【Text/Lu Chao】
In recent years, the concept of "Earth-Moon Economic Zone" has been proposed. For a time, many people did not realize it, and they looked forward to the sea of stars with praise, and sarcastically thought that this was "putting satellites" and "great leap forwards". I think it's important to look up at the stars and be down-to-earth. Therefore, we will analyze step by step to see if the "Earth And Moon Economic Zone" is feasible for construction.
If you want to "colonize space", it would be unwise to take various materials out of the earth," and you must consider "in-situ resource utilization" (ISRU). Think from this perspective, the direction and business opportunities will all come.
NASA's 1989 description of the lunar colony
First, water
People cannot survive without water. There is a saying: "In the desert, gold is useless, only water is priceless." "Compared to 70 percent of earth covered by oceans, the moon is a super desert.
We can't always carry a bucket of water moon.
Moon ~~~Walk up~~~
However, there is indeed water on the moon. Probes from the United States, the Soviet Union, India, and China's Chang'e-1 have all found evidence of icy water on the moon. There are many places at the north and south poles of the Moon that are "dark and dark" all year round, and they cannot touch the sun's illumination, which is a "permanent shadow area". Water can only be preserved in these places, otherwise it would have been heated and evaporated by the sun.
In contrast, Antarctica has more moisture. So, near the moon's south pole, it is likely to be the first stop of colonization of the moon.
Go ahead! Towards the south pole of the moon!
The lunar south pole (left) and north pole (right) are distributed in the surface ice, with blue indicating the location of the ice
So, the first business opportunity is a water company on the moon, which works by extracting water from frozen soil.
According to previous sampling, the surface permafrost of the "permanent shadow zone" contains about 5.6±2.9% water, which is also mixed with ammonia, sulfur dioxide, hydrogen sulfide, carbon dioxide, methane, ethylene and other substances, and more hydroxyl (OH) attached to other inorganic substances.
The diagram below shows a "thermal mining" process. A well-designed mirror or lens is used to shine sunlight into the "permanent shadow zone" of the crater, sublimating the ice into water vapor, and placing a lyophilizer on each side to allow the water vapor to condense into water and collect it.
An imaginary thermal mining technique that uses a mirror to shine sunlight into a permanent shadow in a crater, turning the water there into water vapor and extracting it
The next step is purification, this is not difficult, ion exchange resin + reverse osmosis membrane can be done, this can be brought from the earth, can be used for a certain cycle, regular replacement can be.
RO film needs to be brought with several sets (Image: LG chem.)
On the moon, water is not only a necessary condition for human survival, but also has other wonderful uses, which we will slowly look at later.
Second, oxygen
After the problem of water is solved, the second core problem is breathing. We can't always bring oxygen bottles up, that thing is old and heavy.
The moon calls the earth, come a few cans of this thing. Earth: Well, wait a few days. Moon: ~~~~
Now in spacecraft, astronauts' oxygen mainly comes from the electrolysis of water, and there is a method called solid fuel oxygen generator (SFOG), also known as "oxygen candle" - sodium chlorate (NaClO3) and iron powder (Fe) are mixed, and oxygen is produced after ignition, and the reaction formula is as follows:
A kilogram of SFOG can provide an adult with 6.5 hours of oxygen, which obviously does not supply a long colonial career. On the moon, water is an extremely scarce resource, and direct electrolysis of water is a "violent object". Therefore, on the moon, it is really unreliable not to carry out "in-situ resource utilization".
Astronauts examine the SFOG components on the spacecraft
The chemical composition of the lunar surface mainly includes: quartz (silicon dioxide SiO2), alumina (Al2O3), calcium oxide (CaO), iron oxide (Fe2O3), magnesium oxide (MgO), titanium dioxide (TiO2), sodium oxide (Na2O), all of which are oxygen-containing substances. Jomo estimates that about 40-45% of the oxygen in the lunar soil. But to extract the oxygen element in it, it is not a simple thing.
