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#26 2016-08-13 05:51:56

elderflower
Member
Registered: 2016-06-19
Posts: 1,262

Re: Desalinating water

It is (almost ) always my intention to focus on early exploration and installation of permanent bases. I will be long dead before any thing else by way of human activity happens on Mars. Hence anything said about the future beyond these first steps is going to be overtaken by new knowledge and other circumstances. I think it was Macmillan who was asked what he thought was the main threat to his plans and responded with "Events, dear boy".
I would like to be able to see proven resources which could be used to support a base and exploration activities, The first of which is water for consumption, crops and electrolysis. I envisage mining of water in large lumps and removing unwanted contaminants. Water will almost certainly be required in construction as well.

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#27 2016-08-13 17:50:56

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,940

Re: Desalinating water

I agree elderflower as we need to first take the baby step and foot hold to mars before we can even think of building or expanding what will be the first crews manning level, habitat area, food supply or crop growing and mining capability.

Construction or expansion is maybe possible if we go to the same site otherwise it is on the back burner until we can deliver the tonnage to the surface that we will need as we will be making use of materials brought and not materials made insitu.

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#28 2016-08-14 18:04:28

SpaceNut
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From: New Hampshire
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Posts: 19,940

Re: Desalinating water

Oh this is try 2 to make this post.......

Not sure why this ended up in the report posting area but it does apply to the topic in general

elderflower wrote:

The major essentials that I see for early exploration, to be made from local resources, are fuel, water and breathable gas.

It isn't difficult to make these given a supply of power and a suitable water resource and atmosphere. Fuel is needed for the rovers and for the ascent/return vehicles and for a back-up power source.

So a small gas cooled reactor, a water purifier, an electrolyser, a peroxide plant and a CO2/ methanol plant for rover and rocket fuels and tanks for breathable air and potable water should be in place along with habitat, service and construction and mining tools, the rovers and the ascent vehicle and, obviously, means of life support before the arrival of humans.

These need to be located near a known source of water. The higher the purity, the better.

So we need to find the water.

I agree the question of water is important and so is the energy source as we will not be going with a nuclear reactor, a Large or multiple RTG units and we are at a limit with solar source of about 430 w for a meter when compared to earths 1100 w at the surface.

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#29 2016-08-15 10:27:31

Void
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Registered: 2011-12-29
Posts: 3,564

Re: Desalinating water

Actually, if you are scouting to get "Ground Truth", I would recommend a rather small still which would use freezing and evaporation to minimize labor, and maximize results.

A brine ice "Pot" could be connected with a plastic tube to a vapor receiver pot.
The brine pot could be loaded with mined ice, and also some waste water.  It would use solar collection methods to achieve a higher average temperature than the receiver pot.  The receiver pot could be kept in the shadows, and also fabricated to be colder than the brine pot over average time.

The connecting tube could run horizontally between them and on it top portions have reasonable transparency.  On its bottom, a solar energy collecting opaque coloration.  The connecting tube could be made of a plastic which includes Fluorine chemistry for the plastic film.

The film would not block UV, but that is fine as you would not want critters growing in your still anyway, and such a plastic would have longer term stability under Martian conditions than other films.

The processing of water would  be batch.  You would fill the brine pot with mined water, or briny water from a RSL, you could also add recycle discard water to that.  That would constitute the largest amount of manual labor for this system other than moving it to another location.

The whole system could work under rather low pressures, not much higher than the atmospheric pressure on Mars, so that would reduce the rigors that the system would endure.

The two pots would have quick disconnect and reconnect fittings, being attached to the horizontal tube as required to do the process.

A liquid phase of water would not be required, but depending on location, it could occur within a narrow range of temperatures and pressures which might occur inside the device when it was fully deployed for desalinization.

The two devices which would "Overheat" would be the "Brine Pot" and the "Horizontal Tube".  They would "Overheat" during the days sunshine.

The "Receiver Pot / Condenser Pot would condense the vapors created by the overheated "Other" elements of the system, due to the arrangement to typically have it be colder than the other two elements, at least during the day.

