If you've ever been to the Moon (and who hasn't?), then you'll know that the clingy dust which covers its surface can damage spacesuits. According to a new study, a spray of liquid nitrogen may offer the best method of getting the stuff off – while leaving suits intact.
Scientifically known as lunar regolith, moon dust isn't like most natural dust here on Earth.
For starters, because it isn't subject to erosion by wind or water, the fine particles are quite jagged and abrasive. Additionally, because regolith is saturated with solar radiation, it has a positive charge which causes it to cling to anything with which it comes into contact.
On the Apollo moon missions, astronauts discovered that brushes were quite ineffective at removing regolith from their spacesuits – in fact, brushing just served to grind the dust in. Some of the suits were actually rendered unusable after the regolith damaged their seals.
Needless to say, the particles also aren't great for electronics or engines. They even caused respiratory problems in some astronauts, which persisted after they returned to Earth.
Seeking a more effective and less harmful alternative to brushing and other proposed methods of regolith removal, scientists at Washington State University recently looked to liquid nitrogen.
When an ultra-cold spray of the liquid was applied to warmer samples of spacesuit material covered in simulated regolith, the dust particles beaded up and floated away in the nitrogen vapor. This reaction was due to what's known as the Leidenfrost effect, in which a drop of liquid gets suspended above a surface by a layer of vapor. It is what's at work when cold water beads up and skitters across the surface of a hot frying pan.
The technique was tested both in normal atmospheric conditions and in a vacuum similar to that in outer space. It worked in both but performed better in the vacuum, where it removed 98.4% of the dust particles.
Additionally, whereas just one brushing of the dust-covered material samples damaged them, they stood up to 75 cycles of the liquid nitrogen treatment before any damage was observed.
The scientists now plan on conducting further tests under conditions which more closely simulate those on the lunar surface. A paper on their research – which is being led by Assoc. Prof. Jacob Leachman – was recently published in the journal Acta Astronautica.
Source: Washington State University
