Author Topic: Water, Methane, and Oxygen ISRU on Mars  (Read 18602 times)

Online redliox

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Water, Methane, and Oxygen ISRU on Mars
« on: 05/15/2016 05:35 PM »
This relatively fresh study sparked the need for a[nother][1] dedicated ISRU thread: http://mepag.jpl.nasa.gov/reports/Mars_Water_ISRU_Study.pdf
I'm honestly surprised there hasn't been a thread directly made for ISRU despite how prominently it is mentioned in numerous Mars threads here at Nasaspaceflight.com.  Do post commentary about the subject and especially new developments related to extracting and manufacturing resources on Mars, especially water and methane.

Regarding the M-WIP Study, they've begun to consider the importance extracting Martian water is to both life support and propellant for a Martian Ascent Vehicle.  On the side, I suspect somewhere Robert Zubrin of the Mars Society is laughing, although at least pleased some aspects of NASA are finally moving toward the water/lox/methane manufacture he championed over 20 years ago.  But seriously, the discovery of abundant water/hydrogen as both ice and minerals thanks to the Odyssey and MRO probes has probably eased the transition toward ISRU.  Now we have proof there are definite resources to use; both the hydrogen and carbon dioxide for the Sabatier reactions are on Mars.

The study identifies 4 areas to extract water from:
A) Glaciers
B) Poly-hydrated minerals
C) Phyllosilicate minerals
D) Regolith

While glaciers are the most obvious source of water, the disadvantage pointed out is they: 1) outside of the poles, they're buried under a lot of regolith, and 2) become unstable when exposed because the ice naturally sublimates.  It will take a lot of effort to dig it up, and after that you have to extract it asap before the ice evaporates.  In a worst case, a base built on a glacier might tilt or fall apart if the area around it is unearthed.  Methods are being considered for glacial extraction, but it considered a less mature option compared to the other 3 resource options.

Outside of resource discussion, there is some acknowledgement NASA is indeed considering at least partial resource utilization; LOX production seems to be already on the table, with MOXIE via the 2020 rover being a prelude.  So now it is coming down to deciding how the methane and water will be obtained.  This in turn warrants further missions to demonstrate both Sabatier reactors and robotics to harvest material.

As news develops for ISRU, do mention them here and inject the occasional opinion, so long as it relates to ISRU on Mars.

1 - Edit/Lar (thanks to A_M_Swallow)
Here are links to two previous ISRU threads.

Advanced Concepts / Making a Lunar Ascent rocket fuel on the Moon
http://forum.nasaspaceflight.com/index.php?topic=9434.msg176666#msg176666

Advanced Concepts / ISRU techniques and uses
http://forum.nasaspaceflight.com/index.php?topic=11824.msg241841#msg241841
« Last Edit: 05/16/2016 10:27 PM by Lar »
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Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #1 on: 05/15/2016 06:30 PM »
The amount of water needed for a NASA base as planned may be extractable from all kinds of sources. However the amounts needed for a SpaceX architecture with MCT and a colony with many people is much higher. IMO it can only be effectively extracted from glaciers.

The regolith cover as determined by orbital radar is no more than 10m. That's not too much given there is a need for many thousands of tons of water. Removing a max amount of 10m of regolith may be a lot easier than mining the ice which is as hard as concrete at Mars temperatures. I don't see sublimation as a major problem as long as the ice is shaded from direct sunlight. Even sublimation needs the same energy as normal heating to liquid and then gaseous form. That's a lot of energy for much ice to sublimate and energy comes from sunlight.

Building the base directly on a glacier may not be a good idea. Though if the regolith cover is 10m that may become a problem only when the base becomes large, becomes a city.

I don't see

Offline nadreck

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #2 on: 05/15/2016 07:02 PM »
My understanding of the findings is that they would not have any information about glaciers that have more than 10 meters of regolith coverage. I think there may be deeper ones, and that they could be drilled into directionally or horizontally to be harvested.

However, there may also be boundaries between glacier and bedrock that could prove advantageous.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Online redliox

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #3 on: 05/15/2016 07:18 PM »
The amount of water needed for a NASA base as planned may be extractable from all kinds of sources. However the amounts needed for a SpaceX architecture with MCT and a colony with many people is much higher. IMO it can only be effectively extracted from glaciers.

Trying to avoid this from becoming clogged with SpaceX fandom, but I knew it would be brought up sooner or later.  My only statement for SpaceX along with Red Dragon, in regards to ISRU, is that it seems the obvious candidate for field testing ISRU; the trouble with standard probes is that you end up competing for payload space with scientists - MOXIE was lucky to get room on 2020.  I suggest holding off on MCT talk until SpaceX declares what's needed in September.

The regolith cover as determined by orbital radar is no more than 10m. That's not too much given there is a need for many thousands of tons of water. Removing a max amount of 10m of regolith may be a lot easier than mining the ice which is as hard as concrete at Mars temperatures. I don't see sublimation as a major problem as long as the ice is shaded from direct sunlight. Even sublimation needs the same energy as normal heating to liquid and then gaseous form. That's a lot of energy for much ice to sublimate and energy comes from sunlight.

10 meters is still over 32 feet deep...as in over five and a half times the height of an average man...as in hundreds and hundreds of pounds/kilos of material...some of which may also be as hard as concrete and in irregular chunks dropped by ancient Martian seas and glaciers.  Moving all of that will drain batteries hard, more so if nuclear power is limited if allowed at all.  That's no idle work, and it is more conservative of energy to draw on easy-to-access regolith heavy in hydrogen, be it ice or gypsum.

The best option for ice is akin to plans for exploring Europa; drill and use a crybot to melt the ice, essentially making a well with the vapor getting collected by the excavator above.  Glacial ice isn't exactly the first choice, but neither is it off the table.  Most likely if ice is considered it will have to be shallowly covered, as in 3 meters or less.  It is a juicy fruit for ISRU, but unless you're flying to the (Martian) north pole it isn't easy to pick at the moment.

My understanding of the findings is that they would not have any information about glaciers that have more than 10 meters of regolith coverage. I think there may be deeper ones, and that they could be drilled into directionally or horizontally to be harvested.

However, there may also be boundaries between glacier and bedrock that could prove advantageous.

There's still a lot they don't know about ice on Mars, obviously since we've only seen a direct hint of it via Phoenix (but no one's driven to the north pole yet).  There's better knowledge about chemically-bound water via Spirit, Opportunity, and Curiosity which is why there's a slight favor towards it for the moment.  I wouldn't be surprised if they opt for a little of both ideally, at least for something in mid-lattitudes; many of the sites for both the 2020 rover and human exploration state they're going for a mix of both kinds of water whenever possible.
« Last Edit: 05/15/2016 07:20 PM by redliox »
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Online A_M_Swallow

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #4 on: 05/15/2016 09:07 PM »
Here are links to two previous ISRU threads.

Advanced Concepts / Making a Lunar Ascent rocket fuel on the Moon
http://forum.nasaspaceflight.com/index.php?topic=9434.msg176666#msg176666


Advanced Concepts / ISRU techniques and uses
http://forum.nasaspaceflight.com/index.php?topic=11824.msg241841#msg241841

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #5 on: 05/16/2016 04:36 AM »
My understanding of the findings is that they would not have any information about glaciers that have more than 10 meters of regolith coverage. I think there may be deeper ones,

The argument for max 10m was that radar could see and measure regolith covers of more than 10m, not that they could not see water deeper than that. They do not have enough depth resolution to see covers less than 10m in radar reflections from orbit. So it seems there are no or no very large glaciers with regolith covers of more than 10m because they don't see regolith covers over glaciers.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #6 on: 05/16/2016 04:47 AM »
Trying to avoid this from becoming clogged with SpaceX fandom, but I knew it would be brought up sooner or later.  My only statement for SpaceX along with Red Dragon, in regards to ISRU, is that it seems the obvious candidate for field testing ISRU; the trouble with standard probes is that you end up competing for payload space with scientists - MOXIE was lucky to get room on 2020.  I suggest holding off on MCT talk until SpaceX declares what's needed in September.

I understand this is not a SpaceX thread and acknowledged it by arguing both NASA and SpaceX situations. I don't think you can reasonably exclude the SpaceX situation from an ISRU thread.

10 meters is still over 32 feet deep...as in over five and a half times the height of an average man...as in hundreds and hundreds of pounds/kilos of material...some of which may also be as hard as concrete and in irregular chunks dropped by ancient Martian seas and glaciers.  Moving all of that will drain batteries hard, more so if nuclear power is limited if allowed at all. 

I already argued that removing a regolith cover that thick is only worth it if you need a lot of water. There is also the chance that they find areas where the cover is only 1m deep as is the lower boundary of cover determined by the fact that less cover would cause long term sublimation of the ice below.

That's no idle work, and it is more conservative of energy to draw on easy-to-access regolith heavy in hydrogen, be it ice or gypsum.

That's only true as long as the amount of water needed is low. Extracting water from regolith requires a lot more energy than melting water from glacier ice.

