Crops

Void · 2013-03-24 16:13:57

I can agree that it is at least work a continuing consideration.

I am a bit of a skeptic on domes, not that they should not and cannot be done, but I think the more of them you would have the more maintenance, and also the more risk to lifes.

I guess I would think to have two basic classes of domes, those which are more for human life satisfaction and safety, and Industrial agriculture ones that would require safety measures such as wearing a suit for partial or full protection.

If aquaculture would be more efficient at growing bulk crops, then that would be used as much as possible.

I also see the possibility of having domes where something like a weed or grass could grow, only requiring a degree of improvement from the natural environment.

In that case, a fish like catfish, bullheads, or carp could be feed those vegitations.

But in the end it will need to be technical ability guided by economics. Variety of methods would also assure that if indeed one method met with some unexpected drawback like a parasitic organism, then the others might not be affected, so the colony would meet the problem with less potential for starvation.

GW Johnson · 2013-03-25 12:53:14

I agree that domes are not what we want to do, primarily because the material from which to build them does not exist (yet).

The "mushroom" structure is different. The center "stalk" and the outer ring wall hold up a flat roof. On top of that roof you pile up enough regolith to ballast down the air pressure load that wants to blow the roof off, with the outer ring wall being a cylindrical pressure vessel that is also your transparency. It does need a good foundation. The regolith on the roof is also your radiation shield against cosmic rays and solar flares.

With the materials we have available, think a ringwall made of many columns with flat panes between them, of some kind of glass or similar. These need to be multiple layered panes for both safety and insulative effect. You socket-in the columns into both the foundation and the roof panel, that's what holds them against the radial blow-out loads.

This kind of structure would even work in vacuum on the moon. Most of it can be masonry, with a local substitute for concrete where possible. Steel can help, where available. So can Plexiglas or Lexan.

GW

Void · 2013-03-25 18:06:51

A pleasing converstation sir.

If I understand, the walls are the transparency. The roof is not transparent but weighted. I like it. Place reflective foil on the ground around that then to get more light in.

I have an inni for your outi. A ring shaped berm. Inside that then place a vertical wall to hold the berm. A central space within. A glass wall, concave inside the concave wall holding the berm. Reflective foil on the floor of the hollow space inside the berm.

While the pressure pushes outward against the berm retaining wall, the transparent inner wall is also pushed inward towards the center. But you may also place struts or cables between the walls, where tension of the struts fastens the outer retaining wall to the inner "Glass" or "Plastic" wall. A ring of beneficiated environment between the two walls. A ceiling of manufactured materials, weighted down by rigolith.

I see your mind and I like it. I offer my toys just as you also offer yours to me.

RobertDyck · 2013-03-25 21:48:08

If you want to get into building design, I argue for growing crops in long narrow greenhouses. For one, we can simply use glass. That's easier to make from in-situ material than fancy polymers like PCTFE. Plants do not require radiation protection on Mars. Plants are more hardy than humans, and radiation is on average only half that of ISS. If you get into specifics, the worst forms of radiation are exactly what Mars atmosphere blocks most effectively. If you choose a location below the datum, ideally 2km below the datum, then Mars atmosphere blocks 99% of heavy ion cosmic galactic radiation. Mammals, including humans, have thin membranes that are highly sensitive to radiation. Plants and insects don't. So just grow crops in a surface greenhouse with ambient light.

The reason I'm so adamant about this is life support redundancy. All life support systems have a single point of failure: power. A greenhouse is the only means to generate oxygen with no power what so ever. I'm tired of hearing complicated light pipe schemes; on Mars you need to Keep It Simple Stupid. That means a simple greenhouse.

The reason I said long and narrow is for mirrors. Yea, I know, I just harped about light pipes and now I mention mirrors. But they have to be kept simple too. A greenhouse oriented perfectly east-west with mirrors on both long sides. The mirrors do not have to track the Sun. In morning when the Sun rises in the east, the mirrors will just reflect light slightly westward into the greenhouse. At dusk the Sun sets in the west, so mirrors will just reflect light slightly eastward. If you build such a greenhouse perfectly on the equator, then on the spring and autumn equinox the mirrors would be angled at 45°. As the seasons progress, the mirrors will have to be tilted. But they just have to change tilt by 1° once every second week. That's so little movement that an astronaut could do it by hand. Build mirrors supported by a notched rod, move to the next notch ever second week. Or if it's a large industrial operation, a motor that only activates once a week.

