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#76 2016-02-16 15:46:59

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,281
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Re: New idea for Mechanical CounterPressure suit

I had argued for 80 denier Goretex for the outer layer. I got that from the shell of an Alpine mountain climbing parka. However, NASA likes their fancy stuff, so arguing for Tenara is less of a difference vs the current Orthofabric. I already talked to one engineer who said they *WILL* include micrometeoroid protection for any Mars surface suit or surface habitat. He just wouldn't listen when I told him there aren't any micrometeoroids there.

You're right, Dr. Webb uses an inelastic fabric to contain his rubber bladder vest. The idea of squishing it close to the body is my idea. It's just to make the suit more serviceable vs Michelin Man. My idea is a vacuform plastic sheet, not anything thick. The front and back sheets could be held to each other with straps and buckles. For those of us who aren't round.

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#77 2016-02-16 17:18:15

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,146
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Re: New idea for Mechanical CounterPressure suit

Hi RobertDyck:

I thought reading the original reports of Webb that his inelastic jacket squished the breathing bladder close to the chest,  and it was nowhere near round in shape.  It filled the space between body and jacket.  Whether fabric jacket or rigid carapace plates,  the exact same thing happens.  Or should,  at least,  close enough. 

The body more-or-less conforms to the available pressure within the available confined space,  while the elastic jacket more-or-less conformed to the varying but not necessarily round body shape (inhale vs exhale).  In Webb's report,  the bladder was called a tidal volume breathing bag.  It got thicker on exhale,  and thinner on inhale.  That's all it really did. 

But nothing was ever "truly round".  The applied pressure gradient along any given direction along the body wasn't zero either,  but I thought Webb addressed how far off it could be,  in one of his reports.  The gradient difference was significant enough to cover the inadequacies of his garment made of 6 or 7 layers of pantyhose material,  plus that bladder and jacket.

The tidal volume bag is actually something tried earlier with some of the earlier high-altitude pressure breathing schemes that were not successful circa 1945-1946 until the lesson of counterpressure was finally learned.  At least,  that's what I read. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#78 2016-02-16 20:45:57

kbd512
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Registered: 2015-01-02
Posts: 3,840

Re: New idea for Mechanical CounterPressure suit

GW Johnson wrote:

Using MCP together with an uninflated balloon suit is a unique idea.  But,  it does guarantee a body-overheat condition because you are inside the rubber balloon,  the same problem full pressure suits have had from their very beginnings in the 1930's.

The temperature range is 123C to -153C for a lunar environment.  At those temperatures, the spandex fabric from the original MCP suit is near or has exceeded mechanical properties limits with respect to melting point or glass transition.

GW Johnson wrote:

My question is this:  why would you want to combine the worst problems of both suit approaches?  Why not instead treat the MCP as vacuum-protective underwear,  that you can sweat through,  and then just use whatever thickness and color of insulating outerwear suits the task at hand,  unpressurized,  and bought from the local retail store?

What articles of clothing you can buy at a retail store that will keep you cool when its 123C outside and warm when its -153C outside.  I can't think of any.  The temperature range is too wide.

GW Johnson wrote:

I would think that for daylight operations near Earth or Mars,  a white coverall (or hunting pants and coat,  take your pick,  whichever is easier to don) will turn sunlight well enough.  Near Venus,  we might want to tailor an additional outer reflective layer out of an aluminized space blanket.  Just pick the insulation thickness of the coverall (or hunting pants and coat) to match the level of cold experienced when not in sunlight.

You can't guarantee that the astronauts will remain within a rather narrow temperature range when they're doing donuts around a planet.  Coveralls won't provide debris protection, either.

GW Johnson wrote:

Add to that heavy or insulated hiking boots to wear over the compression booties-as-socks.  Carry a selection of light leather work gloves,  heavy leather work gloves,  and insulated gloves to wear over the relatively-thin compression gloves. You're pretty much prepared to handle just about anything you find.

You want the astronauts to cover themselves with garments that are every bit as thick as a space suit.  Why not just use the space suit?

GW Johnson wrote:

Rather than complicate the helmet with too many visors,  what's wrong with an oversized broad-brimmed hat?  Take it off in the shade,  put it back on out in the sun.  Tether it to your suit so it doesn't drift away in zero gee,  or burden your hands walking on a surface in gravity.

