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So SpaceX and the like are well underway to colonizing the Moon, but they've hit a snag. The colonists, of course, need water--and lots of it, for drinking, preparing food, growing plants, breathing, and other important stuff. Originally, the plan was to "mine" the lunar regolith, which contains a small amount of liquid water which could be extracted.
Unfortunately, the International Court of Justice recently ruled that the Outer Space Treaty prevents the mining of the Moon, which means that the lunar colonists must now find another way to obtain water. (Assume that the legal ruling cannot be overturned in any way, I'm more interested in the scientific possibilities.)

Criteria:

  • The method of delivery should be both "reliable" and regular--it shouldn't only work half the times it's expected to, and the colonists should be able to expect when it comes so they don't get stranded without water.
  • The method of delivery should be scientifically plausible within more or less the limits of cutting-edge technology, with reasonable extrapolations. This is in the near-future, so physics as we know it has not been massively overturned, and the rocket equation is tyrannical as ever. Assume that the cost of sending 1 kilogram of payload to the Moon is approximately 2500 USD.
  • The method of delivery should be scalable to large populations (>10,000 people). As the colony grows, they don't want to have to keep changing their water supply methods, and would much rather pick one method and stick with it.
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    $\begingroup$ This is waaaay too broad and opinion based. There are entire papers written on how we should do something like this, and even now nobody knows which of the possible options are the best/most feasible since realistically, if you're talking "near future", a slightly plausible method hasn't been found yet. $\endgroup$ – Aify Feb 20 '18 at 7:20
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    $\begingroup$ Requirements make little sense. Water will be in a closed loop, so you need only one delivery to bootstrap colony, and then little amounts to make up for the loses. $\endgroup$ – Mołot Feb 20 '18 at 7:46
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    $\begingroup$ No, the Outer Space Treaty does not prevent mining of the Moon. On the contrary, in Article I: "Outer space, including the moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies.". So unless the Outer Space Treaty has been re-written (for plot purposes) in your fictional future, your premise does not fly. $\endgroup$ – MichaelK Feb 20 '18 at 7:49
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    $\begingroup$ Your question is worded like the colonists are already on the moon and they were blindsided by this surprise legislation. Is this a emergency situation, or do the participants have time to think about it? $\endgroup$ – Muuski Feb 20 '18 at 15:12
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    $\begingroup$ If the space treaty prevents mining on the moon, then what is the reason for being there? Tourism? You just made it into a protected ecological park - 'Take nothing but pictures, leave nothing but footprints'. $\endgroup$ – Justin Thyme Feb 20 '18 at 18:24
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As noted, there is lots of water both in the Moon and in objects in the Solar System.

In the very short term, the colony can be placed on the Lunar South Pole. Exploration by remote spacecraft dating back to Clementine in the 1990's confirmed the existence of ice in the South Pole, and by analogy, there should also be ice in the shadowed craters on the North Pole as well. The primary disadvantage of the scheme is the amount of deltaV needed to reach the polar sites, and the availability of solar energy (requiring tall towers, mirrors or beaming energy from a power satellite at the L1 or L2 points.

enter image description here

NASA's Moon Mineralogy Mapper, an instrument on the Indian Space Research Organization's Chandrayaan-1 mission, took this image of Earth's moon. Blue shows the signature of water, green shows the brightness of the surface as measured by reflected infrared radiation from the sun and red shows an iron-bearing mineral called pyroxene

It is also possible to extract water directly from mineral grains in lunar regolith. Reexamination of Apollo samples revealed that water molecules are trapped in the crystal matrix of various types of lunar rock, and this can be extracted as a byproduct of mining operations.

Finally, in the long term, ice can be delivered directly to the moon from sources in deep space, extracted from asteroids, comets or the icy moons of the Gas Giant planets.

Perhaps more speculatively, the nebula which the Earth and Moon formed from had a great deal more water than the current Earth and Moon seem to have. A controversial theory suggests that many oceans worth of water might be trapped in the minerals deep in the Earth's mantle, and it may be possible that a similar situation occurred during the Moon's formation as well. If true, then some colossal drilling rigs capable of reaching into the Lunar mantle and then supporting a process similar to fracking might free that trapped water for colonies on the surface.

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Assuming we already have the kind of vessels that can move that many colonists and thier supplies around Its not a stretch to begin capturing ice-water comets and placing them in orbit around the moon. You can cut them up with automated robotic landers that ferry couple hundred kilo chunks of ice from orbit to the lunar surface. You have hundreds such drones making atleast one trip per day. If each chunk of ice was 300 kilograms thats about 100 gallons of water. You could be supplying 10,000 colonists per day with 3 gallons of water each with 100 landers making one trip per day. Frankly you could use only 10 300kg ice landers and just make more trips over a long time period to build up a good stockpile prior to habitation.

In addition to this you have strict water rationing and recycling procedures in place. Obviously no system is 100% efficient but once the initial stockpile of water is in place you only need to monitor your loss rates and replace them requiring fewer ice-cracking drones making fewer trips.