Size: design the greenhouse so it is twice as wide as it is high. And the mirrors extend from the ground to the equal height as the greenhouse. That is a plumb bob hung from the top edge of the mirror would be the same height above ground as the roof of the greenhouse. With the bottom edge of the mirrors just touching the glass wall of the greenhouse itself. That would provide as much light from the sides via mirrors as direct overhead illumination from the Sun. That doubles total illumination on plants. Since sunlight that reaches Mars orbit is 47% as much as sunlight that reaches Earth orbit, this doubling illumination compensates nicely. I said "orbit" to avoid calculation of light filtration from Earth's ozone layer, clouds, etc.

I said the greenhouse should be long because if a greenhouse is X units wide, then the first X units of length won't get double illumination at dawn. And the last X units won't get illumination from mirrors at dusk. But everything in between will. So the ideal location is between these. I suppose we could just make the mirrors a bit longer than the greenhouse. But for efficiency, the length should be many times the width.

You can lay several of these greenhouses side-by-side. Just space them so their mirrors don't hit each other. And they don't have to be perfectly on the equator; mirrors can be skewed toward the south in the northern hemisphere, and vice versa.

Yes, such a greenhouse would require artificial light during a dust storm. But every other time it provides oxygen and water recycling without power.

To recycle water, just place a water collection trough along the bottom of the window walls. Cold at night will cause condensation. Plants can be irrigated with processed waste water, transpiration through their leaves produces humidity, that condenses. This condensate is much more pure than the best filtration system humans have devised so far.

Glass has to be coated in a spectrally selective coating to keep UV out. Silver oxide in that coating reflects IR, helping control radiant heat. Next we need a design that keeps plants warm using passive solar. That would require some serious thermal engineering. Any takers?

Last edited by RobertDyck (2013-03-26 04:26:40)

GW Johnson · 2013-03-25 22:07:05

Hi RobertDyck:

Long greenhouse. Hmmmm. Intriguing.

Generally speaking down here on Earth, solar thermal for simple heating is simpler and cheaper than solar PV for electric power. Or at least it can be, unless you try to get too high-tech with it.

I'm curious about the pressure vessel aspects of your long greenhouse. Would it not have about the same tie-down difficulties as the classic sci-fi dome? You'll have to provide an environment inside the greenhouse of a suitable gas composition (needs some O2, not too much CO2, and a fair amount of humidity, and maybe a diluent gas as well, plus I dunno what else), and at a water vapor partial pressure significantly exceeding the absolute cold minimum of 6 mb at 0 C. The total gas pressure will have to be far higher than that, in the neighborhood of maybe 200 mb (just a guess). That's a lot of blowout load, and a lot of bending on unsupported long spans of flat glass.

But, I really like the mirror idea. I thought about using reflective surfaces in a ringwall around my mushroom building for the exact same purpose. For Earth plants, you do need a little UV in the received light, although the absorbed peak is green in wavelength. Most glass reduces UV a little, there are versions of the plastics that cut it down quite a lot. Depending upon your mirror surface material choice, you can reflect more or less UV. There's a lot of simple passive control possibilities there. Even using just light-colored dirt.

I suggested a deep regolith-covered roof for both blowout-load ballast and for radiation shielding. If you do it that way, you are unrestricted as to site on Mars, you could even build such things on the moon or any other airless world with usable gravity. Something to think about, anyway.

GW

RobertDyck · 2013-03-26 05:22:54

NASA uses vapour deposited metal coatings on windows. It's very thin layers of gold, nickel, and silver oxide. Only silver is oxidized. Before they did this, astronauts were exposed to full UV in space. Mercury astronauts experienced cataracts in their eyes later in life. Since they applied this coating, it fixed the eye problem. This technology has been commercialized: Low-e and Heat Mirror are commercial brand names. For buildings here on Earth they focus on radiant heat; windows prepared for southern climates reflecting more short wavelength IR from extremely hot things like the Sun, while reflecting less long wavelength IR from warm objects like the floor or furniture. This lets radiant heat out, causing a net cooling effect. For northern climates, they reflect more long wave, less short wave, trapping radiant heat in. This radiant heat control is mostly silver oxide. Gold and nickel is primarily for UV. When applied to plastic, NASA's coating will block 98% of UV-B and UV-C. Its' response to UV-A tapers from 98% at the wavelength boundary between UV-A and UV-B, to 20% blockage (or 80% transmission) at the boundary with visible light.

Everything I've read states photosynthetic dye in plants does not require UV. It does require both blue and red. Actually plants don't need green; chlorophyll reflects green, which is why it looks that colour. In fact I have absorption spectra for a pigments in an aquatic plant called anacharis. You don't need to give plants the full spectrum, but each photodye requires energy, so you need to provide at least one wavelength in its absorption spectrum. Primary energy requirement is for chlorophyll A and B, which provide energy for photosystem 1 and 2. To put it in numbers, plants require light at wavelengths 400-475nm and 625-680nm.