The brine pot could be disconnected periodically, to scrape it clean of residual solids.  This could occur outside of the "Habitat".

The "Receiver Pot / Condenser Pot" could be disconnected, and brought into the habitat to thaw out, producing distilled water.  Distilled water is not the best water to drink, so additives would be brought from Earth, which would be a very small burden I think as it should not require much of it by weight.

When moving to another "Campsite", the Condenser Pot should be smaller than the Brine Pot, so that they will take minimum space, and the horizontal connecting tube should be foldable to go inside the condenser pot  to minimize volume consumed.

In addition, an inflatable bag should be attached, which would be deflated at night, but would inflate as the system pressurized due to solar heating.  The bags purpose would be to receive the volume of air in the system during the day, so that what would be in the heated sections would be more materials to process and steam.  This would help to reduce an "Air Bound" situation for the steam path, increasing efficiency.
....

As for the minimization of my previous posts, I have to say, that when you first calibrate a device, you don't do it by "Fine Adjustments".
You might start by a coarse adjustment, then fine adjustments.

So, if you are setting up a first permanent base, you should consider what expansion in the future would look like, because it is not a good idea to expend a lot of effort to build a first permanent base that will not fit into the future.  Maybe there would be a reason to do so, but I suggest they it is a thing to ponder.

....

Although I previously suggested vapor tubes for transport of bulk water from source to usage, I am also aware of ideas involving tossing ice blocks as sub-orbital transport from source to use, but of course your aim would need to be precise, or your habitat would get very serious damage.  I believe "Antius" suggested the projectiles. 

I would suggest a combination of methods.  Project the ice blocks to a nearby location, and use vapor tubes to complete the transfer to the usage site.  This would reduce the need for precision accuracy for the projectiles.  It might also be efficient, and helpful to reducing the investment in vapor transport tubes.

Last edited by Void (2016-08-15 13:37:37)


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#30 2016-08-18 08:05:14

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: Desalinating water

Small inflatable, plastic, solar stills are supplied for use in marine liferafts to provide drinking water distilled from the sea water. I'm not sure they would work satisfactorily on Mars due to the very low vapour pressure of water that could be achieved there, but this could be tested in a polar station on earth.

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#31 2016-08-18 10:21:18

Void
Member
Registered: 2011-12-29
Posts: 3,564

Re: Desalinating water

elderflower,

First let me compliment you on being patient and working logically.  I did bombard this thread rather heavily and it takes patience for other people to endure that.

First of all, some background.  I have been contemplating ice covered liquid water reservoirs on Mars for perhaps 40 years.

Also, at some point in my life I attempted to get a patent on a desalinization process for Earth.  I dropped it, as the strain was just too much for me.

So, I chalk it up to a learning experience, where I exercised my imagination, but was subjected to intense rigor in attempting to properly file for a patent.  But yes, I quit.  So, don't roll over just because I say something.

elderflower said:

Small inflatable, plastic, solar stills are supplied for use in marine liferafts to provide drinking water distilled from the sea water. I'm not sure they would work satisfactorily on Mars due to the very low vapour pressure of water that could be achieved there, but this could be tested in a polar station on earth.

It's apples and oranges.

Such solar stills on Earth typically use a liquid to vapor to liquid phase change at ~1 bar of air pressure.

The type of still I am contemplating would use solid to vapor to solid as its primary method, but a temporary liquid phase could occur if your pressures were above 6 mb, and temperature and near 0 degC / 32 degF for instance.  But liquid phase would be incidental and not required.

On Mars, if most of the air were pushed into the inflatable bag, then the vapors inside of the path from evaporator to condenser would be mostly water vapor steam at a low pressure.  Not so on Earth unless you achieved a dominant temperature at or above 100 degC / 212 degF.

So, the physical operations would be rather different, and the Martian still would not work very well on Earth, especially under Earth polar ambient conditions.

For the Martian process, think Sublimation in the evaporator, and direct condensation from vapor to ice.

During my attempt at a patent, I was required to work with aspects which were the whole of the sum of the parts, and particular details.

