Living inside Mountains / Caves on Mars?

martienne · 2018-02-04 17:17:02

Is it possible that there are natural large cave systems on Mars, like on many places on Earth?
If so, would it be possible to live inside of these, and seal them off to create a human habitat...?
I.e.seal the caves off, raise temperature and actually fill with air and vegetation.
Do we have the technology for this and is it feasible?

RobertDyck · 2018-02-04 19:36:15

You've watched the 1964 movie "Robinson Crusoe on Mars". One of the "unrealistic" plot devices was Mars rocks that release oxygen when burned. That was thought ridiculous, but now we know about perchlorates. Could this work? There are all sort of silly Hollywood things in this film.

First, how are caves formed? On Earth, caves are normally formed when water percolates through limestone, dissolving it and leaving a cavity. There is evidence of an ancient ocean, rivers, and canyons. Could there be caves? There is calcite and dolomite, but large limestone deposits? Perhaps not. Not completely out of the question, but at least not as common as on Earth. However, there are lava tubes on Mars. In fact, orbital images indicate larger lava tubes than on Earth. Lava tubes form when a volcano erupts, lava pours down the side, surface of the lava stream hardens creating insulation so remaining lava can remain hot and flow quickly. When the eruption stops, the tube drains. The empty tube will have a layer of hardened lava on the floor. The roof will be cooled lava, with drips forming small sharp stalactites. The ground uneven, with sharp rocks. Some times the roof collapses, creating an opening called a "skylight".

Last edited by RobertDyck (2018-02-04 23:35:01)

SpaceNut · 2018-02-04 20:28:56

It is possible as there have been deep pits found by the MRO
https://www.geek.com/tech/nasa-discover … s-1702306/

https://www.nasa.gov/mission_pages/MRO/ … 829-1.html

https://www.space.com/37077-mars-crater … photo.html

Antius · 2018-02-05 07:03:51

If we find perchlorate rich brines on Mars and methane gas reservoirs in similar locations, maybe we generate power from both using some sort of stationary PEM fuel cell?

Void · 2018-02-05 13:32:14

Here is the skunk at the garden party

I mention lava tubes on Mars in the following thread:
Index
» Life support systems
» A possible life support "System" to be rehearsed on Earth then to Mars

While lava tubes may present dangers, they also offer life supporting potentials.

Probably some sections are safer than others. So these should likely be assessed and designated for specific functions.
The most safe could serve as habitats for humans with shirt sleeve environments.

Less safe sections could serve a purpose to be a low pressure water vapor steam reservoir.

The purpose of a low pressure water vapor steam reservoir would be to store energy from the day to be used at the night.
Boiling water perhaps with intentional solar concentrating mirrors, the section could be filled with a low pressure steam during the day. Or the low pressure water vapor might be created by cooling industrial equipment which would be manufacturing needed products. The boiling process to produce the steam might actually produce electricity during the day (It would be an option to consider).

During the very cold Martian night, a double condensing process could be used to generate distilled water and to generate electricity.

One system would need to be sealed radiator/condenser elements on the surface to remove heat. What would condense in inside would be a fluid with much lower vapor pressure than water. Ammonia for instance.

That very cold Ammonia would be pumped into the lava tube with low pressure water vapor, and would do two things.
1) Cause water vapor to condense to liquid water on the outside of heat exchangers with the Ammonia on the inside.
2) Cause the Ammonia on the inside to evaporate, and to be used to drive a electrical power generation system. Turbines are a more sure method but for quite some time I have been trying to come up with something else.

So to section off the parts of tubes, I would suggest permafrost earthen dams. (And likely some further measures such as a impermeable membrane placed on the surfaces of such dams.

Ideally a low pressure steam section at each end of a habitability section, so that if the air seal for the habitability section failed, the low pressure steam sections would sufficiently rescue the situation by stopping a drop in pressure to Martian ambient.
......

Further Tricks:
1) Ideally, it would be possible to frack/drill for natural gas from within a shirt sleeve lava tube.
2) Otherwise get your Methane from elsewhere, if possible.
3) Generate Hydrogen Gas for various uses store it in storage containers in the low pressure steam sections (More on the logic of that later).

We don't know what the actual potential for the existence of Methane is, so I am not going to be specific on where it might come from.