Edit: fixed quotes
« Last Edit: 05/16/2016 04:49 AM by guckyfan »

Offline Rei

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #7 on: 05/16/2016 09:14 AM »
A basic summary of my reading of that document: "high importance, low TRL"

I think we all here already knew that  ;)  The differences in system mass between a with-ISRU and without-ISRU mission are tremendous, making ISRU tremendously important.  But our experience with "low maintenance low mass Martian bobcats and water isolation systems" is, let's just say, "lacking" - as is our quantification of the scale, homogeneity of mechanical and chemical properties, etc of the various potential resources.  We've got plenty of broad orbital data and tons of spread-out individual surface analyses.  But that does not a reserves characterization make.

It's good to see the reality check, particularly on the "glacial ice" concept (the overburden problem, the sublimation problem, the rocks-and-sand-and-who-knows-what mixed in problem, the hardness problem, etc).  Even though they're still being generous on a lot of cases, for example assuming that weathering has already basically mined the minerals for you in B, C and D.  Maybe if you let purely ISRU factors determine the landing site, but scientists prefer sites where the strata haven't been weathered into a homogenous mess.    But, who knows.  :)

Also, it appears that they're assuming nothing more than simple distillation, which is quite the assumption - they just leave it open with their "not addressed" remark on page 60.  Distillation only removes non-volatile chemicals - to pick an example example, it won't remove the HCl from decomposing perchlorates.  And even paired with RO, the best RO membranes tend to be attacked by chlorine, and the non-chlorine sensitive ones tend to be pH-sensitive.

That is to say, there's some very significant engineering work and an awful lot of testing ahead.  But also, the importance of the task means it'll probably get done sooner or later.

Nice excavator design for loose soils on P.38.  :)  I worry about rocks jamming it up, though.  Apparently they do too.

Good presentation  :)
« Last Edit: 05/16/2016 12:43 PM by Rei »

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #8 on: 05/16/2016 09:52 AM »
That was a funny part of the NASA workshop about selecting landing sites. A glacier expert said, glacial ice is always very clean. Get a block of that ice into the habitat, let it melt and drink it.

An expert on ECLSS was shocked. She said, get us a sample of that ice, give us 15 to 20 years development time and we will give you a space rated device that can make it drinkable.

I guess the truth will be somewhere inbetween.

Online redliox

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #9 on: 05/16/2016 10:32 AM »
That was a funny part of the NASA workshop about selecting landing sites. A glacier expert said, glacial ice is always very clean. Get a block of that ice into the habitat, let it melt and drink it.

An expert on ECLSS was shocked. She said, get us a sample of that ice, give us 15 to 20 years development time and we will give you a space rated device that can make it drinkable.

I guess the truth will be somewhere inbetween.

...and that beautifully illustrates how not all rocket scientists are experts.  8)

Of course, regarding ice, I'd hope for some testing before drinking it, but it sounds consistent with how I've heard frozen water can be surprisingly pure.  The real limitation with glaciers on Mars is how to access them, hence why I stressed that particular resource; it's big and obvious but good luck rigging a solar-powered rover to dig it out.  Yet, especially for mid and high lattitudes, the abundance is enough to keep them on the list.

IMO, reading the M-WIP gave me the impression gypsum should be pursued.  Aside from the mineral being water heavy, there is a very solid scientific motivation to seek it out: gypsum forms in seawater and hot springs.  Wherever you find the stuff, odds are you will find many things related to the deep history of Mars prior to the dry Amazonian Era, with or without fossils.  However, in fairness this could also be said of the other various minerals; gypsum just stands out as the least intensive to harvest, including the fact it's a soft chalk less abrasive to equipment.
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Offline Rei

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #10 on: 05/16/2016 11:44 AM »
Of course, regarding ice, I'd hope for some testing before drinking it, but it sounds consistent with how I've heard frozen water can be surprisingly pure.

On a planet full of ubiquitous toxic dust, IMHO that's beyond optimism.  You'll be drinking perchlorates, hexavalent chromium and arsenic just from dust contamination alone.

Quote
IMO, reading the M-WIP gave me the impression gypsum should be pursued.  Aside from the mineral being water heavy, there is a very solid scientific motivation to seek it out: gypsum forms in seawater and hot springs.  Wherever you find the stuff, odds are you will find many things related to the deep history of Mars prior to the dry Amazonian Era

Indeed - but as you'll note in the article, they're looking for gypsum that's already been weathered to fine sediment - they don't even consider (apart from relatively quickly to dismiss it) hard rock mining.  By contrast, geologists generally want their layers intact.

But hey, you might get lucky and find a place with both highly weathered and bare, unweathered gypsum  :)  That's certainly possible. 

Hmm, just thinking here, are there any good routes to sulfuric acid production from gypsum applicable to a Mars environment?  Sulfuric acid usually tops the list of most widely consumed important industrial chemicals on Earth, and I'm just thinking about future local production here.
« Last Edit: 05/16/2016 11:45 AM by Rei »

Offline Rei

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #11 on: 05/16/2016 11:51 AM »
A glacier expert said, glacial ice is always very clean.
What sort of glacier expert would make a statement like that?  Here's what glacial ice looks like around where I live:

http://i.telegraph.co.uk/multimedia/archive/02167/dark-blue-impact_2167404k.jpg

I wouldn't even dream of calling that "very clean".  And we're not constantly blanketed in a cloud of fine dust - that just comes from dusting events once every couple dozen years for a given location (which is why it forms stripes).  Glaciers ability to trap dust is not only well known, but a very important part of glaciology - it's used to study past climates.

Here's what shallow subsurface water ice looks like on Mars:

https://en.wikipedia.org/wiki/Phoenix_%28spacecraft%29#/media/File:Phoenix_mission_horizon_stitched_high_definition.jpg

There's no way that that is in any way pure and clean.  Leading contention from Phoenix seems to be "frozen dusty brine".

As per Wikipedia, which cites five references on the topic:

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

Quote
Like glaciers on Earth, glaciers on Mars are not pure water ice. Many are thought to contain substantial proportions of debris, and a substantial number are probably better described as rock glaciers

https://en.wikipedia.org/wiki/Rock_glacier
« Last Edit: 05/17/2016 08:38 AM by Rei »

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #12 on: 05/16/2016 01:11 PM »
Glaciers can contain rocks, true. The water is still very clean.

It was said the glaciers on Mars they were talking about contain very little rocky material. It would show up as scatter in the signal. From lack of scatter they can safely assume very clean water.

Online RonM

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #13 on: 05/16/2016 01:49 PM »
Glaciers can contain rocks, true. The water is still very clean.

It was said the glaciers on Mars they were talking about contain very little rocky material. It would show up as scatter in the signal. From lack of scatter they can safely assume very clean water.

The question is how did the glaciers form?

If the glaciers formed by the accumulation of snow, then the ice can be clean. Then again, with thin layers of a light coat of dust mixed in and then melted, dangerous chemicals can dissolve in the water and contaminate it. Sublimating the ice could avoid contamination from non volatiles in the dust, but removing volatiles would be more complex.

If the glaciers formed by ground water freezing, the water can be heavily contaminated.

Considering what we know about Mars surface chemistry, water extracted from glacial ice will require testing and purification.

When scouting base or colony locations, drilling into the ice and chemical analysis will be needed to determine which location has the ice requiring the least purification.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #14 on: 05/16/2016 02:13 PM »

The question is how did the glaciers form?

My understanding is that glaciers form by precipitation. So if they did not form from precipitation they are not glaciers. Given the discussion I assume they are glaciers and have been formed by precipitation. That would make it likely that they do include dust.

Glaciers that contain rocky material have gathered it while flowing.

Quite possible that my line of thought is too simplistic and wrong.

Online redliox

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #15 on: 05/16/2016 09:07 PM »
My understanding is that glaciers form by precipitation. So if they did not form from precipitation they are not glaciers. Given the discussion I assume they are glaciers and have been formed by precipitation. That would make it likely that they do include dust.

Glaciers that contain rocky material have gathered it while flowing.

Quite possible that my line of thought is too simplistic and wrong.

Not necessarily; we simply don't know what the Martian climate was like eons ago.  The current one is full of dust storms littered with polluting fines (i.e. very powdery dust), but in a wetter era that would have been confined as silt and less of an issue.  My educated guess would be that the more ancient the glacier, the more pure it will be, with layers formed in the Amazonian Era will have dust embedded.

Ironically, the same fines would be perfect mining material as it doesn't need to be ground up, just shoved into a vat for processing.
« Last Edit: 05/17/2016 05:21 PM by redliox »
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Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #16 on: 05/17/2016 04:53 AM »
BTW, whenever there would be significant fuel production on Mars, there would be an excess of oxygen because rocket engines run fuel rich. CO2 extraction from the atmosphere would produce nitrogen, or rather a mix of nitrogen and argon, which is breathable. So a breathable atmosphere would be a welcome byproduct. Only CO2 removal should be necessary.

Offline the_other_Doug

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #17 on: 05/17/2016 02:18 PM »
BTW, whenever there would be significant fuel production on Mars, there would be an excess of oxygen because rocket engines run fuel rich. CO2 extraction from the atmosphere would produce nitrogen, or rather a mix of nitrogen and argon, which is breathable. So a breathable atmosphere would be a welcome byproduct. Only CO2 removal should be necessary.