How big a sombrero would an astronaut require to fit his helmet?

A hat only protects your eyes from the sun when the light is not otherwise reflected into your helmet.  That might be difficult to accomplish.

GW Johnson wrote:

This kind of dress-for-space doesn't require over-engineering-for-profit.  The only part of MCP that needs some engineering attention is the vacuum-protective underwear and helmet/tidal bag/backpack pressure-breathing rig.  That the bulk of that is really equipment trials and improvements;  the feasibility was done about half a century ago.  The rest of it you buy at Wal Mart,  or at worst adapt and tailor from stuff you buy at Wal Mart.

I don't think it's quite as simple as you're making it out to be.  Nobody purchasing clothing from Wal-Mart will be pelted with debris traveling at orbital velocity and they'll never go outside when it's 123C, let alone -153C.

GW Johnson wrote:

There's no need to add to the gravy-train giant-corporate welfare projects to make this stuff space-ready.  You give it to the "usual crowd" (which includes NASA itself as well as its favorite suit contractors),  and you'll never see it come to be.  We'll just continue seeing what happened the last 50 years:  nothing.

There's no need to continue to use outmoded or dangerous technologies, but space suits are a minor cost in NASA's overall budget.  Current space suit technology is clearly not feasible for a planetary environment like Mars.  That's why I support MCP suit development, not because I expect MCP suits to be a single solution to protecting humans in space.

GW Johnson wrote:

I'm getting awfully old,  but John Glenn was older when he rode the shuttle.  I'd be willing to take Webb's 1970-vintage design with the breathing bag,  plus some coveralls boots,  and gloves from Walmart (or wherever) and try it out myself in an EVA on the space station.  How many hours of EVA would convince you guys?  How many do you think it might take to convince NASA?

GW

In the 1970's there wasn't nearly as much debris floating around in LEO.  Given the amount of debris that bombards ISS on a regular basis, if I was planning ISS EVA's there's no way in hell I'd ever recommend leaving the heavily protected modules of the station wearing spandex and a pair of hunting coveralls from Academy.  I'd not hesitate to recommend the enhanced puncture protection that a MCP suit can provide, either, for the same reason.

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#79 2016-02-16 22:12:47

RobertDyck
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From: Winnipeg, Canada
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Re: New idea for Mechanical CounterPressure suit

Space Activity Suit, from Dr. Paul Webb's article published in 1968...
sas.jpg
Updated version, with Apollo helmet but no vest, 1971...
jsasuit.jpg
My point is fabric is in direct contact with skin. It won't be much colder than body temperature. A thermal and micrometeoroid garment goes over this. As a comparison here is the Apollo spacesuit, A7L. The first is without the outer garment, the second is with. Also note the "visor assembly", which is an outer helmet worn over the pressure helmet. You can click Apollo images for a larger view...
120px-S71-24537-A7L_without_outerlayer.jpg 134px-Buzz_Aldrin_Apollo_Spacesuit.jpg

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#80 2016-02-16 23:08:27

kbd512
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Re: New idea for Mechanical CounterPressure suit

Rob,

What type of thermal and debris protection garment do you imagine would permit natural perspiration to cool the astronaut at 123C that won't also cause freezing of perspiration at -153C?

The gore tex fabric you proposed can actually function as intended over those temperature extremes, but how thick would such a garment be to protect the wearer from oven-to-cryogenic temperatures?  What is the wearer supposed to do during hot/cold transitions?  We already know what happens when a person wearing warm and wet clothing transitions to a much colder environment and it's not good.

Regarding debris protection, as far as I know there aren't any materials that permit perspiration to escape that can also stop orbital velocity debris.  No debris protection is required on Mars and the temperature range is less extreme compared to complete vacuum environments.  Stopping to change clothes to contend with temperature changes also poses less of a problem than in microgravity environments.

I don't believe there is a single solution to the pressure, temperature, and debris protection problems that space presents.  I see the MCP suit as a worthwhile and necessary first step towards divesting ourselves of complete reliance on inflatables for environments where inflatables are simply infeasible.

