Latest / Daniel and Kelly’s Extraordinary Universe / How can we keep solar panels clean on Mars?

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How can we keep solar panels clean on Mars? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Kelly, how are things running on the science farm?
• 0:10
  Speaker 2: Pretty well? But our house is like over one hundred
• 0:14
  Speaker 2: years old, so there's the usual number of issues that
• 0:16
  Speaker 2: you'd expect from a house of that age.
• 0:18
  Speaker 1: And so who's the like fixer upper in your family?
• 0:21
  Speaker 1: Is it the biologist or the cartoonist?
• 0:23
  Speaker 3: Oh, it is absolutely the biologist.
• 0:25
  Speaker 2: I have a series of Twitter posts actually where I
• 0:28
  Speaker 2: secretly record Zach trying to use tools, and each video
• 0:34
  Speaker 2: is better than the last. Every time a contractor comes
• 0:37
  Speaker 2: through and is like, ma'am, where is your husband? Should
• 0:40
  Speaker 2: we discuss this with him? I laugh out loud because
• 0:44
  Speaker 2: because Zach, he's just not interested in this stuff at all.
• 0:47
  Speaker 2: So all right, how about in your family?
• 0:49
  Speaker 3: Is it?
• 0:49
  Speaker 2: So let's see, you're an experimentalist. So does that make
• 0:53
  Speaker 2: you the one who's handy with tools?
• 0:56
  Speaker 1: Ooh, I wish. Technically I'm an experimentalist, but in practice
• 1:00
  Speaker 1: I do more computer stuff, so that means I fix
• 1:03
  Speaker 1: like the brooken laptops and the iPhones. Like in your family.
• 1:05
  Speaker 1: My wife is much more hands on than I am,
• 1:08
  Speaker 1: and so is she.
• 1:09
  Speaker 2: The one who usually is doing the fixing.
• 1:11
  Speaker 1: She's actually too busy fixing stuff in her lab to
• 1:14
  Speaker 1: fix stuff around the house. So we don't really have
• 1:17
  Speaker 1: anybody fixing stuff.
• 1:19
  Speaker 2: So what do you do when the stuff breaks? Stuff
• 1:23
  Speaker 2: doesn't just not break because there's no one available to
• 1:25
  Speaker 2: fix it.
• 1:26
  Speaker 1: I've learned that our strategy is to live with it
• 1:29
  Speaker 1: as long as possible. The house is pretty new when
• 1:31
  Speaker 1: we moved in, and so we're just going to see
• 1:33
  Speaker 1: how long that works.
• 1:36
  Speaker 2: This is all horrible plan, Daniel, Houses are not disposable.
• 1:40
  Speaker 3: You think you can't just break it down and then
• 1:42
  Speaker 3: move out.
• 1:44
  Speaker 1: We'll see.
• 1:46
  Speaker 3: Good luck.
• 2:02
  Speaker 1: Hi, I'm Daniel. I'm a physicist and a professor at
• 2:04
  Speaker 1: UC Irvine, and I'm not good at fixing broken stuff.
• 2:08
  Speaker 2: Hi. I'm Kelly Weener Smith. I'm adjunct at Rice University.
• 2:12
  Speaker 2: And if I didn't fix things, the house would fall
• 2:14
  Speaker 2: down around us.
• 2:15
  Speaker 1: It sounds like you're going to be actually useful when
• 2:17
  Speaker 1: the end times come.
• 2:19
  Speaker 2: I hope. So you know Zach Garden, so he might
• 2:21
  Speaker 2: be useful when the end times come. We joke about
• 2:24
  Speaker 2: the apocalypse a lot, but we're pretty sure that when
• 2:26
  Speaker 2: it comes to self defense more donners.
• 2:30
  Speaker 1: I pretty much have no useful skills. I mean, I
• 2:33
  Speaker 1: can write programs, I can record podcasts, I can think
• 2:36
  Speaker 1: deeply about the nature of the universe, but you know,
• 2:39
  Speaker 1: none of that's going to translate into like whiskey or
• 2:41
  Speaker 1: gold in the end times.
• 2:43
  Speaker 2: Yeah no, so you like probably wouldn't make it to
• 2:45
  Speaker 2: the second season of The Walking Dead. I like to
• 2:48
  Speaker 2: think that I'd still be around on The Walking Dead,
• 2:50
  Speaker 2: but I'm not sure I'd have to get good with
• 2:52
  Speaker 2: the sword or something.
• 2:53
  Speaker 1: You know, The Walking Dead actually does teach people to survive.
• 2:57
  Speaker 1: There is this incredible story about a young woman in
• 2:59
  Speaker 1: Irvine who's attacked in a parking garage in real life
• 3:03
  Speaker 1: by huge ex marine and she managed to wrestle the
• 3:06
  Speaker 1: blade away from him and kill her attacker. And when
• 3:09
  Speaker 1: they asked her how she managed to do that, she said,
• 3:12
  Speaker 1: I watch The Walking Dead. I know it's kill or
• 3:14
  Speaker 1: be killed.
• 3:15
  Speaker 3: Oh my gosh.
• 3:16
  Speaker 2: I mean she must have like she must work out
• 3:22
  Speaker 2: or have had some prior martial art training or so.
• 3:24
  Speaker 2: There's got to be more to it than I watched
• 3:26
  Speaker 2: The Walking Dead, because I've seen it all.
• 3:28
  Speaker 1: Turns out there's a lot more grit in Orange County
• 3:31
  Speaker 1: than you might expect.
• 3:32
  Speaker 2: I guess, so I believe it. That's incredible.
• 3:34
  Speaker 1: But speaking about grit and survival. Humanity needs to have
• 3:38
  Speaker 1: a sustainable way to live here on Earth and out
• 3:41
  Speaker 1: in the Solar System. And on this podcast we like
• 3:44
  Speaker 1: to think about the future, but what science and technology
• 3:47
  Speaker 1: hold for our future exploration of our neighborhood. So welcome
• 3:50
  Speaker 1: to the podcast Daniel and Jorge explain the Universe, in
• 3:53
  Speaker 1: which we talk about exactly those things, how the universe works,
• 3:56
  Speaker 1: how it all comes together, and how we can take
• 3:59
  Speaker 1: advantage of our knowledge of physical laws to build ourselves
• 4:02
  Speaker 1: a sustainable life here on Earth and perhaps also on
• 4:05
  Speaker 1: neighboring planets. Thanks very much Kelly for being a guest
• 4:08
  Speaker 1: host on today's episode.
• 4:09
  Speaker 2: Thanks for having me back. I always love being on
• 4:12
  Speaker 2: the show, and.
• 4:12
  Speaker 1: I always love talking to you about fancy technology in
• 4:15
  Speaker 1: space because you bring that bracing dash of skepticism.
• 4:20
  Speaker 2: Yes, everybody loves to have the wet blanket around. I'm
• 4:27
  Speaker 2: glad I'm appreciated somewhere.
• 4:29
  Speaker 3: Well.
• 4:29
  Speaker 1: You know, it's fun to blue sky think about what
• 4:31
  Speaker 1: might be possible. But if we're actually going to make
• 4:33
  Speaker 1: it out into the Solar System, if we're going to
• 4:35
  Speaker 1: send our probes and one day our children out into
• 4:38
  Speaker 1: deep space, we better have stuff that actually works, that
• 4:40
  Speaker 1: somebody has actually thought through and maybe even tested.
• 4:43
  Speaker 2: Well, you know, you need the wet blankets to put
• 4:46
  Speaker 2: out the fires, and so that I offer a service
• 4:49
  Speaker 2: I like to think.
• 4:52
  Speaker 1: And fire turns out to be quite essential. We use
• 4:55
  Speaker 1: it to hear on Earth, to keep ourselves warm, and
• 4:57
  Speaker 1: also to transform various kinds of energy in to electricity.
• 5:01
  Speaker 1: We have mammoth amounts of coal and gas still being
• 5:03
  Speaker 1: burnt to turn steam turbines to convert it into electricity,
• 5:07
  Speaker 1: as well as huge amounts of the planet covered in
• 5:09
  Speaker 1: solar panels to generate electricity for our lifestyle. But when
• 5:13
  Speaker 1: we send our robots into outer space, they don't necessarily
• 5:16
  Speaker 1: have access to coal fired power plants, so they need
• 5:20
  Speaker 1: to think about other ways to stay warm and keep running.
• 5:23
  Speaker 3: And the environment of space is a tough.
• 5:25
  Speaker 1: One, as we've talked about several times on the podcast.
