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Extraction Method for Frozen Lunar Water Ice

Posted by: sanman - Mon Mar 08, 2010 3:51 am
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Extraction Method for Frozen Lunar Water Ice 
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Space Walker
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Post Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 3:51 am
You want to think about technology you can patent? Come up with a way to extract frozen water ice in the shadowed craters on the Moon, which are at temperatures approaching absolute zero.

Given that this frozen water could very well be the most precious commodity on the entire lunar surface, then people would pay an arm and a leg for a convenient way to extract and harvest it.

How do you grab ice that may be frozen at some ridiculously low temperature, in an area also at the same low temperature?

Microwave cutting? Simple hot knife?
How to grab any pieces you've chopped free?
What kind of apparatus would you use?

There's no way to suction anything in a hard vacuum. Is it better to pound on the ice and create ice chips, to then scoop them up like gravel? Ahh, now here's a better patent application for a jackhammer.

What is the best way to grab this stuff and handle it, especially if you're doing it at the bottom of a deep cavity?

Should there be an X-Prize competition for this?

He who controls the lunar water, controls the Moon.


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 8:52 am
good call, but also good luck... we don't even know what the deposits are like, what they look like, how thick they are, how concentrated they are, etc. i think this will have to wait till a rover/lander gets down in there somehow and takes pictures. otherwise, any patent would be purely speculative and quite probably useless.

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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 2:15 pm
instead of waiting, why not take a pre-emptive step?
isn't google funding a prize for a lunar rover? why not a Lunar Prospector Prize? for the first to accurately determine how the water is locked away in the polar regions. from there, you can go into the extraction/recovery projects/prizes. you could even go so far as to combine them into a single prize with multiple payoffs.

of course there are many hurdles to even the first part of this, besides the obvious "how to get it there". Once it's there, what do you use to power it with? Solar is likely not an option, unless you are collecting it in an orbiting constellation and beaming it via microwave down to the prospector. (they could even double as comm relays too :) )

why not turn the extraction/recovery part into a high school competition project, much like First Robotics? you want to bolster and excite the students into ScienceTechnologyEngineeringMathematics programs, engage them in a project like this.

lol, its a monday, and i'm rambling on again. Sanman, you got the gears turning, and now they won't stop :)


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 3:00 pm
LoL, great ideas, MFL :)

So even with just a single competition, you can set multiple goals to achieve
- navigation of rover to target area
- identification of target material
- acquisition/extraction of target material
- analysis of target material

A rover competition is much more suitable for mass-participation than a lander competition. Not everyone has the expertise for rocket engines, nor the safety infrastructure. But ground-based rover tech with some kind of mining/digging and analytical capability would be much more within the realm of ordinary people.

There are plenty of people who have practical industrial/trade experience and understanding around issues of digging, extraction and processing of materials like dirt, water and ice.
This would be the kind of challenge that even garage tinkerers and workshops could pursue.

With that kind of broad-based competition, you'd be sure to get a wider variety of participants and ideas - which is exactly what such competitions need.


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 4:46 pm
Crazy Idea Time:
Stretch a transparent covering over a small polar crater. It doesn't need to be perfectly sealed. Use a few orbiting space mirrors to warm up the regolith in the crater. Use vacuum pumps to collect the H2O gas that builds up inside the "tent". Mining and distillation all in one process.

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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 5:08 pm
thinking about that... its not as crazy at your title suggests.
would be fairly easy to set up, and if microwave emmitters were used instead of solar mirrors, it may simplify things further (in some ways).
at that temperature and pressure, does anyone know how much energy it would take to get the water to sublimate out of the ice?


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 6:23 pm
I'd suggest treating the ice like any conventional semi-crystalline solid mined from the ground. Just jackhammer it into gravel/chips, then scoop up the pieces and dump to them into a sealable chamber. Then you can heat up the stuff to distill/fractionate it, etc.

So if this activity is happening at the bottom of a crater, you would then pump up(pressure feed?) your distilled/fractionated vapor product via a hose to some larger tanker vehicle situated up top near the crater rim. The tanker could be equipped with solar panels to gather solar power to send down to the extractor along a power line that runs along the same hose.


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 7:15 pm
MFL wrote:
thinking about that... its not as crazy at your title suggests.
would be fairly easy to set up, and if microwave emmitters were used instead of solar mirrors, it may simplify things further (in some ways).
at that temperature and pressure, does anyone know how much energy it would take to get the water to sublimate out of the ice?