4) Use the low pressure water vapor sections as a passage to the outside. Air locks filled with water vapor from the low pressure sections would allow you into the airlock. Presumably you already passed through an airlock from the high pressure habitable section into the low pressure water vapor section.

As you seek to enter the Martian outside environment, the water vapor in the air lock can be either compressed into water and ejected into the low pressure steam section, or frozen.

As a last step, you would purge the remaining water vapor into the low pressure steam section using outside Martian air.

The three items would contaminate the low pressure steam section:
1) Martian atmosphere during the final purge of the last mentioned airlock.
2) N2 and O2 during the passage from the habitable zone into the low pressure steam section.
3) Hydrogen leaking from the Hydrogen storage devices in one of the two likely low pressure steam sections.

The methods to recover those gasses would be to condense the steam into water, and then to use vacuum to pull the gasses out of the liquid water resulting.

For the one low pressure steam section, where only Hydrogen is a contaminant, you can quickly return the leakage to containment.

For the other low pressure steam section, where a mix of Martian atmosphere and escaped gasses from the human living sections was the issue, you could degas the condensed water, and use that gas mix to give Carbon to your greenhouses. That then would add Carbon to your biosphere, and also create a Nitrogen concentration flow.

Nitrogen being desirable.

Last edited by Void (2018-02-05 14:00:51)

elderflower · 2018-02-05 13:46:30

I'm still concerned about slope stability. Those skylights are at the bottom of conical holes. The cone angle will be the same as the rest angle of a pile of loose regolith unless something binds it or somehow reduces the cone angle below the angle of repose of regolith material.

Void · 2018-02-05 14:05:29

There is some hope that those would be cemented by permafrost, but of course hope is not enough.
Proof is required.

martienne · 2018-02-05 17:27:06

Fantastic responses, very interesting. How hard is it to insulate the cave so air can't escape... and keep the skylight?

SpaceNut · 2018-02-05 21:36:35

For the images that RobertDyck posted of the string of underground caverns once in the opening play mine shaft miner and start to brace up the ceiling with posts and beams ... oh wait these will need to be steel girders....
martienne for the skylight use the favorite plastic that RobertDyck likes for the greenhouse... now if we only had dozen of roll several miles long..
I guess we are going to need to search for something smaller to start mans conquering of mars.

martienne · 2018-02-08 12:16:39

Yeah, I'm thinking that it would look a bit like the blue line in the Stockholm Metro. Plus natural light from above. You could put up mirrors in a clever way and actually get plenty of daylight.

This metro is built by hollowing out the mountainous Northern bedrock with explosives. It was supposed to be able to double as a relatively comfortable cold war nuclear war shelter for a huge number of people, if needed. If this could be built in five years in the 1970s, it should be feasible on Mars in the 2030s or something, right...? Particularly since they have no planning permits or environmental concerns to consider.

image.axd?picture=%2F2013%2F01%2Fadrag_121118_7D_9249.jpg

Last edited by martienne (2018-02-08 12:35:12)

Void · 2018-02-08 12:35:33

This article is primarily about the Moon, but Mars is mentioned:
http://www.foxnews.com/science/2018/01/ … -moon.html

Quotes:

Lunar lava tubes may provide access to vast polar ice reservoirs on the moon

This area might even be a good location for a long-term lunar base, according to Science Alert. Not only would exploration of the subterranean caves provide invaluable insight into how the moon was formed, it could pave the way for further lunar missions and even expeditions to Mars.
“Exploring lava tubes on the Moon will also prepare us for the exploration of lava tubes on Mars,” Lee explained. “There, we will face the prospect of expanding our search for life into the deeper underground of Mars where we might find environments that are warmer, wetter, and more sheltered than at the surface.”

https://www.inverse.com/article/36777-m … lava-tubes

purdue-scientists-say-that-philadelphia-could-fit-in-a-moon-lava-tube.jpeg?auto=format%2Ccompress&w=700

There is speculation that they could be that big on the Moon. On Mars they would likely be much smaller, but presumably larger than the Earth's lava tubes.

I think it could be rather likely that some parts of the Martian ones would be filled with ice, and maybe liquid brines.

