the MCP is basically junk once any part of it becomes degraded or damaged. Lastly the MCP suits fit is so exacting that normal changes in body fat or muscle mass may compromise the fit, if we send people to Mars with suits that fit initially, their is significant risk that they won't fit well enough after nearly 2 years.

I don’t see why an MCP suit cannot be modular in the same way that other clothing is modular. We really are talking about a thin piece of fabric clothing that goes under your other clothes. Why not construct the suit in overlapping pieces that are buttoned or zipped together? A pressure of 2-3PSI is the same pressure that you feel diving into a swimming pool. Not trivial, but well beneath the yield stresses of most fabrics. If you were to connect a jumper top to some elasticated trousers, you would have an internal force of 60-90kg (600-900N) pulling the two apart. A polyester strand strong enough to resist that force would be 3.9x3.9mm. So I would suggest a ring of buttons as the simplest solution. As for tares in the suit, there are two radical inventions that come to the rescue. One is polyester fibre and the other is a needle.
The issue of fitting is a problem, but hardly a difficult one. To a limit extent, the body would expand into the suit in certain places and would be over compressed in others. Again, this happens to a degree with a lot of normal clothing (especially female clothing) and we can expect it to be tolerable up to a certain point. Again, an MCP suit is simply a set of elasticated under garments. If you lose weight, change to a smaller size. It is light and cheap enough to allow that sort of flexibility.

Impaler wrote:

5) Bodily orifices not on the head are ignored by the MCP suit. As gross as it is to think about a spacesuit has an adult diaper in it, MCP suits basically pretend that these orifices don't exist and bodily functions don't happen, when in reality the application of pressure mechanically to the skin is going to make stuff want to come out of these orifices more not less because were squeezing the body and not plugging the holes with air pressure. Urine collection is going to make the jock problem even more tricky, though catheterization might be a solution. Unless the crew on on a liquid-diet as was done in Apollo the solid waste problem has to be dealt with too and that means a diaper which will likely interferer with mobility in such a tight fitting suit.

Again, I would suggest rubber lined pants that trap a small volume of air around the genitals. At 2-3PSI this is achievable without being unbearably tight.

RGClark · 2015-08-07 11:20:05

RGClark wrote:

RGClark wrote:
Weird Crystal Can Absorb All The Oxygen In A Room -- And Then Release It Later.
Popular Science
This could potentially make fuel cells, space travel, and scuba diving a lot more efficient.
http://www.popsci.com/article/science/w … m9tRRgO.30
The Martian atmosphere contains a small percentage of oxygen:
Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars
While this is a low percentage, it's a much higher percentage than that of CO2 in the Earth's atmosphere on which all plant life on Earth is dependent, and therefore on which all animal life is also dependent.
Because of the presence of free O2 in Mars atmosphere, conceivably you could have unlimited spacesuit time on Mars with the oxygen drawn from the surrounding atmosphere. However, the amount of O2 on Mars is so small you would need a fan to draw in more atmosphere. How much air flow would there have to be to get the required amount of breathable oxygen for a person?

I can make an estimate based on what NASA uses on their spacesuits. According to this page, with recycling, 0.54 kg of oxygen is enough for 7 hours of EVA:

The Primary and Secondary Life-Support Systems.
http://quest.nasa.gov/space/teachers/suited/5emu4.html

Let's see how much oxygen is in the Mars atmosphere as a mass percentage. To convert from a mole fraction to mass fraction you multiply the mole fraction times the molecular weight to get a mass in grams. Then the mass fraction for a component is the fraction of this mass divided by the sum of the masses of all the components. This gives a mass fraction of oxygen of about 1/1000 for Mars. For Mars atmospheric density 1/100th of Earths, this is 1.2 /(100*1,000) = 1.2*10^-5 kg/m^3.

At an oxygen usage rate of .54 kg for 7 hours, this is .54/(7*60) = 1.28*10^-3 kg per minute. So you would need about 100 cubic meters of Mars air flow per minute. Say your life support backpack had a 1 square meter area. This would require your fan to move the Martian air at about 100 meters per minute, 1.67 m/s, though the backpack.

Because of the low density of the Martian air this takes surprisingly low power. See this page for the power generated by a wind mill:

Power generated from the wind.

The theoretically available power in the wind can be expressed as
P = 1/2 ρ A v^3 (1)
where
P = power (W)
ρ = density of air (kg/m^3)
A = area wind passing through perpendicular to the wind (m^2)
v = wind velocity (m/s)

http://www.engineeringtoolbox.com/wind- … _1214.html

Assume that operated in reverse the amount of power input will generate the corresponding amount of air flow. Then the power needed for 1.67 m/s airflow speed at an atmospheric density of .012 kg/m^3 and area of 1 m^2 would be P = .5*.012*1*1.67^3 = .028 watts. Even at 20% efficiency this would be about .14 watts of power.

Bob Clark

Last edited by RGClark (2015-08-08 09:24:42)

RobertDyck · 2015-08-07 12:55:02

The Popular Science article links to a science paper published by Chemical Science. here Quoting that paper...

Oxygen desorption for the parent [{(bpbp)Co2III(O2)}2(bdc)]4+, crystallized with four different counteranions, was measured by heating up to 160 °C at 5° min-1 under a steady flow of N2 gas.
...
At approximately 100 °C the nitrate salt has lost both O2 molecules, whereas the PF6- salt is completely deoxygenated first at 160 °C.

Figure 2 of that paper shows thermal cycling from +30°C to +140°C. How much energy for that thermal cycling? What is the specific heat for this material? What mass of material per unit mass of oxygen? Then there's energy efficiency: is the material compatible with radio frequency heating, like a microwave oven? If you use electro-resistive heating, there's thermal mass to the heating element and container.

RGClark · 2015-08-07 13:20:23

It occurs to me a bigger energy cost will be involved in increasing the tiny oxygen partial pressure to that used in NASA spacesuits, ca. 0.3 bar. I'll look up some formulas for that.

Bob Clark

Last edited by RGClark (2015-08-07 13:21:24)

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