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#81 2016-02-17 00:17:49

RobertDyck
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From: Winnipeg, Canada
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Re: New idea for Mechanical CounterPressure suit

The Spacesuit Taskforce by Chris Vancil organized a symposium as part of the 2005 Mars Society Convention. We invited Dr. Paul Webb. I actually got to talk to him there! I asked him about perspiration. I was worried about a neoprene rubber air bladder over the chest and upper abdomen; how would that affect cooling by perspiration? He said it isn't a problem, that vacuum wicks perspiration to the edges where it evaporates.

So I envision a thermal and scuff garment for Mars made out of something that breathes. Jacket and pants, the two garments not sealed to let perspiration evaporate between them. I was thinking of Tenara fabric. I actually have a sample, I ordered 8.5"x11" swatches of Ortofabric and Tenara fabric from the manufacturer. The same manufacturer that makes Orthofabric for NASA EMU suits. So I have samples, and brought them to Mars Society conventions. I find it amazing how supple they are, considering thread weight measured in denier is as heavy as canvas. They're actually more supple than denim jeans. But the material is PolyTetraFluoroEthylene (PTFE), the same material as Teflon but spun as thread. It was invented by a division of the Gore Textile Company, initially sold under the brand name GoreTex. However, the division that makes Orthofabric and Tenara architectural fabric has been sold. PTFE is hydrophobic, meaning it repels water. Goretex for clothing normally uses two layers of normal fabric, such as nylon, with a film of PTFE sandwiched between. The PTFE film has tiny holes. Since PTFE is hydrophobic and the holes are so small, liquid water can't get through. But vapour can. So evaporated sweat from your feet can get out, but liquid water from a puddle cannot get in. This lets moisture out, but keeps water from getting in. Brilliant! Of course that only works briefly: if you stand in water for any length of time the water from the puddle will evaporate through those holes into your boots. However, Orthofabric does not use the film. Instead the outer layer is threads of PTFE. That's to protect the suit from mono-atomic oxygen in LEO. Apollo used Teflon coated fibreglass, called Betafabric, but the EMU suit used on ISS today uses Orthofabric. It's a plain weave with two layers woven together: PTFE fabric facing, with Nomex backing, and every 3/8" in both warp and weave directions 2 thread of Nomex are replaced with Kevlar. All three types of thread are 400 denier weight. Nomex is the same material as a fire fighter's jacket and pants. The combination makes Orthofabric very tough against micrometeoroids, and strong in extreme temperatures: -156°C to +121°C (-250°F to +250°F). That's the extremes for LEO. The Moon can swing -153°C to +123°C. So I would use Orthofabric on the Moon as well.

For the Moon, the thermal and micrometeoroid garment would use the same multilayer insulation as currently used. And the same Orthofabric as EMU. However, an MCP suit would have separate jacket and pants, with the jack and pants not sealed. This allows perspiration to escape at the waist. You would probably want vapour vents in arm pits, and of course ends of sleeves would not be sealed. Backs of knees would require vents as well, and ends of pant legs would not be sealed. The neck would not be sealed to the helmet. See GW Johnson's comments about how the helmet is mated to the MCP suit. This allows perspiration to escape from the neck opening of the vest.

Dr. Paul Webb's design had pressurized boots. He didn't know how to deal with details of feet and toes, so just used pressurized boots with a neoprene air dam at the ankle. I keep thinking of Telemark ski boots, which have a hinge at the ankle. That means you don't want to smell the boots when you take them off.
garmont-ener-g-telemark-boot.jpg
(Boots advertised on the internet are ridiculously expensive, and have overly elaborate complication to make them look fancy to justify the price. The feature I like is a hard boot, but with a hinge at the ankle.)

Mars: the outer garment for Mars will be quite different. It would still be a jacket and pants, but Thinsulate insulation and Tenara outer fabric. The jacket would be an Alpine parka. Mars temperature can get up to +24°C at ground level during the day. I heard it can get even higher, but the highest I saw reported by Mars Global Surveyor for the entire planet during the first year it was in orbit was +24°C. When the surface is that warm, atmosphere can be 10°C colder just 2 metres above the surface, so your toes could be +24°C and your head +14°C. However, Mars at night can get down to -80°C. At higher latitudes in winter at night it can get even colder. I checked the entire data archive of the Viking 2 lander, hour by hour for more than a Martian year. The coldest recorded was -111°C. That was at night and in winter. That was mid-latitude; I imagine a human mission would land closer to the equator. Because it's warm. And crew would not stay out at night. Mars Pathfinder only reported weather for 3 days, the coldest it recorded was -77°C. The absolute coldest was the Mars south pole in southern winter, that was -140°C. Again, you wouldn't send crew there.