A thing to consider is if a section could be made more or less shirt sleeve, and drilling equipment from Earth and perhaps partially insitu could be set up inside of it, to drill for brines or just maybe petrochemicals as well.

https://en.wikipedia.org/wiki/Petrolithium

Petrolithium is lithium derived from petroleum brine, the mineral-rich salt solution that is brought to the surface during oil and gas production and exploration.
Oil companies manage petroleum brine as a waste product, usually by reinjecting the brine back into the ground for enhanced oil recovery or disposal. A small percent is also used for "beneficial reuse," which can include production of drilling fluids, irrigation or dust and ice control.
In recent years, several companies have explored technologies to extract the abundant minerals that are found in brines, including from petroleum brine. These minerals include lithium, silicon, magnesium and potassium.

Mining Brines:
http://www.geo.msu.edu/extra/geogmich/salt_brines.html
Quote:

Several hundred chemical and pharmaceutical products are made from the brines and have many commercial uses. When we see a motion picture or ride in a car with a purring motor we seldom remember that it may be bromine from the Marshall brine that was used for the silver bromide that makes the film possible. When we ride over a dustless country road we do not remember that it may be calcium chloride from the Marshall brines that settles the dust. And it is almost beyond imagination to realize that the light truck that passes us or the airplane flying overhead was made from metallic magnesium taken from these brines and that some of the magnesium salts went into the making of milk of magnesia. True, Michigan’s other brines are also a source of chemicals from which hundreds of products are made and are byproducts of the salt and of the petroleum industry, but until 1940 the only metallic magnesium produced in the United States was from those long buried imprisoned sea waters, the Marshall brines under Midland County. Plants now extract magnesium from sea water and also from the several magnesian minerals and rocks. Nonetheless, buildings, water supplies, material for medicines and airplanes, material for dustless roads and knockless motors, chemicals whose proper use as rock solvents make it possible to drill deeper wells, open up tight rocks and let more oil escape, materials for the new plastics-all these and many more were stored up for us in a gray brown sand deposited on a sea floor nearly 310 million years ago.

And then of course water from brines could be used for drinking water (Distillation of course), and to make Methane, if there are no Hydrocarbons.

I hope I have not messed up your topic martienne.

Last edited by Void (2018-02-08 12:58:08)

martienne · 2018-02-08 15:41:55

i loved all the info on the lava tubes and the link was super interesting.

Humanity could be on Mars already for the cost of a small chunk of the US military budget, or the annual expendiiture on soft drink ads, across the globe.
Sick priorities....

Void · 2018-02-10 11:59:53

Martienne, I have noted your comments. Though a vast cultural divide persists between us, understand that people like myself wish your kind only the best.

From SpaceNut:
Quote:

For the images that RobertDyck posted of the string of underground caverns once in the opening play mine shaft miner and start to brace up the ceiling with posts and beams ... oh wait these will need to be steel girders....
martienne for the skylight use the favorite plastic that RobertDyck likes for the greenhouse... now if we only had dozen of roll several miles long..
I guess we are going to need to search for something smaller to start mans conquering of mars.

You do bring up a very important point. Lava tubes on Mars, will be quite a big meal. Too big at first I think. How can we scale down, and then evolve towards utilizing this presumed natural resource on Mars?

I am not shy about using other peoples ideas, but I always what to attribute to them what is their intellectual property, if I can possibly keep my own head and ego strait.

I start with G.W. Johnson and his Mushroom houses.

A mushroom house in a lava tube could provide an initial habitat. I am going to presume that some type of Nuclear would be used for energy. A wall of rocks and perhaps plastic bags of ice being a shield against radiation.

As I see it there are two primary human needs after you satisfy those that let you live for a day or two (Breathing air, water, absence of serious illness). Food, and Psycholocial health.

For food we likely have RobertDyck and Spacenuts work. I also have some wild alternate works. (Not necessarily welcome )

For Psycholocal health we have Louis. His covered gorges. Pretty much a narrow gorge, with a window on top. As I visualize it is would be a convex structure to the high pressure inside, and concave to the low pressure outside. I think most likely a good plan would be to have a circular gorge, that joins itself so that a runner can run a circular path with real sunlight above. In the walls perhaps could be potted plants. Granted the agricultural worth of that might be small, but still a contribution. The Psychological Value might be very good.