Hmm... this is a semantics note, but I have a bit of a hiccup seeing the concept floated of just removing the CO2 from Mars' atmosphere and you have a useful atmosphere left.

That's sort of like saying if you're looking to produce salt, all you need to do is remove the water from salt water, and you have useful salts.  I would look at it a lot more as removing the salt from the water, not vice-versa.

So, yeah -- what you describe, I would think of as purifying the CO2 in Mars' atmosphere by removing the less than 4% of trace gasses, which are almost entirely composed of nitrogen and argon.  That tracks logically a lot better than looking at it as a "CO2 removal" operation... ;)
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Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #18 on: 05/17/2016 03:02 PM »
I think that's a misunderstanding. What I mean by CO2 removal is remove the rising CO2 from the breathable atmosphere inside the habitat. Otherwise it can be maintained by adding surplus oxygen from propellant production. No need for a closed loop ECLSS early on. Can wait with a closed loop system until it is a biological system, not similar to attempting closed loop on the ISS or in a spacecraft.

Online A_M_Swallow

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #19 on: 05/17/2016 03:33 PM »
BTW, whenever there would be significant fuel production on Mars, there would be an excess of oxygen because rocket engines run fuel rich. CO2 extraction from the atmosphere would produce nitrogen, or rather a mix of nitrogen and argon, which is breathable. So a breathable atmosphere would be a welcome byproduct. Only CO2 removal should be necessary.

Hmm... this is a semantics note, but I have a bit of a hiccup seeing the concept floated of just removing the CO2 from Mars' atmosphere and you have a useful atmosphere left.

That's sort of like saying if you're looking to produce salt, all you need to do is remove the water from salt water, and you have useful salts.  I would look at it a lot more as removing the salt from the water, not vice-versa.

So, yeah -- what you describe, I would think of as purifying the CO2 in Mars' atmosphere by removing the less than 4% of trace gasses, which are almost entirely composed of nitrogen and argon.  That tracks logically a lot better than looking at it as a "CO2 removal" operation... ;)

Removing the CO2 is easy, just cool to -78.5 °C; −109.2 °F; 194.7 K at 1 atmosphere.

Offline lamontagne

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #20 on: 05/17/2016 07:41 PM »
Why do they condemn atmospheric extraction of water?  The method they propose, using compressors, on page 26, is not the most likely one, IMHO.  Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper?  Or has that technology been disproven?
I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems.  84 000 cfm is not that much in ventilation equipment terms.  a big machine, but nothing extraordinary.  And at the very low air densities, the fan power required should be tiny.  The main power drain would be the regeneration heat.
Similar methods can be used to extract the CO2 from the atmosphere as well.
If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.
The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.


Online redliox

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #21 on: 05/17/2016 09:37 PM »
Why do they condemn atmospheric extraction of water?  The method they propose, using compressors, on page 26, is not the most likely one, IMHO.  Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper?  Or has that technology been disproven?

Matter of practicality not so much technology.  The dry, thin air of Mars makes the Mohave Desert look like a rain forest.  To the point, the dehumidifiers would have to run for hours...and hours...and likely weeks if not months to yield much.  A shovel load dug from a gypsum deposit would give you the same amount of water in less time; weeks versus a single day, which is more economical?

Similar methods can be used to extract the CO2 from the atmosphere as well.
If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.
The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.

Carbon dioxide pretty much is the Martian atmosphere, with nitrogen and argon the only others with significance, and ubiquitous; hence why both fuel cells and Sabatier reactors are viable because their resource is everywhere.  Water vapor sadly doesn't have this advantage, hence why it was turned down in the M-WIP study.  If you want water on Mars, digging for it is the best option; I will say near the Martian poles (particularly the northern one) would be the region to consider this...but only if you don't have the means to mine the water literally under your feet there.
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Offline lamontagne

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #22 on: 05/18/2016 12:26 AM »


Matter of practicality not so much technology.  The dry, thin air of Mars makes the Mohave Desert look like a rain forest.  To the point, the dehumidifiers would have to run for hours...and hours...and likely weeks if not months to yield much.  A shovel load dug from a gypsum deposit would give you the same amount of water in less time; weeks versus a single day, which is more economical?

Carbon dioxide pretty much is the Martian atmosphere, with nitrogen and argon the only others with significance, and ubiquitous; hence why both fuel cells and Sabatier reactors are viable because their resource is everywhere.  Water vapor sadly doesn't have this advantage, hence why it was turned down in the M-WIP study.  If you want water on Mars, digging for it is the best option; I will say near the Martian poles (particularly the northern one) would be the region to consider this...but only if you don't have the means to mine the water literally under your feet there.

The air extraction paper suggested 3 kg per day, or about 1,5 tonnes for the 480 days of the study cited in the first post, for 880 kg of equipment.  To get the 16 tonnes requires as per the first post would require about 8 to 9 tonnes of equipment.  The reference site was the Viking lander site.
How does that compare to mining?  The mining equipment seems rather light, good, but I see no mass numbers for ore processing.
It's not that I don't believe in mining, it's just that the paper's dismissal of atmospheric mining seems wrong.  It's using the wrong comparison base. The conclusions may be the same.
« Last Edit: 05/18/2016 12:27 AM by lamontagne »

Offline TakeOff

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #23 on: 07/09/2016 06:28 PM »
KISSCaltech has a few presentations of ISRU on Mars, just a week old, on their youtube channel.
https://www.youtube.com/user/KISSCaltech

I'm surprised to learn that solar panel power production varies so very much (on the MER rovers). Some kind of cleaning mechanism would help. Why not a set of layers of thin plastic foils that could be removed and discarded? Still 45% change of insolation over a Martian year and blocking dust in the atmosphere varies too. Solar power is not so easy on Mars as I thought.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #24 on: 07/09/2016 10:00 PM »
Still 45% change of insolation over a Martian year and blocking dust in the atmosphere varies too. Solar power is not so easy on Mars as I thought.

Not easy true. Possible that the base value for production is just good enough to keep the colony running. Fuel ISRU and other energy intensive activities may need to be limited to times when enough power is available. It is a calculation what is more efficient. Having more solar power and keep the ISRU equipment running all the time or having more mass in ISRU equipment and run it only when energy is available.

Constant supply from nuclear power would make things easier. You could keep ISRU running all the time, even at night.

Offline Bob Shaw

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #25 on: 07/09/2016 10:32 PM »
There's lots of easily accessible, crushed up ice on Mars; just land your demo ISRU plant next to a nice, fresh impact crater somewhere on the northern plains. There are fresh craters each year - no need to worry about finding one that's not suffered too much sublimation. Land either in the ejecta field, or even *inside* the crater, and shovel up the goodies!

Offline Impaler

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #26 on: 07/10/2016 08:48 AM »
Failure to even consider atmospheric water collection is a major over-site in the paper.  It is clearly the source which is most widely distributed and most easily processed, the technical challenge is basically just a sufficient power supply which is something that needs to be cracked anyway.

Offline Hotblack Desiato

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #27 on: 09/05/2016 05:50 PM »
Regarding a glacier as water source, how about underground mining?

One entrance at the side, with airlock to have a higher air pressure inside, and then dig tunnels and caverns into the glacier.

Excavating these tunnels will provde lots of water and more importantly, it's several 10s of meters below the surface. That layer will block any radiation, effectively turning the mine into a radiation shelter and storage room, with the additional benefit of being refrigerated.l

The sides and bottom layers of the glacier can then be used for testing other excavation methods for larger underground structures inside the bedrock (again with perfect radiation shielding).


Offline CuddlyRocket

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #28 on: 09/05/2016 10:56 PM »
... effectively turning the mine into a radiation shelter and storage room, with the additional benefit of being refrigerated.

I see the advantage of being refrigerated for a storage room; less so for a radiation shelter! :)

Offline Dalhousie

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #29 on: 09/06/2016 07:42 AM »
Why do they condemn atmospheric extraction of water?  The method they propose, using compressors, on page 26, is not the most likely one, IMHO.  Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper?  Or has that technology been disproven?
I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems.  84 000 cfm is not that much in ventilation equipment terms.  a big machine, but nothing extraordinary.  And at the very low air densities, the fan power required should be tiny.  The main power drain would be the regeneration heat.
Similar methods can be used to extract the CO2 from the atmosphere as well.
If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.
The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.

The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere.  That 2.7 million m3 per sol for 600 sols.  Or 74 m3 a second for 10 hours per sol (when solar power can be used)
« Last Edit: 09/06/2016 07:46 AM by Dalhousie »
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Offline KelvinZero

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #30 on: 09/06/2016 08:14 AM »
The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere.  That 2.7 million m3 per sol for 600 sols.  Or 74 m3 a second for 10 hours per sol (when solar power can be used)
Finding a way to run at night would be good, but how insurmountable is that value?

http://quest.nasa.gov/aero/planetary/mars.html
"The maximum wind speeds recorded by the Viking Landers in the 1970's were about 30 meters per second (60 miles an hour) with an average of 10 m/s"

That implies 70m3 pass through a given 7 square-meter area per second on average.