• 5:29
  Speaker 1: So on today's episode, we're going to think through some
• 5:31
  Speaker 1: of the details of how our little robots can keep
• 5:34
  Speaker 1: chugging away on the surface of alien planets. More specifically,
• 5:38
  Speaker 1: on today's episode, we'll answer the question how can we
• 5:46
  Speaker 1: keep solar panels clean on Mars? But maybe we should
• 5:50
  Speaker 1: start closer to home. How do you keep your solar
• 5:52
  Speaker 1: panels cleaning, Kelly, HAA, I don't. You can't just let
• 5:57
  Speaker 1: these things break and then move on.
• 6:00
  Speaker 2: Oh, I you know it's possible.
• 6:03
  Speaker 3: I'm a bit of a hypocrite.
• 6:04
  Speaker 2: Sometime now, I actually, well, I was thinking about today's episode.
• 6:08
  Speaker 2: I realized that I have never cleaned the solar panels
• 6:10
  Speaker 2: that are up on top of one of our barns.
• 6:13
  Speaker 2: I just don't know how i'd reach them. But we
• 6:15
  Speaker 2: do live in a dusty you know, we've got Virginia
• 6:17
  Speaker 2: dusty clay. So I guess I just hope it rains
• 6:20
  Speaker 2: a lot. And it does.
• 6:22
  Speaker 1: Don't You have small children. They're good at climbing, and
• 6:24
  Speaker 1: their little fingers are great at cleaning tiny little electronics
• 6:28
  Speaker 1: that yes.
• 6:29
  Speaker 2: No, absolutely, And I haven't read the child labor laws
• 6:32
  Speaker 2: to know if I'm allowed to do this or not,
• 6:34
  Speaker 2: but probably it's fine, And so maybe that's what they'll
• 6:37
  Speaker 2: do this weekend.
• 6:38
  Speaker 1: Well, I hear they're loosening labor laws all across the South,
• 6:41
  Speaker 1: So maybe soon your children can legally work for you.
• 6:43
  Speaker 2: Yay, thank you politics.
• 6:45
  Speaker 1: So if Kelly can't even keep her solar panels clean
• 6:48
  Speaker 1: on Earth, how it could be possible for NASA to
• 6:51
  Speaker 1: keep solar panels clean on Mars, a famously dusty and
• 6:55
  Speaker 1: very distant environment where there aren't even child laborers available
• 6:59
  Speaker 1: to clean those little robots.
• 7:01
  Speaker 3: Gosh, I hope we can fix that one day.
• 7:04
  Speaker 1: That's why we have to send people to Mars, starting
• 7:06
  Speaker 1: with children. Yes, absolutely, but we reached out to our
• 7:09
  Speaker 1: audience to ask them if they had thoughts about how
• 7:12
  Speaker 1: to keep solar panels clean when there are thousands and
• 7:15
  Speaker 1: millions of miles away and also essential to the operation
• 7:19
  Speaker 1: of remote robots. If you would like to answer questions
• 7:22
  Speaker 1: for this segment of the podcast, please don't be shy.
• 7:24
  Speaker 1: We would love to have your voice on the podcast.
• 7:27
  Speaker 1: Just send me an email to Questions at Danielandjorge dot
• 7:30
  Speaker 1: com and I will set you up. So think about
• 7:33
  Speaker 1: for a moment, do you have clever ideas for how
• 7:35
  Speaker 1: to keep solar panels clean on Mars. Here's what people
• 7:39
  Speaker 1: had to say. You know what, that's a good question.
• 7:41
  Speaker 2: The rover has got a lot of batteries.
• 7:42
  Speaker 1: It's not solar powered. It's not solar powered.
• 7:46
  Speaker 4: That's why I would say that the reason why they
• 7:48
  Speaker 4: don't have wipers is because we would have to probably
• 7:53
  Speaker 4: have fluid to spray on the solar panels to wipe
• 7:56
  Speaker 4: and clean, and that's probably just too much to do
• 8:01
  Speaker 4: with the rover.
• 8:02
  Speaker 1: I've never really thought about that.
• 8:04
  Speaker 4: My guess is that, you know, using a regular wiperd
• 8:07
  Speaker 4: would scrape the lens.
• 8:08
  Speaker 1: So I'm guessing they blow the dust off with some
• 8:10
  Speaker 1: type of compressed air system. I don't know. That's a
• 8:13
  Speaker 1: really good point. Maybe the solar panels have.
• 8:16
  Speaker 2: A self cleaning technology, like self cleaning glasses that are
• 8:20
  Speaker 2: available in civil construction.
• 8:22
  Speaker 4: Hm.
• 8:22
  Speaker 1: I don't know. If it's a dry maybe that would
• 8:26
  Speaker 1: just scratch the lenses. Maybe you need like the film
• 8:30
  Speaker 1: that just keeps replacing itself.
• 8:33
  Speaker 3: I thought these were really great answers.
• 8:35
  Speaker 2: The listeners identified a lot of the actual big problems
• 8:38
  Speaker 2: and had some good ideas.
• 8:39
  Speaker 3: And to be honest, I hadn't.
• 8:41
  Speaker 2: Heard of self cleaning window technology. Do you know about this, Daniel,
• 8:46
  Speaker 2: Do you know how it works?
• 8:47
  Speaker 1: I'm not an expert in self cleaning windows. But later
• 8:50
  Speaker 1: in the episode we're going to talk about self cleaning
• 8:53
  Speaker 1: solar panels. This is actually technology people at MIT are
• 8:57
  Speaker 1: working on.
• 8:58
  Speaker 3: Ooh, very cool.
• 8:59
  Speaker 1: So you're right, our listeners are on point. These are
• 9:02
  Speaker 1: some smart people we have listening to the podcast, and
• 9:04
  Speaker 1: good looking too.
• 9:06
  Speaker 3: Yes, that's called the halo effect, I think. Yeah.
• 9:09
  Speaker 2: I bet they're also good at video games and probably
• 9:13
  Speaker 2: very fast.
• 9:14
  Speaker 1: Did think correlation applies causation, Like the more episodes of
• 9:16
  Speaker 1: the podcast you listen to, the better looking you are.
• 9:19
  Speaker 2: Yeah. No, And I hope that if I co host
• 9:22
  Speaker 2: enough that I'll be even more good looking than just listening.
• 9:25
  Speaker 2: So that's what I'm banking on. I'm not here just
• 9:27
  Speaker 2: because you're fun to talk to, Daniel.
• 9:30
  Speaker 1: I'm not sure it might go the other way.
• 9:32
  Speaker 4: You know.
• 9:32
  Speaker 1: If we have faces that are good for podcasting, it
• 9:35
  Speaker 1: might just mean that they get better and better for podcasting.
• 9:39
  Speaker 3: Daniel.
• 9:39
  Speaker 2: I'm sorry I have to go. It's been fun, but
• 9:45
  Speaker 2: I'm doing something else with my time, all right.
• 9:46
  Speaker 1: But we do want to keep our little robots powered
• 9:49
  Speaker 1: on alien planets. I mean, we send these devices off
• 9:52
  Speaker 1: to Mars to measure earthquakes, to gather samples, just to
• 9:56
  Speaker 1: drive around and see the geology and understand what used
• 9:59
  Speaker 1: to be on Mars, maybe even discovering water, evidence of
• 10:02
  Speaker 1: life or potentially even existent life on Mars. The questions
• 10:07
  Speaker 1: are still open, and well beyond Mars, we send things
• 10:09
  Speaker 1: to other planets. We'd like to drive them around and
• 10:12
  Speaker 1: even fly them around those planets. And for all these things,
• 10:15
  Speaker 1: they need power. None of this stuff comes for free, and.
• 10:19
  Speaker 2: We need to get really good at this stuff if
• 10:20
  Speaker 2: we're ever going to have humans living in space, because
• 10:22
  Speaker 2: you really can't have your power ever break down if
• 10:25
  Speaker 2: you're living in space.
• 10:26
  Speaker 1: That's right in space. You can't just wait till your
• 10:28
  Speaker 1: space station breaks down and then move out into another one.
• 10:31
  Speaker 1: Space stations are not disposable.
• 10:33
  Speaker 2: Well, I mean, we've burned a lot of them up
• 10:35
  Speaker 2: in the atmosphere, but you better have another plan before
• 10:38
  Speaker 2: that happens.
• 10:39
  Speaker 1: Yeah, we like to do some repairs before we recycle.
• 10:42
  Speaker 1: But solar power actually isn't the only way to power
• 10:45
  Speaker 1: some of these distant devices.