For my part I am the water boy, and also into Chemosynthesis. My feeling is that we should see how far we can get with all of these, and eventually lava tubes can be incorporated into a "Civilization" on Mars.

I have my own proposed methods.

I think I "May" be similar to one of the rocketmen on this sites in my distrust of domes/greenhouses, more power to those who can make them work and make them safe.

So, like RobertDyck, I actually favor an initial settlement at the equator, near water of some kind, and a safe place to land.

However once the initial settlers get a second wind, I favor looking into lava tube potential and drawing up a plan for them.

I am currently also formulating some devices which might serve well for that purpose. This post is too long already however.

Last edited by Void (2018-02-10 12:18:56)

Oldfart1939 · 2018-02-10 13:08:18

Are any others here familiar with a method used in the construction industry using a method of concrete application called "gunite?" It sprays on a thick slurry which doesn't use any retaining forms, but adheres directly to the surface where it's applied. I'm proposing a modified form using a thick slurry of an epoxy-type monomer/accelerator self curing blend for the walls of these caves or lava tubes. It can be applied in several layers by repeated application, but in principle will seal the surfaces to a gas tight consistency.

martienne · 2018-02-10 13:53:38

Oldfart1939 wrote:

Are any others here familiar with a method used in the construction industry using a method of concrete application called "gunite?" It sprays on a thick slurry which doesn't use any retaining forms, but adheres directly to the surface where it's applied. I'm proposing a modified form using a thick slurry of an epoxy-type monomer/accelerator self curing blend for the walls of these caves or lava tubes. It can be applied in several layers by repeated application, but in principle will seal the surfaces to a gas tight consistency.

I think that method is what is visible in the Metro pictures I posted above. It's used in the metro and in various types of mountain rooms we have in my country. I didn't know what it was called but I heard it referred to as sprying cement. It looks like cement and is sprayed on the bare mountin so it can be painted and made to look less intimidating with relatively low effort and cost.

Perhaps this also insulates?

Void · 2018-02-10 17:33:50

I would like to be allowed to mention some proposed methods and structures.

I think that on Mars unless the whole planet is terraformed somehow to a very substantial atmospheric pressure, then their will be several pressures used. I don't think that the lava tube sections would typically be pressurized to 1 bar pressure. There could be exceptions, but I anticipate that the tube sections would usually be pressurized to lesser pressures. One case could be 333 mb of Oxygen. I don't expect that to happen for some time however. As I have said I have structures and methods to propose.

One item would be an hourglass shaped building which would be repetitively built inside the lava tubes. It will reach from the floor to the ceiling, and will not just be a pressurized habitat, but a lava tube roof support.

Collections of these devices could be connected to each other with tubes suitable for humans to walk through. There should be tow of these systems.
1) 333 mb O2.
2) Approximately 1 bar (Maybe less) of an O2/Nitrogen mix suitable for human health.

The people who live in #1 could use counter pressure suits to work at lower pressures.
The people who live in #2 will need to use balloon suits.
I expect that their would be a service rotation where people spend some time in #1, and then spend some time in #2.

If eventually the section of the lava tube that system #1 & #2 are in is pressurized to 333 mb O2, then #1 will be added to #2 to have a near 1 bar pressurization.

......

A cheep trick to do in a lava tube might be to build water impoundments. Here I am presuming that sufficient water is available.
If not then the question will be "Why mess with lava tubes?".

Some of the hour glass support structures could be partially filled with water, for warm water aquaculture. They being hour glass shaped, the upper portion could be lit by artificial lighting if you wanted to grow duck weed for food.

https://en.wikipedia.org/wiki/Lemnoideae
Quote:

Duckweed is an important high-protein food source for waterfowl and also is eaten by humans in some parts of Southeast Asia. As it contains more protein than soybeans, it is sometimes cited as a significant potential food source. The tiny plants provide cover for fry of many aquatic species.

Grow lights would be needed of course.
https://en.wikipedia.org/wiki/Grow_light

For efficiency using just the wavelengths might be good. But if people want to spend time in this "Swimming Pool/Garden", then it should be made possible to turn on enough of the other wavelengths, to contribute to "Human Psycholocial Health".