(obviously I am brushing over the fact that you need to somehow sieve this wind for every atom of moisture. I have no idea of the efficiency or drag of that)

I think there are also canyons with notorious winds.. Are those also the ones speculated to have ice ten meters down, ie good long term targets?
« Last Edit: 09/06/2016 08:16 AM by KelvinZero »

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #31 on: 09/06/2016 08:21 AM »
I think water content in the atmosphere will vary a lot with location and season.

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #32 on: 09/06/2016 01:38 PM »
Why do they condemn atmospheric extraction of water?  The method they propose, using compressors, on page 26, is not the most likely one, IMHO.  Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper?  Or has that technology been disproven?
I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems.  84 000 cfm is not that much in ventilation equipment terms.  a big machine, but nothing extraordinary.  And at the very low air densities, the fan power required should be tiny.  The main power drain would be the regeneration heat.
Similar methods can be used to extract the CO2 from the atmosphere as well.
If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.
The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.

The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere.  That 2.7 million m3 per sol for 600 sols.  Or 74 m3 a second for 10 hours per sol (when solar power can be used)
If the batteries are lighter than the equipment they'd be powering, then you might want to run the entire sol.
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Offline Norm38

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #33 on: 10/11/2016 08:39 PM »
If Curiosity isn't allowed to go anywhere near water, then how will anyone be allowed to use ice/water to make fuel?  Wouldn't that cause microbe contamination just the same?

Or would any human base just fundamentally have to be considered tainted and contamination allowed?

http://www.nature.com/news/mars-contamination-fear-could-divert-curiosity-rover-1.20544

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #34 on: 10/11/2016 11:22 PM »
Peak atmospheric moisture occurs during the northern summer near the poles as the ice cap is actively sublimating away and air temperatures are highest which gives the atmosphere maximum moisture holding capacity.  Solar power is naturally maximized during a polar summer, but you have the difficulty of surviving during the polar winter unless your doing a brief surface stay in which case the north pole is clearly the best location as you can get to have your cake and eat it too.

The WAVAR concept described here http://www.lpi.usra.edu/publications/reports/CB-955/washington.pdf would produce several times it's mass in water over a martian year at most sites on mars and at the simulated average martian moisture level, only at particularly dry locations like Viking-2 would it be inadequate.  The system proposed here was for life-support water but multiplying it a few times would get the desired water quantity of 16 tons.
« Last Edit: 10/12/2016 04:11 AM by Impaler »

Offline savuporo

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #35 on: 10/12/2016 05:55 AM »
Failure to even consider atmospheric water collection is a major over-site in the paper. 
Ask yourself why isn't every desert settlement on earth littered with "atmospheric water collection" plants.
The tech exists by the way, Fraunhofer and Simon Fraser university have active R&D programs for various methods of absorption and refrigeration.
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Offline john smith 19

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #36 on: 10/12/2016 06:52 PM »
Reading the thread I can't quite shake the idea people seem to think they are building a well by hand

IIRC in several parts of the US people get their water from individual boreholes. Pulling some numbers off the web gives figures around a 200-600 feet with an 8 inch diameter.  Such boreholes can be drilled in less than 10 days. A quick check on eBay suggests these run 16Hp

This suggests a borehole of < 32 feet is well within the SoA. Building a drilling rig that can do this would be a high energy task by space probe power levels, around 12Kw. You're also looking at quite a heavy package once the drill pipe is included. Obviously the shorter length helps and lowering the drill rate should reduce the Hp requirements.

But that's the easy part  :(

Phase changes release and absorb huge amounts of energy and water is among the highest (behind LH2). That said the very low atmospheric pressure suggests any water will immediately vaporize, once that energy has been added.

The joker in the pack is what state such glacier water will be in. Will be be (more or less) pure ice or more like permafrost IE frozen mud? This sounds like a case of "Hope for the best, plan for the worst" as the worst will need to shift a lot more mass to recover the same volume of water.

One thing I have not seen anything about is the use of focused sunlight to provide most of the heating. This would replace PV arrays with reflectors and concentrators with minimal conversion losses.   

Just my $0.02

I quite like the University Of Washington concept of water recovery from the atmosphere. yes it is low density and quite variable but accessing it is mechanically simpler and enough is known about the Mars atmosphere to predict the best sites for collection.
« Last Edit: 10/12/2016 07:01 PM by john smith 19 »
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Offline lamontagne

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #37 on: 10/12/2016 07:48 PM »
Why do they condemn atmospheric extraction of water?  The method they propose, using compressors, on page 26, is not the most likely one, IMHO.  Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper?  Or has that technology been disproven?
I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems.  84 000 cfm is not that much in ventilation equipment terms.  a big machine, but nothing extraordinary.  And at the very low air densities, the fan power required should be tiny.  The main power drain would be the regeneration heat.
Similar methods can be used to extract the CO2 from the atmosphere as well.
If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.
The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.

The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere.  That 2.7 million m3 per sol for 600 sols.  Or 74 m3 a second for 10 hours per sol (when solar power can be used)

The Washington paper, for 3,3 kg/day, proposed a velocity of 8 m/s over the Zeolite beds for 95% separation efficiency. The required fan power was 12 kW.
In our case, at 27 kg/day, That would mean an area of about 10m2 for the Zeolite beds. 
They also proposed using a fan, at 20m/s, so about 4m2.  That would be about 1.2m in diameter.
In our case the required fan power would be almost 100 kW.  That's a big motor!

Wind alone could not provide enough energy to push the air through the Zeolite bed.

The solar panel area would be 600 W/m2 x .2eff = 150 W/m2 = 665 m2.  At 10 kg/m2, almost 6 tonnes.

Doesn't seem insurmountable, but not very good at our scale of operation.

However, looking all the way to the conclusion of the report, there are emplacements where the average concentration of water is higher, and their simulations achieved 46 kg per day with 15 kW.  That would be OK for our needs, and avoid the humongous motor I just calculated.  Location is key.

As far as melting water goes, 335 kJ/kg x 27 kg/day = 8736 kJ/day = 0,24 kJ/s or 240 Watts.  Melting is the clear winner here, by I to2 orders of magnitude!  So we have a lot of energy difference available for digging up the ice.  On that basis, digging wells is the more energy efficient solution.  And the well digging equipment will probably weigh less than the extra solar panels...

So I would conclude that atmospheric is possible, but well digging is much better.
« Last Edit: 10/12/2016 08:01 PM by lamontagne »

Offline KelvinZero

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #38 on: 10/14/2016 03:53 AM »
Failure to even consider atmospheric water collection is a major over-site in the paper. 
Ask yourself why isn't every desert settlement on earth littered with "atmospheric water collection" plants.
The tech exists by the way, Fraunhofer and Simon Fraser university have active R&D programs for various methods of absorption and refrigeration.
Earth has bodies of fresh water, roads, pipes, cheap trade with near and distant neighbours, and is nervous about giving every desert settlement it's own nuclear capability? :)

Offline AncientU

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #39 on: 10/14/2016 10:55 AM »
Failure to even consider atmospheric water collection is a major over-site in the paper.  It is clearly the source which is most widely distributed and most easily processed, the technical challenge is basically just a sufficient power supply which is something that needs to be cracked anyway.

Atmospheric extraction was considered and ruled out.  See p26 of presentation.
Quote
1 kg water is contained in 250,000m3 of atmosphere

Quote
The air handling system implied by these calculations would be on the same order of magnitude as the largest air compressors known on Earth: ~600,000 CFM, requiring 65 megawatts to run, and roughly 5x5x10m in size.
CONCLUSION: The mass, power, volume, and mechanical complexity of the system needed for this approach are far outside of what is practical for deployment to Mars.

And here they didn't even include the power required to get water back out of the zeolite... which is far from trivial.
« Last Edit: 10/14/2016 11:00 AM by AncientU »
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Offline Warren Platts

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #40 on: 10/16/2016 12:02 AM »
There might be groundwater in certain places underneath permafrost. Permafrost is impermeable to liquid water, so makes a good cap rock that prevents escape to the surface. As you go deeper, the temperature must of necessity increase to a point that is not subfreezing anymore. At such depths, the overburden pressure is over an atmosphere, so liquid water would necessarily form.

It is much easier to drill for such water--assuming it exists and can be found--than practically any other option on the table IMHO. It would take some prospecting for sure, but maybe not a whole lot, relatively speaking.

The other strategy extreme seems to be to engineer for average conditions. That way the entire prospecting step can be eliminated, while success is guaranteed. But the latest round of studies has mainly succeeded in showing how difficult that is.

YMMV

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Offline Warren Platts

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #41 on: 10/16/2016 12:05 AM »
Very old school (1970) study of groundwater in permafrost regions in Alaska. Of relevance to Mars ISRU however, IMO.

http://pubs.usgs.gov/pp/0696/report.pdf
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Offline lamontagne

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #42 on: 10/16/2016 12:19 AM »
Failure to even consider atmospheric water collection is a major over-site in the paper.  It is clearly the source which is most widely distributed and most easily processed, the technical challenge is basically just a sufficient power supply which is something that needs to be cracked anyway.

