Thanks to Linode for  supporting this SciShow video!

You can check them out at linode.com/scishow. That link gives you a $100 60-day  credit on a new Linode account. [♪ INTRO] When humans eventually get back to the Moon, they’re going to run into  a few familiar challenges.

There’s the low gravity which makes  everyone skip around like school children, and the nonexistent atmosphere. But the peskiest problem  might just be all the dust. Dust clogs spacesuits and  sandblasts other equipment.

It’s a huge threat to the safety  and success of any lunar mission. But while scientists can’t do much  about the Moon’s gravity or air, they actually have a solution for the dust. And it involves microwaving the lunar surface.

Moondust, technically known as lunar regolith, is the ugly craft glitter of the solar system. It gets everywhere and scratches everything up, without adding a little sparkle to your day. And it got that way because  the Moon’s surface has spent the past few billion years being broken  up by countless micrometeorite impacts.

That made the regolith  particles very fine, very rough, and very difficult to pack down. Plus, with the Moon’s low  gravity and lack of atmosphere, they’re super easy to kick up. And once they are, it’ll be a long time  before they fall back to the ground.

During the Apollo missions, regolith clouds completely obscured landing  sites and ruined some equipment. So with national space  agencies and private companies eager to get humans back to the Moon, and eager to build permanent bases up there, they’ve got to figure out a  way to stop kicking up dust with every rocket launch or landing, or  with every jaunt in a lunar golf cart. One obvious solution is to construct  a more solid base of operations, build stuff like landing pads,  roadways, and other structures that can protect more delicate equipment.

And on Earth, materials like steel and  concrete are our cheap, easy go-tos. But shipping those ingredients all the  way to the Moon is ridiculously expensive. Like, right now, it costs around $1 million to get a kilogram of stuff from  Earth onto the lunar surface, giving your average landing pad a sticker  price of, oh, a trillion dollars or so.

So instead, scientists have been looking  to kill two birds with one stone: Cut costs by using a building  material that’s already on the Moon, and get rid of that meddlesome moondust  by using it as that building material. And they want to do this by  beaming a bunch of microwaves into the Moon’s surface,  and sintering the regolith. Sintering might not be something  that you hear about all the time, but I can almost guarantee that you have something sintered in your home right now.

The technique takes powdered minerals or metals and heats them up just enough  so that they don’t melt, but the edges of the grains are  gooey enough to fuse together. In fact, that’s what’s going on inside a  pottery kiln whenever you fire ceramics. All those teeny, tiny, wet clay particles  are heated up, using high intensities of infrared radiation, until they can  fuse into one big solid coffee mug.

By using different minerals, sintering  can create some incredibly hardy stuff. For example, the ceramic  silicon carbide can be found inside turbines and jet engines. And it just so happens that the  Moon’s regolith contains some great stuff for sintering, like  silicates and small amounts of iron.

But if we tried to heat it  up in a large lunar kiln, it would take a lot of time and use  up a lot of our energy resources. Some scientists have proposed using lenses to concentrate the infrared  radiation coming from the Sun, but it would still limit how  effective the sintering would be.   See, infrared rays don’t penetrate very far into the surface of whatever they’re heating up. They only reach a depth of about 6 millimeters.

So a several centimeter-thick structure  that’s sturdy enough to drive a lunar rover on or land a rocket on would  need to be built up in successive layers. And that comes with its own risks: the  layers could flake away from each-other, or could crack with subsequent passes. That’s where microwaves come in.

And yeah, they’re going to heat up the  Moon like they would last night’s pizza. While a microwave oven timer ticks down, the microwave radiation bouncing around inside makes the water molecules flip-flop back  and forth millions of times a second, giving them an energy boost and making them jostle against the molecules next door. And as you might notice when you rub  your hands together really quickly, with enough molecular jostling, that pizza can reach mouth-scalding temperatures.

But microwaves don’t just interact with water, and they don’t need to be  confined to a countertop box. A microwave ray gun can heat up  any molecules that are polar, meaning they have areas of  differing electrical charge. In this way, microwaves can heat up  the polar molecules in lunar regolith, and do it incredibly quickly.

I’m talking about 1000 degrees Celsius per minute. Which means it’d take less than two  minutes to reach the temperatures needed to sinter the grains together. And the cool thing is that scientists  can use the exact same kind of waves that are made by the microwave  oven sitting on a home countertop.

They just have to crank up the power  to help the waves penetrate further. According to some experiments,  microwaves that are 300 times stronger than in the average oven will penetrate  about half a meter into the lunar regolith. That’s plenty for building a sturdy landing pad.

So far, scientists have mostly  experimented with lunar regolith simulants, which are approximations of the real thing made by crushing up Earth rocks with  the right chemical composition. But they’ve also tried sintering real  moondust that Apollo 17 brought back. Interestingly, it seems that the real  deal works even better than the simulant.

That’s because the Moon’s  silicate grains tend to be coated in extremely thin layers of iron, and  scientists can’t really replicate that here. Now, it’s a terrible idea to put metal  forks or foil inside a microwave oven. Those large chunks of metal  tend to reflect microwaves, creating electric currents and impressive,  not to mention dangerous, sparks.

But powdered metals are much  better at absorbing microwaves, generating proportionally more  heat for the energy put in. So in general, a mineral powder that’s  been enriched with metals like iron can make the sintering process  even more energy efficient. But the fact that the Moon’s regolith  has iron mixed in could also help us out in a different way, because iron  is famous for being magnetic.

We could use magnets to sort  through the lunar regolith grains, and make sure the stuff that’s  easiest to sinter is laid down where we actually want to build stuff. You know, instead of just blasting the  surface with microwaves willy-nilly. Now, all this microwaving  still means we have to ship some equipment up to the Moon, but all our astronaut contractors  will need is the microwave hardware, a solar or nuclear power source, and  some robotics to move everything around.

And according to one estimate, until  shipping costs drop below $110,000 per kilo, this microwave sintering technique  is probably the best way to go. The next step in all this research is to test how sintering would actually  work in the lunar environment, and design the equipment  that would be used up there. One day, astronauts may use the power  of microwaves to build landing pads, lunar highways, maybe even brick buildings.

And if you want to go even further  out there in the applications, one team proposed sintering  the inner curve of a crater to create a smooth parabolic antenna. It’s innovative solutions like  these that will really pave the way for the future of lunar operations,  whether it’s exploration, mining, or as a stepping stone to deep space. This SciShow video is supported by Linode, a cloud computing company from Akamai.

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And don’t forget to be awesome! [♪ OUTRO]