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    $\begingroup$ 3 gallons water is insufficient for a human's needs. In addition to drinking, there's hygienic needs, and then there's water used for irrigation and industry. Your theory is sound, (at least, I remember reading something like that in SF books,) but it would need significantly more water for the same number of colonists. $\endgroup$ – Galastel supports GoFundMonica Feb 20 '18 at 17:38
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    $\begingroup$ @Galastel Are you suggesting that the colonists should just vent all used water into space instead of recovering any of it? Any sane system would be as closed a loop as possible - there should be minimal losses. $\endgroup$ – pluckedkiwi Feb 20 '18 at 19:04
  • $\begingroup$ @pluckedkiwi Absolutely true - the system should be as closed as possible. Sewage water should be recovered and is recoverable (Israel recovers 90% of sewage, to be used in irrigation, for example). However water still evaporates - from plants, from irrigated earth, from colonists as sweat. And some water gets too contaminated to be safely used as drinking water. With the moon's reduced gravity, some of the evaporated water would get lost into space. I guess domes or some such could reduce that. But I was talking about how much water must be made available per person, from whatever source. $\endgroup$ – Galastel supports GoFundMonica Feb 20 '18 at 19:22
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    $\begingroup$ @Galastel Then the only input of water is equivalent to what is non-recoverable - if that exceeds 3 gallons per person per day, the colony must be in a non-survivable state regardless. If there is any significant loss of water vapor to the outside, the loss of breathable air will be dramatically greater and of more immediate concern. Nothing should render water beyond recovery aside form some highly-toxic industrial production, and such industry would never be implemented in water-constrained habitats. $\endgroup$ – pluckedkiwi Feb 20 '18 at 20:09
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    $\begingroup$ 3 gallons is perfectly sufficient for survival. You dont need nearly that much to survive. As for hygene, sorry, no 45 minute showers in space. Plus thats a PER DAY delivery capacity. With recycling measures in place youd quickly stockpile a surplus. $\endgroup$ – TCAT117 Feb 21 '18 at 5:14
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If you are proposing for the purpose of a story that the courts have overturned the part of the treaty that says:

"...the moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind..."

I propose mining the Moon for water.

It is simple. You are there and they are not. How are they going to stop you?

Think about Robert Heinlein's The Moon is a Harsh Mistress.

Also, there is likely ice sitting on the ground in some polar craters; no mining involved.


Alternatively....

It sounds like you want the world government to stealth close the ability to colonize space. There are easier ways to do that.

Until recently it was nearly impossible for anyone but one of the big launch companies to get a launch license. I was there for the fight to make launch licenses available to anyone with a viable rocket and launch plan. It wouldn't be too hard to reverse that decision by throwing red tape at anyone who wants to launch "the wrong things."

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There is plenty of ice in the solar system. The problem is how to get it, but assuming the extrapolation of current technology to the point where colonizing the Moon is a feasible proposition, I would expect that it would be quite feasible to send a (probably) unmanned spacecraft off to get some from beyond the asteroid belt. This should be a relatively cheap (compared with taking it from Earth) regular supply and completely scalable.

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Any comets placed in orbit anywhere near earth will evaporate quickly (on a geological timescale).

Furthermore, there is no need to bring water to the moon as it's already estimated to be there.

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

Chandrayaan-1 had discovered more than 40 permanently darkened craters near the Moon's north pole that are hypothesized to contain an estimated 600 million metric tonnes (1.3 trillion pounds) of water-ice

Specifically at the south pole:

NASA re-confirmed water on moon with its LCROSS space probe which detected a significant amount of hydroxyl group in the material thrown up from a south polar crater by an impactor;[10] this may be attributed to water-bearing materials[11] – what appears to be "near pure crystalline water-ice".

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You actually don't have to mine to moon to get at the ice. It's on the surface near the poles.

https://www.nasa.gov/mission_pages/Mini-RF/multimedia/feature_ice_like_deposits.html

NASA's Mini-SAR instrument, a lightweight, synthetic aperture radar, found more than 40 small craters with water ice. The craters range in size from 1 to 9 miles (2 to15 km) in diameter. Although the total amount of ice depends on its thickness in each crater, it's estimated there could be at least 1.3 trillion pounds (600 million metric tons) of water ice.

ice map

There is no need to mine it...it's at the surface, just go get it.

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Make water on site using oxygen from regolith.

There is plenty of oxygen in the lunar regolith.

https://en.wikipedia.org/wiki/Regolith#Moon enter image description here

I assume also you will have loads of power from solar panels as well.

Send up hydrogen as liquid hydrogen. Water is H2O and the mass of the hydrogen in a molecule of water is 11% of the mass of the water molecule. Given that the energy of moving mass is the main consideration for getting things to the moon, you can get 9 times the water for the same energy by using local oxygen extracted from regolith.

Probably you will use solar power to electrolytically refine aluminum oxide in regolith into aluminum metal to build things. Oxygen is a waste product. Capture it with the hydrogen you have brought up to produce water.

If this scheme could work Feasibility of Capturing Hydrogen from the Solar wind maybe you could capture hydrogen from the solar wind instead of importing it from earth. The moon colonists might need some sort of umbrella anyway and it could serve double duty.

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