• 10:47
  Speaker 3: How else do we do it?
• 10:48
  Speaker 1: Daniel, Well, another option that's really fascinating are at nuclear batteries.
• 10:53
  Speaker 1: I mean, if you want to power something for a
• 10:55
  Speaker 1: long long time, you need a steady source of energy,
• 10:58
  Speaker 1: then you definitely don't want to bring gas along. You
• 11:01
  Speaker 1: want a very very dense source of power. You want
• 11:03
  Speaker 1: some kind of fuel that releases a lot of energy
• 11:05
  Speaker 1: and doesn't have a lot of kilograms and so in
• 11:08
  Speaker 1: the same way that we power like our aircraft carriers
• 11:11
  Speaker 1: and our submarines. We turn to atomic physics to produce
• 11:14
  Speaker 1: that energy. You know that aircraft carriers can go for
• 11:17
  Speaker 1: like decades without refueling because they have nuclear power plants
• 11:21
  Speaker 1: on board, like fully functioning fission reactors on board, turning
• 11:25
  Speaker 1: uranium into electricity. Same with submarines sliding around the Earth's ocean.
• 11:31
  Speaker 1: It's really pretty amazing.
• 11:32
  Speaker 2: Hang would take me a little while to get used
• 11:35
  Speaker 2: to knowing that I was living that close to a
• 11:37
  Speaker 2: nuclear reactor. On the other hand, it would be good
• 11:40
  Speaker 2: to know that you have a reliable power source.
• 11:42
  Speaker 1: But these things are delicate and dangerous, and you can't
• 11:45
  Speaker 1: put a whole nuclear power plant on a satellite or
• 11:48
  Speaker 1: on a little rover and it's going to be driving
• 11:50
  Speaker 1: around the surface of Mars. Instead, they have a different
• 11:53
  Speaker 1: way to extract energy from radioactive elements. These things are
• 11:58
  Speaker 1: called RTGs radio isotope thermoelectric generators. Basically, it's a big
• 12:04
  Speaker 1: block of material which decays radioactively and turns the heat
• 12:08
  Speaker 1: from that decay into electricity. So that's one of the
• 12:12
  Speaker 1: ways that we can power things in space. Kelly, here's
• 12:15
  Speaker 1: something of an expert in the history of nuclear power
• 12:17
  Speaker 1: and space. Have humans ever launched an actual working fission
• 12:20
  Speaker 1: reactor into space?
• 12:22
  Speaker 4: Oh?
• 12:22
  Speaker 2: Man, we've done it more times than you're probably comfortable knowing.
• 12:26
  Speaker 1: More than zero is more times than uncomfortable knowing.
• 12:29
  Speaker 2: Yeah, exactly. And so in nineteen sixty five, the US
• 12:32
  Speaker 2: did it for a satellite. It was like a test
• 12:35
  Speaker 2: and it didn't go great, but then we boosted it
• 12:38
  Speaker 2: into a graveyard orbit. So we actually have one of
• 12:40
  Speaker 2: these reactors still orbiting the Earth. But the USSR loved these.
• 12:44
  Speaker 2: They did it a.
• 12:45
  Speaker 3: Bunch of times.
• 12:46
  Speaker 2: I think they sent up thirty three or maybe even
• 12:50
  Speaker 2: more of them. And so, yeah, there have been a
• 12:53
  Speaker 2: lot of little nuclear reactors that have been sent to
• 12:55
  Speaker 2: space to power our satellites. I don't think any of
• 12:57
  Speaker 2: them have gone to like Mars or the Moon Tower rovers,
• 13:00
  Speaker 2: but we do have some experience with using these as satellites.
• 13:03
  Speaker 3: Also.
• 13:04
  Speaker 2: Fun fact, if your definition of fun is raining nuclear
• 13:08
  Speaker 2: waste over the Earth. One of the USSR's satellites that
• 13:13
  Speaker 2: was powered by a nuclear reactor. This one's called Cosmos
• 13:17
  Speaker 2: nine fifty four accidentally re entered when it wasn't meant
• 13:20
  Speaker 2: to re entered and it sprayed nuclear material all over Canada.
• 13:25
  Speaker 2: The US and Canada had to clean it up.
• 13:27
  Speaker 1: That sounds bad.
• 13:29
  Speaker 2: It was bad. Russia agreed to pay for half of it.
• 13:31
  Speaker 2: I think it's the only time in which the Liability
• 13:34
  Speaker 2: Convention through the United Nations has been invoked as a like, dude,
• 13:39
  Speaker 2: this is kind of your responsibility. And I think the
• 13:42
  Speaker 2: Soviet Union tried to be like, well, it's hard.
• 13:46
  Speaker 3: Maybe not, but eventually they went have these with US.
• 13:49
  Speaker 1: Well, sending working fission reactors into space doesn't seem like
• 13:52
  Speaker 1: a great idea, but fortunately these other devices, the radioisotope
• 13:55
  Speaker 1: thermoelectric generators, are simpler solid state devices. They don't have
• 13:59
  Speaker 1: any moving parts, they can't like melt down. Basically, you
• 14:02
  Speaker 1: just have like a block of radioactive material which is
• 14:05
  Speaker 1: decaying and releasing energy as those decays happen, which heats
• 14:09
  Speaker 1: up the block, and then you just got to turn
• 14:11
  Speaker 1: that heat into electricity.
• 14:13
  Speaker 2: Yeah, and most of the time you don't end up with,
• 14:16
  Speaker 2: for example, one of the lunicons breaking up over the
• 14:19
  Speaker 2: Soviet Union and sending colonium all over the place when
• 14:22
  Speaker 2: they're radioactive.
• 14:24
  Speaker 3: What is it?
• 14:24
  Speaker 2: This was a thermoelectric generator. That broke up and you know,
• 14:29
  Speaker 2: dropped waste over the USSR.
• 14:30
  Speaker 1: You're right, this is definitely a danger if you're launching
• 14:32
  Speaker 1: radioactive materials, whether it's for an RTG or a working reactor,
• 14:36
  Speaker 1: you're risking blowing that over the surface of the Earth
• 14:38
  Speaker 1: at launch, because launches are still violent and risky events.
• 14:41
  Speaker 1: No matter how good we get at it, sometimes these
• 14:43
  Speaker 1: things still blow up, and if your payload is dangerous,
• 14:47
  Speaker 1: then that presents a danger to the population on Earth.
• 14:50
  Speaker 2: There are ways to make it safer, you know, there's
• 14:52
  Speaker 2: like new cladding that you can get, and you can
• 14:54
  Speaker 2: send up smaller and smaller amounts on different rocket launches
• 14:57
  Speaker 2: and then put them all together when you get to space.
• 15:00
  Speaker 2: But certainly our history is littered with radioactive accidents.
• 15:05
  Speaker 1: So these things are dangerous. They're also super duper expensive.
• 15:09
  Speaker 1: I mean often they use like plutonium two thirty eight,
• 15:11
  Speaker 1: for which we have a very limited supply because until
• 15:14
  Speaker 1: recently we stopped making plutonium, and so it's not easy
• 15:17
  Speaker 1: to get this stuff. If it blows up on launch,
• 15:20
  Speaker 1: it's very dangerous. On the flip side, it lasts for
• 15:23
  Speaker 1: a long time. Like you can build one of these
• 15:24
  Speaker 1: things and it will steadily produce power for ten to
• 15:27
  Speaker 1: fifteen years just pumping out electricity, doesn't require the sun,
• 15:32
  Speaker 1: there's no moving parts, it's very very stable. So these
• 15:36
  Speaker 1: things are sort of the gold standard for NASA if
• 15:39
  Speaker 1: it wants to power something that goes to like the
• 15:41
  Speaker 1: outer Solar system, where even solar panels are not going
• 15:44
  Speaker 1: to be effective because you're so far away from the Sun.
• 15:47
  Speaker 2: Well, not going to say, if I was moving to Mars,
• 15:48
  Speaker 2: I would really like to have a tiny nuclear power
• 15:51
  Speaker 2: plant on Mars rather than relying on anything else. And
• 15:56
  Speaker 2: there are engineers working on it, and they all really
• 15:58
  Speaker 2: like the Simpsons, and they name all of their designs
• 16:01
  Speaker 2: after Simpson stuff.
• 16:03
  Speaker 3: Oh no, so what let's see.