So, I am also very interested in the freeze thaw process you are putting forward.   I think it is an important aspect of a whole spectrum of effects which could be utilized on Mars due to it being different than Earth.

But, I think it's most useful utilization might be for a first settlement, but would still be useful in a planetary civilization.

As and example, tests have shown that Lichen might have chances to adapt to living in cracks in rocks on Mars.  Two primary aspects make that assertion somewhat supportable.  #1 There is relief from the U.V. spectrum in those cracks in the rock. #2 Where there is a frequent freeze thaw cycle, a "dew" would occur in those cracks in the rock.  This would only have to be a frost, as Lichen can absorb water from frost.  So, in this particular way, Mars might offer life to Lichen.  Often nature points the way to a good method to use.  (Lichen does not have much tolerance for salts however).

So, good on you keep going with the freeze thaw thinking.

Last edited by Void (2016-08-18 11:14:45)


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#32 2016-08-19 11:36:29

elderflower
Member
Registered: 2016-06-19
Posts: 1,262

Re: Desalinating water

Subliming ice directly leaves a surface coated in contaminants, eg dust, which would reduce the rate of sublimation. In addition, you would need a liquid condensate to remove the product from the chilled surface. If the still can have its internal temperature and pressure raised above the triple point of water it would work, albeit slowly.
If we have a process with a large amount of waste heat available this could be used in an evaporation process, as can be done on Earth.
If Mars has already done the separation for us, we might be able to dig up ice and use it with little further purification.

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#33 2016-08-19 15:10:30

Void
Member
Registered: 2011-12-29
Posts: 3,564

Re: Desalinating water

I would have to think that if you warmed the temperatures to 50 degF, at a pressure of about 6 mb, the evaporation rate would be high.  Surely higher temperatures could be achieved by having it in the sunlight, and with a reflective foil on the ground in front of it.

Actually for the removal of the condensate, I expect to disconnect the connected condenser, and move it into the habitat, perhaps at night to thaw out overnight.  Probably a good idea to put a pinch of sugar into it to hope to neutralize Hexavalent Chromium, if any is present in the condensate.

Dealing with toxins will be important for any scheme for utilizing water on Mars.  Just possibly the buried water at the mid latitudes might be extracted without much of a toxin content, but I would not count on it.

But again, I urge you continue with your idea(s), one thing about this board that irritates me is when members have a hard time entertaining multiple options when there are multiple situations.

Last edited by Void (2016-08-19 15:15:10)


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#34 2016-08-19 17:15:28

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 3,312
Website

Re: Desalinating water

If you have heat available... I'm been musing on an idea that works on the same principle of evaporative air conditioning, that of forcing warm air through a wet fabric, which results in cooler, moist air being produced. I've been thinking, if you have hot air and salt water, you could use such a system to condense out distilled water.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#35 2016-08-20 10:57:37

Void
Member
Registered: 2011-12-29
Posts: 3,564

Re: Desalinating water

Terraformer,

Quite an order.  I have worked on it.

First of all there is a moral issue, if this were formulated for Earth.  Cultural interference.  Giving a loaded gun to a unenlightened entity, and then expecting good results.  I really didn't formulate anything dangerous in that fashion for an Earth implementation anyway.

So, for Mars (Which is appropriate anyway).

I will include your "Wick", and salt water, heat, and differential pressure flow of gasses as I go along.

The first questions are: What is your salt water source?  Where on Mars are you going to do this?

Unless new discovery provides disappointment as to real ability, I choose, RSL (Natural, or created), Fossil Ice at low latitudes, mechanically moved ice from mid latitudes, and mechanically moved polar ice, in that order of implementation, as the sources to be investigated and perhaps implemented.   For location, I choose low latitudes for various reasons well known to the various people who frequent this place.

An alternate and much less desired location, would be mid latitudes where a high probability of a substantial buried glacier exists.

