In Robert Zubrin's "The Case for Mars" he outlines a plan to settle Mars by(among other things) finding water and using electrolysis to break up water into Hydrogen and Oxygen. This provides fuel for vehicles and air for the crew to breathe. Can a similar plan work to settle the moon? Are there enough resources on the moon for a settlement to be self-sufficent? Is there enough water on the moon for this to be viable?
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3$\begingroup$ Probably a better question at Space Exploration, but this does concern planetary science (analysis of Moon water) which is on topic here. $\endgroup$– called2voyage ♦Commented Oct 1, 2013 at 20:02
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$\begingroup$ I think it comes down to if the lunar axial tilt is stable. If not, then volatiles in the polar craters may not have had long time to accumulate. Here's a short recent talk by Dr. Paul D. Spudis about Lunar ISRU: youtube.com/… $\endgroup$– LocalFluffCommented Jun 8, 2014 at 16:06
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$\begingroup$ At 18:50 in the video I linked to above, Dr. Spudis says that the estimated quantity of water ice in lunar polar craters is 600 million metric tons. Enough to fuel a space shuttle launch (from Earth) every day for 2200 years. $\endgroup$– LocalFluffCommented Jun 8, 2014 at 16:32
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2 Answers
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Self-sufficiency is an incredibly broad term. We could argue that yes, there is water on the Moon, and that yes, there are viable ways to produce required electricity in self-sustainable ways, but the real question is, are there areas on the Moon that would be viable for both at the same time.
You see, the most likely place where surface or near subsurface water could exist on the Moon and be suitable for mass extraction are its polar, permanently dark regions. Indeed, the ISRO (Indian Space Research Organisation) Chandrayaan-1 spacecraft has detected evidence for water locked in surface lunar regolith minerals in lunar south polar region, water that likely originates from asteroid and comet impacts embedding it deep within the lunar core and released as magmatic water closer to the surface. Any free-form water in other regions of the Moon that are exposed to sunlight and Solar radiation would sublimate to its gas form directly and with ionisation lose hydrogen atoms, so while hydrogen and oxygen atoms might still be present to some extent embedded into the surface layer minerals, extraction would likely be too elaborate there.
But, wherever you'd find your water source, you would still require a great deal of electricity to power your extraction plant, later use electrolysis to separate molecular water into its constituent atoms, and compress it in cryogenic conditions to their diatomic liquids that are suitable as propellant components, diatomic liquid oxygen (or LOX) as your oxidizer, and double as much in molecular quantity of diatomic liquid hydrogen (or LH2) as your rocket fuel. Problem with electricity is, unless you brought your own and a great deal of it on you to power your plants, you will likely want to use be it solar power, or tap into the in lunar regolith embedded helium-3 (or 3He) and power your third-generation Helium-3 fusion reactor. See for example this answer of mine on Space Exploration on how that could be done.
So the main conundrum to exploiting Lunar resources, for the time being, remains finding sufficient and viably mineable resources of water where there is also self-sustainable ways of generating required electricity. One option that I can think of is staying on the most exposed to the Sun lunar equator and extracting deuterium and tritium hydrogen isotopes, as well as helium-3 from lunar regolith, all of them embedded there from Coronal Mass Ejections (CME). Required oxygen could be produced by crushing oxidized minerals and letting them sweat with the presence of hydrogen isotopes into ionized water, and helium-3 could be used as previously mentioned to sustain a fusion reaction producing required electricity to later break water molecules into its constituent atoms of hydrogen and oxygen by electrolysis.
How much of these hydrogen and helium isotopes are actually embedded in the lunar regolith, and how long these deposits persist in it, possibly staying there for at least some time due to the static charge of the regolith as it is bombarded by the Solar radiation, this is however a whole different question and one we can't currently yet answer. The study of the Lunar exosphere and dust environment is the sole purpose of the LADEE (Lunar Atmosphere and Dust Environment Explorer), that we barely just launched there. We will know in roughly one year, if it will be able to provide conclusive scientific evidence for these theories I've just mentioned.
answered Oct 1, 2013 at 22:05
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$\begingroup$ The energy problem is smaller at the poles than at the equator which suffers from 14 days of darkness. At the lunar poles, crater ridges with near constant insolation are situated next to permanently shaded crater bottoms with water ice. Solar panels could power robots in the crater below them by cable or maybe microwaves. Mining operations consists of only heating the ground and collecting the volatiles as they sublimate. $\endgroup$ Commented Jun 8, 2014 at 13:08
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$\begingroup$ @LocalFluff The Moon does have a slight axial tilt too, so those regions of permanent sunlight would be rare and far between. IIRC only a handful of peaks at the lunar North pole around a single crater qualify, and none at the South pole as far as we know. So yes, what you say is possible, assuming that single larger crater holds sufficient water ice reserves. You'd be dealing with huge temperature differential though, and require several relay satellites in lunar polar orbit, if comms with the Earth are needed. All this might be a lot simpler to do at lunar equator IMO. But post a new answer. $\endgroup$ Commented Jun 8, 2014 at 14:15
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$\begingroup$ Ah yes, here it is; a bit more detailed info on that in Wikipedia article on the Moon: Seasons. It mentions ... four mountainous regions on the rim of Peary crater at the Moon's north pole. $\endgroup$ Commented Jun 8, 2014 at 14:23
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$\begingroup$ The map linked to below shows the insolation time on the lunar south pole. The brightest crater rims represent over 95% insolation time. That means less than 36 hours a month in hibernation or on stored power (such as fuel cells using local resources). apod.nasa.gov/apod/ap110423.html Same with line of sight communication with Earth, no lunar comm sat needed. Ground temperature is lower at the poles because of the angle to the Sun, and more stable where insolation is almost constant. The optimal areas and resources are large compared to forseeable rocket launch capability. $\endgroup$ Commented Jun 8, 2014 at 15:29
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1$\begingroup$ @LocalFluff OK, no need to convince me of an alternative possible answer. I wrote mine based on information that I had and what seemed to make the most sense to me. You seem to have different information and ideas about feasibility, so please write another answer. The more, the merrier. I'm not married to what option I suggested here. ;) $\endgroup$ Commented Jun 8, 2014 at 15:54
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Additionally, Mars has a much more substantial atmosphere composed of ~95% CO2 (which is one of the major points Zubrin makes), whereas the atmosphere of the moon pales in comparison. Why is this important? Combined with the supply of Hydrogen which would be brought along, you could combine the CO2 with H2 to produce methane (CH4) which can be used as rocket fuel; water can also be produced. See the Sabatier reaction.
Page 60 in "The case for mars" also talks about the merits and drawbacks of CH4/O2 and CO/O2 propellant systems, the former is really the better alternative if hydrogen were available. Also, when talking about settlements, exploration is a crucial function. Fuel for vehicles can also be supplied through the use of the Martian atmospheric CO2.