So Mars temperatures aren't as extreme. I'm thinking parka and ski pants, with pit zips. That's zipper openings in arm pits. The temperature on Mars can swing so much that you need the garment to adjust. Yes, that means zippers on a spacesuit. But the zippers will not be involved with pressure, and you could use an air compressor to blow out dust at the hab. A separate parka with fibre insulation is machine washable. Anything with multilayer insulation is not, because that's aluminized Mylar. So the Mars suit will be washable, the Moon suit not. So the arm pit zippers (pit zips) could be washed clean.

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#82 2016-02-25 15:50:55

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,146
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Re: New idea for Mechanical CounterPressure suit

With regard to meteroid protection with an MCP suit at ISS (post #78 above,  near end),  what would be wrong with a white kevlar jacket and pants over your white Walmart-or-similar insulating coveralls.  These kevlar outer-layer garments,  combined with the padding of the insulated coveralls,  would be exactly equivalent to bulletproof and flak jackets we have down here.  I'm not at all sure that one can do any better than that.  But if they really can,  I'd like to know how. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#83 2020-02-16 19:16:08

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 20,263

Re: New idea for Mechanical CounterPressure suit

Here is the right topics for these posts:

RobertDyck wrote:

One concern is getting into a spacesuit. Shuttle and ISS use Earth sea level pressure, which is absolutely not necessary. That creates major problems when an astronaut has to go outside in a spacesuit. Shuttle astronauts had to pre-breathe pure oxygen for 17 hours to flush nitrogen out of their blood. If they don't, decompression would result in nitrogen dissolved in blood coming out of solution, creating bubbles. Those bubbles will block blood flow, starving tissues that are supposed to be fed by those blood vessels. Starving tissues of blood will cause tissues to die. Tissue can withstand blood flow blockage about as long as you can hold your breath; a little more, but not much. After that the tissue starts to die. This is a medical condition called "The Bends".

There is a maximum partial pressure of nitrogen for zero pre-breathe time. Take total pressure of the lower pressure environment (spacesuit), multiply by 1.2, that's the maximum partial pressure of nitrogen in the higher pressure environment (habitat, spacecraft, space station, etc).

Apollo used 3.7 psi pure oxygen for spacesuits. Apollo Command module used 5.0 psi pure oxygen. After the Apollo 1 fire there was much discussion about using a mix for fire safety, but the additional weight of carrying nitrogen bottles and pressure regulators needed to balance gas pressures were considered too much. So Apollo used natural air from the launch site for launch, then "bled out" that air as the Saturn V ascended. Apollo continued to bleed out air, reducing pressure and flushing out air to replace with pure oxygen. When finished Apollo had 5.0 psi pure oxygen. This was done slowly enough that astronauts did not risk "The Bends". It was important that Apollo not use 14.7 psi (Earth atmosphere at sea level) pure oxygen, because pure oxygen at that pressure is dangerous. Velcro will smoulder in Earth air, but will not sustain a flame. That means Velcro will stop burning once you take a flame way; it will not burn on its own. I believe Velcro will smoulder but not burn in 3.0 psi pure oxygen, not sure if it'll burn in 5.0 psi pure oxygen. But the test that was posthumously called "Apollo 1" used 16.7 psi pure oxygen; in that much oxygen Velcro will ignite like the head of a match. In 14.7 psi pure oxygen, Velcro will not burn quite as vigorously, but still quite vigorous.

Skylab also used 5.0 psi total pressure, but used 60% oxygen / 40% nitrogen. That works out to 3.0 psi partial pressure oxygen + 2.0 psi partial pressure nitrogen. Apollo spacesuits used 3.7 psi pure oxygen, so maximum partial pressure nitrogen would be 3.7 * 1.2 = 4.44 psi. Skylab used 2.0 psi nitrogen, so well below the maximum. This allowed astronauts to don a spacesuit and go through the airlock at any time, no oxygen pre-breathe.

The EMU suit was designed for Shuttle, and currently used on ISS. It uses 4.3 psi pure oxygen. Maximum partial pressure nitrogen for a habitat to allow using that suit without oxygen pre-breathe: 4.3 * 1.2 = 5.16 psi. Earth at sea level has 3.0 psi partial pressure oxygen, so if a habitat uses that then 3.0 psi O2 + 5.16 psi N2 = 5.16 psi total. That's the absolute maximum, it would be a good idea to reduce nitrogen a bit for safety.

