Astronaut pee could help build 3D-printed moon bases
Scientists are exploring the potential of using the urine of astronauts to help build some of the first moon bases. By using resources harvested from the Moon, with a little help from astronauts too, it is hoped that lunar settlers will be able to cut down on the prohibitive cost of transporting construction materials from Earth.
Its presence has been woven into the fabric of our society. It has had a transformative effect on our understanding of the cosmos and our place in it, and has been woven into the fabric of our culture, featuring in great works of poetry and art.
Every human being that has ever lived has gazed upon the surface of the Moon. We finally gained the technological prowess (and will) to venture to that surface in 1969 with the Apollo 11 mission, and the following years saw five further crewed missions touch down, but none stayed for so much as a week.
Decades later humanity is finally looking to create semi-permanent habitats on the lunar surface, and classy race that we are, they may just be built with the help of astronaut pee – or more specifically, the urea it contains.
But why? The answer is rooted in the massive cost and logistical effort that is expended getting materials into space. It can costs roughly US$10,000 to transport just 0.45 kg (1 lb) to orbit from the Earth’s surface, and so, as you can imagine, simply shipping all of the building equipment and construction materials to the Moon is out of the question.
Scientists are therefore exploring the potential of using resources already present on the lunar surface to create the habitats.
Numerous studies have already begun to explore whether concrete-like structures could be 3D printed from lunar soil – also known as regolith – using a robotic workforce.
Such a shelter would help protect explorers from the vacuum of space, alongside the high levels of radiation, extreme temperature fluctuations, and micrometeorite strikes that scour the lunar surface.
Now, fresh research undertaken by an international team of scientists has looked into whether another resource – human urine – could be used to make lunar building materials more workable.
The team examined whether the urea present in urine could be used as a plasticizer in a 3D printing mixture suitable for use on the lunar surface. A plasticizer is essentially an additive that can be included in a concrete mixture to soften it, and make it easier to work with before it hardens.
Urea allows hydrogen bonds to break, lowering the viscosity of a mixture to which it is applied.
As part of the study, the researchers 3D printed a series of "mud" tubes from mixtures that included a lunar regolith-like material created by the European Space Agency to which urea and other plasticizers were added.
It was discovered that, as well as being exceptionally unattractive, tubes printed using urea as a plasticizer were able to bear heavy loads, and largely retained their stability. After being heated to 80 °C (176 °F) the tube’s resistance was tested, and was found to improve after enduring eight freeze-thaw cycles similar to temperature variations that would be experienced on the lunar surface.
“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,” comments one of the study authors professor Anna-Lena Kjøniksen of the Østfold University College’s Faculty of Engineering in Norway.
“The actual water in the urine could be used for the mixture, together with that which can be obtained on the Moon, or a combination of both.”
The researchers stress that further study is needed to discover the ideal material from which to construct the first lunar habitats.
The paper has been published in the Journal of Cleaner Production.