ESA PAVER technology is making roads on the moon.
Table of Contents
When astronauts return to the lunar surface, they will most likely be driving rather than walking, but roads will be required to keep billowing moondust at bay. The European Space Agency’s research described in today’s Nature Scientific Reports explored the development of roadworthy surfaces by melting artificial moondust with a strong laser.
Roads come with civilization, and this will be especially true on the Moon to keep the lunar dust at bay. The lunar dust is extremely fine, abrasive, and sticky. Dust clogged equipment and degraded spacesuits during the Apollo period.
Notably, when the Apollo 17 lunar rover lost its rear fender, the vehicle became so engulfed in driven-up dust that it threatened to overheat, until astronauts devised a solution utilizing recycled lunar maps. The Soviet Union’s Lunokod 2 rover died from overheating after its radiator became dusty.
When the Apollo 12 Lunar Module landed roughly 180 meters away, it sandblasted the Surveyor 3 lander. According to current NASA modeling, when lunar landers touch down, their thruster plumes might disperse tons of dust, potentially clinging to lander surfaces and coating the entire landing area.
The most practical solution is to keep dust at bay by paving over active areas on the Moon, such as roadways and landing pads. The concept of melting sand to create roads was initially proposed for Earth in 1933.
ESA PAVER—paving the road for large-area sintering of regolith—project investigated the feasibility of this same approach for lunar roadmaking, led by Germany’s BAM Institute of Materials Research and Testing with Aalen University in Germany, LIQUIFER Systems Group in Austria, and Germany’s Clausthal University of Technology, with support from the Institute of Materials Physics in Space of the German Aerospace Center, DLR.
The ESA PAVER consortium made use of a 12-kilowatt carbon dioxide laser to melt simulated moondust into a glassy solid surface as a way of constructing paved surfaces on the face of the Moon.
According to ESA materials engineer Advenit Makaya, the project is returning to the original 1933 concept: “In practice, we would not bring a carbon dioxide laser on the Moon.” Instead, the existing laser serves as a light source for our studies, replacing lunar sunshine, which might be intensified using a Fresnel lens a few meters wide to generate equal melting on the Moon’s surface.
“During past in-situ resource utilization projects – including brick building using mirror-concentrated solar heat – we’ve been looking at surface melting limited to relatively small melt spots, from few millimeters to a couple of centimeters in diameter. For building roads or landing pads, a much wider focal point is required to be able to scan a very wide area in a practical timescale.”
At facilities installed at Clausthal University of Technology, the consortium achieved a spot size of 5-10 cm.
Proceeding through trial and error, they devised a strategy using a 4.5 cm diameter laser beam to produce triangular, hollow-centered geometric shapes approximately 20 cm across. These could be interlocked to create solid surfaces across large areas of lunar soil which could serve as roads or landing pads.
“It actually turned out to be easier to work with regolith with a larger spot size, because at millimeter scale heating produces molten balls that surface tension makes hard to aggregate together. The larger beam produces a stable layer of molten regolith that is easier to control. “The resulting material is glasslike and brittle, but will mainly be subject to downward compression forces. Even if it breaks we can still go on using it, repairing it as necessary.”
The team found that reheating a cooled track can cause it to crack, so they moved to geometries involving minimal crossovers. A single melt layer is about 1.8 cm deep; built structures and roads might be composed of several layers, depending on the load forces required.
“Such high depth of melting to produce massive structures can only be reached by large laser spots.”Jens Günster, heading the Multimaterial Manufacturing Processes Division at BAM, explains
The team estimates a 100 sq. m landing pad with a thickness of 2 cm of dense material might be constructed in 115 days.
This project originated from a call for ideas run by the Discovery element of ESA’s Basic Activities through the Open Space Innovation Platform (OSIP).
This sought out research ideas related to off-Earth manufacturing and construction.
The call was answered no less than 69 times. Of those, a total of 23 ideas have been implemented – based on an evaluation by a panel of ESA experts, who scored the ideas on their novelty.
“This initial call has been an effective investment from our point of view,” notes Advenit, “It has opened up multiple promising tracks for follow-up investigation.”
Read more about ESA’s Terrae Novae exploration program, leading Europe’s human journey into the Solar System, focused on the destinations of low-Earth orbit, the Moon and Mars.