I did say Garden, as it seems reasonable to me that plants could be included with the duckweed, either hanging from structure, or in floating rafts.

I would add chemosynthesis to this scheme.

One method would be to obtain Hydrogen and Oxygen most likely from Electrolysis. Or if there is significant Methane available by drilling, then reformation could obtain Hydrogen from the Methane.
https://en.wikipedia.org/wiki/Steam_reforming
I think it most likely that electrolysis would be used.

The Hydrogen could be added to the bottom of the hour glass aquarium, and the Oxygen to the top. Of course at a rate that inhibits an explosive consequence.

Fish could live in this hour glass aquarium. If you are not vegan, then you could have fish.

So, Duckweed, land plants and fish.

I will start another post for another structure I am interested in.

Last edited by Void (2018-02-10 18:05:24)

Void · 2018-02-10 18:47:24

I have talked about Louis's covered gorges. In some cases they would be toroidal. That is you would be able to run around in a circle at the bottom of them, if they were wide enough for your body size.

I want to make something with some similarity, but it will not be in a cave. It will involve metal and perhaps some transparent materials.

So imagine that a spiral staircase was inside of this and spiraled all the way from bottom to top. Now imagine that the gorge walls had a metal liner, and that the steps attached to each metal wall.

Now forget the transparent top. Make that metal as well.

Now take the whole metal apparatus out of the gorge and set it on the surface of Mars. (Later when I am finished describing the options, we can consider inserting this device into a lava cave skylight hole).

So this thing is sitting on the surface. Add a berm of rock and soil all around it, all the way to the top.

There will be a large cylindrical cavity in the middle, and two walls with a spiral staircase within between the walls. Put a transparent lid on top of the cavity. A lid sufficiently strong to hold a pressure. Put a floor under the cavity, a floor of metal most likely.

Fill the cavity with water.

If you want, put portal windows in the wall that retains the water fill.

You definitely have good radiation protection.

martienne. I believe you previously suggested using mirrors to get light into caves. So lets build a scaffold above this apparatus and have mirrors on it. Heliostats. So now you can shine extra light into the water filled cavity, and also through the portal windows.

Lets talk about the relationship between the Heliostats scaffolding and the transparent "Lid" I previously mentioned.

The Heliostats scaffolding can be integrated into the lid and will serve as counter pressure to help hold it against the higher than ambient Martian air pressure under the lid.

Now the question is how much higher would that air pressure be? It depends on what you intend.

A pleasant thought is that you pressurize this water filled cavity to 1/3 bar, and heat the water. You can heat it with the Heliostats. So now you have a swimming pool. That's nice, but you could have a swimming area inside of an hour glass structure inside a lava tube cave.

So lets forget the swimming pool, and drop the pressure to Martian ambient. In doing that it will be necessary to freeze the top of the water. That process might do damage to the structure, so it is likely necessary to provide engineering to prevent such damage.

Now all the lid needs to do is hold in the moisture. The pressure under the lid will be perhaps just a bit above that of Martian ambient.

If the water inside is fresh, then the ice surface might be -20 degC and the water at the bottom of the cavity could be 3.88888889 degC. (I was nice, I converted to C).

You could preform aquaculture in this environment, but burr! That's cold water. I would rather do something like this:

https://newatlas.com/nemos-garden-terre … ter/38283/

gopr0004.jpg?auto=format%2Ccompress&fit=crop&h=200&q=60&w=200&s=c18c5230643c664db72758c28fc518a8

dscn1759.jpg?auto=format%2Ccompress&fit=crop&h=200&q=60&w=200&s=9a05ecaa5e8e7fbef4f0fa3aefeb51c7

Better, but lets just bond the domes to the bottom of the water chamber, and make it possible to walk into that greenhouse from the bottom of the spiral staircase.

The water column pressure above this greenhouse will be sufficient to hold in the air pressure.

About the ice on top of the water. It will most likely make a good window, especially if the water composing it is degassed so that little or no bubbles will be in the ice.

Another possible good thing about it is that it may block some U.V. light. If not then a pigment can be put into it to do so.

About the relationship between the heliostats and the greenhouse at the bottom of the water:
-By correctly aiming the heliostats, most of the heat from sunlight would enter the greenhouses, and by day, the greenhouse(s) would warm up. By night the temperature would fall no lower than 3.88888889 degC.