It's hard to say exactly. Each time a water molecule sublimates, it will cool the remaining regolith because of the latent heat of fusion and evaporation. According to this phase diagram (http://en.wikipedia.org/wiki/Water_(data_page)#Phase_diagram) ice will sublimate at about 190K in a vacuum. Ignoring everything else, and just taking the latent heat capacities and specific heat capacity, warming the regolith from 30K to 190K and getting 1kg of water vapour would require (160{1}*2.05{2})+334{3}+2260{4}kJ = 2922KJ

{1} Delta temperature
{2} Specific Heat Capacity
{3} Latent Heat Capacity of Fusion
{4} Latent Heat Capacity Of Evaporation

It sounds good, but remember that you'd have to warm up all the regolith along with the volatiles so that will add to the real energy costs. And the H2O wouldn't start to sublimate until the regolith hits 190K. Maybe an IR reflective layer could be used with the transparent cover, that would work to insulate against heat losses while letting the visible light through. I'm against using microwave sats btw, there's too much that can go wrong with them and a thin mylar sheet will do as a visible light reflector instead of using bulky solar panels.

A caveat to my original post is that this wouldn't exactly give you pure distilled water, since all volatiles in the regolith would sublimate at some rate. However they could easily be separated in a fractioning tower before final collection, and would all be useful resources to a colony on the moon.

johno


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 8:04 pm
What I don't understand is how you manage to prevent the vaporized materials from leaking away after you heat them. To me, this requires heating inside a sealed chamber. I don't see how you can heat stuff under an open dome/tent/funnel/catch and hope to capture a significant amount of vapor without losing most of it to the lunar vacuum. To me, that imposes a batch process rather than a continuous process.

Could electromagnetic fields be used usefully here? I'm thinking of magnetohydrodynamics (eg. Hunt for the Red October), whereby a strong magnetic field generated by superconductive magnets would corral the water vapor and direct it somewhere for capture.

Alternatively, isn't there something called a "plasma valve" whereby an ionized gas/plasma can be used as a barrier against other gases? I've heard devices like these were created for the Large Hadron Collider.


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 8:24 pm
sanman wrote:
What I don't understand is how you manage to prevent the vaporized materials from leaking away after you heat them. To me, this requires heating inside a sealed chamber. I don't see how you can heat stuff under an open dome/tent/funnel/catch and hope to capture a significant amount of vapor without losing most of it to the lunar vacuum. To me, that imposes a batch process rather than a continuous process.


Yeah, fair enough, I admit that's a major flaw in this idea. What I was thinking is you drape a large sheet of polymer material over the crater, and use a lunardozer to pile regolith onto it all around the edges. It wouldn't give a perfect seal but I don't expect the internal pressure to ever get above a few mmHg pressure. Possibly enough to cause the tent to dome slightly but definitely not enough to cause it to lift off the crater. You'd probably have to build a tunnel with an airlock into the wall of the crater before doing that to allow access, and possibly for the vacuum pump machinery.

I know it's far from perfect, but I spent a total of about 1 minute thinking of it before my original post. :)

johno


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 8:57 pm
sanman wrote:
I'd suggest treating the ice like any conventional semi-crystalline solid mined from the ground. Just jackhammer it into gravel/chips, then scoop up the pieces and dump to them into a sealable chamber. Then you can heat up the stuff to distill/fractionate it, etc.


That route is certainly what most researchers are considering at the moment. One possible problem they are encountering is how to deal with the volatile nature of the materials they will be handling. Drilling, hammering and especially exploding, will all cause the material being worked on to heat up. This can cause premature sublimation and loss of the material you are trying to collect. It's impossible to eliminate all sources of heating completely, but letting too much happen could mean you end up dropping some dessicated gravel into your cooker.

johno


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Mon Mar 08, 2010 10:37 pm
What about blasting?

Suppose your lunar ice really is a giant sheet just a few meters thick spread across a wide area. You drill a hole in the middle of the sheet and into the ground beneath it, where you implant an explosive charge. You set off the explosive, and hopefully the vibrational shockwave would pry loose large sections of the sheet from the floor underneath.

What other physics can be exploited to make dissimilar layers break apart from each other? Ultrasonic vibration into the sheet and the ground?


There must be some kind of subterranean doppler radar that could sense underground liquid water, which would be the ideal source. Or what about terahertz radiation or even magnetic resonance, for near-surface scanning?

One of the things here is that this bulk ice is likely going to be distributed horizontally rather than vertically, since it's condensing across an ultra-cold surface area - unless you've got a cold crevasse that's accumulated ice in it from the bottom up.


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Post Re: Extraction Method for Frozen Lunar Water Ice   Posted on: Tue Mar 09, 2010 4:43 pm
here's a "simple" idea, lol

drill down diaganally under the 'ice pack' eventually leveling off under the desired location. now, assuming that you are not very deep down, insert an inflatable device under the ice pack and slowly inflate, the goal being to lift and break up a small area of the pack without the use of explosive force and without introducing too much heat to the pack. think of how a tree root breaks up a sidewalk, but faster, lol.

alternatively, cut out the sides of the first block, and use a similiar method to lift out the block, then use that pit to continue excavation.

makes me wonder though.... what would happen if heat were added from the underside of the ice pack? using the top layers as a cap to prevent sublimation loss, and having a small channel/pipe with which to draw any 'runoff'.


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