I've done quite a bit of research into greenhouse design. The reason I mentioned PCTFE is I found that plastic film best for an inflatable greenhouse. It's impermeable to oxygen and moisture, very strong, and can withstand cold so well it can handle 100°C colder than the coldest temperature recorded on Mars. You could embed fibreglass gauze within the plastic film for rip-stop. And an inflatable greenhouse will require tie-down straps. A glass greenhouse would have some sort of window frames around each glass panel. Those frames form structural support. I'm not thinking of a single blown glass structure.

As for diluent gas: yes. Plants can actually withstand lower pressure than humans. University of Guelph demonstrated spinach will grow in reduced pressure, and the pressure does not affect rate of plant growth. The catch is plants transpire more water through their leaves at lower pressure. As long as you provide plenty of water, the rate of carbon fixation remains constant. In a sealed greenhouse, that water condenses on walls and is recycled, so increased rate of transpiration does not require more water, it just speeds the rate it cycles through plants. Numerically, they found pressure down to and including 10 kPa (100 mbar) was fine; anything below that caused the plant to wilt, it completely stopped growing. They tried one experiment: reduced pressure to Mars ambient, held it there for an hour, then restored pressure. The plant wilted, but as soon as pressure was restored it perked back up. The lead researcher argued this demonstrates plants can survive a catastrophic loss of pressure.

But you want pressure sufficient that humans can work without a spacesuit. And the easiest means to provide nitrogen to soil is to grow nitrogen fixing plants, and add nitrogen gas to the air. Legumes (peas, beans, etc) have a bacterium that grows in nodules in their roots. This bacteria fixes nitrogen from air. It's symbiotic: plants provide carbohydrates for energy, bacteria provides nitrogen for protein. That's why legumes have more protein than other plant crops. I worked out the maximum habitat pressure assuming diluent gas has the same argon:nitrogen ratio as Mars atmosphere. So the diluent gas can be made by removing CO2. And you want zero pre-breathe time for decompression to spacesuit pressure. That worked out to 8.4133 psi (580 mbar). But that was maximum, you could always reduce diluent gas. Lower pressure means less stress on greenhouse structure.

Last edited by RobertDyck (2013-04-02 07:22:05)

RobertDyck · 2013-03-26 05:57:06

GW Johnson wrote:

I suggested a deep regolith-covered roof for both blowout-load ballast and for radiation shielding.

The reason for choosing a low altitude landing location is radiation protection for humans. Not for plants, for humans. Plants can withstand radiation at high altitude locations such as Meridiani Planum using an ambient light greenhouse, no regolith at all. So greenhouse design does not restrict landing location, humans do.

At 2km above the datum, Meridiani Planum still has enough atmosphere to block 90% of heavy ion galactic cosmic radiation. It's not 99%, but 90% is still pretty good. Meridiani Planum is right on the equator, has plenty of underground water, flat and smooth for landing, has hematite concretions for iron ore, and interesting science. It's only problem is altitude.

Void · 2013-03-27 20:12:28

If it can be done effectively the various greenhouses including the Mushroom and the long ones would be attractive.

I found this:

http://environmentalresearchweb.org/cws … news/52857

Mars having a dominantly CO2 atmosphere, it attracts me. However, you are still stuck with generating Hydrogen from water.

But would acrylics be useful for building such greenhouses? I am thinking 3D printer for the build, and also maybe for patching leaks.

Someone took me to task who understood the chemestry of plastics, and said that I/we do not have a source for such, but the above suggests that it may be a method to obtain what is needed to build structures.

Perhaps in time a robotic system with 3D printers might partially build such structures on a massive scale in suitable locations on Mars.

Then reflectors and perhaps rigolith as balast to help add counterforce.

Although I tilt towards wanting some type of hardy weed to grow at a partial pressure quite low, I can see that if accomplished, and if structurally reliable, it would be great to have greenhouses that could grow normal crops, and allow shirtsleeve human presence.

Glandu · 2013-03-28 04:41:37

Void wrote:

(.../...)
But would acrylics be useful for building such greenhouses? I am thinking 3D printer for the build, and also maybe for patching leaks.

(.../...)
Perhaps in time a robotic system with 3D printers might partially build such structures on a massive scale in suitable locations on Mars.

This 3D printing madness must stop. There is no added value for building a greenhouse having a 3D printer. It is the opposite. If you take the polymer path, extrusion is much more efficient for making surfaces or long beams. It you go with metals, rolling is the way to go.