Do I have to mention that EMU uses higher pressure to reduce oxygen pre-breathe time? So EMU uses higher pressure because Shuttle and ISS use higher pressure.

Original design work for Apollo spacesuits intended to use 3.3 psi pure oxygen. Since Earth at sea level has 3.0 psi partial pressure O2, astronauts can breathe that just fine. This allowed for a 10% pressure leak in the suit without jeopardizing astronaut health. In the end they chose to increase pressure a bit because extreme low pressure causes lung tissue to dry out. If lung tissue gets too dry, it will crack and bleed. This can be managed with high humidity in breathing air (suit oxygen), but high humidity can cause the visor to fog.

Dr. Paul Webb did the initial work on mechanical counterpressure (MCP) spacesuits. He used 170 mm mercury (3.287 psi) pure oxygen. His papers describe problems at 130 mm mercury (2.51 psi): mild tachycardia and small collection of edema fluid in the hands. Of course the solution is stick to 170 mm mercury (round off to 3.3 psi). Recently Dr. Dava Newman of MIT said designing an MCP suit to work with 20 kPa (2.90 psi) pressure is easy, designing for 30 kPa (4.53 psi) is hard. Of course the solution is don't. By that I mean don't use the higher pressure of an EMU suit, instead use the original pressure MCP was design to work with.

Dr. Paul Webb designed a second generation suit, described in his contractor report to NASA, filed November 1971. That report describes. A then-new high-tech material that would work much better. Dr. Webb worked with cotton threads dipped in rubber for his elastic fabric, because that was state-of-the-art at the time. In fact he hired a company that manufactures women's girdles to manufacture his elastic spacesuit garment: Playtex. But his contractor report describes a new material that would work better: Spandex. Yup, the same material as 1980s exercize/gym wear. In 1971 it was new. Today we have even newer materials, but my point is we don't need anything radical, just tight Spandex. Dr. Webb's second generation suit used a neoprene rubber air bladder vest over the thorax (chest) and upper abdomen. This vest had a non-elastic outer fabric; as the subject inhales that squishes air out of the bladder, but volume in the lungs increase by exactly the same volume. Exhale does the reverse. Connecting the air bladder to breathing air (helmet or breathing mask) ensures constant volume. This is done with Navy diver rebreathers; it's called a "counter lung". Ensuring constant volume prevents restrictions to breathing. I would further recommend a breathing mask over nose and mouth, similar to a fighter pilot breathing mask. This allows breathing air to have higher humidity than air inside the visor. Yes, EMU suits today use an anti-fog spray on the inside of the visor, but a breathing mask is an easy way to reduce this problem.

Furthermore, MDRS found safety concerns wearing a shoulder-worn helmet when driving a 4-wheel ATV. Some crews take off their helmet, breaking sim, when driving an ATV. I would argue for a spacesuit helmet that is head-worn, like a motorcycle helmet. That would allow the helmet to be a crash helmet; literally providing the same protection as a motorcycle helmet. An MCP suit can do this. Mercury and Gemini spacesuits did this, but found a gas bag suit made turning the head difficult. Apollo suits went to shoulder-worn to resolve that. However, an MCP suit uses a neoprene air dam over the neck, to hold air pressure in the helmet. The suit is an elastic fabric. So an MCP suit doesn't have the same problem turning the head. So this solves the "crash helmet" problem. And a head-worn helmet can easily include a breathing mask.

Dr. Paul Webb worked with 170 mm mercury because that's what NASA was working with at the time. I would recommend dropping pressure even further to 3.0 psi pure oxygen. That makes moving easier. And using the original Apollo rule of suit pressure being 10% higher than oxygen partial pressure the astronauts are used to, in case of pressure loss, then I would drop habitat oxygen to 2.7 psi partial pressure. Note: oxygen on Earth at sea level is 3.0 psi partial pressure, but at Boulder Colorado it's 2.54 psi.

