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Thanks to billions of years of geothermal activity and biological development, there is an abundance of material to make that life comfortable. We have everything we need to build homes to protect us from the elements.
The first human colonisers on our nearest remotely hospitable neighbours will not be so lucky. The Moon and Mars are not optimised for human life – high levels of radiation, extreme temperatures and meteorite bombardment threaten the survival of the first brave pioneers. They are both rich in useful minerals, however, and are believed to hold water.
Unfortunately, there is an acute lack of heavy equipment. Various projects are developing mining robots and construction tools for off-Earth projects, but, even if they can be successfully built and operated, getting them into space is another challenge entirely. Transporting 0.45kg of materials into space costs roughly $10,000, making it prohibitively expensive to send up fleets of mining and construction machines, or building materials.
To stand a chance of surviving, astronauts will need to use their ingenuity to maximise scarce resources. Colonies will have to reuse and recycle any available material. In The Martian, this was demonstrated by NASA engineer and botanist Mark Watney using his own solid waste to fertilise and grow potatoes, to survive a long stay on the Red Planet.
Urea acts as a plasticiser
A group of researchers believes the same approach could make a vital contribution to future colonisation missions. Teams could build moon bases using surface material, water and another ingredient – urine.
According to the researchers from Norway, Spain, the Netherlands and Italy, the urea in urine could work as a plasticiser, an additive that is incorporated into concrete to soften the initial mixture and make it more pliable before it hardens. Urea allows hydrogen bonds to be broken, reducing the viscosities of aqueous mixtures. The main ingredient for the geopolymer concrete would be regolith, loose material from the Moon’s surface.
To test the idea, the team used a regolith-like material developed by the European Space Agency, along with urea and various other plasticisers. Using a 3D printer, they built cylinders from the ‘mud’.
Surviving freeze-thaw
The experiments, carried out at Østfold University College in Norway, revealed that the samples with urea supported heavy weights and remained almost stable in shape. Their resistance was tested after heating to 80°C, and it was found to increase after eight freeze-thaw cycles like those on the Moon.
“We have not yet investigated how the urea would be extracted from the urine, as we are assessing whether this would really be necessary, because perhaps its other components could also be used to form the geopolymer concrete,” said Østfold researcher Anna-Lena Kjøniksen. “The actual water in the urine could be used for the mixture, together with that which can be obtained on the Moon.”
The work was published in the Journal of Cleaner Production. The team stressed the need for further testing to find the best building materials for Moon bases, which they hope will one day be mass-produced with 3D printers.
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