3D printing focuses on smaller elements, where the shape is the essence of the piece. It will be very useful for avoiding molding of complex parts(especially if we make steam machines), yet, it is not a magic bullet that solves every problem. It is very unadapted for mass production, or production of big elements, or elements with specific mechanical requirements, or specific surface requirements.

In the specific case of the greenhouse, the size of elements is the main obstacle. There will also be the need for assembling everything together; a tough task, even for modern robots.

RobertDyck · 2013-03-28 07:22:43

Void wrote:

Someone took me to task who understood the chemestry of plastics, and said that I/we do not have a source for such

The basics are described in Robert Zubrin's book "The Case for Mars". I took that a step further, wrote a simple description of how to make basic plastics. This doesn't include fluoropolymers, which require fluorine. Ironically, those are the ones we need for outdoor use on Mars. But it does include polycarbonate, commonly sold under the brand name Lexan. That one is used for spacesuit helmet visors.

http://chapters.marssociety.org/winnipeg/plastics.html

Void · 2013-03-28 08:12:11

OK, reply's appreciated.

May I suggest a different "3D" printer. I observed a paper wasp making a nest a long time ago. Reguratating the paper, and with pinching mouth parts, it made a wall from paper, adding to it. I am thinking of a robotic "Extruder" functioning with some characteristics like a 3D printer.

Usually an "Extruder" must have dimensions similar in cross section to the part it is making. However such a system as described above might be able to make parts that are 3D larger than itself. I will elaborate some time later.

Later:
bth_Scan0003_zpsbea5dfeb.jpg?t=1364513337

I will explain later, the picture is rather small, but I am thinking of spherical, Torus, or linear versions of this cross section.

A double shell. The outer shell has a small air pocket at the top, but is otherwise filled with water and the inner shell.

The inner shell is filled with air and at the bottom of it soil.

Radiation protection. Temperature moderation. A combination of tensile strength and hydrostatic pressure to compress the inner shell to a higher pressure than the interior of the outer shell. Outer shell 1/16 bar? Inner shell 330 mb?

I have borrowed the side mirrors and other notions from you guys.

I will explain the other features that could make it stronger later along with what I think it could accomplish.

Later:

I would like to see a reduction in the number of "Joins" in a pressure shell. In the end there must be some though.

So I am thinking that being able to develop a "Extruder-3D-Robotic" system might be able to do this similar to how a paper wasp makes its nest.

Although I have drawn the two shells as circular, they do not have to be restricted to that.

As for the outer shell, I think that after it was formed, tension bands could be wrapped around it to give it greater strength.
Metal straps, or cables, or tethers. If people can contemplate space elivators, I am guessing that they could come up with some super strong tension straps that would not block much light.

The outside of the inner shell would be immersed in water, so the selection of such tensioning devices will be limited to a smaller spectrum of possible materials.

I envision several different modes of use:
1) Just using the outer shell and the mirror suggested here by others, you then have a low pressure boiler, and a potential source of steam to condense into distilled water, for industrial and other uses.

2) Aquatic weeds and fastened algae. I have seen the discussions on how reduced pressures cause increased evaporation from land plants, and I have also read that even if supplied with all the water they might need, they still go into drought mode. I am thinking that aquatic weeds, and algaes submerged continually in water will not do this. This scheme could work with just the outer shell, or with the outer shell sterile (No disolved gasses, no nutrients), and using an inner shell to achive higher pressures, and filling the inner shell with water also, and making those waters fertile.

3) Using both shells, it would be possible to have a floating plant like duckweed in the air space of the outer shell. I don't know it's potential to grow at 1/16 bars, but of course I just picked that pressure out of the air. Perhaps the outer shell if propperly re-enforced could have higher pressures. The duck weed should be able to be havested by a suction device.
If the light for the inner shell comes in from the sides from mirrors, then the duckweed would not be a shading problem for the plants in the inner shell which could be aquatic or dry land. Of course if there is growing duckweed, there will be problems with microorganisms attaching to all inner surfaces of the outer shell and blocking light. This could be addressed with snails to a degree, or some fish that might be able to survive those conditions that likes to feed on algae on solid surfaces. Or a mechanical robot might serve as a cleaner.

It is to be noted that the inner shell is not only pressurized by tensile strength of the two shells, but by the hydrostatic pressure of the water in the outer shell bearing down on it.

As for using rigolith to bear down on parts of the dome, that is not out of the question either.

I do not see what I have presented as a set of ideas as in any way nullifying the value of the other schemes previously presented by others, I simply want to add a additional set of options. Mars may not be a one size fits all solution. Perhaps any of the listed notions can be used for a best purpose at certain times or places depending on the state of developement and also the further advancements of technology, which is not allways predictable.