Spacesuit design is critical, because you don't want to require multiple hours of oxygen pre-breathe just to put on a suit and go outside. Dropping suit pressure to 3.0 psi, means optimal habitat oxygen will be 2.7 psi, and maximum habitat nitrogen will be 3.0 * 1.2 = 3.6 psi. If that's all you have then that totals 2.7 + 3.6 = 6.3 psi. But Earth's atmosphere is 0.9340% argon, you're breathing a tri-gas mix right now: oxygen, nitrogen, argon. I recommended making the nitrogen:argon ratio exactly the same as Mars atmosphere, simply because that means we don't have to separate them. Just harvest Mars atmosphere, filter out dust, use a freezer to convert CO2 to dry ice, and keep the rest. Turns out that's not quite enough: there's carbon monoxide and ozone, but a rhodium based catalyst can combine CO with O2 to form CO2. Turns out there's more oxygen in Mars atmosphere than carbon monoxide, so this works. Furthermore, that same catalyst breaks down ozone: 2 O3 → 3 O2. This provides slightly more oxygen while CO is being converted. The result will still have a bit of CO2, a freezer is good at removing the bulk but can't remove the last big. However, a habitat life support system can remove the rest. I call this gas "diluent gas" because it's used to "dilute" oxygen. A habitat filled with oxygen / diluent gas can support humans right away, it'll just smell stuffy until the life support system reduces CO2. Assuming Mars atmosphere has the same gas mix measured by Viking lander in 1977, and assuming 3.6 psi partial pressure nitrogen, that works out to 2.133 psi partial pressure argon. However, modern Mars rovers have measured a slightly different N2:Ar ratio. I wouldn't think it would vary, but looks like it does. Samples taken decades apart, and different locations on the planet. But using the data from Viking 2, that adds up to: 2.7 psi O2 + 3.6 psi N2 + 2.133 psi Ar = 8.433 psi total.

A small operation would use the same air for greenhouse and habitat. This allows the plants to recycle oxygen, so no power is necessary for oxygen generation. As a safety factor, this allows life support with completely power failure. It also means you can just walk from habitat to greenhouse, extending total living space. Yes, artificial lights would be needed in case of dust storms, and artificial life support would be needed as a backup. But using plants in an ambient light greenhouse as primary life support reduces power demands under normal operation. And means power failure only becomes life threatening if it occurs the same time as a major dust storm.

A large commercial greenhouse would most probably elevate CO2. That increases plant growth. And pressure could be reduced. Guelph University did an experiment with spinach grown in a hypobaric chamber. They found plants grow just fine, but water transpiration through leaves increases as pressure drops. As long as there's enough water, plant growth continues at the same pace. In a sealed greenhouse, water transpired through leaves will condense on walls/windows, dripping down through to collection trough that routes the water back to plant roots. So the water goes in a big circle, it's not consumed. Below 10 kpa pressure (1.45 psi) the plants wilt, stop growing. The university did an experiment where they dropped pressure to Mars ambient for one hour, then restored pressure. The plant wilted, but perked back up and continued to grow as soon as pressure was restored. So plants can withstand lower pressure than humans.

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#84 2020-02-16 19:16:55

SpaceNut
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Posts: 20,263

Re: New idea for Mechanical CounterPressure suit

kbd512 wrote:

RobertDyck,

If you vomited into your oxygen mask, you could die in an otherwise perfectly good suit.  A heating element in the helmet visor could take care of the fogging issue caused by respiration.  Other than that, I think woven CNT and elastic fabric could supply sufficient mechanical counter-pressure while not significantly impeding the mobility of the wearer nor weighing more than conventional cotton polyester clothing.  The additional weight of the life support equipment should not significantly impede movement on Mars.  It would be like carrying a 45 pound pack here on Earth, which is routinely done on extended hikes.

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#85 2020-02-16 19:17:35

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 20,263

Re: New idea for Mechanical CounterPressure suit

RobertDyck wrote:

Vomiting in a spacesuit is a problem for any spacesuit. Heating element is a good idea. I wouldn't use carbon nanotube, because that's expensive and very stiff; non-elastic. You could use fancy new fabric; for example a fabric over the knee that provides strong elastic radially around the leg, but weak elastic longitudinally along the length of the leg. So it acts like a convolute joint of a gas-bag suit. Along the side of the knee the fabric could be completely non-elastic longitudinally while providing the same elastic counter-force radially. So again, it works the same as the knee joint of a gas bag suit, but instead of neoprene rubber and metal rings it's done entirely with fabric.

