This episode is sponsored by Skillshare. You might have lived in some places you thought
were real holes. But for future residents of the Moon, that
would actually be a good thing... So today we’re returning to the Moon, something
humans haven’t physically done in the almost 50 years since the Apollo program. That will
be fairly important to our discussion today about setting up large scale and permanent
facilities in craters on the Moon, because when we think about going back to the Moon
a major question that always comes up is “Why?” And what will be achieved by walking around
collecting rock samples for a few days? And the answer to that really is “not much”.
Those Apollo rock samples were of great scientific worth and more would be handy but not enough
to justify a mission there at outrageous expense and more than a bit of danger. And why wouldn’t
we just send robotic sampling missions? That’s a lot of why the US hasn’t gone back and
nobody’s worked too hard to be the second to get there. It’s also why when we talk
about returning we tend to talk seriously about long term or permanent facilities. Not
only would a permanent base let us get some serious science done, but it allows us to
begin exploiting the Moon as a gateway to space development and off-world industry,
as we looked at last time in Moon: Industrial Complex.
Inevitably when the topics of bases on the Moon and where to locate them come up, the
popular answer tends to be one of the major craters and usually one of the ones nearer
the poles. We’ll explain why that is today but also some reasons that’s not always
ideal or necessary. Polar craters probably are our best bet, as we’ll see today, but
there are some good competitors, such as equatorial craters or lava tubes.
Our focus today though will be on how such cities will look and how those communities
might develop. We’re interested in cities and settlements, not early bases, stations,
or outposts. So we have to start by explaining why certain places are attractive as colony
locations. To do that, we must first say that these craters
are often huge. Now, the Moon is covered in craters and the vast majority of them are
tiny, but most folks picture a moon crater as several meters across or maybe the size
of a football stadium. And of course many are, but the ones we tend to be interested
in and talk about for bases are much larger, and we have craters on the moon larger than
most nations on Earth. Now while a crater is usually a lot shallower
than they are wide, this still means the big ones can have rim walls many kilometers high
and basins many kilometers deep. That tends to make us think of big domes over these mostly
circular craters, be it the small ones or big ones, their shape having the potential
to facilitate construction of a dome is not the reason for our interest in craters, rather,
the steep and high sides is what we are interested in..
A big deep crater that gets little sunlight can, we believe, get a lot of ice and other
elements down in that bottom, which is obviously a big boon for any developing base or colony.
Those rim walls are an even bigger deal though, because the moon has very long nights and
also has no atmosphere, so when the sun sets it gets way darker.
If you’re on a mountain, you’ll see the Sun set later than those on the ground do,
and not by a small amount either. This is even more the case on our airless moon that
is a lot less wide than Earth and much more sharply curved. As an example, on Mount Everest
on Earth, you can see about 230 miles or 370 kilometers away. That’s almost 1% of the
Earth’s circumference, so the Sun is going to rise about 1% earlier and set 1% later
there as a result. That probably doesn’t sound like too much, but it does mean the
day starts 14 minutes earlier and ends 14 minutes later, if it were at the equator anyway.
For stuff like solar power and agriculture that’s not a trivial difference. It’s
far more extreme on the Moon, about seven extra hours of daylight is added to any position
that high up on the Moon on its equator. However, that much extended daylight time
is not because the Moon is less wide. Indeed, the horizon is actually closer to you as a
result. If you transplanted Mount Everest to Moon, you’d only be able to see half
as far before the horizon was reached, and that horizon distance covers when the Sun
sets or rises. Rather, what mostly controls that altitude-induced extension of the day
length is that the Moon’s day is a month long. So being up high is less effective than
on Earth for letting you see far distances, but that’s more than counteracted by that
really long day. The reverse is also true, that being in a
crater at the bottom will massively shorten your horizon and thus your daylight hours
too, which makes for a very big temperature difference between rim wall peaks, crater
bottoms, and general lunar surface – there’s obviously no sea level on the Moon, not yet
anyway. We can take advantage of that temperature difference, by using heat engines, solar thermal
power, to make some pretty efficient power generators, but more on that later.
Now, I mentioned what these are like on the equator but it’s different at the poles.
