Texas researchers seek out ‘ideal’ material for lunar base
SAN ANTONIO — Making strong bricks on Earth is hard. Making strong bricks on the moon is harder.
But some researchers in a University of Texas at San Antonio laboratory are working to make it possible. They’re studying how to melt moon rocks, and the knowledge they glean could someday help humans build lunar outposts.
A moon base requires a place to land, and one concept for building such sites sites envisions robots melting moon dust, or regolith, to create special bricks. Think robots with built-in furnaces and specialized nozzles doing large-scale 3D printing with molten moon dust.
In April, San Antonio-based Astroport Space Technologies, a division of space startup company Exploration Architecture — or XArc — received a $136,000 NASA Small Business Technology Transfer deal to develop a prototype furnace and nozzle by June 2022.
Astroport’s main partner in the endeavor is UTSA, and that’s where Alan Whittington, a professor of petrology and planetary geology, and his team of graduate students come in. They’re learning about moon rock melting points, viscosity and other chemical and physical properties.
“Our collaboration with UTSA with the applied research Alan and his team are doing for us is instrumental to Astroport’s objectives of solidification of lunar regolith material,” said Sam Ximenes, founder and CEO of XArc and Astroport.
That material “can be transformed into durable bricks for our surface construction applications.”
The data researchers are collecting will help Astroport understand how much energy they’ll need to run the furnaces and which types of moon dust work best.
“What we’re working on is the ideal recipe to make the lowest cost, lowest energy, strongest brick,” said Whittington, 48. “We’re trying to optimize the recipe.”
That’s easier said than done. The first problem is the scientists don’t have any moon rocks.
“Obviously, we can’t use actual lunar soil,” Whittington said. “Samples exist on the earth, but
they’re priceless and locked away.”
So researchers are using the next best thing: earth rocks that mimic lunar chemical and physical properties. Some of the samples come from the Knippa Quarry off Texas 90 between Sabinal and Uvalde.
“Most of these things that we’re working with are good physical simulants in that they’re the right size with mostly crystals and a bit of glass, but each one of them has a different chemical composition,” he said. “The regolith on the moon has different compositions in different places, so we’re studying the different simulants that are available and trying to figure out which ones are going to be the best match.”
The next problem is melting the samples.
Besides lab coats, Whittington, and Anis Parsapoor, 42, a postdoctoral researcher, must don welder helmet-like face masks and thick, arm-length gloves before opening the mini fridge-sized furnace sitting on a lab worktable.
One of them slowly opens the furnace door while the other uses special tongs to either place or remove a crucible holding a small sample of lunar soil simulant. The crucible, a $5,000 tumbler-sized cup made of platinum and rhodium, can survive temperatures up to 4,000 degrees Fahrenheit.
They leave the sample in the furnace for about 20 minutes.
When Parsapoor opens the door to remove it, the furnace’s bright orange light fills the room. Even from 15 feet away, the heat can be felt.
Whittington pours the lava-like substance onto a metal plate. It glows orange and fades to a sort of glossy black glass as it cools.
While the molten stone is cooling, researchers must be cautious. Whittington said the thermal stresses can cause it to explode. Soon after pouring, the cooling stone made a sound like glass breaking and a piece slid across the tray.
“That’s not exploding, that’s more like enthusiastic cracking,” he said.
Whittington said the moon’s geology is interesting because not much has happened there for the past three billion years besides meteorites slamming into the lunar surface.
“There’s no atmosphere. There’s no weathering. There’s no transport by wind or anything like that,” he said. “It just sits there and gets bombarded with differentsized things. Every now and again, we’ve got a large impact and that can actually melt the surface.”
Those impact melts create a different substance that’s glassier than the moon’s original rock, which is crystalline.
Whittington said the moon’s surface is composed of two main components. The plains “mare” is basalt and the highlands are composed primarily of feldspar. Humans will have to understand both materials to work with it, because there are different compositions of the two in different places on the moon.
“I would be surprised if SpaceX and Blue Origin hasn’t thought about this,” Whittington said of the work. “What I think Astroport is hoping to do, as far as I can tell, is to become a service company for the infrastructure on the moon.”