Atmospheric extraction was considered and ruled out.  See p26 of presentation.
Quote
1 kg water is contained in 250,000m3 of atmosphere

Quote
The air handling system implied by these calculations would be on the same order of magnitude as the largest air compressors known on Earth: ~600,000 CFM, requiring 65 megawatts to run, and roughly 5x5x10m in size.
CONCLUSION: The mass, power, volume, and mechanical complexity of the system needed for this approach are far outside of what is practical for deployment to Mars.

And here they didn't even include the power required to get water back out of the zeolite... which is far from trivial.
Using compression to extract water from the air is a really kind of silly.  I don't feel their investigation into atmospheric water was serious or complete.  However, this in not very important as mining for water is by far more effective than extracting it from the atmosphere, even if we use the best atmospheric extraction system, rather than the worst ;-)

Offline AncientU

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #43 on: 10/17/2016 12:59 AM »
I believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed.  Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.
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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #44 on: 10/17/2016 02:08 AM »
I believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed.  Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.
There may be ways to use natural flow to extract water from the atmosphere.

In fact, you could mine gypsum, extract water from the gypsum, and dump the anhydrite back onto the surface where it will slowly reabsorb water from the atmosphere and become gypsum again. In fact, you could have sheets of something like gypsum or other hydrated minerals that you harvest periodically, dehydrate, then place back onto the Martian surface to reabsorb water. Perhaps arranged vertically along with the direction of the wind to maximize flow rates and areal density of plates.

I bet that'd be more energy efficient.
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Offline AncientU

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #45 on: 10/17/2016 11:14 AM »
I believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed.  Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.
There may be ways to use natural flow to extract water from the atmosphere.

In fact, you could mine gypsum, extract water from the gypsum, and dump the anhydrite back onto the surface where it will slowly reabsorb water from the atmosphere and become gypsum again. In fact, you could have sheets of something like gypsum or other hydrated minerals that you harvest periodically, dehydrate, then place back onto the Martian surface to reabsorb water. Perhaps arranged vertically along with the direction of the wind to maximize flow rates and areal density of plates.

I bet that'd be more energy efficient.

Would b much more efficient... that's exactly what 'mining' the regolith is.  It will naturally (gradually) recharge by condensing the atmosphere's load of water each sol.
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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #46 on: 10/18/2016 02:36 AM »
It's really more like farming, isn't it? If you just had fields of these hydrating minerals, it'd be more efficient than raw regolith, since you have to heat up all the regolith, but only part of it yields water.
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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #47 on: 10/18/2016 04:15 AM »
It's really more like farming, isn't it? If you just had fields of these hydrating minerals, it'd be more efficient than raw regolith, since you have to heat up all the regolith, but only part of it yields water.

Very flexible on when/if processing steps are done as well. Once the stuff's spread out it can be picked back up early if you want some water at lower yields, Just left there if there's no need for it or collected and dumped into a storage pile if a new batch is ready to go back out.

Of course somebody making maps is going to have to label the area Tatooine. It's practically mandatory.  :D

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #48 on: 10/18/2016 09:19 AM »
Of course somebody making maps is going to have to label the area Tatooine. It's practically mandatory.  :D

Or Arrakis, Vulcan, Geonosis, Korhal...

Desert planets are a surprisingly overdone theme in sci-fi I realize.  :P
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Offline Chris_Pi

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #49 on: 10/19/2016 06:09 AM »
Of course somebody making maps is going to have to label the area Tatooine. It's practically mandatory.  :D

Or Arrakis, Vulcan, Geonosis, Korhal...

Desert planets are a surprisingly overdone theme in sci-fi I realize.  :P

It's not the desert planet reference, It's the moisture farm one. Maybe Arrakis can kind of squeeze in there too if if a structure that increases airflow over the anhydrite beds makes sense. Some sort of windtrap or something...  :P

Offline john smith 19

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #50 on: 10/19/2016 11:24 AM »
Of course somebody making maps is going to have to label the area Tatooine. It's practically mandatory.  :D

Or Arrakis, Vulcan, Geonosis, Korhal...

Desert planets are a surprisingly overdone theme in sci-fi I realize.  :P
Well in that case I'd suggest calling the place Beta Colony except for the issues around such a name.
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Offline sevenperforce

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #51 on: 04/28/2017 03:25 PM »
Seems like a good a thread as any for this question:

Is there any concrete idea about sizing a reusable soil-mining ISRU unit? Suppose you have a vehicle which can deliver and deploy up to 40 tonnes of payload to the surface of Mars, in a cross-section roughly the size of the Falcon 9 fairing. Is that enough for a reusable LOX/CH4 ISRU system -- one which can be deployed by the vehicle, process regolith to extract water, convert the water and collected atmosphere into LOX+CH4, fill the vehicle's prop tanks, dump the used regolith, and start again?

Kicker: it needs to be re-stowable in the vehicle, so that the vehicle can head back up to orbit, transfer the collected propellant to a tanker, and then return to the Martian surface in another location to start again.

Doable?

Online Steven Pietrobon

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #52 on: 01/23/2018 03:19 AM »
This looks very interesting. One step production of carbon dioxide (CO2) and water (H2O) into ethylene (C2H4) and oxygen (O2).

CO2 + H2O → 0.5C2H4 + 1.5O2

http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b02110

Compare this trying to make methane (CH4):

CO2 + 4H2 → CH4 + 2H2O (Sabatier)
4H2O → 4H2 + 2O2 (electrolysis)

Overall reaction is

CO2 + 2H2O → CH4 + 2O2

That is, making methane requires twice as much water as ethylene as well as having a lower density and Isp compared to ethylene!

Propellants  MR   dp (kg/L)  ve (m/s) Id (Ns/L)
O2/CH4       3.6   0.8376     3656     3062
O2/C2H4      2.7   0.9007     3678     3313
« Last Edit: 01/23/2018 03:21 AM by Steven Pietrobon »
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Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #53 on: 01/23/2018 05:59 AM »
Propellants  MR   dp (kg/L)  ve (m/s) Id (Ns/L)
O2/CH4       3.6   0.8376     3656     3062
O2/C2H4      2.7   0.9007     3678     3313


I note the above paper contains the phrase
Quote
When liquid fuels such as ethanol and n-propanol were included, the total solar-to-fuel efficiency was 2.9%.

Then you've got more exotic stuff, like CO/acetylene / O2.
Acetylene (C2H2), and CO to stabilise it, and reduce the fierce combustion temperature a little, while getting rather better ISP than CO alone.
https://arc.aiaa.org/doi/abs/10.2514/3.26350?journalCode=jsr ( https://ntrs.nasa.gov/search.jsp?R=19920049575 )

Under half the hydrogen of C2H4/O2.

Plus, at least one process for C2H4 begins with CH4, so 'flex fuel' generation might be possible, tuned to available water and power.
« Last Edit: 01/23/2018 03:57 PM by speedevil »

Offline oldAtlas_Eguy

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #54 on: 01/23/2018 08:48 PM »
Although Ethylene may not be used for prop it still is useful in the creation of synthetic materials fibers such as polyester. I am sure that the Colony will find the mass manufacture of polyester based materials cloths/ropes/etc will be very useful. Plus ground equipment may use Ethylene and LOX to power heavy mobile equipment via ICE (internal combustion engines) or Fuel Cells. Using less energy to make also means that less energy is stored in the liquids and released when burned. For Rockets that is a bad thing but for rover/ground equipment that is not a major concern.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #55 on: 01/25/2018 06:43 AM »
Forgive me for not reading the whole thread but has there been discussion of extraction of atmospheric water.

I do believe this was studied using adsorption and has the advantage of being relatively simple.

Edit: The paper I'm thinking of is here

https://www.google.com.au/url?sa=t&source=web&rct=j&url=https://www.lpi.usra.edu/publications/reports/CB-955/washington.pdf&ved=2ahUKEwjTz7Gt0fTYAhUJv7wKHVX4AtAQFjABegQIBhAB&usg=AOvVaw0rs4OMSQRlfZ81Mx5L_q-O

Edit: Apologies but ny earlier skim missed the posts on water vapor. The volumes of air needed to be processed are large but they don't particularly bother me. The real question is how reasonable/unreasonable you wish to be regarding your target quantity water/hydrogen
« Last Edit: 01/26/2018 02:14 AM by Russel »

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #56 on: 01/26/2018 01:49 AM »
Another issue I don't think has been mentioned is that food imported from Earth will contain carbon and more interestingly hydrogen. Ordinary metabolism creates CO2 and H2O. In a well sealed environment with water reclamation, humans will actually generate an excess of H2O and this H2.

This may not help if you want hundreds of tonnes of propellant, but if you want a few tonnes, that bit of H2 might be usefull.

It certainly qualifies how much water you think you might need for life support.
« Last Edit: 01/26/2018 02:16 AM by Russel »

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #57 on: 01/26/2018 02:33 AM »
Although discussion of importation of hydrogen may be seen as OT, I think it is relevant given the sheer cost/difficulty of going after ISRU hydrogen (versus Oxygen). And in the context of the relative ease of importing hydrogen.