As for the backpack, the cooling system is greatly simplified. A gas-bag suit uses an undergarment with plastic tubes carrying cool water. An aluminum heat exchanger in the backpack actively cools the water. A bottle of water sprays water on the outside of the aluminum heat exchanger, which immediately freezes in the vacuum of space. That sublimates into space, carrying away heat. It consumes water, requires a water pump and battery to power the pump. An MCP suit is fabric, so the human body sweats into space. Temperature regulator is the human body itself. The fabric is not sealed; Dr. Paul Webb found human skin is air tight, only requires counter-pressure to ensure fluids inside the body remain pressurized. He found skin can withstand a gap in fabric 1mm square with no damage what so ever. "Insensible perspiration" means the vacuum of space will "suck" water out of pours, causing the subject to cool when he doesn't need to. Dr. Webb measured this, found heat loss due to that is less than heat produced by an astronaut just standing at rest. This means the astronaut will get warm, and will sweat to get rid of that heat. If the astronaut works at 300 kcal/hour for 4 hours, he will lose just over 2100 grams water over the whole period. Note 1 gram water = 1 cubic centimetre (cc) = 1 millilitre (ml), so 2000 grams water = 2 litres. So the entire cooling system is a bottle of drinking water. This would be a 2 litre plastic bottle, made exactly the same way as a 2 litre pop bottle. Pressure in a pop bottle is less than pressure differential between spacesuit pressure and space. You may want to make it of something that could withstand the cold of space, even though it has to remain warm enough that the water won't freeze. So you could get fancy and make it of PCTFE, which is the most impermeable to water of any known polymer, and becomes brittle at -240°C. Place that bottle in the backpack, positioned so astronaut body heat will keep the water warm. Inside the plastic bottle will go a plastic bag, a "bladder" liner. Water would go inside the bladder, air would go between the bladder and bottle. A drinking hose would go from the bladder to helmet, and a second hose from bottle to breathing air. So as you suck water out of the bladder, the bottle back-fills with air to ensure no pressure problem. But you want the water in a bladder so the drinking hose get water, not air. Especially important in zero-gravity.

Would you make the bottle smaller? One litre? That could result in dehydration if you work hard, especially if you work for a full 8 hour shift. But no pump, no heat exchanger, no mechanism. Simple, reliable, light.

I would also design the breathing mask with one-way valves. Exhaled breath would go through one hose to the vest, with a one-way valve to ensure air can't come back. The vest would have a direct connection through the back to the CO2 sorbent cartridge; again with one-way valve so air can only pass from vest to cartridge, not back. Another hose would go from CO2 sorbent cartridge to breathing mask; and again one-way valve ensures not back. This means action of breathing alone would circulate air. No need for any fan.

Apollo used lithium hydroxide because it's light, but that isn't reusable. EMU suits for ISS have been modified to use silver oxide, which is heavier but CO2 can be baked out. In any case the CO2 sorbent would have activated charcoal to absorb bad smells, like bad breath. That can also be baked out.

With 100% oxygen for spacesuit air, plus exhaled CO2 and humidity, that means the human body will convert O2 to CO2, then the sorbent will remove CO2. This will reduce pressure in the breathing system. As pressure drops, a pressure regulator will top-up pressure from an oxygen tank. Again, no valves or pump or actuator or motor, nothing electrical. This means the breathing system works in case the spacesuit battery completely fails. The suit would most likely have fancy electronics, monitoring equipment for pressure and airflow rate, sensors for CO2 and O2 content in breathing air, temperature, etc. All available via space-hardened smartphone installed in a suit forearm. With touch screen designed to work with gloved hands. But if the electronics and completely electrical system fails, the suit continues to provide breathing air using nothing but one-way valves, a pressure regulator, and breathing action of the astronaut's own lungs.

How does that reduce the backpack?

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#86 2020-02-16 19:18:15

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 20,263

Re: New idea for Mechanical CounterPressure suit

RobertDyck wrote:

The suit could connect the vest to the backpack with only one air connection. A "T" connection in the backpack to the back of the vest, with a one-way valve from the "T" to the sorbent canister. The other side of the "T" would be a one-way valve to a hose to the helmet. So both hoses from the helmet go to the top of the backpack. Furthermore, the helmet could have the breathing mask integrated with ducts to connections in the back. So both hoses go from the back of the helmet to the top of the backpack. That keeps them out of the way.