Scope:  I anticipate that prior to this attempt at implementation, scouting by whatever method has supplied sufficient "Ground Truth' per G. W. Johnsons prior expressed cautions.  I also intend that this would be the first substantial base/settlement.  And I use the notion of an ice covered body of water presumably created artificially.  It is highly unlikely that any such "Lake/Pond" could be found as natural.  I also presume that any issues of bio-contamination from Earth to Mars or vice versa, have been properly addressed.  Although I choose to include a ice covered body of water, it is not strictly required for the method(s), so the proposal can have broader potential implementation, and this allows for unknown innovations to be included later.

Your specific reference appears to describe an active system where air is forced through a wick to produce a vapor, and that process also creates a cooled wick.  You want to involve the coolness of the wick to facilitate condensation of a substantially improved water for use.

elderchild has mentioned the hope of using thermal variances to act on a freezing process to produce a substantially improved water for use.  Although as mentioned it appears to be a relatively passive method, it actually would also require a fair amount of activity to produce the improved water.  In fairness to elderchild, perhaps I should more correctly describe what I think he said.  I think he indicated that he hopes to find a already processed buried mass of frozen brine, where the top layers are already suitable for extraction.  That is good, since waiting around for multiple Martian years to produce suitable water, would be a long wait.

I intend to include variations of both methods in a greater process, which I hope will expose humans to a minimized danger to health and life, and perhaps produce good results at the same time.

Taking another break.

One reason I prefer low latitudes, is that barring a dust storm, you will have multiple freeze thaw opportunities, in each Martian year.  Several hundred perhaps.  That will be hard to use, if the idea was to project the cold of the nights through a layer of ice.  The ice is insulating after all, and the thickness of the ice is likely to be substantial.  And then there is the partner question, "How do you get heat into the lake?".

To make some level of the lake comfortable for human habitats you would want a brine layer of at least room temperatures, with a water column pressure of at least 1/3 bar, and preferably an average of 1 bar.  That would require a combination of Martian air pressure (~6mb), and ice layer, and brine layers, where the water and ice would be about 100 feet (American thinking), somewhere in the lake.  Not a small lake.

In order to use day/night + Solar energy, I suggest containers be built over the surface of the ice or on the "Shore" of the lake.  These are to provide the energy to create brine layer separations.  They will have to be able to handle variations in pressure, up to at least 70 mb, I think.  They may incorporate solar energy with a typical thermal solar collection method, or use heliostats, or they could perhaps use both.
They would also serve as radiators at night.

Two things to avoid in these containers would be solid salt, and slabs of ice, because the later could damage the equipment, and the former would require mechanical removal.

Your system would be active, and also any method to use slab ice would also require an active method as well.

So, I want to form slush at night in these containers, from brine.  Think washing machine cycles.  You would pump brine into the containers, and then allow them to radiate the heat off.  You would drain the remnant brine off before the whole mass froze into a slab, and before salts precipitated out of the solution.  The slush mix would still contain a substantial salt remnant, so it would thaw at a relatively low temperature as the sun warmed up the containers during the day.  Lets say, the temperature of the melted solution would be several degrees below the melting point of fresh water.  You would then drain that solution, into the upper layers of the lake just under the ice.

You would then fill the container with your colder denser brine layers and allow the containers/solar collectors to heat the solution to room temperature and above.  This will of course require solar heating methods which I previously mentioned.  When this has reached it's maximum result for the day, then that solution would be drained to the lower layers of the lake.

So, if this first process were implemented, the lake would be primed for extraction of electrical energy by way of the salt methods, where differential saltiness can produce electrical energy.  The process for that would be built in enclosures in the warm brine layer, adjacent and connected to human habitat in the same layer.  This does not forbid the use of other methods to extract electrical energy from say solar panels of that type.

On towards your issue Terraformer.

Your method reminds me of a forced distillation process that is used in industry.  They compress steam from an evaporator until water condenses, and the recycle the heat produced to the evaporator.  And cold from the vacuum used in the evaporator is directed to the condensation process as well.

