Dr. Carlos Calle, lead scientist in Kennedy Space Center’s Electrostatics and Surface Physics Lab, is developing instrumentation that addresses the problem of electrostatic dust. The technology will be used for future exploration missions on Mars and the Moon.
NASA Tech Briefs: Where is the electrostatic dust coming from, and what kinds of problems does it create?
Dr. Carlos Calle: The electrodynamic dust shield (EDS) originated in 1967, in a white paper that a NASA scientist wrote on possible technologies to remove dust — something that had been an issue during the Apollo missions. A professor at the University of Tokyo put that technology into practice. He developed the basic concepts, and later on abandoned it and moved on to develop other methods to remove dust for terrestrial applications. The professor was not interested in space applications and ended up working on what is called electrostatic precipitators, which is a very mature technology used in large, dusty industrial settings on Earth.In 2003, we joined forces with the University of Arkansas at Little Rock and wrote a proposal together to the NASA Science Mission Directorate. We won a NASA Research Announcement (NRA) award to work on using the idea of the “electric curtain,” as the professor at the University of Tokyo had named it, to maintain solar panels on Mars and free them of dust. We developed that technology for about 4 years and applied it to the glass covers that are used to protect the photovoltaic arrays.
At the end of that grant, NASA had started working on the possible missions to the Moon. We changed gears a little, and we began to apply it to the lunar problem, which was how the technology was introduced in the 1960s, to solve the problem of dust accumulating on surfaces, space suits, and visors during the Apollo missions.
NASA had an agency-wide project, funded by the ESMD (Exploration Systems Mission Directorate).We worked on that for three years and developed that technology further for the lunar environment, which was a much more challenging environment. The moon has essentially no atmosphere, and the dust is highly charged due to the electrostatic environment of the moon, the solar wind, and the cosmic rays. We were able to overcome all of those difficulties and develop the technology for different applications.
NTB: How does the technology work? What does today's electrodynamic dust shield technology look like?
Calle: It involves a very thin coating of electrodes that are embedded in a substrate. We activate the electrodes with a very low-power electric signal. The signal is applied to the electrodes, and we generate an electric field wave that propagates through the surface. It’s pretty much like when you throw a pebble on a pond, and you see the ripples propagating away. In this case, it’s an invisible electric field that is propagating across the surface, and that propagating electric field carries along the dust particles that are electrostatically charged.
NTB: How is this version different from previous EDS technologies?
Calle: The original technology production that took place at the University of Tokyo used metallic conducting copper wires that were attached to different insulating surfaces. In principle, it is the same technology. What is different now is we don’t use actual wires. In the case of an application for solar panels, astronaut visors, or viewports, in which the application needs to be transparent, we start with a transparent conducting film. We use indium tin oxide, a film that is used on touchscreens for computers and tablets. To generate the wave, we end up etching the film off of the glass, for example, leaving only the electrode traces that we then apply the electric signal to. These electrodes are no longer actual copper wires but conducting films.
In other cases, in which the application does not need to be transparent, like thermal radiators, we place a copper film electrode that we attach to the metallic aluminum surface. The surface is painted over with reflective paint. From the outside, you don’t see any difference from a regular painted reflective surface, but underneath we have these thin electrodes that we activate to produce the wave that carries the dust off of the surfaces. That is what’s different.