So the greenhouse would be good for some crops and not others that don't care for that temperature at night. Of course if you had thermal storage or a energy source you could heat the air at night.

While this device could go into a lavatube skylight hole, there is no reason devices like this could not be built in many locations on Mars.

I'm done with this post.

Last edited by Void (2018-02-10 20:52:08)

SpaceNut · 2018-02-10 20:05:07

Depending on the amount of open sky due to the radiation question then light tunnels, light pipes and fiber optics would also work to bring light inside the cave or lava tube.

Void · 2018-02-10 20:58:13

Agreed.

The device I described could facilitate passage for those methods. A heliostat or heliostats could point as the source into them when desired, but otherwise when not desired, the light could be used to grow plants in the greenhouse.

Last edited by Void (2018-02-10 21:00:33)

martienne · 2018-02-11 07:31:08

For the "sky-light" in the lavatube, you'd need to do something with the glass for to protect against radiation, right? Like "double glazing" with water in-between. Are there any other methods that you could treat the glass?

Also all the suggestions sound like something that COULD be achieved with existing technology, assuming it could be shipped intact to Mars and the crew had the necessary skills to carry out the tasks and operate the equipment. This could be tried now! We've done so many other amazing things already. The biggest challenge with this, is that you'd have to make it to Mars with the equipment and survive while the work is taking place. People would be queing up in their millions to risk their life to be part of this project. Yet Elon Musk is the only one trying and he has to fund it himself.

VOID thanks for converting to C... I can't get used to F apart from a few reference points I picked up from TV. Important to be conscious of this though....Mars Orbiter etc.

Void · 2018-02-11 08:08:40

I don't think that would be necessary.

The bottom of the scaffolding above the device that held the mirrors would have a plastic glazing attached to it. Something that can tolerate U.V. for long periods of time, but also allows U.V. through. RobertDyck knows of such. It is a plastic with Fluorine in its structure. It's only purpose would be to hold moisture in, and at times if the ice layer were melted and refrozen, it would hold back some tiny additional air pressure.

If you were standing on the ice, it would be sensible to have this glaze within reach, perhaps with a step platform, so that if needed the glazing could be replaced. The air pressure between the glaze above you and the ice you would be standing on would typically be very near Mars ambient 5.5 mb +/- some small number of mb.

The ice would be used to block U.V. Either naturally or by adding some pigments. After a long period of searching I am under the impression that at least some U.V. does not pass through ice. But maybe I find out I am wrong about that. Well if so then add pigments to the ice to block the U.V.

RobertDyck · 2018-02-11 10:48:05

Google is wonderful. This shows absorption of light by water per metre in various frequencies, including UV.

However, NASA has a coating that can be applied to windows to block UV. They found Mercury astronauts got cataracts in their eyes in later life. Apollo spacecraft windows and spacesuit helmet visors have this coating. Skylab, Shuttle, and ISS use it. I also reflects IR, so controls radiant heat gain and loss. It has been commercialized, the IR portion is used for commercial building such as office buildings. Commercial brand names are "Heat mirror" and "Low e". When applied to plastic the full NASA coating will block 98% of UV. Glass also blocks UV, so when applied to glass it blocks 99%. That's a reflective coating, there are also dyes that absorb UV, using them in addition to the reflective coating can block even more. Scientists and NASA call this "spectrally selective", which means some parts of the spectrum (some colours) get through, others don't.

The plastic is PolyChloroTriFluoroEthylene (PCTFE). It's similar to Teflon. Polyethylene (PE) is a plastic common today, it's used for many things. Basic Teflon is PolyTetraFluoroEthylene (PTFE), although the manufacturer Dupont now has a few other chemicals they sell under the same brand name. The molecular structure of normal polyethylene is a chain of carbon atoms, with a single hydrogen atom bonded to each side of each carbon. Like this:

Teflon replaces the hydrogen with fluorine, like this:

The plastic that I recommend for Mars is similar, but a little different. Instead 3 of the 4 hydrogens are replaced by fluorine, the last hydrogen for each monomer is replaced with chlorine. That's why the chemical name is "tri fluoro" meaning 3 fluorines, instead of "tetra fluoro" meaning 4 fluorines. And there's "chloro" meaning there's a chlorine atom.