Last edited by Void (2013-03-28 21:25:42)

RobertDyck · 2013-03-30 12:26:38

To be precise, rather than water, I would suggest a double shell inflatable greenhouse filled with gas.

For the inflatable shell, use PCTFE sold by Honeywell under the name Clarus. Plastic film 2 mil thick, with fibreglass fabric gause bonded to it for rip-stop. "Thermal bonding" means heat it so it melts the plastic. NASA already has a way to use chemical vapour deposition in a vacuum chamber to deposit the layers of gold, nickel, and silver oxide. Deposit this on the inside surface of the outer layer. So the fibreglass gauze is on the inside surface, then the metal is applied on top of that.

Inflate the double shell so the gap between layers has more pressure than Mars ambient, but less than the interior of the greenhouse. That way air pressure alone holds the shape of the greenhouse. That pressure can be monitored to detect leaks. If pressure in the gap goes down, then you have a leak in the outer shell. If pressure goes up, then the inner shell has a leak. And fill the gap with argon gas, which conducts heat less than oxygen or nitrogen. Argon is a noble gas, so it doesn't chemically react with anything. Earth's atmosphere is 0.9% argon, Mars has 1.6% argon.

Yes, you will need hold-down straps. Use large tent pegs driven into the ground, something like a piece of steel re-bar with a hook at the top for the strap. Re-bar is normally used for reinforcement in concrete, ribs in those bars are to prevent them from pulling out of concrete. For a tent peg, those same ribs prevent them from pulling out of the ground. The inner shell would also need straps, so you need something built into the outer shell that a strap can hook onto, and something on the inside where a strap for the inner shell can hook to. Only the outer shell experiences wind, but the straps squish the shell from a cyclinder to a flattened oval. You only want plants inside the greenhouse as high as a person can reach. So the roof shouldn't be much higher. But you want it wider so you can grow more plants.

As for gasses. I presented a paper at a Mars Society convention about harvesting diluent gas. Start with Mars atmosphere, pressurize to 10 bars and freeze to -100°C. This will freeze out most of the CO2. As dry ice forms, continue to pump in more Mars atmosphere to maintain 10 bars pressure. Inside this same vessel, put a platinum or paladium or rhodium catalylist at the top of the vessel, and the catalyst will have to be warmed to +25°C. Yup, freezer coils at the bottom, and a small heater at the top. Might not make sense at first, but it's needed. Mars has a little carbon monoxide. Not a lot, but once you remove CO2, everything else including CO is increased. That is enough to increase CO to toxic levels. The catalyst will combine CO with O2 to make more CO2. This is done in the same canister that freeze out dry ice, so that CO2 is frozen out too. There isn't much O2 in Mars atmosphere, but more than enough to combine with all the CO. And there's also a little ozone in Mars atmosphere; the same catalyst will break it down to O2, adding more O2 which will help decompose CO. The result is mostly nitrogen (N2) and argon (Ar), with a little CO2, and trace amounts of oxygen (O2), neon, krypton, and xenon. Those last 3 are also noble gasses, also present in Earth's atmosphere, and also don't chemically combine with anything. Simply adding O2 to this mixture makes air that Mars settlers/astronauts can breathe. It will have a little too much CO2, it'll smell stuffy. A freezer is great to remove the bulk of CO2, but not any good at removing that last little bit. You need a sorbent to get rid of that last bit. But a habitat life support system already has a sorbent to remove CO2, so just let that do it's job.

Diluent gas: 61% N2, 36.1% Ar, 2.1% O2, 0.75% CO2, 0.0% water, 56 ppm Ne, 6.8 ppm Kr, 1.8 ppm Xe

To make argon for the gap, take this diluent gas, do not add O2, but use a sorbent to remove the last bit of CO2. Then add hydrogen and burn that with a catalyst. This will combine nitrogen with hydrogen to form ammonia. Then freeze the ammonia out at -100°C. It freezes as ammonia ice at -78°C, but vapour pressure becomes zero at -100°C. Ammonia can be use as nitrogen fertilizer. Remaining gas will be over 99% argon, with trace amounts of ammonia, neon, krypton, xenon.

Last edited by RobertDyck (2013-03-31 10:04:08)

Void · 2013-03-31 09:45:55

RobertDyck said:

To be precise, rather than water, I would suggest a double shell inflatable greenhouse filled with gas.

I like your variation, and hope that you will continue to persue it.

We are not required to reach a concensus at this time so it is great that each person makes their own variation/s.

I will study yours again, more.

