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

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,043
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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
Registered: 2011-12-04
Posts: 2,712
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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: 1,187

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
Registered: 2002-08-20
Posts: 5,043
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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
Member
Registered: 2015-01-02
Posts: 1,187

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
Member
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,043
Website

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
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 2,712
Website

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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