PCTFE used to be sold by 3M under the brand name Kel-F, but they haven't made it since 1995. Honeywell now makes it under 2 brand names: Aclar and Clarus. The first is sold for pharmaceutical packaging. It's the most impermeable to water of any known polymer (plastic), so keeps pills dry. Are you familiar with "blister packs"? Aluminum foil backing and plastic film front? Often they use cheap plastic because the packaging with be thrown away, but if the manufacturer really wants to ensure the pills stay dry, they'll use a very thin layer of Aclar bonded to thicker layers of cheaper plastic. Clarus is a brand name for the same stuff, made in the same factory, but sold to military and aerospace industries. For an inflatable greenhouse on Mars, we would buy Clarus. I suspect Clarus is more expensive, even though it's the same stuff. But to ensure quality, a real space mission would use the expensive stuff. Beside Clarus can be customized, such as the spectrally selective coating mentioned above. Aclar is only available in standard sizes. I would like to see the greenhouse at MDRS use Aclar.

One feature of PCTFE is service temperature is -240°C to +132°C. The coldest temperature I saw recorded on Mars by Mars Global Surveyor (MGS) was at the south pole during winter: -140°C. So this stuff can endure 100 degrees Celcius colder than the coldest spot on Mars. Below the service temperature the plastic becomes brittle, can break. Most plastics become brittle at much warmer temperatures, celophane used for sandwich wrap becomes brittle at -6°C. Mylar at -60°C. Most plastics become brittle somewhere between those two. PCTFE just won't get brittle on Mars. And the hottest I saw recorded by MGS was +24°C (+75.2°F). Others claim to have seen +30°C (+86°F), but that's the hot spot for the entire planet, and temperature of the surface recorded by the IR camera on MGS. When temperature is "warm" on Mars, temperature at head height of an astronaut is 10°C colder than surface temperature. This is an issue because atmosphere temperature at night gets down to -76°C to -80°C in summer. Winter at night it gets down to -88°C to -102°C. That was the coldest temperature recorded over a Martian year by Viking 2 lander, however Curiosity recorded -104°C (different location).

Another feature of PCTFE is that it's the most impermeable to oxygen of any polymer (plastic) that can has embrittlement temperature that can withstand Mars night. There are a couple plastics more impermeable to oxygen, but they become brittle at temperatures far too warm; they would never survive on Mars. And it's the most impermeable to water of any polymer period. Oh! What does that mean? "Permeable" means gasses will pass right though, so "impermeable" means they won't. A thin film could be very impermeable, but not completely. That means gas will slowly leak through. Polymer film can be made more impermeable with a very thin metal coating. The metal clogs pours in the polymer. NASA's spectrally selective coating is vacuum deposited metal, so that coating makes it even more impermeable.

And it's highly resistant to UV. Not because it blocks UV, but because UV just passes right through. Of course that means we will need the coating.

However, PCTFE requires fluorine to make it. I recommend this material for an inflatable greenhouse, or inflatable tunnel from greenhouse to habitat. If you bring the material from Earth, this material is great because it's so light. However, it's difficult to make so I would recommend windows made on Mars use something else. I would recommend just normal glass. Well, tempered glass. It's heavy and you know how easy a window will break, but making glass from Mars sand means it doesn't have to be transported by rocket.

Furthermore, durability is an issue. Plastic is softer than rock, or more importantly softer than sand. That means a dust storm will cause tiny scratches causing the plastic to become cloudy. Tempered glass is harder than sand, so just won't scratch. Car windshields are made of tempered glass. Actually, "safety glass" is 2 panes of tempered glass with a thin layer of plastic between. The plastic is melted to the glass, so there's no air bubbles, and most importantly if the glass breaks then the pieces stay bonded to the plastic film. Glass used for house windows isn't tempered. Some windows used by store fronts are tempered glass. Glass is tempered by heat treatment. When normal glass breaks, it breaks into large pieces with sharp edges. Tempered glass is stronger, harder, but when it breaks it becomes tiny pieces with edges that are less sharp. The feature useful for Mars is that tempered glass is harder than minerals of sand, so it just won't scratch from a sand storm or dust storm.

Void · 2018-02-11 11:13:37

Thanks for your very nice materials Robert.