• 16:04
  Speaker 2: In twenty eighteen they tested the Kilo power reactor using
• 16:09
  Speaker 2: sterling technology, and by like picking the right letters out
• 16:13
  Speaker 2: of those various words, they come up with crusty and
• 16:18
  Speaker 2: like the clown. I think they also had one called Duff,
• 16:21
  Speaker 2: like after Duff beer. And anyway, one of the engineers
• 16:24
  Speaker 2: has been at this for like decades. But anyway, it
• 16:26
  Speaker 2: is a nice reliable power source if you could get
• 16:28
  Speaker 2: it to work safely, it is.
• 16:29
  Speaker 1: Very cool and it uses an interesting effect where you
• 16:31
  Speaker 1: turn heat into electricity by having two different kinds of metal,
• 16:36
  Speaker 1: one is hotter and one is cooler, and that generates
• 16:39
  Speaker 1: an electromotive force across them. Basically like the electrons and
• 16:43
  Speaker 1: hotter side are moving more and electrons and the cooler
• 16:46
  Speaker 1: side are not, and that creates a flow of current
• 16:48
  Speaker 1: across the threshold. And so you can turn this heat
• 16:51
  Speaker 1: into electricity again with no moving parts. You don't need
• 16:54
  Speaker 1: like a steam engine or a turbine or anything. It
• 16:57
  Speaker 1: just produces electricity. And yeah, if I was living on
• 16:59
  Speaker 1: this surface of Mars, I would like a backup source
• 17:02
  Speaker 1: of energy, especially if it didn't come with me to Mars.
• 17:05
  Speaker 1: If you're like landed separately, so I didn't have to
• 17:07
  Speaker 1: worry about radiation firmative it broke.
• 17:10
  Speaker 3: Down, Yeah, no doubt well.
• 17:11
  Speaker 2: And also there's lots of reasons in space why you'd
• 17:14
  Speaker 2: like to have heat, And these reactors also produce heat,
• 17:17
  Speaker 2: so you could, you know, I don't know, maybe heat
• 17:18
  Speaker 2: up your ice and turn it into water.
• 17:20
  Speaker 1: But because these things are expensive and they are dangerous,
• 17:23
  Speaker 1: and they're also in limited supply, NASA tends to be
• 17:26
  Speaker 1: pretty stingy with these things. They reserve them for like
• 17:29
  Speaker 1: the deepest, longest, high priority, lowest risk missions. And so
• 17:33
  Speaker 1: when people started talking about putting a rover on Mars,
• 17:36
  Speaker 1: the Mars program wasn't really in great shape, that had
• 17:38
  Speaker 1: a bunch of losses. It seemed very high risk. They
• 17:41
  Speaker 1: were thinking these rovers were only going to cruise around
• 17:44
  Speaker 1: for like a few weeks at most, so they didn't
• 17:46
  Speaker 1: have the option of using one of these nuclear batteries,
• 17:49
  Speaker 1: and they had to go for solar panels.
• 17:51
  Speaker 2: And after the break, we'll tell you about how those were. Okay,
• 18:06
  Speaker 2: so we've decided that nuclear power is reliable, but it's
• 18:10
  Speaker 2: expensive and sometimes things go wrong, and one way or another,
• 18:14
  Speaker 2: solar panels are really popular on space voyages. So how
• 18:18
  Speaker 2: about you tell us a bit how solar panels in
• 18:20
  Speaker 2: space work.
• 18:21
  Speaker 1: Yeah, solar panels in space work the same way the
• 18:23
  Speaker 1: solar panels do here on Earth, which is essentially transforming
• 18:27
  Speaker 1: the energy of the photons into current. And photons interacting
• 18:32
  Speaker 1: with electrons is of course very famous in physics. It's
• 18:35
  Speaker 1: the basis of the photoelectric effect for which Einstein won
• 18:38
  Speaker 1: the Nobel Prize more than one hundred years ago. When
• 18:41
  Speaker 1: photons hit a piece of metal, they don't just interact
• 18:44
  Speaker 1: with the whole metal, and they're not classical electromagnetic waves
• 18:47
  Speaker 1: where they deposit their energy broadly. Where they come in
• 18:50
  Speaker 1: terms of photons, which means that a single photon hits
• 18:53
  Speaker 1: a single electron and deposits its energy. The photoelectric effect
• 18:57
  Speaker 1: is when there's so much energy in that photon that
• 19:00
  Speaker 1: electrons boil off the surface. Like you can knock electrons
• 19:04
  Speaker 1: off of a piece of metal by shining high energy
• 19:07
  Speaker 1: light at it. So that's the photoelectric effect. The photovoltaic
• 19:11
  Speaker 1: effect is the principle underlying solar panels, and it's the
• 19:14
  Speaker 1: sort of like lower energy cousin of the photoelectric effect.
• 19:18
  Speaker 1: If you dial down the energy to photons so that
• 19:21
  Speaker 1: they don't have enough energy to kick the electrons out
• 19:24
  Speaker 1: of the metal, you know, boiling electrons off the surface. Instead,
• 19:27
  Speaker 1: you're just exciting the electrons. You're giving them more energy
• 19:30
  Speaker 1: so they can flow around.
• 19:32
  Speaker 3: And then how do you get energy out of them
• 19:34
  Speaker 3: flowing around?
• 19:35
  Speaker 1: Yeah, so you need to build a special kind of material.
• 19:38
  Speaker 1: So here we use silicon diodes. And silicon, remember is
• 19:41
  Speaker 1: a semiconductor, so it's not quite an insulator where all
• 19:44
  Speaker 1: the electrons are like trapped in the lattice of the crystal,
• 19:47
  Speaker 1: and it's not quite a conductor where there's no gap
• 19:50
  Speaker 1: between where the electrons live in the crystal and where
• 19:53
  Speaker 1: the electrons flow freely, So electrons are just zooming everywhere.
• 19:56
  Speaker 1: A semiconductor has like a little bit of a gap there,
• 19:59
  Speaker 1: so it's like hard for the electrons to flow, but
• 20:02
  Speaker 1: not impossible. And if you put the right kind of
• 20:04
  Speaker 1: materials into the silicon, and if you dope it with
• 20:07
  Speaker 1: other kinds of elements, then you can subtly tune the
• 20:10
  Speaker 1: size of that gap. So a diode has two different
• 20:14
  Speaker 1: kinds of silicon in it. They call it end doped
• 20:17
  Speaker 1: and P doped. Endoped silicon has like extra electrons in it.
• 20:21
  Speaker 1: It's endoped, it's more negative. P doped silicon has more
• 20:25
  Speaker 1: positive charges, basically has holes for the electron. So you
• 20:29
  Speaker 1: have these two kinds of silicon next to each other,
• 20:32
  Speaker 1: and you apply an electric field to keep the electrons
• 20:34
  Speaker 1: from flowing from the end side to the P side,
• 20:37
  Speaker 1: So it's sort of like having a bunch of water
• 20:38
  Speaker 1: behind a dam. Then when the photons come in, they
• 20:41
  Speaker 1: push some of those electrons basically over that ridge and
• 20:44
  Speaker 1: they flow across the material, and that creates a current,
• 20:47
  Speaker 1: and that's what you want. The current is your electrical energy,
• 20:51
  Speaker 1: so it turns those photons into motion of electrons across
• 20:55
  Speaker 1: the silicon, which then adds to the voltage on your battery.
• 20:58
  Speaker 3: I did not know that.
• 21:00
  Speaker 2: And I'll also note that I've never heard the word
• 21:03
  Speaker 2: dope using a scientific context, and it's great. I actually
• 21:08
  Speaker 2: feel like I should write a song, maybe like a
• 21:11
  Speaker 2: rap song about how diodes work.
• 21:13
  Speaker 3: Maybe not, maybe let's pull that out.
• 21:15
  Speaker 1: Doping is for smarty pants.
• 21:16
  Speaker 3: It turns out that's right, that's right.
• 21:18
  Speaker 1: I always thought of it doping more in the lance
• 21:19
  Speaker 1: armstrong sense than in the like you're a dope sort
• 21:22
  Speaker 1: of sense.
• 21:23
  Speaker 2: Well, no, I so you're a dope is like negative,
• 21:25
  Speaker 2: But I I was thinking of it as like, that's dope, man,
• 21:28
  Speaker 2: Like that's and when I said it sounded incredibly uncool.
• 21:34
  Speaker 3: So anyway, this is where I am in the universe.
• 21:37
  Speaker 1: The silicon is definitely dope material.
• 21:39
  Speaker 2: Yeah, right, okay, so now we know how you get
• 21:42
  Speaker 2: energy from it, Is this like a good way to
• 21:44
  Speaker 2: do it?
