Researchers have developed a method that could one day be used to build roads on the moon.
The novel approach, described in a proof-of-concept study published in the journal Scientific Reports, would involve melting lunar soil with focused sunlight to turn it into a more solid substance. This could be used to create paving for roads and other infrastructure like landing pads.
In experiments conducted on Earth, a team of scientists demonstrated the viability of the technique using lasers—instead of concentrated sunlight—to melt a lunar soil substitute. Their findings indicate that the technique could be replicated on the lunar surface, although several challenges remain to be overcome.
The latest study comes in an era when NASA is aiming to establish a long-term presence on the moon as part of its Artemis program, while the space agencies of Russia and China are also planning to develop their own lunar base.
Being able to construct paved roads and landing pads on the moon will be an important component of planned lunar settlements in order to mitigate issues encountered by previous missions. Low levels of gravity at the lunar surface can result in dust floating around when disturbed by exploration vehicles, which can potentially damage equipment.
“The spreading of lunar dust when moving a vehicle on the lunar surface is a major concern for lunar exploration,” Juan Carlos Ginés Palomares, an author of the study with the Faculty of Mechanical Engineering and Materials Science at Aalen University in Germany, told Newsweek.
“Apollo astronauts reported that the dust stuck to their suits and covered all the instruments due to their surface adhesion. In addition, the sharp edges of the dust particles are a risk to the exploration equipment,” he said. “Manufacturing roads is a way to avoid the formation of dust clouds while facilitating the movement of vehicles and rovers.”
In the study, Ginés Palomares and colleagues conducted experiments that involved manufacturing tiles by heating and melting the moon dust substitute. These tiles were then allowed to cool, producing a robust, consolidated piece with an interlocking design that measured around 25 millimeters (one inch) in thickness. Such tiles could be placed alongside each other to cover a wide area of lunar soil, according to the researchers.
Some previous studies have explored the use of solar concentrators or lasers to fabricate parts with lunar materials, but parts of this size have never been fabricated before, according to the researchers.
In the experiments, the scientists used high-powered carbon dioxide (CO2) laser beams to heat the dust substitute, replicating the effects of concentrated sunlight. The spot of the beam had a maximum diameter of 100 millimeters (4 inches) and 12 kilowatts of maximum power, which has never been used before in previous studies.
To reproduce this approach on the moon, the scientists propose the use of a special type of lens measuring over 7 feet across that would focus sunlight like a magnifying glass.
This lens would enable the manufacture of tiles using only sunlight and lunar soil. Such a solution would be simple and low weight—a significant advantage given that transporting construction materials from Earth is costly and logistically challenging.
“This process has some outstanding advantages over other suggested manufacturing methods on the moon,” Ginés Palomares said. “The first is the use of virtually inexhaustible materials and energies: sunlight and moon dust. We consider that paving can be created sustainably with this technique.”
Another advantage is the simplicity of the design and low weight of the required equipment compared to other ideas that have been proposed for the heating of moon dust, such as using microwave or electric ovens.
“This equipment could be easily transported to the moon in a space rocket,” Ginés Palomares said.
Kevin Farries, a structural engineer at the University of Adelaide in Australia, who was not involved in the study but has undertaken similar research, told Newsweek that the latest paper was a “significant” addition to the field.
“The method is very promising, and is probably the most effective demonstration to date,” Farries said.
But the researcher said there are still many unknowns with this method. For example, he said the authors have not been able to produce a complete seal between the interlocking tiles, leaving gaps within and between the units.
“This might still be effective in reducing dust from passing vehicles, but it is not certain it will eliminate it,” he said.
Before this method could be applied to the moon, more research would need to be conducted. For example, the performance of the tiles beneath a rocket thruster would need to be tested, the researchers said. Manufacturing the tiles in low gravity conditions would also need to be addressed. This could be achieved by using parabolic flights that mimic the effects of low gravity in Earth’s atmosphere.
Furthermore, the technology would need to be approved by space agencies, although once this happens the system could be easily transferable to the lunar surface, the researchers said.
“We have laid the foundations for paving roads on the moon, using raw materials widely available on the moon and using relatively simple equipment,” Ginés Palomares said.
Alex Ellery, a researcher in the Department of Mechanical & Aerospace Engineering at Carleton University in Canada, who was also not involved in the research, told Newsweek the latest study is interesting and that its strength lies in characterizing the properties of the melted lunar soil substitute.
Another positive result was that the tiles displayed superior compressive strength to most concretes, he said.
But Ellery said he is not convinced that a CO2 laser is a good analogue of concentrated sunlight as would be generated by the type of lens used in the study.
“So, I regard this as a valuable material science background study but not a direct simulation of a lunar-specific optical technology,” he said. “However, I think they have shown that developing paving on the moon is a work in progress.”
Update 10/13/23, 4:09 p.m. ET: This article was updated with comment from Alex Ellery.