One way to import hydrogen is to land amonia (NH3) which is 17% hydrogen by mass and is is dense, stable and storable. The bonus is that you've also got a reserve of Nitrogen.

16 tonnes of CH4/O2 propellant is about 12 tonnes of Oxygen (relatively easy) and about 4 tonnes of CH4. That's 1 tonne of Hydrogen or 5.6 tonnes of NH3 (from which you get 4.6 tonnes of usefull N2)

That cuts the problem down to a third. Yes you need power/mass to process NH3 but you then don't need power/mass to extract native Nitrogen/Argon.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #58 on: 01/27/2018 02:48 PM »
One thing I'd like to ask here. Fairly simple.

If you only consider sites on Mars that are of relevance for exploration. Which I presume tends to limit things to under 20-25 degrees from the Equator.

What do we actually know about the presence of water, how deep and in what form and quantity?

In other words, given realistic landing sites, what are we dealing with and also how probable is it? In other words do we need to land a probe beforehand to be certain of the resource?

It seems to me that ISRU for water on Mars comes on one of the following forms:

1. Water vapour
2. Hydrates and other forms of water bound to soil.
3. Thin layers of ice of some reasonable purity of unpredictable depth and possibly localised scope near surface (1-2m at most)
4. Thicker ice, but with some certainty and located deeper (up to about 30m).

Lets consider those in turn.

1. Water vapour varies by season and and location but is to some extent predictable. It also requires relatively non complicated and robust equipment. It is certainly capable of producing life support quantities (hundreds litres to several tonnes or more depending on power source). I dispute the need to source local hydrogen for small scale exploratory missions so I'm happy to simply have a local source of life support water. However this method can in theory supply enough hydrogen for a bare-bones ascent.

2. This method is limited to areas where there is reasonable depth of soil that is not too rocky and not too compacted. One can imagine relatively robust scrapers. Not exactly high-throughput by Earth standards but sufficient to accumulate enough soil (hundreds of tonnes) for the extract of a modest quantity (5-20 tonnes) of water. Like any activity that engages soil this is subject to unknowns. Uneven depth. Uneven consistency. Clogging. Damage. Repair. I cannot see this being done as an automated process. However it could be semi autonomous with day by day radar imaging and sampling. Having said this, any scale implies robotic maintenance and replacement of ground engaging tools (blades, teeth). It is by no means straight forward. Another issue that comes with scale is that if you have thin soil you have to cover a sizeable area and you start dealing with specialised transporters.

3. I concede this might be a possibility near a site of interest. Firstly as a matter of engineering this ups the scale by at least an order of magnitude since you're interested in the ice, not the overburden. You have major issues with wear and damage and replacement of parts. It also takes time and a lot of energy. When you get to the ice you may only be dealing with a thin layer. You also have to deal with very hard ice which is laced with abrasives and which you have to recover quickly. Besides the engineering issue you are now skating close to planetary protection issues.

4. I have reservations that any substantial thickness of ice will be found at a site of interest at a depth that can be reached by realistic boring machinery (say 30m, but even 100m may not find this type of ice deposit). In theory this is an easier process than the above. You just drill a hole and inject hot air and recover the water vapour. Although it does not require the same kind of machinery for open cut work, its still a difficult process even on Earth. The worst thing is that when you find a deep source of ice you are almost certainly running into planetary protection issues - until that area has already been subject to very careful study and deemed not just sterile but incapable of being infected with Earth organisms.

I haven't even begun to talk about all the other engineering issues including what happens to hydraulics and bearings in near vacuum. The erosive and corrosive nature of the materials involved. And the demands for power, power transmission, batteries or chemical fuels. I feel this sort of thing belongs in a specialised thread.

So. All I'm saying here is that my belief is that ISRU on the scale that would sustain a settlement or a SpaceX style launch requires a lot of hardware and a lot of stuff that needs maintenance/repair and quite probably human control if not localised tele-operation. In short, any mission that requires a lot of return-to-earth fuel is begging for so much mas to be landed on Mars that you might as well land the hydrogen or methane you need instead.

On the other hand, if you're purpose is scientific/exploratory life gets a lot easier. For a start it makes sense to limit the amount of ISRU propellant you need (in other words an indirect return). Secondly what methane/hydrogen you do need for the ascent might as well be landed as part of the cargo (which will be a lot bigger than the few tonnes of methane needed). And thirdly to the extent that you are game enough to make some of the hydrogen you need, its going to require a lot less plant and equipment to use atmospheric water vapour.

Since my background is in electronics for mining machinery I'd welcome a separate thread on the mining hardware front. Its just not that easy, even on Earth.
« Last Edit: 01/27/2018 02:53 PM by Russel »

Offline Lar

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #59 on: 01/29/2018 12:58 AM »
I would love to see a mining machinery thread. I don't think we have one at this time.
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Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #60 on: 02/01/2018 12:39 AM »
I believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed.  Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.
There may be ways to use natural flow to extract water from the atmosphere.

In fact, you could mine gypsum, extract water from the gypsum, and dump the anhydrite back onto the surface where it will slowly reabsorb water from the atmosphere and become gypsum again. In fact, you could have sheets of something like gypsum or other hydrated minerals that you harvest periodically, dehydrate, then place back onto the Martian surface to reabsorb water. Perhaps arranged vertically along with the direction of the wind to maximize flow rates and areal density of plates.

I bet that'd be more energy efficient.

This is working its way back to using specialised reusable adsorption media like zeolites. What I wonder is whether there aren't better materials even if the process of re-extracting the water is a bit more energy intensive than an addorptive media.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #61 on: 02/04/2018 09:43 AM »
The following may end up going in the advanced concepts section if I signed up.
However I'll post it here for now and see what you think.

I've been trying to devise a method to extract water vapour from Martian air that relies upon a simple heat pump. The energy required to extract the vapour is itself not much. Its just the heat of vaporisation of water or about 0.6KWhr per Kg. Of course no real process will get close to this but as an order of magnitude issue its not a real concern.

The issue is that the water vapour is a tiny fraction of the air. For what follows, I'm going to use the figure of 20 parts per million. That's the fraction of water vapour extracted (not all of the available water vapour).

So, for 1Kg of water we need to process 50,000Kg of air, which for current purposes can be treated as if its all CO2. Of course this is back of the envelope but if you were to take 50,000Kg of CO2 and lower it by 50 degrees (sufficient to freeze most of the water and yeah I know it does vary) then its going to cost you 2GJ of energy. About 555KWhr. With a steady 10KW of power that's 400 grams of water per day. Perfectly fine for life support but we can do better.

You're wasting a lot of energy cooling CO2 and venting it. Why can't you use that cold CO2 to cool the incoming CO2? In fact you can do just this and its the overall coefficient of performance that multiplies the quantity of water you get out.

What does it look like in practice? Just like a refrigerated dehumidifier on Earth, only with some attention to efficiency. A working fluid (nitrogen? argon? refrigerant?) is compressed and run through a heat exchanger. This transfers heat from the working fluid to the outgoing air. Its a reverse flow heat exchanger which reduces the effective temperature differential the heat pump is working with and that's where high COP is possible.

The working fluid passes through a mechanical expander (to recover some energy). It then goes through another reverse flow heat exchanger where the working fluid collects heat from the incoming air. In this way heat is being pumped in a loop out of the incoming air and then back into the outgoing air. There's nothing particularly "advanced" about this. It just requires careful design.

Now, what does require some special thought is the efficiency of the heat exchangers, the surface area onto which ice can form and minimising the flow loses. Sounds like a job for a PhD thesis.

My take on this is a composite graphene/polymer heat exchanger that is 3D printed for maximum surface area to mass ratio. It may even be coated or otherwise surface treated to increase the surface area. The incoming air is filtered (down to a few microns) and then run through the heat exchanger. Water molecules form a frost on the surface of the heat exchanger. Remaining dust particles may actually help the process here.

At some point heat is applied to the heat exchanger and the ice turns to water and runs off. It takes with it the finer fraction of Martian dust which is itself filtered out.

The cold (and dryer) Martian air then passes through the other heat exchanger (which is probably going to be of a similar design).

I'd like to see an overall performance of under 100KWhr per Kg but under 50KWhr/Kg is entirely possible. If that pans out then a 10KW source of electricity will get you 4.8Kg of water per day. That's getting close to being useful as a source of propellant.

Incidentally that 4.8Kg/day of water means an air flow of about 140m3/s. Yes, its big, but its also implementable. This is after all low density air.

Now all of this is truly back of the envelope. It does depend on humidity and there's a lot of things that have to be designed very carefully. But I hope it inspires someone with better thermodynamics knowledge to comment.

Once you have a source of clean, dry Martian air its then possible to tap off a small fraction and from this freeze off the CO2. What you have left is primarily Argon, Nitrogen, Oxygen and Carbon Monoxide - all of which are useful.
« Last Edit: 02/04/2018 09:45 AM by Russel »

Offline Lar

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #62 on: 02/04/2018 03:33 PM »
Russel:

Sounds very reasonable. (I got a D in P-Chem which included heat transfer so I am not competent to comment on the math)

I would be interested in further trades on this vs. water mining from the soil vs drilling and heating. But your filter and dewatered atmosphere stream feeds nicely into a trace gasses extraction unit. That, however, may push the heat exchange somewhat downstream as it will benefit from the coldest possible stream input.