• 21:45
  Speaker 1: Yeah, it's a pretty good way to get energy out
• 21:47
  Speaker 1: of the photons. It's frustratingly not one hundred percent efficient.
• 21:50
  Speaker 1: Some of the energy is lost just a diffusion and
• 21:52
  Speaker 1: just a heat is not all directly converted from the
• 21:56
  Speaker 1: energy of the photon to the energy of the electron.
• 21:58
  Speaker 1: They have like researchystems where they try to optimize all
• 22:01
  Speaker 1: the conditions and they can get it up to like
• 22:03
  Speaker 1: maybe forty five to fifty percent. That's like the record
• 22:06
  Speaker 1: in research. In terms of the photovoltaic panels like on
• 22:10
  Speaker 1: your house or on big power plants, they're typically like
• 22:14
  Speaker 1: twenty percent efficient, which means like eighty percent of the
• 22:17
  Speaker 1: energy is just lost. You know, stuff gets heated up
• 22:20
  Speaker 1: or it's not ending up in your battery.
• 22:22
  Speaker 2: That's interesting, And of course as a biologist, what I'm
• 22:25
  Speaker 2: wondering is how far behind are we lagging nature? So,
• 22:29
  Speaker 2: you know, photosynthesis is all about capturing the Sun's energy.
• 22:33
  Speaker 3: How efficient is photosynthesis?
• 22:35
  Speaker 1: Weirdly, photosynthesis is a lot less efficient. It's something like
• 22:39
  Speaker 1: three percent efficient. Yeah, compared to the photovoltaic method.
• 22:43
  Speaker 2: Come on, evolution, you're letting me down.
• 22:46
  Speaker 1: But photosynthesis is pretty awesome because you know, it builds itself, right,
• 22:50
  Speaker 1: like my solar panels aren't making more solar panels. And
• 22:53
  Speaker 1: in addition, as you know, like it turns the energy
• 22:56
  Speaker 1: the photons into like complex chemicals that store energy. It's
• 23:00
  Speaker 1: much much better than a battery, right, It's like it's
• 23:03
  Speaker 1: literally creating fuel out of sunlight, whereas all we can
• 23:07
  Speaker 1: do is like convert it into electricity, which then stays
• 23:09
  Speaker 1: in a battery, and that's hard to transmit across long distances,
• 23:13
  Speaker 1: et cetera, et cetera. So plants are doing something that
• 23:15
  Speaker 1: we're definitely not doing.
• 23:17
  Speaker 2: All right, evolution, I'm sorry about what I said about you,
• 23:20
  Speaker 2: Let's be friends again.
• 23:21
  Speaker 1: On the other hand, photobo take cells can use like
• 23:23
  Speaker 1: infrared light and u V light. They can use a
• 23:26
  Speaker 1: broader spectrum, whereas plants mostly get their energy from the
• 23:29
  Speaker 1: visible spectrum. So there's pluses and minuses. But yeah, I
• 23:32
  Speaker 1: would like free solar panels that grow themselves and maintain themselves.
• 23:36
  Speaker 1: That would be pretty awesome.
• 23:37
  Speaker 2: That would be solid and if you were starting a
• 23:39
  Speaker 2: settlement on Mars, that would really give you a leg up.
• 23:42
  Speaker 3: But we don't know how to do that yet.
• 23:44
  Speaker 2: But speaking of Mars, so you know on Earth we're
• 23:48
  Speaker 2: closer to the Sun than Mars, which probably helps with
• 23:51
  Speaker 2: gathering energy. What is the situation like on Mars it's
• 23:54
  Speaker 2: farther out so how much less sunlight does it get.
• 23:56
  Speaker 1: Yeah, Mars is much further out than Earth, so the
• 23:58
  Speaker 1: solar energy is like a order of what lands on Earth,
• 24:02
  Speaker 1: but you know, it's closer than a lot of other planets.
• 24:04
  Speaker 1: You want to send something to Urinus or Neptune. By
• 24:07
  Speaker 1: the time you get out there, the Sun is a
• 24:08
  Speaker 1: distant dot in the sky and it's really very little
• 24:12
  Speaker 1: solar energy. So Mars is in a pretty good spot
• 24:14
  Speaker 1: for solar panels because it's close enough to really be
• 24:18
  Speaker 1: able to gather some energy. And when they were building
• 24:20
  Speaker 1: the first rover, that's what they went with. Sojourner in
• 24:23
  Speaker 1: nineteen ninety seven was only supposed to last for like
• 24:26
  Speaker 1: seven days or seven souls actually, so they didn't even
• 24:30
  Speaker 1: ask for like a nuclear power plant that would last
• 24:32
  Speaker 1: for ten to fifteen years. They thought that would be
• 24:34
  Speaker 1: a waste, and this is a very experimental technology. So
• 24:36
  Speaker 1: they put a little solar panel on top, and that
• 24:38
  Speaker 1: little guy well outperformed its mission. Instead of only going
• 24:42
  Speaker 1: for seven souls, it worked for eighty three and it
• 24:45
  Speaker 1: traveled up to one hundred meters. This is like the
• 24:48
  Speaker 1: first time people are really driven around on an alien planet.
• 24:51
  Speaker 1: It was pretty awesome.
• 24:52
  Speaker 2: That's totally incredible, And so since then, how many of
• 24:56
  Speaker 2: our rovers have used solar.
• 24:58
  Speaker 1: Spirit in two thousand and three also used solar panels,
• 25:01
  Speaker 1: and it went like eight kilometers before getting trapped in
• 25:04
  Speaker 1: the sand. Opportunity in two thousand and three was amazing.
• 25:06
  Speaker 1: It lasted for fifty three hundred souls and drove forty
• 25:10
  Speaker 1: five kilometers until dust storms blocked its solar panels.
• 25:15
  Speaker 2: I gotta be honest, I'm not like a very uh
• 25:18
  Speaker 2: sentimental person. I don't cry very often, but when I
• 25:21
  Speaker 2: when I read about some of these rovers, I get
• 25:24
  Speaker 2: like kind of choked up, Like when Curiosity landed. I
• 25:26
  Speaker 2: remember watching the landing and like shedding the single tear.
• 25:30
  Speaker 2: I feel like some of this stuff is just like
• 25:32
  Speaker 2: the best humans have to offer. The fact that we've
• 25:34
  Speaker 2: managed to land a rover and then operate it for
• 25:37
  Speaker 2: fifty three hundred souls is just like amazing.
• 25:40
  Speaker 3: So sorry, okay, Opportunity.
• 25:41
  Speaker 1: Yeah, Opportunity was great. And by then the Mars rover
• 25:44
  Speaker 1: program had really sort of earned its strife. People believed
• 25:47
  Speaker 1: that it could work and that it could last for
• 25:49
  Speaker 1: a while, that you weren't sending something up there that
• 25:51
  Speaker 1: was just gonna drive around for a week. So Curiosity
• 25:54
  Speaker 1: actually has a nuclear power plant, and that's one reason
• 25:57
  Speaker 1: why it's still going like it doesn't matter how dusty
• 26:00
  Speaker 1: it is or what the weather is like on Mars.
• 26:02
  Speaker 1: Curiosity gets its power from its nuclear battery.
• 26:06
  Speaker 2: Nice and I think some of the ones that have
• 26:08
  Speaker 2: solar also have radioactive heaters. They're not like Thermo coupled
• 26:12
  Speaker 2: to generate electricity, but you still got to it gets
• 26:15
  Speaker 2: pretty cold up.
• 26:15
  Speaker 1: There, exactly. And Insight Lander, which doesn't have a roverb
• 26:19
  Speaker 1: but is operating on Mars and doing a bunch of science,
• 26:21
  Speaker 1: it also has solar panels and they have to worry
• 26:24
  Speaker 1: about keeping them clean. Perseverance, which land in twenty twenty,
• 26:27
  Speaker 1: which is the one with the helicopter on top. That
• 26:30
  Speaker 1: one also has a nuclear plant. So these days we
• 26:33
  Speaker 1: still see some with solar panels, but it's sort of
• 26:35
  Speaker 1: transitioning to the nuclear power plants because these are longer lasting,
• 26:40
  Speaker 1: lower risk missions.
• 26:42
  Speaker 3: I'm probably being too picky.
• 26:44
  Speaker 2: Are those power plants or are those thermoelectric generator couplers.
• 26:48
  Speaker 1: No, you're right, these are not fission plants. These are
• 26:51
  Speaker 1: like nuclear batteries.
