In 1972, dust sticks to the boots of the Apollo 17 astronaut and geologist Harrison “Jack” Schmitt. Photo credit: NASA
A team led by the University of Colorado Boulder is working on a new solution to the problem of spring cleaning on the moon: why not zap the dirt away with an electron beam?
The research recently published in the journal Acta Astronautica, marks the very latest to explore a persistent and perhaps surprising hiccup in human dreams of the colonization of the moon: dust. Astronauts walking or driving across the lunar surface throw up huge amounts of this fine material, also known as regolith.
“It’s really annoying,” said Xu Wang, a research fellow in the Atmospheric and Space Physics Laboratory (LASP) at Boulder University. “Moondust sticks to all types of surfaces – spacesuits, solar panels, helmets – and can damage equipment.”
So he and his colleagues came up with a possible solution – one that uses an electron beam, a device that shoots a concentrated (and safe) stream of negatively charged, low-energy particles. In the new study, the team used such a tool to target a number of dirty surfaces inside a vacuum chamber. And they discovered that the dust just flew away.
“It literally pops off,” said lead author Benjamin Farr, who graduated from Boulder CU as a physics student.
Researchers still have a long way to go before real astronauts can use the technology to carry out their daily cleanup. However, according to Farr, the team’s early results suggest that electron-beam dust jets may become an integral part of the lunar bases in the not too distant future.
Gunpowder consumed
The news could be music to the ears of many Apollo-era astronauts. Several of these space pioneers complained about moon dust, which often resists cleaning attempts even after vigorous brushing. Harrison “Jack” Schmitt, who visited the moon in 1972 as a member of Apollo 17, developed an allergic reaction to the material and said it smelled like “spent gunpowder”.
The problem with moondust, Wang explained, is that it has nothing to do with the stuff that builds up on bookshelves around the world. Moon dust is constantly immersed in solar radiation, a bombardment that gives the material an electrical charge. This charge, in turn, makes the dust extra sticky, almost like a sock coming out of the dryer. It also has a distinctive structure.
A microscope view of a NASA-made lunar simulan that resembles moondust. Photo credit: IMPACT lab
“Moondust is very jagged and abrasive like broken glass,” said Wang.
The question that his group was then faced with was: How do you dissolve this naturally adherent substance?
Electron beams offered a promising solution. According to a theory developed from recent scientific studies of how dust naturally falls on the moon’s surface, such a device could turn the electrical charges on dust particles into a weapon against them. When you hit a layer of dust with a stream of electrons, that dusty surface collects additional negative charges, Wang said. Pack enough charges in the spaces between the particles and they can push each other away – much like magnets do when the wrong ends are squeezed together.
“The charges get so big that they repel each other, and then dust is expelled from the surface,” Wang said.
Electron showers
To test the idea, he and his colleagues loaded a vacuum chamber with various materials that were coated in a NASA– Manufactured “moon simulant” that resembles moon dust.
Indeed, after an electron beam was aimed at these particles, the dust usually flowed off in a few minutes. The trick also worked on a variety of surfaces, including spacesuit fabric and glass. This new technology aims to clean up the finest dust particles that are difficult to remove with brushes, Wang said. The process was able to clean dusty surfaces an average of 75-85%.
A vacuum chamber on the CU Boulder campus. Photo credit: IMPACT lab
“It worked pretty well, but not enough to finish,” said Farr.
The researchers are currently experimenting with new ways to increase the cleaning performance of their electron beam.
However, study co-author Mihály Horányi, professor of LASP and physics department at CU Boulder, said the technology has real potential. NASA has experimented with other strategies for dumping moon dust, such as embedding electrode networks in spacesuits. However, an electron beam could be much cheaper and easier to roll out.
Horányi envisions that one day lunar astronauts could just hang their spacesuits in a special room or even outside their living spaces and clean them after a long day throwing dust outside. The electrons would do the rest.
“You could just go to an electron-beam shower to remove fine dust,” he said.
Reference: “Dust Reduction Technology for Moon Exploration Using an Electron Beam” by B. Farr, X. Wang, J. Goree, I. Hahn, U. Israelsson and M. Horányi, August 8, 2020, Acta Astronautica.
DOI: 10.1016 / j.actaastro.2020.08.003
Other co-authors of the new research include John Goree of the University of Iowa and Inseob Hahn and Ulf Israelsson of the Jet Propulsion Laboratory.