See the prior thread on chemical industry on Mars.

Here it is:
Proposed ITS Cargo Modules to Initiate a Chemical Industry on Mars
http://forum.nasaspaceflight.com/index.php?topic=42053.0
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Offline sghill

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #63 on: 02/04/2018 03:56 PM »
One thing I'd like to ask here. Fairly simple.

If you only consider sites on Mars that are of relevance for exploration. Which I presume tends to limit things to under 20-25 degrees from the Equator.

What do we actually know about the presence of water, how deep and in what form and quantity?

In other words, given realistic landing sites, what are we dealing with and also how probable is it? In other words do we need to land a probe beforehand to be certain of the resource?

It seems to me that ISRU for water on Mars comes on one of the following forms:

1. Water vapour
2. Hydrates and other forms of water bound to soil.
3. Thin layers of ice of some reasonable purity of unpredictable depth and possibly localised scope near surface (1-2m at most)
4. Thicker ice, but with some certainty and located deeper (up to about 30m).

Lets consider those in turn.


You are over thinking this. To make methane and oxygen rocket fuel from the atmosphere, you need to capture the mix of ambient gases first, then you must separate the gases from each other.

The simplest means to do this is cryogenic air separation. You store martian atmosphere, then cool it off.  As the gas gets colder, each molecule liquifies. First all the water comes out, then the CO2, then the argon, nitrogen, oxygen, hydrogen, etc.

H2O, argon, and nitrogen are found in very small amounts in the martian atmosphere, but they are extremely valuable, and have to be separated out first anyway to get down to the oxygen.

Thus, if you are making rocket fuel, the process gets you all the other stuff too.

Air separation is a critical path technology for Mars, along with electricity generation.  These two technologies will be on the first BFR flights before people get there, IMHO. Otherwise, no return trips.

https://en.wikipedia.org/wiki/Air_separation
From Wikipedia, here's how the process works:

To achieve the low distillation temperatures an air separation unit requires a refrigeration cycle that operates by means of the Joule–Thomson effect, and the cold equipment has to be kept within an insulated enclosure (commonly called a "cold box"). The cooling of the gases requires a large amount of energy to make this refrigeration cycle work and is delivered by an air compressor. Modern ASUs use expansion turbines for cooling; the output of the expander helps drive the air compressor, for improved efficiency. The process consists of the following main steps:

Before compression the air is pre-filtered of dust.

Air is compressed where the final delivery pressure is determined by recoveries and the fluid state (gas or liquid) of the products. Typical pressures range between 5 and 10 bar gauge. The air stream may also be compressed to different pressures to enhance the efficiency of the ASU. During compression water is condensed out in inter-stage coolers.

The process air is generally passed through a molecular sieve bed, which removes any remaining water vapour, as well as carbon dioxide, which would freeze and plug the cryogenic equipment. Molecular sieves are often designed to remove any gaseous hydrocarbons from the air, since these can be a problem in the subsequent air distillation that could lead to explosions.[6] The molecular sieves bed must be regenerated. This is done by installing multiple units operating in alternating mode and using the dry co-produced waste gas to desorb the water.

Process air is passed through an integrated heat exchanger (usually a plate fin heat exchanger) and cooled against product (and waste) cryogenic streams. Part of the air liquefies to form a liquid that is enriched in oxygen. The remaining gas is richer in nitrogen and is distilled to almost pure nitrogen (typically < 1ppm) in a high pressure (HP) distillation column. The condenser of this column requires refrigeration which is obtained from expanding the more oxygen rich stream further across a valve or through an Expander, (a reverse compressor).

Alternatively the condenser may be cooled by interchanging heat with a reboiler in a low pressure (LP) distillation column (operating at 1.2-1.3 bar abs.) when the ASU is producing pure oxygen. To minimize the compression cost the combined condenser/reboiler of the HP/LP columns must operate with a temperature difference of only 1-2 K, requiring plate fin brazed aluminium heat exchangers. Typical oxygen purities range in from 97.5% to 99.5% and influences the maximum recovery of oxygen. The refrigeration required for producing liquid products is obtained using the Joule–Thomson effect in an expander which feeds compressed air directly to the low pressure column. Hence, a certain part of the air is not to be separated and must leave the low pressure column as a waste stream from its upper section.

Because the boiling point of argon (87.3 K at standard conditions) lies between that of oxygen (90.2 K) and nitrogen (77.4 K), argon builds up in the lower section of the low pressure column. When argon is produced, a vapor side draw is taken from the low pressure column where the argon concentration is highest. It is sent to another column rectifying the argon to the desired purity from which liquid is returned to the same location in the LP column. Use of modern structured packings which have very low pressure drops enable argon with less than 1 ppm impurities. Though argon is present in less to 1% of the incoming, the air argon column requires a significant amount of energy due to the high reflux ratio required (about 30) in the argon column. Cooling of the argon column can be supplied from cold expanded rich liquid or by liquid nitrogen.

Finally the products produced in gas form are warmed against the incoming air to ambient temperatures. This requires a carefully crafted heat integration that must allow for robustness against disturbances (due to switch over of the molecular sieve beds[7]). It may also require additional external refrigeration during start-up.
« Last Edit: 02/04/2018 03:59 PM by sghill »
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Offline Lar

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #64 on: 02/04/2018 06:07 PM »
That's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component.  Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.
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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #65 on: 02/05/2018 01:29 AM »
That's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component.  Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.

Carbon Dioxide has a significantly higher triple point than the other gasses. Is there some way of turning it into snow that falls into a container whilst filtering off the gasses?

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #66 on: 02/05/2018 03:54 PM »
That's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component.  Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.

You freeze out the CO2 and water vapor, then remove the pure precipitates. You're then left with the remaining gases and can utilize gas separation to purify and capture each element.

You have the advantage that ambient temps at night are already cold enough to precipitate CO2, which lowers your energy need.
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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #67 on: 02/06/2018 04:41 AM »
That's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component.  Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.

Carbon Dioxide has a significantly higher triple point than the other gasses. Is there some way of turning it into snow that falls into a container whilst filtering off the gasses?

I've toyed with this problem for quite some time. It works out to be two different problems. One is extracting water vapour. The other is extracting the minor gasses, Ar, N2, O2 and CO.

To obtain enough water vapour you need to process very large quantities of air. Roughly 50,000Kg of air for 1Kg of water.

The only way I can see doing this that approaches the ideal therodynamic limit is to cool the air, extract the water ice and then warm the air. The key to efficiency is using reverse flow heat exchangers and keeping the difference between Thot and Tcold for the heat pump  as small as possible. Remember that because of the heat exchangers that temperature difference is not the change in temperature of the air being processed. You might cool air from -20C to -100C, but the heat pump may only see a 25C differential.

Getting the minor gasses is a different proposition. For every Kg of O2 you need about 700Kg of air. But you need to extract the CO2 in a thermodynamically reversible fashion.

My initial take on this is to compress the CO2 in a multi stage process. The heat being transferred to several heat exchangers. Eventually the CO2 ends up as a warm gas at about 20-30 atm.

A heat pump lowers the temperature to the point that the CO2 liquifies. This liquid is now separated (along with a residual ice fraction).The gases are Ar, N2, O2 and CO. This is your fedstock.

Now the liquid CO2 is pumped past its critical pressure and heated (energy recovery from compression). You now have supercritical CO2. To this you can add any waste heat source (such as nuclear). The supercritical CO2 now spins a turbine and generates electricity.

Separating N2/Ar from O2 would be easy if not for the fraction of CO. These have close melting/boiling points and its unclear to me if ordinary fractionation can reduce the concentration of CO  sufficiently. The answer may lie in separation/freezing at different pressures. But its a non trivial problem.


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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #68 on: 02/06/2018 01:42 PM »
Separating N2/Ar from O2 would be easy if not for the fraction of CO. These have close melting/boiling points and its unclear to me if ordinary fractionation can reduce the concentration of CO  sufficiently. The answer may lie in separation/freezing at different pressures. But its a non trivial problem.

I have not looked up the temperatures at elevated pressures, or mixed gasses, but at 1 bar, CO is further from O2 than N2 is. If you think you can separate out N2 from O2 easily, why is CO harder?

Ar is annoyingly close to O2, being ~2C away, not >10C.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #69 on: 02/08/2018 03:50 AM »
Separating N2 from O2 on Earth is relatively easy because you're not interested in absolute purity. CO on the other hand you need to get below a very low percentage not to be poisonous.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #70 on: 02/08/2018 07:19 AM »
Separating N2 from O2 on Earth is relatively easy because you're not interested in absolute purity. CO on the other hand you need to get below a very low percentage not to be poisonous.

It should be possible to remove any impurities catalytic. Oxidize the CO to CO2. As a last step so not much of the O2 is lost.

Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #71 on: 02/08/2018 11:36 AM »
It should be possible to remove any impurities catalytic. Oxidize the CO to CO2. As a last step so not much of the O2 is lost.