As an example, on a sphere that was spinning on the exact same plane as the sun it orbited,
no axial tilt, the north and south pole never actually get dark, there’s no rock rotating
between you and your light source. Almost everything has an axial tilt and indeed the
Moon has one relative to Earth, which it orbits, and relative to the Sun, which Earth orbits.
So the poles of the Moon do get dark. However you don’t need to be up too high there to
be sticking up so much that you get constant sunlight, and indeed those bigger crater rim
walls near the poles stick up enough that they get an awful lot more light than the
half on, half off, you would expect to get on a smooth rotating body.
What’s more, there is no air there so there is no wind, and the gravity is weaker, so
it’s very easy to build tall skinny towers on the moon with great big parabolic mirrors
on them shining light down onto that crater. Done right, you can keep sunlight on there
for a very long portion of the lunar day, even rotating some away on a 24 hour schedule
to mimic something earth-like. So that’s our first big concept change when
looking at crater cities. They’re not a big crater with a big dome on them. Indeed,
a single dome is mostly rather pointless, it’s vulnerable to catastrophic failure
and has to be built all at once. At most you might have a big crater basically bubble-wrapped
in smaller domes built as needed with another big one over top as a secondary shell or shield.
Instead what we’d expect initially is a few small facilities inside a given crater
with some rim wall towers with mirrors on them that also served as transmitters. Along
that rim wall you’d see towers stretching up high enough to be able to keep catching
the Sun and beaming it down to the crater wall, or the smaller facilities in it initially,
adding more towers as you went. Those would probably swivel their light away on a 24 hour
basis to simulate daytime better. That excess light in night-phase probably being cast onto
some of the thermal wadis we discussed for solar thermal power generation in the Industrial
Complex episode. Indeed, if LED lighting is the preferred method of illumination for manned
facilities, beamed and piped light may be limited to industrial uses and growing food.
I should also note that you’d likely be using mirrors for lighting farms as opposed
to classic domes anyway. Everything weighs less there, so it’s very easy to scoop up
tons of rock and pile them on top of structures for added protection, you can then bounce
light in, filtered of harmful frequencies of light, through windows on the side to a
reflective ceiling that lights the place up. Those windows can be down tunnels so you have
thick walls too and with pressure sensitive hatches able to slam shut if the window was
damaged. This approach is a little more work intensive than a dome to initially build,
but far sturdier, safer, and probably more productive and cheaper to maintain in the
long term. As time goes on you’d add more towers and
bigger mirrors to that rim wall. Depending on crater size you might need millions of
people to comfortably fill such a crater and it could easily spill out onto the outside
of the crater wall and the plain beyond. You also have the option of foregoing those towers
in favor of satellites that beam down power and light and signals too, but I suspect the
towers will tend to be the preferred method. Transmission is a big deal on the moon as
we only have line of sight, no atmospheric bouncing of signals, and that horizon is shorter,
so everything has to be via tall towers or off satellites. That’s not for communicating
home to Earth particularly, one side of the moon always points at Earth and the other
side does not. Those dark-side bases, at least dark in terms of having line of sight to Earth,
that are fairly near the Earth-Side might employ very large towers or multiple towers
serving as relay stations to achieve a direct connection to Earth that’s not dependent
on satellites. Odds are though that as the Moon develops
we’d see transmitter towers pop up on every peak, particularly as you can’t really do
geosynchronous, or lunar synchronous satellites for the Moon, and even if you tried you’d
be introducing an enormous signal lag. That’s one way we might see crater villages pop up
too, you put up a tower for power and transmission relay and a small settlement develops around
it. There’s no fossil fuels on the Moon and
no air to use to burn it, so electric power for vehicles and robots is probably going
to be the big thing from Day 1, and while batteries are always good as a reserve, I
suspect we’d see a lot of wireless microwave power transmission incorporated into everything,
which means blanketing the surface with power relays and that can be done incrementally
too. Now, back to those crater cities themselves.
First, I want to stress again that we are looking at cities today, or at least large
settlements, this episode is not about initial bases except as telling us where those bigger
settlements would likely originate from. Those initially tiny bases would logically tend
to be where a city arose from so we need to consider initial base placement, and we looked
at early Bases more themselves in Moon Base Concepts and Battle for the Moon.