In his article "The Process of Obtaining Oxygen on the Moon", Larry Friesen of the United States mentioned 7 methods of extracting oxygen, all of which require very high energy.
Elemental analysis of lunar soil, oxygen (Oxygen) accounted for 42%
One of the most mature methods is to reduce ilmenite (Fe2TiO5 or FeTiO3) with hydrogen, the reaction formula is as follows:
FeTiO3+H2----> Fe+TiO2+ H2O
The question is, where does hydrogen come from?
Of course, it is still electrolyzed water:
2H2O ----> 2H2+O2
Didn't you just say that water is expensive? Don't be stingy now?
See clearly, this is a "circular economy"! The first step of the reaction has been obtained with water, which can be reused for reuse, and the total reaction formula is as follows:
2FeTiO3----> 2Fe+2TiO2+O2
Ilmenite, iron and titanium resources on the moon are relatively abundant
Ilmenite itself will capture some protons (hydrogen) in the solar wind, and its processing process will also produce hydrogen, a valuable resource on the moon, so the above oxygen production process will net produce some extra water or hydrogen, which is good.
The solar wind will bring some hydrogen and helium resources to the moon
When the "lunar colony" first sees its scale, it can carry some plant seeds past, cultivate green plants indoors, and increase oxygen concentration.
Moon gardener, walk up ~~~
Third, energy
From the first two points, we can see that water or oxygen need energy support. Upfront can carry some nuclear batteries, which can work permanently.
The Curiosity rover uses nuclear batteries
NASA's nuclear batteries are very mature, and have been used very commonly in places such as the Curiosity Mars rover. The main compounds used are plutonium-238, such as plutonium dioxide, which radiates mainly α particles, which can be blocked by a piece of paper, so it is very safe.
The core material of the nuclear battery: plutonium dioxide (PuO2), which glows red due to internal radioactive decay
But in the spirit of "in-situ resource use" (ISRU), priority must also be given to natural energy sources on the moon. Before controlled nuclear fusion developed, the cheapest thing on the moon was, of course, solar energy.
The moon cycles day and night once a month (27-28 days), and if we choose to first "colonize" the site of a certain crater at the south pole of the moon, some prominent places can receive the sun's illumination permanently, and it is ideal to build a solar power station here!
Fantasy Diagram: Build a mirror to reflect sunlight in the perimeter protrusion of the crater, projected onto the permanent shadow area of the crater, or lighting, or hot water, or electricity generation
Carrying solar panels to the moon in large quantities is not realistic, and it is necessary to use materials from the lunar surface. 45% of the lunar soil is silica, according to the current level of human science and technology, it is not difficult to extract the silicon in it continuously. So the third step on the moon is to build a solar cell factory. Over time, building a complete solar array on the moon could provide energy for the entire "lunar colony", and may even be transmitted back to Earth to supply future "Mars colonies".
The risk lies in the impact of micrometeorites, which is a later story.
A hypothetical array of solar cells on the moon
Fourth, architecture
Don't think about building a house. Large-scale real estate is too laborious, and there is a fear of micrometeorites.
Again, the phrase: "Use resources in place"! "Local resource utilization"! "Local resource utilization"! Say the important words three times!
On Earth, we humans have "caved" in the past. On the moon, you may also have to consider going through the "caveman" stage first.
On the moon, there is really such an ideal place - the lunar lava tube.
Imagine: Astronauts are probing lunar lava tubes as their own habitat
Volcanic eruptions have also occurred on the ancient moon. Magma is ejected through the volcano's pipes, and when the surface of the lava flow hardens, the liquid magma inside will rewind, and the pipe may be emptied, forming a hollow void, which is the "Lunar lava tube".
On the moon, which has cooled down today, several lava tubes have been found. Some lava tubes are slender, and some are more spacious. For example, in 2011, NASA's Orbiter lunar reconnaissance orbiter observation of lava tubes in the Marius Hills showed that the lava tube was 36 meters deep but 65 meters wide inside. Later, the American Gravity Probe (GRAIL) discovered the presence of some lava tubes up to 1 km wide on the moon. This provides a huge space for our future "cave dwelling" life on the moon.
