Dust clings to the boots of Harrison “Jack” Schmitt, Apollo 17 astronaut and geologist, in 1972. Credit: NASA
A team led by the University of Colorado Boulder has come up with a new solution to the problem of spring cleaning on the Moon: Why not remove the dust using an electron beam?
The research, published recently in the journal Acta Astronautica, is the latest to explore a lingering, and perhaps surprising, hiccup in humanity’s dreams of colonizing the moon: dust. Astronauts walking or driving on the lunar surface kick up huge amounts of this fine material, also called regolith.
“It’s really boring,” said Xu Wang, a research associate at CU Boulder’s Laboratory of Atmospheric and Space Physics (LASP). “Moon dust sticks to all kinds of surfaces – spacesuits, solar panels, helmets – and can damage equipment.”
So he and his colleagues developed a possible solution: an electron beam, a device that projects a concentrated (and safe) stream of negatively charged, low-energy particles. In the new study, the team aimed such a tool at a series of dirty surfaces inside a vacuum chamber. And, they discovered that the dust just flew away.
“She literally jumps,” said lead author Benjamin Farr, who did this work as an undergraduate physics student at the University of Boulder.
Researchers still have a long way to go before astronauts can use this technology to do their daily housework. But, according to Mr. Farr, the team’s initial findings suggest that electron-beam dust collectors could be installed on lunar bases in the not-too-distant future.
The news may be music to the ears of many Apollo-era astronauts. Several of these space pioneers have complained about moon dust, which often resists cleaning attempts even after vigorous brushing. Harrison “Jack” Schmitt, who visited the moon as a member of Apollo 17 in 1972, developed an allergic reaction to this material and said it smelled like “spent gunpowder”.
The problem with moon dust, Wang explained, is that it looks nothing like what accumulates on Earth’s shelves. Lunar dust is constantly exposed to solar radiation, a bombardment that gives the material an electrical charge. This charge, in turn, makes the dust very sticky, almost like a sock just out of the dryer. It also has a distinct structure.
“The moon dust is very jagged and abrasive, like shards of broken glass,” Wang said.
The question facing his group then was: How do you peel off this naturally sticky substance?
A microscope view of a lunar “simulator” designed to mimic moon dust. Credit: IMPACT lab
Electron beams offer a promising solution. According to a theory developed from recent scientific studies of how dust naturally lodges on the lunar surface, such a device could turn the electrical charges of dust particles into a weapon against them. If you hit a layer of dust with a stream of electrons, Wang says, that dusty surface will accumulate additional negative charges. By building up enough charge in the spaces between the particles, they can begin to repel each other, much like magnets do when the wrong ends are forced together.
“The charges get so big that they repel each other, and then the dust ejects from the surface,” Wang said.
To test the idea, he and his colleagues loaded a vacuum chamber with various materials coated into a NASA-made “lunar simulator” designed to look like lunar dust.
And sure enough, after aiming an electron beam at these particles, the dust came off, usually in just a few minutes. The trick also worked on a wide range of surfaces, including spacesuit fabric and glass. The new technology aims to clean the finest dust particles, which are difficult to remove using brushes, Wang said. The method has cleaned dusty surfaces in an average proportion of about 75 to 85%.
“It worked pretty well, but not enough to get us done,” Mr. Farr said.
Researchers are currently experimenting with new ways to increase the cleaning power of their electron beam.
But study co-author Mihaly Horanyi, a professor at LASP and the University of Boulder’s Department of Physics, said the technology has real potential. NASA has experimented with other strategies for releasing lunar dust, such as integrating electrode arrays into space suits. An electron beam, however, could be much cheaper and easier to deploy.
Horányi imagines that one day, lunar astronauts could simply leave their spacesuits hanging in a special room, or even outside their habitat, and clean them after spending a long day kicking dust outside. The electrons would do the rest.
“You could just step into an electron beam shower to remove the fine dust,” he said.