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#87 2020-02-16 19:19:12

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 20,263

Re: New idea for Mechanical CounterPressure suit

We would not what any vomiting in any area that we would occupy, a suction tube in the helmet that can be moved to swipe in the area to remove would work to vacumn it out of the visor area. For inside one would want to do about the same with cleaning of both areas after we can get out of the suit in the habitat area as well.

RobertDyck wrote:

Another advantage of a MCP is that it's machine washable. A gas-bag spacesuit certainly isn't. Apollo had a problem with contamination with Moon dust. An MCP suit consists of several layers: the MCP layer is Spandex or equivalent. The vest is neoprene rubber with a non-elastic outer cover fabric. There could be a hard shell to squish the air bladder close to the body. The shell would be light-weight, not the hard fibreglass shell of an EMU suit. Just a chest piece of vacu-formed plastic, with ridges for added strength, but the ridges would have to be rounded to ensure they don't dig-into/cut the bladder. The point of the shell is so it isn't a barrel, it's close to the body. The ridge pattern could be made aesthetically pleasing: muscle plate for men, or breast plate for women. With an air-filled bladder over breasts and a thin plastic shell formed over each breast, the result would "augment" the woman's "natural assets", making her look "well endowed". Robert Zubrin argued against MCP suits claiming that middle-age astronauts (40s or 50s) would suffer middle-age spread so a skin-tight suit wouldn't look good. So one reason for this muscle plate is to counter that. Besides, the whole thing will be covered by the thermal and micrometeor protection garment. For an MCP suit that's a parka and ski pants.

On the surface of Mars, there's no micrometeorites. Micrometeorites are the size of a grain of sand, or smaller. Some the size of a grain of dust. But in LEO they travel 10 to 20 times the speed of a bullet. On Earth they burn up in the atmosphere 100km above the surface. On Mars they burn up 30km above the surface. A Mars surface suit doesn't need micrometeoroid protection, but will need scuff protection from sharp rocks and spacecraft parts. EMU uses Orthofabric, which is a double-layer fabric. Surface is Goretex with thread weight 400 denier. Every 3/8" two threads are replaced with Kevlar, also 400 denier. The back is Nomex; the same fabric as a firefighter's jacket and pants. On Mars you don't need a fire proof suit, the atmosphere is 95+% CO2. And this suit is not intended to wear inside the spacecraft. So a Mars suit doesn't need Nomex. It doesn't need Kevlar either. Goretex of Orthofabric is fibres of PCTFE polymer, the same polymer as Teflon. Tenara architectural fabric is the same material, from the same factory. You could use 400 denier thread weight Tenara, or even 80 denier. Arctic parkas have an 80 denier Tenara fabric shell.

Multi-layer insulation is aluminized mylar separated by "fish net". In the vacuum of space, this works very well. The aluminum layers reflect radiant heat (infrared light). In vacuum there is no heat loss from conduction or convection. That works in LEO, interplanetary space, and the surface of the Moon. It won't work on Mars. Mars has an atmosphere; it's thin, but enough that multi-layer insulation won't work. You need something else. Thinsulate is light-weight insulation used for ski jackets and ski pants. Simply use Thinsulate for the surface of Mars. So two different sets of outer garments: thermal and micrometeoroid for space, and thermal and scuff for Mars. Both a parka and ski pants.

Hmm... the backpack would require thermal insulation integrated. The water bottle pressed against the back of the air bladder vest, with just a thin "slip" layer to avoid abrasion. With insulation around the water bottle, where it doesn't press against the vest. Electronics in the backpack would also require warmth from body heat, so also pressed against the air bladder vest, also with a "slip" layer, also insulated where it doesn't press against the vest.

Electronics could use a cold weather lithium-ion battery. Even though the electronics would be pressed gainst the back of the astronauts air bladder vest, with insulation outside the electronics, still. A for over heating, pressing against the air bladder of breathing air, would also ensure it doesn't get too hot. The astronaut's body would ensure the small electronic package doesn't get too hot.

The electronic package in the back would probably be smaller than a smartphone. The touch display on the forearm would not have the battery, just touch screen and user interface. A cable sewn into the sleeve to the electronics box in the backpack would provide power and data connection to the processor there.

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