Imagine: A rover is placed in a lava tube for detection, and the lander on the lunar surface provides it with communication and other support
After the site selection is over, the building materials will be considered below.
As mentioned earlier, the main components of lunar soil are silicon, aluminum, and calcium, which are ideal concrete materials. As early as 1985, researchers at the University of Pittsburgh in the United States proposed the idea of processing "lunar concrete" with lunar soil. However, water is needed here, and the water resources on the moon are really "golden".
In addition to this, the abundant silica in the lunar soil can be processed into glass fibers, significantly increasing the strength of building materials and reducing weight.
"Moon Concrete" made by American enthusiasts according to the recipe of moon soil
But it should be noted that the gravity of the Moon is very small, only 1/6 of the Earth's, which is good or bad. On Earth, many building materials are shaped by gravity casting, which is not necessarily applicable on the moon. Although we have mastered the technique of pressure casting, not every material is suitable.
As you must have thought, the 3D printing technology developed in recent years has found the best application scenario on the moon.
3D printing with 1.5 tons of simulated lunar dust to prove the feasibility of building a lunar base using lunar soil
Come on, lunar concrete factories and fiberglass factories HR recruit people, manage food and lodging.
Build houses in lava pipes, build infrastructure, and walk up
5. Crops
When it comes to accommodation, it's a big issue. Especially if we Chinese, we have to live together, and we must eat well. Transporting fresh food from Earth to the moon is another chore.
In the spirit of "local resource utilization", are you reminded of the potatoes grown in "The Martian"?
Stills from The Martian
Simulation experiments have been done in the retrieved lunar soil before, and it has been found that tomatoes and wheat may germinate in the lunar soil, which is our hope! Tomato noodles are expected, whether you can add an egg will see if you can build a chicken farm in the future.
Moon Restaurant's designated food - tomato noodle soup
According to the main components of the lunar soil mentioned earlier, you will find that there are so many inorganic minerals that it is simply a dried up salt lake. Carbon, nitrogen, phosphorus and other elements necessary for life are particularly small, so the early farming work will be very limited. If we want to cultivate more diverse crops, we need to replenish carbon and nitrogen.
What to do? It is extremely uneconomical to carry these elements from Earth on a large scale anyway. There is an old saying that goes: "Fertile water does not flow into the fields of outsiders!" "Suffice it to say, astronauts, please leave your poop, this is a valuable treasure of the lunar colony.
In the words of the Wallfacer: "It's part of the plan." ”
Another more effective way is to use bacteria to modify the lunar soil. The most promising here is the cyanobacteria. On Earth, they are almost ubiquitous: not to mention water, soil and living organisms, and they can be found even in harsh environments (such as ice sheets, salt lakes, deserts).
Dropping them on the moon can break down lunar soil, participate in photosynthesis and produce some nitrogen fixation effects, and cyanobacteria may be the "pioneer creatures" leading the "lunar colonization program".
Cyanobacteria
To summarize, let's make a sequence:
Waterworks - Oxygen plants - Solar wafer factories - Building materials factories - Plantations - Restaurants——......
Well, the "Moon Colony" technology tree I have lined up for you, are you already rubbing your hands and want to feel the "construction complete" that you keep hearing.
come on！ Play Red Alert on the moon ~~~
When the above infrastructure is completed, we can only be regarded as standing on the moon, which is only the first step of "lunar colonization". We still have to roll up our sleeves and work hard, there are still many future super projects waiting for us, and we will meet again in the next period.
Resources:
1，《Commercial Lunar Propellant Architecture——A Collaborative Study of Lunar Propellant Production》
2，https://science.howstuffworks.com/oxygen-made-aboard-spacecraft.htm
3，https://www.nasa.gov/feature/goddard/2018/on-second-thought-the-moons-water-may-be-widespread-and-immobile
4，《Composition of the Moon's Crust》
5，《Lunar Science：A Post Apollo View》
6，《Processes for Getting Oxygen on the Moon》
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