I do agree that liquid water does not block UV very well. However somewhere along the line I believe I got the impression that ice does have some UV blocking characteristics. If so fine, otherwise UV blocking will have to be done the harder way.

I have searched the internet for the possible blocking of UV by water ice, but found only one reference, and that was a question.
"The person said that they had seen reference to ice blocking UV". There were no useful responses. Very frustrating.

Perhaps window tempered window glass is the answer.

In the setup I contemplate, the glass would be a flat surface above the ice layer.

The surface of the ice would normally be at a speculated -20 degC, so the vapor pressure would be very low. Much lower than Martian surface air pressure. Even so, without the glaze barrier the ice would sublimate into the Martian winds. So a glaze is needed.

Tempered glass is a good idea as well, because if heliostats are moving, it could cause sudden temperature variations.

In this scheme, periodically the ice window could be melted at night. The method would be to use an agitator to stir the somewhat warmer bottom water with the ice. Hopefully there would be enough average heat, to bring the whole of the water and ice to slightly above 0 degC. And then of course if it is true that ice is being used to block UV, it would be desired that the ice refreeze before morning.

One other thing that may block UV can be organic matter in the ice. Sort of a sacrifice organics. This might be a reason to melt the ice window periodically, to change out the organic matter.

This contains a reference to such a possible method:
https://www.scienceforums.net/topic/611 … -ver-well/
Quote:

Just small concentrations (of at least >4mg/L) "...are sufficient to act as a biogeochemical shield against UV-B radiation, allowing UV-B to penetrate only a few decimeters into the water column." -p.119

But of all methods, yes I guess I would rather rely on the coating you mentioned if it's cost was reasonable.

Last edited by Void (2018-02-11 11:26:07)

RobertDyck · 2018-02-11 11:29:05

Oh, radiation shielding. First, radiation on the surface of Mars is half that of ISS. So it's something a permanent settler has to take into consideration, but a science mission could just endure it. Furthermore, the habitat for a science mission will have sand bags pilled on the roof, reducing radiation further. A permanent settlement would want 2.4 meter deep Mars soil (regolith) in addition to the pressure hull. Plants can endure more radiation that humans, so I recommend a greenhouse just not worry about radiation. If a permanent habitat has 2.4 metres of regolith or more, then you could restrict radiation exposure to that of a nuclear reactor worker in the US by limiting time outside in a spacesuit to 40 hours per week. That's a work week, so I don't think anyone would object. If a greenhouse has no radiation shielding, then time in the greenhouse counts as time outside.

I noticed a "hot cell" used to work with radioactive materials used a window with mineral oil. That is 2 panes of glass with a transparent liquid between. Mineral oil was used because it was effective at blocking neutron radiation. Space doesn't have neutron radiation, but does have particle radiation. Mineral oil they used was as clear and transparent as water. A permanent settlement on Mars could use the same mineral oil. I envision each bedroom would have a window to look outside. A roof overhang would act like an awning, but made of reinforced concrete, cantilevered and holding 2.4 metre deep regolith soaked with water and allowed to freeze. With a concrete wall at the end of the overhang so the soil doesn't spill off. It would shade direct sunlight, but the point is to "shade" radiation. Then make the window of two panes of tempered glass with mineral oil between.

In a lava tube, none of this radiation shielding is necessary. The roof of the lava tube would do it. A mirror would reflect sunlight, but not reflect particle radiation. And again spectrally selective window coatings can deal with UV.

Void · 2018-02-11 19:47:03

RobertDyck Quote:

A permanent settlement would want 2.4 meter deep Mars soil (regolith) in addition to the pressure hull. Plants can endure more radiation that humans, so I recommend a greenhouse just not worry about radiation.

The greenhouse I have suggested would have at least 33 feet of water and ice above it. I think quite a lot of protection. 10.0584 Meters for the metric people.

But you made me think of a modification. While for now I want the double walled spiral staircase, I also add a cone extension, that being likely of metal, and so instead of heaping all that berm against the outer wall, the builders could heap 2.4 meters of soil on an inclined surface, a partial cone, with the water chamber inside of it. It would work as counter pressure against an interior pressurization as well.

Last edited by Void (2019-04-24 11:23:27)

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