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.
Linode provides you and your company with solutions for cloud computing,
storage needs, databases, and all that fun stuff.
Pretty much any company or organization could
find a way to ramp up their workflow with Linode.
Whether you’re a professor using cloud computing for your grading platform
or a gamer using cloud computing for your streaming needs,
Linode provides the services that you use every day.
Even CEOs that want to keep up with their business analytics
can do that with Linode’s help.
We use cloud computing for our most important activities at work,
so we’re so happy to have the support of Linode for this video as well.
You can put Linode in your corner too by clicking the link
in the description down below or going to linode.com/scishow
for a $100 60-day credit on a new Linode account.
And don’t forget to be awesome!
[♪ OUTRO]