• 26:51
  Speaker 2: These are RTGs, So when we were writing our book
• 26:55
  Speaker 2: about space settlements, I was super surprised because I don't
• 26:58
  Speaker 2: think I had really absorbed it's a magnitude of the
• 27:01
  Speaker 2: dust storm problem on Mars, which of course is going
• 27:04
  Speaker 2: to be majorly bad for solar panels. Can you tell
• 27:07
  Speaker 2: us a bit about the dust problem on Mars.
• 27:10
  Speaker 1: So dust is really a big problem on Mars and
• 27:13
  Speaker 1: a big problem for solar panels in general. Even here
• 27:16
  Speaker 1: on Earth, dust storms are a big issue. Like there
• 27:19
  Speaker 1: are big power plants in the deserts, like in the
• 27:22
  Speaker 1: UAE that produce like ten megawatts, but they estimate that
• 27:26
  Speaker 1: dust storms in the desert have reduced production at those
• 27:29
  Speaker 1: facilities by like forty percent. In order to clean them,
• 27:32
  Speaker 1: they need water because you've gotta spray them clean. You
• 27:35
  Speaker 1: can't scrape them clean or you'll scratch them. So it
• 27:37
  Speaker 1: takes a huge amount of water to clean these desert
• 27:41
  Speaker 1: solar panels. They're currently estimating it costs like ten billion
• 27:46
  Speaker 1: gallons of water per year just to keep those solar
• 27:49
  Speaker 1: panels clean.
• 27:50
  Speaker 3: Oh my gosh, and that's got to get pumped in
• 27:51
  Speaker 3: from somewhere.
• 27:52
  Speaker 1: It's crazy. And you know, for a really big solar installation,
• 27:56
  Speaker 1: even like a one or two percent reduction results in
• 27:59
  Speaker 1: a huge loss annual revenue over the life cycle of
• 28:02
  Speaker 1: these plants. It can be like billions of dollars. And
• 28:05
  Speaker 1: so for most of these facilities here on Earth, the
• 28:08
  Speaker 1: cost of keeping it clean and just keeping the dust
• 28:12
  Speaker 1: off of the panels is about ten percent of the
• 28:14
  Speaker 1: operating cost of these facilities.
• 28:16
  Speaker 2: So it's interesting what we were writing our book. An
• 28:18
  Speaker 2: argument we came across often was like, well, we'll figure
• 28:21
  Speaker 2: out how to do this stuff when the stakes are high,
• 28:23
  Speaker 2: so you know, like we'll figure out how to clean
• 28:25
  Speaker 2: the solar panels on Mars. But apparently the stakes are
• 28:28
  Speaker 2: already super high on Earth. Like, this is tons of
• 28:31
  Speaker 2: money that's being lost. If it was just like finding
• 28:33
  Speaker 2: a slightly better like rags you could buff off the dust,
• 28:37
  Speaker 2: presumably somebody would have like spent the money on that already.
• 28:41
  Speaker 2: But anyway, Okay, wow, I didn't realize the scope of
• 28:45
  Speaker 2: the problem.
• 28:45
  Speaker 1: Yeah. Well, ironically it's kind of good news for space
• 28:48
  Speaker 1: exploration that is also a problem here on Earth because
• 28:51
  Speaker 1: it means that like big money players are going to
• 28:54
  Speaker 1: try to solve this problem. You know. It's just like
• 28:56
  Speaker 1: in particle physics when we need to invent something fancy
• 28:58
  Speaker 1: and new. Look around to see, like, hmm, is some
• 29:01
  Speaker 1: other huge industry invented this already for other reasons, you know,
• 29:06
  Speaker 1: like we use GPUs in our machine learning at the
• 29:09
  Speaker 1: large shad drunk collider. GPUs that were invented for like
• 29:12
  Speaker 1: making Call of Duty a better video game, right, not
• 29:15
  Speaker 1: for unraveling the secrets of the universe. But turns out
• 29:18
  Speaker 1: they're awesome for inverting matrices and solving machine learning problems.
• 29:22
  Speaker 1: And so you know, this is a well worn path
• 29:24
  Speaker 1: in science. Remember, like the NSF's entire budget is a
• 29:28
  Speaker 1: tiny fraction of the amount of money people spend on
• 29:31
  Speaker 1: like cell phones every year. So if you can get
• 29:34
  Speaker 1: like the military or some huge commercial industry involved in
• 29:37
  Speaker 1: your physics problem, then probably they're going to solve it
• 29:40
  Speaker 1: for you in about ten minutes and come up with
• 29:42
  Speaker 1: a really cheap solution. And so fortunately, there are a
• 29:45
  Speaker 1: lot of people working on ways to keep solar panels clean,
• 29:48
  Speaker 1: especially here on Earth, and we hope that some of
• 29:50
  Speaker 1: those might translate to Mars.
• 29:53
  Speaker 2: It sounds like at the moment we don't have a
• 29:54
  Speaker 2: great solution, but on the other hand, Mars does have
• 29:57
  Speaker 2: plenty of water it's not easy to get it's going
• 30:00
  Speaker 2: to be a bit of a pain, but you know
• 30:03
  Speaker 2: you'd be in a lot more trouble if you were
• 30:04
  Speaker 2: on the Moon for example.
• 30:05
  Speaker 1: Yeah, that's true. But Mars also has a whole lot
• 30:08
  Speaker 1: of dust. I mean, there are these huge dust storms
• 30:11
  Speaker 1: that can like choke up Mars for weeks at a time. Anyway,
• 30:14
  Speaker 1: solar panels on Mars face a very similar problem to
• 30:17
  Speaker 1: solar panels on Earth. The wind is going to blow,
• 30:19
  Speaker 1: dust is going to block it. And as the dust
• 30:22
  Speaker 1: blocks the solar panels, the energy output drops. And if
• 30:25
  Speaker 1: you're driving your rover across the surface, you got to
• 30:27
  Speaker 1: keep those panels clean. People might remember in the movie
• 30:30
  Speaker 1: The Martian he spent a good fraction of his day
• 30:33
  Speaker 1: washing his solar panels to keep his energy production up.
• 30:36
  Speaker 2: Stressful, you went through and you talked about a bunch
• 30:39
  Speaker 2: of rovers that sort of extended their stay longer than
• 30:43
  Speaker 2: we thought that they would. In the end, for a
• 30:45
  Speaker 2: lot of them was dust. The thing that killed them.
• 30:48
  Speaker 1: In the end. It was Yeah, now spirit got trapped
• 30:51
  Speaker 1: in the sand unfortunately, So it wasn't a solar panel issue,
• 30:54
  Speaker 1: but like Opportunity, it was a dust storm that blocked
• 30:58
  Speaker 1: its panels and basically killed it. It couldn't stay warm
• 31:01
  Speaker 1: and it couldn't keep moving. The same thing for the
• 31:03
  Speaker 1: inside lander.
• 31:04
  Speaker 2: Mars is far enough way that you can't just sort
• 31:06
  Speaker 2: of like send someone out there to brush something off
• 31:09
  Speaker 2: if you get a dust storm that you didn't expect.
• 31:12
  Speaker 1: If you're not willing to send your kids to climb
• 31:14
  Speaker 1: up on your barn, you're definitely not sending them to
• 31:16
  Speaker 1: Mars with a brush.
• 31:17
  Speaker 3: Probably not.
• 31:18
  Speaker 2: So let's take a break and then talk about methods
• 31:21
  Speaker 2: that we've come up with so far for trying to
• 31:23
  Speaker 2: keep our solar panels clean on Mars. Okay, so we
• 31:38
  Speaker 2: have some experience with trying to keep solar panels clean
• 31:42
  Speaker 2: on Mars. You know, we've sent up enough rovers that
• 31:44
  Speaker 2: we've probably learned a thing or two. So Daniel, what
• 31:47
  Speaker 2: do we do now? And we just hope that there's
• 31:49
  Speaker 2: no dust storms that take out our rovers or can
• 31:52
  Speaker 2: we be proactive?
• 31:53
  Speaker 1: Yeah, Thoughts and prayers don't really work very well when
• 31:55
  Speaker 1: it comes to keeping your mission going on an alien planet.
• 32:00
  Speaker 1: Back to what the listeners were mentioning, you might imagine,
• 32:03
  Speaker 1: like let's just put a rag on the thing, or
• 32:04
  Speaker 1: like put a mechanical arm with a brush to wipe
• 32:07
  Speaker 1: stuff off, but as people mentioned, like it could scrape it.
