Acoustic levitation could be used on Mars
January 25, 2010 by Lin Edwards
Dust storm on Mars. Image credit: NASA/JPL
(PhysOrg.com) -- The presence of fine dust on the Moon and Mars may present problems for explorers, such as coating solar panels, penetrating seals and interfering with machinery. Human explorers would also be endangered if there was a possibility of inhaling the extremely fine dust particles. Now scientists at the University of Vermont are considering a novel solution: acoustic levitation.
Finding ways of dealing with the fine dust is a high priority because the problems it can cause could drastically affect any long-term exploration. The thin atmosphere on Mars means dust particles are not as rounded as they would be on Earth and can remain quite sharp and abrasive, and they have a high electrostatic charge, which means the fine dust clings to everything and can penetrate space suit air locks, and make solar panels inoperable.
The researchers from the Department of Physics and Materials Science Program carried out a feasibility study to develop an acoustic dust removing system for use in space stations or habitations on the Moon or Mars. They found a high-pitched (13.8 kHz, 128 dB) standing wave of sound emitted from a 3 cm aperture tweeter and focused on a reflector 9 cm away was strong enough to dislodge and move extremely fine (<2 µm diameter) dust particles on the reflector surface. The sound waves overcome the van der Waals adhesive force that binds dust particles to the surface, and creates enough pressure to levitate the dust, which is then blown away.
The team tested the system on a solar panel coated with mock lunar and Martian dust. The output of the clean panel was 4 volts, but when coated with dust it produced only 0.4 volts. After four minutes of acoustic levitation treatment the output returned to 98.4% of the maximum.
Study co-author Junrun Wu said acoustic levitation is not new, but this is the first time it has been considered for applications away from Earth. The technology is cheap and uses readily found parts, but there is one enormous problem: it will only work when it is sealed inside a space station or other habitation. It will not work where there is no atmosphere (such as the moon) or where the atmosphere is low pressure and thin (such as Mars) because sound is a pressure wave that travels through the air. This limits its usefulness because inside an enclosed space station there would be relatively little dust, and probably other readily-available means of removing it without resorting to acoustic levitation.
The paper is published in the Journal of the Acoustical Society of America in January.
You need Flash installed to watch this ideo
Acoustic Levitation Lifting. A piece of Styrofoam is levitated then dropped and picked up again using only sound waves. Video: Queen's University.
More information: Dislodgement and removal of dust-particles from a surface by a technique combining acoustic standing wave and airflow. J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 45-50 (January 2010) http://dx.doi.org/10.1121/1.3268507
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3 hours ago
"Hey, Joe, one of your signs is screaming: Better get the neon transformer checked ASAP..."
"Uh, Nik, it is supposed to be too high-pitched for you to hear..."
Hilarity aside, they may do better using ionisers to knock down Martian / Lunar dust *before* it becomes a nuisance...
So what? What about inside airlocks? Surely they didn't think they were going to blow the dust off spacesuits while the astronauts were still outside? Take them into the airlock, pressurize it, blow the dust off, and suck it back outside.
I was also curious about the inside airlock option. Besides dusting off the astronauts, they would need a pressurized area to take equipment/solar panels for cleaning. Seems obvious.
The idea was to use the technique for locations where basic approaches were not practical. The technique described is "cute", but as pointed out, fails at it's most basic requirement: utility in the environment specified, namely Mars atmosphere.
(BTW - pressurize airlock, and "suck it back outside"? Tad wasteful of not-so-readily-available air, wouldn't you think?)
You make sense if you were on the Moon, but this is truly viable on Mars. Martian air could be used instead and then pumped out. This will also suck out most of the dust that might get airborne in the dusting process.