Anchored cables are a interesting notion. I see that you are concerned for warmpth. It will depend what is desired, on what design is implemeted.

However we are mutual on the double shell. I confess, that my notions do not yet converge with real work from NASA, which is a count against them. In time, I may move towards convergence towards what you have communicated.

But as I have said before, I visualize a toolbox, and at this time the more tools to select from the better. Later, when a real mission/implementation of habitation occurs, the selected tools used will need to be the ones that fit the situation on the ground the best. Pride will have no place in that, just ability to survive/prosper.

I absolutely support your variation, and hope you will continue to innovate on it.

My variation, supposes a giant bottle with another bottle inside of it. Perhaps like a beefed up bottle for carbonated beverages. I imagine it to have corrugations around the circumference of the curve, and that in the valley's of each corrugation, a tension band can be tightend to add great strength. A crude illustration is the metal bands around a barrel.

Of course those bands will have to be tightened with some calibrated means, to be optimal.

Now the water jacket has some favorable properties. Radiation protection, which has been explained as not needed so much for plants, but if a 330 mb or greater pressure is possible, then it might be a place where humans can and will like to be, so radiation protection has value for that purpose.

Heat:

I have seen articles that indicate that for greenhouses on Mars, overheating will be a problem. If you use mirrors to move the average levels of light up to Earth normal, then it will be even worse. However if you have a water jacket, that can store cold from night radiation in the water, which will help.

Further there is the option of evaporative cooling with the generation of distilled water, which could be valuable. Either evaporation from a suface of duckweed, or if you like boiling water at the boiling point at 1/16 bar, and then of course having radiators to condense the boiled vapors. This will cool the whole apparatus.

Or there is the option of pumping the heated water out and cooling that in a radiator, perhaps in a dwelling where a reservoir would hold enough heated water to keep dwellings warm through the night.

I am very interested in aquaculture inside of the inner shell as well.

You are taking a dryer path.

Lets continue.

Last edited by Void (2013-03-31 09:52:24)

RobertDyck · 2013-04-02 20:37:32

I mentioned spectrally selective coating. It blocks 98% of UV when applied to plastic, but 99% when applied to glass. That's because glass itself will block some. Here is a chart of commerciallized spectrally selective low-e coating. Graph line #5. It shows transmittance, so 100% means all light gets through, while 0% means none.

And here is transmittance of some plastics, including PCTFE. Glass is included. Note PCTFE is incredibly transparent to everything, including deep into UV. That's why it's so UV resistant: UV doesn't interact with it, UV just passes through.

I recommended applying the spectrally selective coating to the inside of the outer layer of plastic. So UV would pass through the plastic, then reflect off the thin metal, then shine out again. If the coating is applied to the outside, then wind blown sand and dust would quickly "sand blast" the coating off. So a plastic this resistant to UV is important.

Void · 2013-04-02 22:16:49

I could find use for such planning. It is good.

RobertDyck · 2013-04-04 10:29:54

Salt

We would produce "Mars salt". I call it that because it won't be pure sodium chloride. On Earth we have "sea salt", which is made from ocean water or a salt sea. Just create a shallow pond, seal it off and let sunlight evaporate the water. When it's a thick wet paste, scoop it up. What you'll have is mud mixed with salt. So then dissolve this in fresh water, let the mud settle out, then draw off the remaining liquid and boil dry. The result is "sea salt". It's mainly sodium chloride, but also has other salts. "Cations" are sodium, magnesium, potassium, and calcium, while "anion" are chlorine, bromine, and even a little sulphur. Mars soil has all of these.

To make "Mars salt", dissolve some Mars soil in water. Let the mud settle out, then filter to get "fines" out. These fines are extremely fine, so you will need a very fine filter. Not reverse osmosis, but as fine as a HEPA filter, but designed for water. Then boil that dry. The result should be very similar to sea salt.

I could publish results from the APXS instrument on Sojourner, results from Spirit or Opportunity are harder to find, but available. But that instrument measures all elements in a sample, including rock minerals. It doesn't tell you which will dissolve in water.

RobertDyck · 2013-04-04 11:29:51

Baking Soda

This is a single chemical: sodium bicarbonate. First you need sodium chloride; that's pure salt, not "Mars salt". I'll leave separation of salts to other chemists. Then dissolve sodium chloride in water with CO2. Here on Earth the usual means to add CO2 is limestone, so they add ammonia. The by-products are calcium oxide and ammonium chloride. On Mars we could use Mars atmosphere, pressurized and bubbled through water. No calcium oxide, but we will still need ammonia. It will produce ammonium chloride. The chemical steps are, first add ammonia and salt to water:
NH3 + H2O → NH4+ + OH-
NaCl + NH4+ + OH- → NaOH + NH4Cl
Then add carbon dioxide:
CO2 + 2 NaOH → Na2CO3 + H2O
Then add more carbon dioxide:
Na2CO3 + CO2 + H2O → 2 NaHCO3
The last step will preceipitate sodium bicarbonate when sufficient concentration of CO2 is added.