• 32:10
  Speaker 1: These solar panels have a delicate surface, and if you
• 32:14
  Speaker 1: scrape it, it's going to reduce the absorption and then
• 32:16
  Speaker 1: also be a way for dust to gather, right, creating
• 32:19
  Speaker 1: little valleys that are gonna like grab the dust out
• 32:22
  Speaker 1: of the air. And you really don't want anything like
• 32:24
  Speaker 1: mechanical on your rover as much as possible. You want
• 32:27
  Speaker 1: to keep it simple because you know, things that turn
• 32:30
  Speaker 1: and grind, they're gonna break, they're prone to failure. And
• 32:33
  Speaker 1: dust on Mars is particularly tricky because it's really really small,
• 32:38
  Speaker 1: Like there's sand and grit, but the actual dust it's
• 32:41
  Speaker 1: sort of like particles of smoke. It's hyper fine, and
• 32:45
  Speaker 1: so in order to brush that off you need a
• 32:46
  Speaker 1: brush that had really really really fine bristles, otherwise you're
• 32:51
  Speaker 1: just gonna slide right over it. So it's really a
• 32:53
  Speaker 1: tricky problem.
• 32:55
  Speaker 2: So if you send your kids out there, they should
• 32:56
  Speaker 2: have a really good ventilators.
• 32:59
  Speaker 3: That's the lesson.
• 33:00
  Speaker 2: I think one of the listeners suggested, like an air compressor.
• 33:04
  Speaker 2: Could you send the rover with like an air compressor
• 33:07
  Speaker 2: and like blow it off.
• 33:09
  Speaker 1: You might be able to. I mean people have talked
• 33:10
  Speaker 1: about like helicopter blades blowing things off the solar panels,
• 33:13
  Speaker 1: and we do have one helicopter on Mars. Remember, the
• 33:17
  Speaker 1: atmosphere is very very thin, and so helicopter blades don't
• 33:20
  Speaker 1: produce a whole lot of wind, and so that sort
• 33:22
  Speaker 1: of seems very dangerous. In terms of air compression, you know,
• 33:25
  Speaker 1: you're either gonna have to bring compressed air or you're
• 33:28
  Speaker 1: gonna have to compress it, which takes a lot of energy,
• 33:31
  Speaker 1: and so you're probably not going to in the end
• 33:33
  Speaker 1: win by compressing your own air.
• 33:36
  Speaker 2: So we've struck out a few times. Now, what are
• 33:40
  Speaker 2: some other options?
• 33:41
  Speaker 1: But you know, these little guys on Mars have lasted
• 33:43
  Speaker 1: for a long time, so you might wonder, like, how
• 33:46
  Speaker 1: is it possible to keep going for fifty four hundred days.
• 33:49
  Speaker 1: There are a couple of tricks. One of them basically
• 33:52
  Speaker 1: is thoughts and prayers, which means waiting for wind, because
• 33:56
  Speaker 1: you know there are storms on Mars, and sometimes those
• 33:59
  Speaker 1: Martian storms will like deposit a bunch of dust on
• 34:01
  Speaker 1: your solar panels, and sometimes they will blow it clean.
• 34:04
  Speaker 2: It's got to be amazing to have spent like a
• 34:07
  Speaker 2: decade of your life planning a project and then hoping
• 34:09
  Speaker 2: a breeze comes by so that you can keep collecting data.
• 34:12
  Speaker 2: A breeze comes by on Mars. But okay, so breezes
• 34:16
  Speaker 2: work sometimes.
• 34:17
  Speaker 1: Yeah, and spirit and opportunity, both of these relied on
• 34:20
  Speaker 1: breezes for years to keep things clean. The Mars Pathfinder
• 34:23
  Speaker 1: mission unfortunately didn't benefit from such winds, and its solar
• 34:27
  Speaker 1: panels got blocked and never recovered. You know, that's the
• 34:30
  Speaker 1: tough thing about it. Is like if you go down
• 34:31
  Speaker 1: to zero and get too cold, things just stop working.
• 34:35
  Speaker 1: So you really can't like stay cold for very and long.
• 34:37
  Speaker 1: You need like a consistent source of energy. But you know,
• 34:40
  Speaker 1: NASA has clever engineers and they've come up with some
• 34:43
  Speaker 1: like really counterintuitive solutions to this problem. One of them
• 34:47
  Speaker 1: is poor dirt on the solar panels.
• 34:50
  Speaker 2: What no, no, no, no, no, that's that's gonna make
• 34:54
  Speaker 2: it worse.
• 34:54
  Speaker 3: All right, How does that help?
• 34:56
  Speaker 1: It's sort of amazing. It's because the soil, the dirt
• 34:58
  Speaker 1: on Mars has some dust in it, but mostly it's sand,
• 35:02
  Speaker 1: and that sand actually works as a cleansing agent. So
• 35:06
  Speaker 1: you pour like a bunch of the sand on top,
• 35:08
  Speaker 1: and it'll grab those little hyperfine pieces of dust and
• 35:12
  Speaker 1: pull them along with it. And so you pour dirt
• 35:15
  Speaker 1: on top of it, and the sand will pull that
• 35:17
  Speaker 1: dust off of your solar panels.
• 35:19
  Speaker 2: And that's less likely to scratch it than like using
• 35:23
  Speaker 2: a rag.
• 35:23
  Speaker 1: That's less likely to scratch it. Here you're also relying
• 35:26
  Speaker 1: on wind, and this is something they discovered accidentally. They
• 35:29
  Speaker 1: have this seismometer on Mars, which is separated from the
• 35:32
  Speaker 1: inside lander, and there's a tether that connects the seismometer
• 35:36
  Speaker 1: to inside itself, so that like sends along power and information.
• 35:40
  Speaker 1: And they were trying to keep the teather in place,
• 35:42
  Speaker 1: so they dumped a bunch of soil on top of it,
• 35:44
  Speaker 1: and they noticed that when wind came along, it would
• 35:46
  Speaker 1: blow off the soil and leave it shiny, sparklingly clean.
• 35:51
  Speaker 1: So then they thought, all right, let's try this on
• 35:52
  Speaker 1: the solar panels, and so they on purpose dumped sand
• 35:57
  Speaker 1: on top of their own solar panels. And like that
• 35:59
  Speaker 1: must be terrifying, right, Like, you make this mistake, there's
• 36:02
  Speaker 1: no going back. But it worked, and it boosted the
• 36:05
  Speaker 1: energy production by like five percent.
• 36:07
  Speaker 2: Can you imagine telling the funders for this project like, no,
• 36:10
  Speaker 2: hear me out, We're gonna dump dirt on the solar panels.
• 36:15
  Speaker 3: It's gonna be great.
• 36:16
  Speaker 1: They try to time it for like the windiest part
• 36:18
  Speaker 1: of the day, So basically it's like you're building a
• 36:20
  Speaker 1: little thing to catch the wind, which is gonna push
• 36:23
  Speaker 1: the sand along, which is gonna grab the dust with
• 36:25
  Speaker 1: it and clean off the solar panels. So it makes
• 36:29
  Speaker 1: better use of the wind than just waiting for the
• 36:32
  Speaker 1: wind to blow this hyperfine dust away.
• 36:34
  Speaker 2: Fat is incredible and super smart, But so if I
• 36:39
  Speaker 2: was going to be living in a settlement on Mars,
• 36:43
  Speaker 2: I would hope we'd have a better option than dumping
• 36:46
  Speaker 2: dirt on top of the solar panels.
• 36:48
  Speaker 3: Are there any more.
• 36:50
  Speaker 2: Like futuristic options that we're hoping we'll be able to
• 36:54
  Speaker 2: test out in the future.
• 36:55
  Speaker 1: There are people working on ways to clean solar panels
• 36:58
  Speaker 1: here on Earth for all the reasons that we talked to,
• 37:00
  Speaker 1: and billions of dollars in research, not just because we
• 37:03
  Speaker 1: want to have our rowers drive around on Mars, but
• 37:05
  Speaker 1: because we want to have efficient energy production here on
• 37:07
  Speaker 1: Earth without spending lots of time, money, and especially water
• 37:11
  Speaker 1: on cleaning them. What they're looking into our solid state solutions,
• 37:14
  Speaker 1: things with no mechanical moving parts. And one of the
• 37:17
  Speaker 1: most promising technologies is called electrostatic cleaning, and it takes
• 37:21
  Speaker 1: advantage of the fact that these dust particles are not neutral.
