The much-awaited goal of humanity is the return to the moon. But this time, a permanently inhabited moon base is to be created there, inside which people live and work. According to NASA, the lunar outpost can also be used for future missions to Mars. But how can the construction of the base on the moon be realized and what problems have to be overcome? Let’s find out.
In numerous science fiction stories, mankind will have a permanently inhabited base on the moon in the future where people will live and work. But how realistic is such a lunar colony at all and how can the construction of a base on the moon be carried out technically, taking into account the physical peculiarities of the moon?
Although the moon is incredibly close to the earth from a cosmic point of view, we are still around 384,400 kilometers apart. Besides, the two celestial bodies differ in many respects. The moon has no magnetic field to protect its surface from the dangerous cosmic radiation, its gravity is only about a sixth of the earth and it has no atmosphere.
Earth and moon also differ enormously when it comes to surface temperature and texture. During the day it can get around 100 degrees Celsius on the moon, at night the temperatures drop to minus 180 degrees Celsius.
Besides, the entire lunar surface is covered with debris and dust. These facts alone influence numerous factors that must be taken into account when building a base on the moon. The traditional building construction as we know it from Earth will not work here.
But how can buildings be built on the moon in which people can live and work permanently? The large space organizations and some private companies have developed solutions for building a base on the moon, also tackling the problems that we will find on the moon.
Which Side Should the Base on the Moon be Built on?
There is also a day-night cycle on the moon, but unlike on Earth, it takes around two weeks. Due to its synchronized rotation, the same side of the moon always points to the earth, the so-called dark side is permanently turned away from the earth. When choosing the location, we need to first decide on which side of the moon, the base should be built on.
The side facing the earth offers the advantage of direct communication with the earth, while the dark side of the moon offers a better view of the universe and is, therefore, more suitable for astronomical observations.
The latest probe images show that the dark side of the moon differs from the side facing the earth. On the side facing away from the earth, there are significantly more craters from small meteorite impacts. However, since the lunar base should be exposed to the least possible risk, the side facing the earth would be the better choice for a base on the moon.
Along with that, since the base needs to be supplied with energy, one will opt for solar energy as a power source for practical, but also cost reasons. With this choice of energy source, the pole regions of the moon are best suited as a location because, unlike the equatorial region, these areas are almost permanently illuminated by the sun.
The polar regions, primarily the north pole region of the moon, offer two further important advantages as the location of the moon base: Here, the temperatures are more moderate and only fluctuate by around 60 degrees Celsius between day and night. The most important reason is that there is water on the moon here.
In 2009, NASA had a probe (LCROSS) target the moon with a second probe to analyze the approximately 10,000 tons of dust and rock fragments thrown up with special cameras, 90 seconds later. The result surprised everyone as the moon dust contained 5.6 percent water content in the form of ice. The fact that the ice does not melt and then evaporate is because it is protected under the surface or in the permanent shadow of deep craters.
Projections by the scientists indicate that around 600 billion liters of water ice is stored in the north pole region of the moon alone. Since water is an essential raw material and an immense cost factor for the permanent operation of a lunar station, especially if it always had to be replenished from the earth, the future lunar base will most likely be set up somewhere in the north pole region of the moon. With the right machines and equipment, the vital water can be obtained directly on-site and does not have to be constantly replenished from the earth.
When planning and building a lunar station, as on Earth, various devices and construction machinery are required. However, cranes, excavators, wheel loaders, dump trucks, and bulldozers are not only very large, but they are also very heavy. These machines would have to work on the moon under completely different conditions. The lower gravity is not a problem. It is even an advantage because it only weighs around a sixth of the weight on the machines.
There is also a vacuum on the moon and Oils and lubricants might escape into the vacuum. The question is how to get these huge construction machines onto the moon. The answer is we can’t. There are currently no rockets that would be able to carry such a large and voluminous payload to the moon. So there has to be another solution.
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A 3D Printer Will Print the Moon Base
The ESA is already working on 3D printers that will print the future base on the moon. 3D printers are already able to print entire houses. Although the required printers are also huge, they are still smaller and lighter than conventional construction machines from Earth.
For the 3D printers to work on the moon, we need raw material to print the buildings. Bringing the necessary material from the earth to the moon would be far too expensive and too inefficient. After all, transporting one kilogram of payload to earth orbit costs between $ 20,000 and $ 50,000.
Thanks to the Falcon 9 from the private space company SpaceX, the cost per kilogram of the payload can be reduced to a maximum of $ 2,500, but these costs only describe the transport into earth orbit and the transport to the moon would be significantly more expensive.