So if your wick were a bubble, you could have your warm salty solution inside of that bubble, and pull a vacuum on the outside of that wick.
The cooled brine produced could be used to assist the pressurized condensation process.  Your brine source could be the upper layer of less salty water which would be cold, but you could preheat it with a heat exchanger in the warmer, more salty layer further down in the lake.

The machinery for this could be in the 1/3 to 1 bar + layer of the water, along with other equipment and habitats, so this would be a relatively sheltered environment where humans would have relative protection from the normal Martian environment.

........

I will describe a variance of the above which may make it more practical.  I presume actually that Martians will actually create and use electrical solar panels to provide electrical energy during daytime.

This could reduce the rigors on the solar/radiator containers I have described for creating slush and warm brine.  Instead of having to generate warm brine, they would create a warm steam during the daytime, and solar panels could provide the electrical energy to compress that steam into a hot liquid during the day.  Then those containers would not need to hold a differential pressure of ~70 mb plus, but could be more reasonably near the Martian ambient pressure, allowing thinner walls.

The use of salt layers to generate electricity then would be as a battery type back-up for the daytime electric system.

That's it.  I know that most of you want to think about earlier methods for scouting and settlement, but without a comprehensive long term plan, which might provide a strong method to support the lives of a large population later, I am not sure the bother to inhabit Mars would be worth it.

If someone comes up with something better for the purpose, then good on them.

Last edited by Void (2016-08-20 12:22:40)


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#36 2016-08-21 09:35:45

elderflower
Member
Registered: 2016-06-19
Posts: 1,262

Re: Desalinating water

The main point of exploration of Mars, as opposed to some other location, is that Mars may be habitable, or may be so rendered. If this were not the case we would be wasting too much money on it. If it is habitable that money would provide for a refuge from global disaster on Earth. If not we would do better spending money on Callisto, or not on space exploration at all.
I think we should do the exploration and I think the result will give a second home for humans.
We do need to find a means of growing grapes on Mars, and yeast. So we must find some water and devise means of cleaning it up. Membrane technology is one route, but membranes are prone to fouling, so don't last very long. Other methods involve phase changes, and freezing uses a much smaller enthalpy change than does evaporation.

Last edited by elderflower (2016-08-21 09:48:30)

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#37 2016-08-21 12:41:59

Void
Member
Registered: 2011-12-29
Posts: 3,564

Re: Desalinating water

I like to explore multiple possibilities.   Efficiency does not matter as much if you have expanded capabilities, but sure, I will run with that.  Sort of.

Lets say you have three slushy machines comprised of:
-Basin and piping with process control machinery.
-A transparent dome over that (RobertD..k could advise), as a solar collector.

The slushy machines connected in serial fashion.  When you melt the slush from #1, you port it to #2, and from #2 to #3.

Then when you have completed your cycles, you have gone through 3 improvement steps.  So, you have a supply of improved water.

During parts of those processes you will have condensation on the inside of the domes.  Frost in the night, and if the pressure is high enough, liquid water during parts of the day.  That could flow down to a gutter for collection.

If you have surplus electrical power you may also force condensation from the "Atmosphere" of the dome with a compressor.

So you would have 3 types of improved water from the 3 slushy machines, and 2 types from natural condensation/forced condensation.

I would think that for primary wash water you do not need all that fresh of a water.  If you have flush toilets, not requiring that good of a water.  Showering, not that good of a water, but you would want a clean rinse at the end.  For drinking, perhaps you would use a mixture of #3, and natural condensation water.  For chemistry, perhaps in some cases you would want the forced condensation water.

And to top it all off, while you were generating fresher waste water, and dense brines, you would also have been creating a 24/7 energy source.  So the slushy machines would be solar energy collectors.

Last edited by Void (2016-08-21 12:49:00)


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#38 2020-10-16 11:33:02

tahanson43206
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Registered: 2018-04-27
Posts: 3,841

Re: Desalinating water

While searching for information about the chemical elements, I ran across the web site at the link below ...

https://www.lenntech.com/periodic/numbe … number.htm

The company that sponsors the web site appears to specialize in water.  Their web site mentions desalination as one of their activities.

(th)

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