• 37:25
  Speaker 1: They tend to have positive or negative charges. You know,
• 37:28
  Speaker 1: it's not that hard to make something ionized. Like the
• 37:31
  Speaker 1: reason you get static electricity when you walk across the
• 37:34
  Speaker 1: floor or when you rub a balloon against your head
• 37:37
  Speaker 1: is that you're like stripping electrons off the surface of
• 37:40
  Speaker 1: the material. So you know, these electrons in some cases
• 37:42
  Speaker 1: are kind of loosely held, and so dust is like
• 37:45
  Speaker 1: flying around the atmosphere in Mars and ends up losing
• 37:48
  Speaker 1: some of its charges. So these dust particles are charged,
• 37:51
  Speaker 1: which means you can push them with electric fields.
• 37:55
  Speaker 2: So you would like start from the center and sort
• 37:58
  Speaker 2: of move the electric charge outward to move things off
• 38:01
  Speaker 2: the edges of the panels.
• 38:03
  Speaker 3: Is that the idea?
• 38:03
  Speaker 1: Yeah, so you actually build oscillating electric fields. You have
• 38:07
  Speaker 1: the electric fields that go one way and then another way,
• 38:10
  Speaker 1: and in one configuration they will push off like positively
• 38:13
  Speaker 1: charged particles, and then you flip it to push off
• 38:15
  Speaker 1: negatively charged particles and the idea is just to like
• 38:18
  Speaker 1: loosen them so then they drift off. So you like
• 38:21
  Speaker 1: loosen the negatively charged particles and then they drift away.
• 38:24
  Speaker 1: You flip it and you loosen the positively charged particles
• 38:26
  Speaker 1: and they drift away. And this process of oscillating the
• 38:30
  Speaker 1: charges is actually a little bit violent for the uncharged particles,
• 38:33
  Speaker 1: and they can end up stripping them of their electrons
• 38:36
  Speaker 1: charging them so that they can also then get pushed away.
• 38:39
  Speaker 3: Is that good or bad?
• 38:41
  Speaker 1: That's good? Right? So you want to push away the
• 38:43
  Speaker 1: negatives and the positives and the neutrals, So you flip
• 38:46
  Speaker 1: the electric field so you get the positives and then
• 38:49
  Speaker 1: the negatives, and then the process you convert the neutrals
• 38:51
  Speaker 1: to either positive or negative so they can get flipped
• 38:54
  Speaker 1: off in the next cycle.
• 38:55
  Speaker 3: Nice, got it? Awesome?
• 38:57
  Speaker 2: Hey? And how have we been able to try something
• 39:00
  Speaker 2: like this on Earth yet?
• 39:01
  Speaker 1: So this technology is under development in research settings, and
• 39:04
  Speaker 1: what they're working on is like minimizing the amount of
• 39:07
  Speaker 1: electrical current that's needed, just like with the air compressor example,
• 39:11
  Speaker 1: you don't want to develop a system to boost your
• 39:13
  Speaker 1: energy which costs more energy than it saves, right, And
• 39:16
  Speaker 1: so in the case here, they're focusing on using a
• 39:18
  Speaker 1: very small electrical current and one that only needs to
• 39:22
  Speaker 1: be applied for like a couple of minutes every day
• 39:24
  Speaker 1: in order to boost the overall electrical generation power of
• 39:28
  Speaker 1: your system.
• 39:29
  Speaker 3: Nice, I like it.
• 39:29
  Speaker 2: This is clever, all right, babe? You can get me
• 39:32
  Speaker 2: to move to Mars. What else do we have?
• 39:34
  Speaker 1: This involves also like treating the solar panels with like
• 39:36
  Speaker 1: a few nanometers of special material to cover the glass
• 39:41
  Speaker 1: and then applying a voltage across that. There's other system
• 39:44
  Speaker 1: to have, like a little metal bar that passes over
• 39:46
  Speaker 1: the panel, though that's mechanical, so it's less attractive. Otherwise,
• 39:50
  Speaker 1: people are working on systems like vibration, like instead of
• 39:53
  Speaker 1: blowing something on it or brushing something across it, these
• 39:56
  Speaker 1: are tiny, little hyperfine particles. What if you just like
• 39:59
  Speaker 1: shook them a little bit, you know, very very gently
• 40:01
  Speaker 1: shook them. Could the dust just like fall off?
• 40:04
  Speaker 2: I feel like I would worry that over time the
• 40:07
  Speaker 2: panels would hold up less well if they're constantly being
• 40:09
  Speaker 2: slightly vibrated. But I'm I'm sure someone's thought of that.
• 40:12
  Speaker 1: No, You're right, that definitely is an issue. I mean,
• 40:14
  Speaker 1: anytime you're like shaking your system. You're going to be
• 40:17
  Speaker 1: like loosening connections and something that you don't want to
• 40:20
  Speaker 1: shake off might shake off one day. But in test
• 40:23
  Speaker 1: this works pretty well for like the bigger pieces, the
• 40:26
  Speaker 1: very very fine particles don't tend to get shaken off
• 40:29
  Speaker 1: as well using the vibration system. But you know, people
• 40:32
  Speaker 1: are working on this, and people are working in lots
• 40:33
  Speaker 1: of other different directions. It's definitely a big area that
• 40:36
  Speaker 1: people are exploring because we want to be powering our devices.
• 40:39
  Speaker 1: We want them to last as long as possible. You
• 40:41
  Speaker 1: spend like hundreds of millions of dollars developing this thing,
• 40:45
  Speaker 1: and people's entire careers are focused on the questions that
• 40:49
  Speaker 1: might be answered. You don't want it to go up
• 40:50
  Speaker 1: there and then get blocked by a dust storm on
• 40:52
  Speaker 1: like week two and then it's over right. You want
• 40:55
  Speaker 1: to definitely want something beyond thoughts and prayers.
• 40:57
  Speaker 3: Absolutely well.
• 40:58
  Speaker 2: In more long term, you've got human living on Mars.
• 41:00
  Speaker 3: You don't want them to have to.
• 41:01
  Speaker 2: Spend all their day cleaning the like many football fields
• 41:04
  Speaker 2: worth of solar panels that you're going to need to
• 41:06
  Speaker 2: run your settlement.
• 41:07
  Speaker 1: Although you know children have to have something that they
• 41:09
  Speaker 1: complain about, or does it really count as a childhood?
• 41:12
  Speaker 2: You know, they can be maintaining the cricket ranch for
• 41:14
  Speaker 2: the protein. They'll have plenty to complain about if they're
• 41:18
  Speaker 2: living on Mars.
• 41:19
  Speaker 1: Yeah, that's true. Children are creative. They'll always find something
• 41:22
  Speaker 1: to drive about. Mommy, these crickets are too spicy.
• 41:26
  Speaker 2: You're lucky you've got any protein.
• 41:28
  Speaker 1: That's right, exactly. So, as humans think about how to
• 41:31
  Speaker 1: explore the solar system and how to power our little
• 41:33
  Speaker 1: robotic devices that are going to lead the way and
• 41:36
  Speaker 1: tell us where the most promising places are for our
• 41:39
  Speaker 1: humans to maybe one day build colonies, we want them
• 41:42
  Speaker 1: to keep their power, and we want those solar panels
• 41:45
  Speaker 1: crystal clean as well as down here on Earth. If
• 41:48
  Speaker 1: we're converting ourselves into sustainable sources of energy, we want
• 41:51
  Speaker 1: our solar panels to stay clean and dry without requiring
• 41:55
  Speaker 1: a bazillion gallons of water.
• 41:57
  Speaker 2: Absolutely, this is definitely an area where if the space
• 42:00
  Speaker 2: scientists figure out a solution, it would help the.
• 42:02
  Speaker 1: Rest of us too, exactly, And maybe that means that
• 42:05
  Speaker 1: our solar panels will eventually be self cleaning and neither
• 42:08
  Speaker 1: me nor Kelly will have to get up on the
• 42:10
  Speaker 1: roof and do some squeegeing.
• 42:11
  Speaker 3: You mean my kids. It'll be good that they don't
• 42:14
  Speaker 3: have to go on.
• 42:15
  Speaker 1: The exactly all right. Thanks for joining us in this
• 42:19
  Speaker 1: tour of solar panels around the Solar system. We hope
• 42:22
  Speaker 1: they all stay sparkling clean. Thanks very much Kelly for
• 42:25
  Speaker 1: joining us today, and thanks everybody for listening.
• 42:27
  Speaker 3: Thanks for having me have a good time.
• 42:28
  Speaker 1: Everyone, Thanks for listening, and remember that Daniel and Jorge
• 42:39
  Speaker 1: explain the Universe is a production of iHeartRadio. For more
• 42:43
  Speaker 1: podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or
• 42:48
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