The solution to this problem is called lunar regolith. Instead of bringing the essential materials from Earth for the construction of the moon base, we use the raw materials that the moon has to offer. Lunar regolith is nothing more than moon dust but there is more on the moon than sand at the sea.
Moonbase Pressure in Practice
Autonomous rovers collect the moon dust independently and mix it with magnesium oxide. The moon dust can only be printed by adding the oxide of magnesium. A nozzle on the vehicles also applies a layer of binding salt, which turns the lunar regolith in combination with the magnesium oxide into a kind of moon concrete. The magnesium oxide and the salt would have to be brought from the earth. However, these raw materials only make up one percent of the required material – 99 percent of the material is already available on the moon.
Lunar regolith offers another advantage. At 46 to 110 micrometers, it is twice as fine as the sand dust on Earth. This makes the moon concrete around ten times stronger than concrete that we already know from Earth. Also, due to the lower gravity, it only has to carry one-sixth of the load.
The absence of atmosphere on the moon prevents degeneration of the buildings which is another clear advantage in terms of durability and maintenance. However, there are completely new problems with buildings at the base on the moon.
There has to be 1 bar of pressure applied from inside the lunar station. Outside the building, there is zero bar pressure. This means that the pressure load on the building structure acts from the inside out. The problem could just blow away the building from the inside, however, it has a simple solution. The unusual pressure difference on the moon is not a problem since the air-inflated hall is simply covered with the moon concrete and this counteracts the excess pressure with its own weight.
Temperature Fluctuations and Radiation Exposure
As already mentioned, there are extreme temperature fluctuations on the moon. This poses very special challenges for all solid constructions, which must not show any cracks or other signs of fatigue. Another danger is the increased radiation exposure on the moon. Measurements have shown that people who only live on the moon for one month are exposed to a radiation dose that corresponds to that of an entire human life on earth.
To adequately protect the inhabitants of the future moon base, the printed outer wall thickness of the buildings would have to be at least 2.5 meters thick. This enormous thickness also makes sense for another reason. The analysis of 14,000 photos of the lunar surface has shown that our moon is hit by around 180 meteorites annually.
Some of them are as large as refrigerators and tear up craters of up to 43 meters into the surface of the moon. But even smaller meteorites, which we know from the Earth as falling stars, can be a great danger on the moon because the moon has no atmosphere in which, small meteorites that can travel up to 500 kilometers per second, can burn up.
Move the Moon Base Below the Surface
To increase protection for the lunar colony, part of the lunar base could be shifted below the surface. However, the problem is that it is not possible to print the building underground without heavy construction machinery. But there is also a solution to this problem on the moon.
Caves used to be a preferred place to live because they protected us from wind, weather, and other dangers. There are also such protective caves on the moon, which can be found in the lava landscapes of the moon, which are over 100 million years old and have cooled down. These lava caves occur in numerous places on the moon. The largest known lunar caves are several kilometers long and some have a ceiling up to 200 meters thick, which also offers protection against larger meteorite impacts.
As luck would have it, in January 2018 NASA also discovered an open cave entrance on the moon in the preferred north pole region for a lunar base. The lighting conditions are ideal here, sufficient ice is believed to be in the immediate vicinity and the cave seems to offer more than adequate protection.
How Much Space Should a Moon Station Offer?
One of the last questions about the lunar station concerns the size of the base. Of course, this depends on the number of people who are supposed to live and work here and thus indirectly also on the greenhouses needed to produce food and oxygen.
The number of laboratories also determines the ultimate size of the moon base, which ideally has a modular structure and can, therefore, be expanded at any time. But what about life on the moon? What requirements do people make of their living space outside of the earth? How much space does it need and what social needs must base on the moon be able to meet?
Several long-term experiments have already been carried out on Earth. Here scientists have investigated the longer coexistence of people in a confined space. The experiments were carried out in absolute isolation either in desert regions or in the Antarctic.
These results are elementary for the planning of a lunar station but also for manned flights to Mars. NASA concluded that everyone needs a personal retreat. In the smallest case, this should be 20 cubic meters. This results in a footprint of approximately four by two meters. For this purpose, NASA has defined the so-called Man-System Integration Standard.
When do we Start the Construction of the Base on the Moon?
Even if theoretically all problems can be solved, a lot has to be done before the construction of the base on the moon begins. So the building site must be viewed and studied on site. Solutions have to be found for many smaller technical problems and above all the financial means are needed.
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Because one thing is clear, a moon base is much more complicated and expensive than a space station. And even if we fix the schedule, a technical unforeseen problem is enough to overwhelm the entire schedule. Mankind will have a permanent base on the moon in the future, only when is still unknown.