So a chemistry question: what would happen if we start with "Mars salt" instead of pure sodium chloride? Would calcium oxide precipitate out with ammonium chloride? What would magnesium do? And potassium? And sulphur, and bromine?

Baking powder

As anyone who bakes will tell you, this is different than baking soda. You can make baking powder by mixing baking soda with an acid salt (usually tartaric acid) and starch. Under heat of cooking or baking, acid combines with baking soda to make CO2. You might be able to use ammonium chloride, but sodium from baking soda would re-combine with chlorine from ammonium chloride to form salt. Such baking powder would be salty. Tartaric acid is extracted from grape juice. It can be made from bananas, but that would be hard to grow on Mars.

Extracting tartaric acid appears to be by addition of calcium carbonate and calcium chloride. Chill to just below freezing, calcium tartrate will precipitate out. But it will be stained by grape juice. Sift the crystals out, dry, then add sulphuric acid. It will re-form tartaric acid. Then "decolorized by means of active carbon". I think that means soak it in the same carbon sponge used for activated carbon filters that remove bad smells from cabin air. Finally tartaric acid is crystallized under vacuum at 70°C.

So we're going to need grape vines. Yea! I like grapes.

RobertDyck · 2013-04-04 13:21:55

I started this thread to discuss food crops for a permanent settlement of Mars. I started calculating greenhouse size when someone from the Mars Foundation said he's working on another phase of their Mars Homestead project, and wanted to know how big the greenhouse(s) should be. So getting back to this: Grapes

I live in Winnipeg, just 60 miles (100km) north of the border with North Dakota. Not all grapes will grow here. But when I bought my house, I got a couple grape vines from a local nursery. Most varieties of grape will not grow this far north; the growing season is too short, and winters are too cold. There is a Manitoba native grape, but it's basically just a seed and a skin. Valiant grapes were developed at the South Dakota experimental research farm; they're a crossbreed of a Manitoba native grape with a commercial grape. Grapes are as big as a blueberry, with as many seeds as a Concord grape. But there's lots of them! And the vine grows here like a weed. I put a trellis on my 6-foot wooden fence for each vine. The weight of the vines is pulling the fence over, I have to repair the fence every year. Actually, when a new neighbour bought the house next door, she expressed concern over the vines. I told her any grapes that grow on her side of the fence are hers. She perked up and said "Ok!" Problem solved. But although her boyfriend doesn't have any financial interest in the house, he has cut down vines on her side of the fence. She said she misses the grapes. Her boyfriend, her problem; I'm staying out of that. But weight imbalance is pulling the fence over; I have to keep repairing it. The point is this variety grows in a cold climate, with sunlight for a northern latitude. Ideal for Mars?

I make wine. My two vines produce enough each year to fill my 54.5 litre demijohn with wine. That's 12 imperial gallons (160 fluid ounces/gallon), or 14.4 US gallons (128 fluid ounces/gallon). It requires 6kg of sugar.

A couple images from my house in 2004:

An image from the internet:

Greenhouse: my grapes grow on the west facing side of the fence. The vines cover 40 foot length of fence, 6 feet high, and fence plus trellis and grapes are about one yard deep. So using metric, that's 12 metre by 1 metre area of greenhouse. You need somewhere to stand, but there could be vegetables in the ground. As long as the other crop isn't so high it blocks sunlight.

Greenhouse management: Grapes require cold to fully mature. For maximum sweetness (sugar for fermentation), you need to let frost touch the grapes. Don't let them freeze on the vine, or you'll get ice wine. High sugar content is natural anti-freeze. Letting the plant go dormant could trigger another growing cycle. Since Mars year is twice Earth's, could we get 2 crops per Martian year? Assuming settlement location isn't so far toward a pole that Mars winter produces reduced sunlight. Could we reduce the cold "artificial winter" to get more than 2 crops per Martian year?

Do we want to increase that for more wine, um, table grapes or tartaric acid production?

Void · 2013-04-07 14:13:56

Nanocellulose

http://phys.org/news/2013-04-algae-mate … fuels.html

This sounds like something to look into.