To discuss those early settlements better, we have to decide if the Moon’s gravity
by itself is enough for people to live comfortably and healthily, and of course we don’t know
yet. We know it’s unhealthy to live in no gravity but we don’t know if you need Earth-normal,
or close to it, or if even lower gravity than the moon might be just fine. If it isn’t
though, we need simulated gravity in the settlement, potentially spinning the entire thing around
inside that crater, but for today we will assume that Moon gravity is good enough; or
that if not, people’s individual homes or main workplaces could incorporate a small
rotating section. Those would be interesting rotating houses
or apartments, as your door would be in your roof and you’d probably walk down your ceiling
to a floor that was basically a spinning cylinder slight curved to be narrower at the bottom.
You wouldn’t have windows except maybe in that ceiling and I suspect those would tend
to be tilted or wobble just a bit to keep Earth in the same place with the night sky
seemingly whirling around it. It might be rather nauseating to see that whirling around
several times a minute on the smaller ones. That’s an option, as is mega-sizing it to
include a whole crater, but we’ll instead assume that folks can either live in Moon
gravity just fine all the time, or need some minor medical assistance of some sort to do
so, or that years long deployments, with occasional trips back to Earth or a rotating space station,
are adequate. That’s the easiest case and the one that
most favors major moon expansion. If you need to live under spin gravity most of the time,
then expansion around Earth-Moon space is likely to be in Cylinder Habitats and not
on the Moon. The Moon is still industrially and scientifically attractive, thus encouraging
folks to live there, but I wouldn’t expect major residential settlement. Alternatively
if you can live just fine in some personal house or dome of your own, then it’s a lot
more attractive. Incidentally I doubt we’d ever see a ton
of classic single domes. It is possible to flat out terraform the Moon complete with
oceans and air, though quite a pain, but while it’s airless you view the world through
windows with rapid automatic shutters in case of damage, not while sitting in t-shirt and
shorts under a big glass dome. I’m sure that would happen, but more in the way folks
get a kick out of sitting on cliffs or a boat, for a bit of thrill, not to relax and soak
up the Sun. It’s just a lot safer to use a mirror and a lens to bounce such light into
some nice garden and lawn you’ve got growing in something akin to a bomb-proof bunker.
This is especially true if the gravity isn’t enough for constant comfortable living and
so homes need to spin and thus might as well be buried underground too anyway.
This doesn’t really give us the lush fertile crater folks might be picturing though, but
a few caveats on that. First, a local culture gets influenced and built around by what the
major advantages and disadvantages of the area are, and the ever present fear of a catastrophe
breach or puncture is going to be on their minds no matter how safe you make things,
same as Hurricane fears are for folks on coasts, or flooding for those on rivers, or earthquakes
for those on the Pacific Rim. Expect it to influence every aspect of their life, subtly
or overtly. That might diminish with time though, micro-meteors represent no true threat
to a dome and bigger ones are likely to be easily detected and vaporized by the sort
of infrastructure we’d expect in place if the Moon was seriously colonized, but customs
and traditions and building regulations and the architecture and lifestyles resulting
from them are likely to hang around long after the need is gone.