Also, for some uses, mixed O2/CO might be fine.
(low-ISP oxidiser)

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #72 on: 02/11/2018 05:45 AM »
Separating N2 from O2 on Earth is relatively easy because you're not interested in absolute purity. CO on the other hand you need to get below a very low percentage not to be poisonous.

It should be possible to remove any impurities catalytic. Oxidize the CO to CO2. As a last step so not much of the O2 is lost.

O2 0.13%
CO 0.08%

If that's by mass then you need 0.57g of O2 to react with every 1g of CO.

So you lose about a third of your oxygen doing that. I think its possible to lose most of the CO through a physical process and then use a chemical process to further purify.

Otoh if electrolysis of CO2 works out to be robust, low maintenance and energy efficient then you wouldn't bother extracting it this way. Instead you'd worry about getting the N2/Ar. Electrlysis is still an unproven in my book. I don't trust the high temps involved. We'll see.

Offline sevenperforce

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #73 on: 02/12/2018 02:30 PM »
What about LOX-only ISRU on Mars?

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #74 on: 02/13/2018 01:17 AM »
What about LOX-only ISRU on Mars?

Given that oxygen is 80% of the mass of propellant, that idea sits comfortably with me. The interesting question for me is whether the proces of electrolysis (cracking CO2) is going to be to be robust and efficient or whether it is better to extract oxygen direct from the atmosphere.

Offline Michael Bloxham

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #75 on: 02/13/2018 07:00 AM »
What about the idea of bringing seed hydrogen for fuel production? That's 180 tonnes of methane + oxygen (enough to refuel the BFS) for every 10 tonnes of Hydrogen, no?

Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #76 on: 02/13/2018 11:01 AM »
What about the idea of bringing seed hydrogen for fuel production? That's 180 tonnes of methane + oxygen (enough to refuel the BFS) for every 10 tonnes of Hydrogen, no?

One major annoyance is that lifting seed hydrogen to Mars is hard in its raw form.
Hydrogen is around a tenth as dense as methane,which means that it's almost always going to be easiest just to bring methane.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #77 on: 02/19/2018 12:53 PM »
I'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more.

Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.

Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.

In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.

Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #78 on: 02/19/2018 01:37 PM »
I'm puzzled by the 180 tonne figure just used for the BFS.

180 tons of methane is about right for the methane capacity of RP1, and about 800 tons of oxygen.

Offline sghill

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #79 on: 02/19/2018 01:49 PM »
I'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more.

Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.

Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.

In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.

I'm sorry, I just don't see or support the argument for importing ammonia or liquid methane to the martian surface. This discussion is a distraction, IMHO.

Yes, you can transport various gases there in stable forms. And if you do, you are taking many trips to the surface all the way from Earth to collect the necessary ingredients to return once.  Until you send up ISRU equipment, you are stuck in this unsustainable and uneconomical paradigm.

The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.
Bring the thunder Elon!

Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #80 on: 02/19/2018 01:57 PM »
The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.

If, and only if, ISRU seems a cheaper, or more reliable way of doing it for a given mission, including development costs.
Methane and oxygen also exist in earths atmosphere, nobody ISRUs, because you can get them in better ways.

(Buy them)

A lot of the posts in this thread are at best theoretical concepts with regrettably few ties to $ and W.

Offline DrRobin

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #81 on: 02/19/2018 03:20 PM »
The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.
If, and only if, ISRU seems a cheaper, or more reliable way of doing it for a given mission, including development costs. Methane and oxygen also exist in earths atmosphere, nobody ISRUs, because you can get them in better ways. (Buy them) A lot of the posts in this thread are at best theoretical concepts with regrettably few ties to $ and W.
Right. Waaaay back at the start of this thread, the OP pointed to a NASA presentation showing the total mass to Mars was much lower for a complete CH4/O2 ISRU system than for Oxygen-only ISRU. Well, sure, but $'s burned in the process may not be optimized in the most mass-efficient choice. I don't think many are arguing against full ISRU as the long-term sustainable path. Still, it may be the case that shipping say, Ammonia, from Earth to give you both Hydrogen and fixed Nitrogen at the outset while efforts to generate Hydrogen locally are ramping up may be the best initial value to get things going. (My own scientific training is in biochemistry, so I can comment with more -that is to say nonzero- authority on these chemistry issues than for most of the other very interesting topics on this board. Nitrogen fixation, for example, is hard.) No one I have seen is suggesting shipping Ammonia from Earth to Mars as a long-term solution. That's what Ceres is for, silly.  :)

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #82 on: 02/23/2018 03:54 AM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #83 on: 02/23/2018 05:53 AM »
As you mentioned BFR, I chose C. Human operated ISRU.

Offline Lar

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #84 on: 02/23/2018 05:53 AM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

Happily that's not the choice, though. B is no more than 3 "Musk years" later than A  (which is by no means happening tomorrow) and so very much more capable.
« Last Edit: 02/23/2018 06:00 AM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online RonM

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #85 on: 02/23/2018 01:58 PM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

We could have done Option A back in the 1990s when it was suggested, but nobody wants to pay for it. Not an option.

SpaceX is working on Option B. Probably will be done within 10 years, if it works at all. This is the only option being funded and it's cheaper.

There is no "If the choice were between" for Mars exploration. SpaceX may not be able to pull it off, but it's the only game in town.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #86 on: 04/01/2018 05:22 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #87 on: 04/01/2018 05:32 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

How so? They go there, get ISRU going and fly home. No option A with hydrogen needed.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #88 on: 04/01/2018 05:34 PM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

We could have done Option A back in the 1990s when it was suggested, but nobody wants to pay for it. Not an option.

SpaceX is working on Option B. Probably will be done within 10 years, if it works at all. This is the only option being funded and it's cheaper.

There is no "If the choice were between" for Mars exploration. SpaceX may not be able to pull it off, but it's the only game in town.

Well I don't agree here. If you want to know what I honestly think. I think that there will probably be small scale scientific/exploratory missions initially. I also think that its quite likely that the US won't be the main actor because of its political/cultural/economic problems.

I also think that when the initial missions occur they will benefit from very much lower launch costs, new technology and from fresh thinking. So mid 2030s is my best guess.

In that kind of time frame, we'll either see other competitors to Musk that go for mostly reusable boosters, or a British/European SSTO space plane (see my other thread).

I remain highly skeptical of large scale/colonisation ideas. Both for reasons of business case and for reasons that go to the dubious motivations behind such plans which I wont go into here.

I'm definitely in the camp of lets do it. But I also maintain that you have to walk before you can run.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #89 on: 04/01/2018 05:46 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

How so? They go there, get ISRU going and fly home. No option A with hydrogen needed.

You pre-land a small quantity of methane and the problem is solved. The whole story line about ISRU derives from the original assumption that its expensive to get mass into low Earth orbit (and thus hideously expensive to get to Mars). Now that its getting a whole lot cheaper to get stuff to low Earth orbit, getting a few tonnes of methane to Mars surface is becoming a trivial problem relative to the overall cost of the mission. Remember that eventually its development costs that really bite and the simpler it is and the more robust and less risky it is, the less development cost and the sooner we get there.

Oxygen ISRU for small scale exploratory missions is a worthwhile goal (because we need to breath too). And since it doesn't require complex operations and maintenance its also suitable for pre-landing.

Offline Slarty1080

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #90 on: 04/01/2018 05:48 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #91 on: 04/01/2018 05:52 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Offline Slarty1080

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #92 on: 04/01/2018 05:55 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Perhaps this issue alone would make it "easier" to make use of hydrated minerals as a source of water and steer away from ice (at least initialy)?
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Offline CuddlyRocket

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #93 on: 04/02/2018 04:22 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #94 on: 04/03/2018 01:23 AM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Perhaps this issue alone would make it "easier" to make use of hydrated minerals as a source of water and steer away from ice (at least initialy)?

The planetary protection issue is one thing that steers me towards harvesting water from the Martian air, rather than soil.
« Last Edit: 04/03/2018 01:25 AM by Russel »

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #95 on: 04/03/2018 01:52 AM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.

My point is that it makes a difference whether your aim is limited exploration or its outright colonisation.

The former can be achieved without mining. The latter probably cannot be achieved without mining and quite probably will venture into richer sources of subsurface water if at all available.

Offline philw1776

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #96 on: 04/13/2018 02:52 PM »
This looks very interesting. One step production of carbon dioxide (CO2) and water (H2O) into ethylene (C2H4) and oxygen (O2).

CO2 + H2O → 0.5C2H4 + 1.5O2

http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b02110

Compare this trying to make methane (CH4):

CO2 + 4H2 → CH4 + 2H2O (Sabatier)
4H2O → 4H2 + 2O2 (electrolysis)

Overall reaction is

CO2 + 2H2O → CH4 + 2O2

That is, making methane requires twice as much water as ethylene as well as having a lower density and Isp compared to ethylene!

Propellants  MR   dp (kg/L)  ve (m/s) Id (Ns/L)
O2/CH4       3.6   0.8376     3656     3062
O2/C2H4      2.7   0.9007     3678     3313


What does "a solar-to-ethylene energy efficiency of 1.5%." mean?
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

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