Genes from the family of bacteria that produce vinegar, Kombucha tea and nata de coco have become stars in a project—which scientists today said has reached an advanced stage—that would turn algae into solar-powered factories for producing the "wonder material" nanocellulose. Their report on advances in getting those genes to produce fully functional nanocellulose was part of the 245th National Meeting & Exposition of the American Chemical Society (ACS).
"If we can complete the final steps, we will have accomplished one of the most important potential agricultural transformations ever," said R. Malcolm Brown, Jr., Ph.D. "We will have plants that produce nanocellulose abundantly and inexpensively. It can become the raw material for sustainable production of biofuels and many other products. While producing nanocellulose, the algae will absorb carbon dioxide, the main greenhouse gas linked to global warming."

An algae that excretes Nanocellulose. Not that I am too familiar whith it, but it sounds like they think many products that would be useful on Mars could be made. I have to suppose that it might be possible to make bullet proof T.P.?

Anyway I would think that if it would grow in low temperature fresh water, then simple bags of water would be able to host it. Place a clear tarp with the UV protection you mentioned over that, and that should do it.

Otherwise, engineer the thing further so that it could grow in cold brine (Below freezing temperatures), and that would not have a significant vapor pressure, and still of course you would have to keep the Martian air from sucking the vapors off, and you would still want to sheild it from UV, so a evaporation resistant transparancy "Dome" over the brine pools. Little or no pressurization required.

It may be that the bottom of a shallow brine pool could be above freezing during the day while sunlight warms it, while the major body of water was well below freezing.

Last edited by Void (2013-04-07 14:23:42)

StarDreamer · 2013-04-07 14:45:35

It could also grow in airborne ponds on Venus.....

Glandu · 2013-04-10 13:27:16

Void : sorry for the late answer. Anyways, You just need to extrude films, or surface. Those are well-known, mastered systems, whose productivity is well known, & more importantly, who yield better quality products. Same applies to Robert Dyck's solution. No need for low-quality, complex, costly, failure prone 3D printers there. They might be useful on other duties, but not there.

StarDreamer · 2013-04-10 14:41:43

Ok no one followed through on my idea for Venus. I talked about Venus here in these forums about 4yrs ago, with an idea similar to Void's. Imagine a double-walled greenhouse bubble on Venus. The polymer walls would admit light, but also filter light to reduce the harmful parts of the spectrum. The space between the two layers would be filled with water and let algae colonize the water. Inside the bubble, in the airspace part of the greenhouse, soil on the floor of the bubble with more complex plant growth. Equipment in the floor of the bubble to exchange gasses with the water and algae layer. The bubble would definitely not be spherical, but a flattened ovoid kind of bubble. Ok -- flying saucer shaped ... lol. Because of the winds on Venus, it might have a problem keeping This End Up. The algae wouldnt mind getting tossed about, but the soil layer and more complex plants inside might have a problem with that. If such a thing could be perfected, however, it would form the backbone of an agrarian economy on Venus for aerostat colonies of humans. The sky is free -- no such thing as territory or land ownership on Venus. A greenhouse able to sustain itself like a terrarium on Earth can be set free on Venus and just allowed to float. Humans who intercept them can check on them, service them, harvest them, set them free again, or hitch to them for a time. But they can be manufactured with carbon and other real simple elements and then just released.

Terraformer · 2013-04-10 14:57:26

I think we did, but then the Great Crash took them out...

Void · 2013-04-15 18:42:50

Glandu

Void : sorry for the late answer. Anyways, You just need to extrude films, or surface. Those are well-known, mastered systems, whose productivity is well known, & more importantly, who yield better quality products. Same applies to Robert Dyck's solution. No need for low-quality, complex, costly, failure prone 3D printers there. They might be useful on other duties, but not there.

I guess we are looking at two different parts of the elephant. Granted, tried and true can be the thing to do.
Still I might (With respect) say why experiment with railroads, when we do so well with the horse and buggy?

Anyway what I described was an extruder as a part of a robot, where a whole architecture might be built, avoiding quite a few of the joins. I agree that first, second, and third tries are likely to be less than expectations, but you have to nurture child ideas as well as make sure the adult ideas are kept at ready to serve requirements. We are on the same team, and I have no intentions of interfering with the use of extruders (If I ever could).

When the time comes, what works will be used. But we are quite far from the time when major mass architecture is being placed on Mars. We have plenty of time to also play on the playground.

Lions have very little use for inventions, or do sharks, they have what they do and they do it well, but we are humans.

Partly creatures of the known and partly creatures of the new.

Last edited by Void (2013-04-15 18:44:02)

Void · 2013-04-15 18:46:00

StarDreamer and Terraformer,

Get a solution for the acid environment first, and I am on board.

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