Second, keeping that in mind, technology does improve and especially where necessity drives
it. As we mentioned in spaceship design, folks living in a spaceship have this same concern
and might address it by just having ultra-comfortable spacesuits as default clothing, complete with
some self-inflating head-bulb that could trigger if the pressure dropped, or some life-capsule
drone following them around who could expand and swallow them if the dome ruptured and
they got blown out. Indeed it’s pretty probable folks in the future, even just a few decades
from now, we’ll be used to being followed around everywhere by some sort of drone or
a whole posse of them and the low lunar gravity will make buoyancy and lift of such drones
easier. Third, technology improves, and we just won’t
have a bunch of Crater Cities on the Moon this century, regardless of technology. Communities
don’t just emerge and grow that rapidly, even if we got the tech and infrastructure
to do this all tomorrow it would still be generations before there were a bunch of major
settlements on the Moon. That’s a lot of time for other technologies to develop and
grow mundane and routine, like minor cybernetic augmentations that let folks wander around
a vacuum conscious and somewhat safe for a few minutes. Or have clothing that was literally
made of a bunch of microscopic robots that just swarmed into whatever shapes you needed
them to be, be it a spacesuit or a simple tool. I’d also not be surprised if a lot
of folks just had themselves rebuilt so they could just live in an unpressurized hut and
stroll outside onto the airless low gravity surface entirely casually or at least virtually
through advanced telepresence. Fourth, just because homes and workplaces
and other places where folks spent most of their time might tend to be carved into a
rim-wall like some cave or bunker, doesn’t mean the crater would be lifeless. Whether
it’s a big dome or a bunch of small ones connected together, that’s perfectly fine
for crops and parks. Especially for farmland, where most of the farming is probably largely
automated anyway, a catastrophic puncture just means the loss of one plot of land and
the organics inside it. Not a good thing but not some horrible headline reading dome punctured,
a dozen children sucked into the void. I would bet most craters would get terraformed
and have a big lake at the bottom, many having a center island around the peak that often
juts from the center of craters. This isn’t just to be pretty either, you’re very likely
to be setting up your solar thermal power generation to initially take advantage of
that cold crater bottom as one end of your heat reservoir for a heat engine to produce
power, and as that expands or if you’re using nuclear power instead, it’s nice to
have a giant puddle of water to use as a cooling pond, and you could keep that evaporating
and raining on the crater wall in a smaller single dome crater or pump the moisture around
to the other tiers of the crater domes. The center of the crater would also receive more
radiation than the rim areas which are shadowed by the crater walls themselves.
Then you’d probably have many-tiered and individually domed levels, with doors and
windows in them leading into homes and workplaces. This would probably sprawl out onto the exterior
of rim walls and onto plains, though likely in growing crater sprawls as many of them
touch or even combine. More like an upside-down city, with a foam of domes at “street-level”
and the buildings underground. Indeed, while there are a lot of big craters
on the Moon, as mentioned earlier most are smaller, often craters inside craters, and
a lot of these probably would be a single dome. You might dome a crater inside a crater
or near your main crater and turn it into a stadium, for instance. Playing any ball
games there is likely to be interesting though considering how long a ball, be it a baseball
or soccer ball or volleyball, is going to spend in the air before landing. That might
require some rather large stadiums as a result. I’d also not be surprised if a vacuum-version
developed a lot, there’s nothing really stopping you from playing baseball in spacesuits
for instance. Ultimately though I think we’d still see
those major habitats really being built into the crater walls, not down at their bottom
or on their skin, but safely burrowed inside. It’s just easier to have a mirror array
concentrate light and send it down a shaft that can automatically seal if punctured to
be spread out and bounced around inside some places safely tucked away under meters of
sturdy rock, with large gardens and farms inside and out.
Those would be rather beautiful gems for folks to look at from rim-wall and nearby orbital
facilities, but on the Earth-side of the Moon at least, you’d always be able to see Earth
right there anyway, so we might see more of this sort of crater parks and farm on the
Far or Dark side of the Moon. Of course, these might serve as the seeds
to eventually terraforming the Moon, but that’s a topic for another day.
A bit of a recurring theme we have for space colonization is that it will be very skill
intensive, and in our increasingly knowledge and skill-based future, it’s going to be
quite a challenge to ensure small groups of explorers or colonists have rapid access to
all the information they need and in a format they can absorb most easily and quickly. Of
course that’s a problem we have nowadays down here on Earth too, and is where online
videos and classes like those offered by Skillshare can be invaluable.
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graphic design courses, like Aaron Draplin’s “21 Tips for Speeding Up Your Design Workflow”,
to be incredibly helpful in improving my own work, and Skillshare has classes to fit your
schedule and skill level on many helpful topics. A premium membership is less than $10 a month
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this special offer, and start learning today. So next week we’ll head back deep into the
far future to look at the end of the Universe, the Heat Death, and ways we might postpone
that. And in two weeks we’ll look at ways we might avoid potential catastrophes nearer
home in time and space, as we discuss Climate Change Mitigation techniques for natural or
artificial calamities, be it volcanoes, asteroids, or carbon dioxide.
But before then we have a bonus episode coming up this weekend, where we’ll explore how
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