Designing interplanetary rovers requires a blend of math, science, engineering, and design. Every component of a rover undergoes iterative testing, and the rover as whole gets tested as well. Many engineering tests are conducted in lab settings where scientists can control and isolate key variables. Some tests, though, require an environment that approximates conditions on other planets. Maneuverability tests and some system tests are conducted in real-world desert “labs” that give scientists a chance to see how a rover might perform off-world.
NASA’s Desert Research & Technology Studies (RATS) team brings technology, human-robotic systems, and other equipment to desert areas in the southwestern US. The rough, dusty terrain and extreme temperature swings help scientists study the conditions rovers and other NASA vehicles might deal with on other surfaces in space. In essence, NASA is using the desert as a large-scale laboratory.
While Earth-bound vehicles can be cleaned and washed when needed, a dusty rover or capsule on another planet can’t be cleaned in a traditional way. However, since dust and other particles have slight electrical valances, or charge imbalances that leave them positively or negatively charged, they will respond to electric fields. NASA scientists have been exploring how to use electrified surfaces to essentially “self-clean.” The process involves applying an electric field in a syncopated pattern that directs dust and other particles off the surface. As long as the field is powered, the surface can repel and deflect dust. This is useful for camera and sensor surfaces, windows and hatches of capsules, and other sensitive surfaces.
NASA scientists have been testing these dust mitigation systems for several years – both in lab settings and in real deserts. However, real-world analogs to space-based environments can’t fully replicate the conditions in space. No matter how much preparation and testing NASA’s designs undergo, the actual conditions of launch, travel, landing, and extraterrestrial function often bring new challenges. Engineering and problem-solving can’t stop when a rover is launched; they continue for a rover’s entire mission and beyond. Scientists and engineers are constantly making observations, seeing new challenges, and finding new solutions.
BLAIR: We’re here with Dr. Carlos Calle and we’re talking about the dust mitigation system. Now, I worked with your teammates out at Desert RATS where they explained the dust mitigation system, but apparently there’s a lot more to this system that I didn’t know. Explain to me what you do here.
DR. CALLE: We’ve been working with this technology for seven years now. We started to develop a way to remove dust from solar panels on Mars. Mars, being a dusty planet, has a big problem with dust accumulating on solar panels. So, that was our first approach to this technology. Let me show you.
BLAIR: What are some examples?
DR. CALLE: Some examples, yeah. The one we tested at Desert RATS, we have two panels here.
DR. CALLE: …to demonstrate that we could remove dust from the windows that we attached to the door, as you remember.
BLAIR: Right. Exactly.
DR. CALLE: …to demonstrate that we could maintain the hatch clean so when the Rovers mate with the Habitat, before the doors are open you need to clean these things.
DR. CALLE: …so we don’t have dust in the Habitat. This particular type of panel contains two sets of electrodes, which are like sets of fingers interlaced. We apply a signal which is out of phase. So, we apply the signal to this electrode and then to that one and back to this and then to this. A one, two, one, two, one, two.
BLAIR: The reason you do that is if you sent the signal once it would lift the dust but the dust would settle.
DR. CALLE: Back.
BLAIR: …right back down.
DR. CALLE: Right back down. Exactly. So this is the way to make it “walk.”
This is one that we developed to protect optical systems, camera lenses and so on.
BLAIR: It’s just a piece of glass?
DR. CALLE: It’s a piece of glass but it has…
DR. CALLE: …transparent electrodes, which have a different configuration. We have three of those. In this particular case, when we wrap them around in a circle like that then we have an electric field that radiates out.
BLAIR: Got ya.
DR. CALLE: It’s like ripples on a pond.
BLAIR: Right. Otherwise, you could create pockets where the dust wouldn’t move.
DR. CALLE: Right.
BLAIR: So you have to work that way.
DR. CALLE: So, you can have the same panel that I showed you earlier down here in this box.
BLAIR: Oh. You have an example.
DR. CALLE: We have a brush we use to deliver the dust to simulate exploration activities on the moon that would kick up dust. I’m adding actually a lot of dust.
BLAIR: You are adding a lot of dust. I’m feeling uncomfortable, like you’re besmirching the test article. Have you ever added too much and been unsuccessful with your test?
DR. CALLE: Actually, yes.
DR. CALLE: If you pile it up. Actually, it works eventually.
BLAIR: Over time? It takes a little longer. You’re going to just throw a switch?
DR. CALLE: I’m going to throw a switch and activate the three electrodes.
BLAIR: Oh wow! Oh wow!
DR. CALLE: So it goes to the periphery where the electrode system is.
BLAIR: It looks computer generated.
DR. CALLE: Right.
BLAIR: Oddly, it seems to work inward. So there’s not a lot of carryover. Once they get away from the electrodes…
DR. CALLE: That’s it.
BLAIR: …dust settles again.
DR. CALLE: Yeah.
BLAIR: What would happen if you dropped dust now?
DR. CALLE: We can do that.
DR. CALLE: We can do that.
BLAIR: Are you sure?
DR. CALLE: We keep it running and we can drop dust on it and we’ll see what happens. It actually deflects it.
BLAIR: Yeah, it won’t stay on.
DR. CALLE: It’s a shield. Even if you dump large amounts of it, it just deflects it.
BLAIR: Why do you need to do more testing? This looks 100% successful in my untrained eye.
DR. CALLE: It is very successful but it is at a small scale still.
DR. CALLE: For Desert RATS, we scaled it up for this configuration, an 8x10, and a 9-inch diameter circular panel for the window. This year we’re going to try to see if we can cover the entire hatch, which is about a 2 ½ x 4-foot door.
BLAIR: One thought is you’d like to incorporate this technology even within clothing, i.e. a spacesuit.
DR. CALLE: Right.
BLAIR: Is that true?
DR. CALLE: Yeah. We have done some work.
BLAIR: Oh yeah, it’s very flexible.
DR. CALLE: This is actually a piece of cotton. The electrodes are made of carbon nanotubing that was actually developed in our Polymers Lab here at KSC.
DR. CALLE: We tested these in air and a vacuum successfully.
BLAIR: Wow, awesome!
DR. CALLE: The next step, of course, is to go from cotton to a more representative material for spacesuits, and that is the challenge.
BLAIR: Well very good. Thanks so much for your time.
DR. CALLE: My pleasure.
BLAIR: You’re watching NASA EDGE, an inside and outside look at all things NASA, completely dust free.
DR. CALLE: There you go.
BLAIR: Thank you very much. I appreciate it.
DR. CALLE: You are very welcome.
BLAIR: This is awesome. I can’t believe you can keep the dust off there perpetually. It’s great!
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