Upward Bound: Space Farming


Since the dawn of agriculture, few things
have troubled farmers more than clouds in the sky when they want none or their absence
when they’re desperate for a drop of rain. But things change when you’re doing your
farming above the clouds, in space. Last time in the series we discussed power
satellites, a way of potentially bringing vast amounts of renewable and cheap energy
back to Earth. A point we made at the time was that electricity
is what fuels modern civilizations. Of course it’s not what people run on, and
it’s good to remember that people still run on food, and civilization remains dependent
on it too. That is our topic today of course, food and
the farming to make it, and how to do that on other planets or in space. Since we’ll be talking about food for the
next half-hour, it might be a good idea to grab a snack and a drink before continuing. In the grand scheme of survival, getting dinner
is basically priority number one, followed shortly thereafter by not becoming something
else’s dinner. The vast supermajority of cells in your body
are devoted to this. Indeed most are actually bacteria unrelated
to you, growing in your digestive system, and most of the remainder are red blood cells
running down a vast supply highway taking oxygen and nutrients to your other cells. Only a tiny fraction of your cells are actually
neurons, the bits presumably doing all the thinking that makes you, you. Civilization is a lot like that too. Only a fairly small fraction of the land we
use is for people to live in, far more is cultivated farmland, highways, factories,
warehouses, and so on. Needless to say, any portions of that we can
add more verticality to, or get off the planet entirely, and free up space for stuff down
here, either for more people and our other projects, or reforestation and native ecology,
is a good thing. So that will be our other focus later today,
whether or not we could realistically bring food down to Earth to feed folks living in
an ecumenopolis, for example. It should be noted before we jump into discussing
the idea of space farming that we have a few extra considerations. First, we are only interested in farming today,
not generalized ecology, which we’ll look at more in a couple weeks in Exporting Earth,
but at the same time, even when we think of a given crop as growing by itself, it’s
not typically monoculture, it’s just the dominant species of a fairly simplified polyculture. Everything evolved to a certain amount of
mutual reliance, like needing insects for pollination and soil aeration, and so any
space farming will generally need to incorporate these too or you’d end up with inferior
growth or even none at all. The other side of that though is that this
is a futurism channel, and it isn’t unusual for us to discuss genetic engineering or cybernetics
as pathways forward. I want to mostly bypass that today, but we
shouldn’t ignore possibilities like getting people to run on electricity, outright manufacturing
food calories without using plant growth, or highly engineered organisms that are vastly
more efficient at producing calories or able to do it in peculiar environments. Those are topics for another time though. Finally, while plants as food will be our
focus, it’s worth remembering that farming isn’t just growing corn, its growing livestock
and luxury or medicinal crops too. We often skip meat when discussing food in
space, and one of the reasons for that is because it isn’t too efficient. That’s a good place to begin, because efficiency
is very important to farming and it’s also quite variable. One might say an efficient farm is the one
that grows the most calories per acre, another might say it’s the one that produces the
most calories per man hour of work, another the most dollars of revenue and profit, and
so on. Each of these is entirely valid, and will
vary a lot by crop and market. Incidentally, since we normally stick to mostly
metric here, there are two-and-a-half acres per hectare. Even land itself is a pretty iffy term, which
is in part why it’s often hard to get crop yields from historical sources. We’ve standardized a lot of these as we’ve
moved into the modern era, but for instance the Hide, one of the better known old land
terms, was actually the term for the amount of land a single family could survive on and
work, rather than a set area. Which is appropriate since “Hide” was
the old word for family. That varied a lot by local soil fertility,
generally somewhere between 60 to 120 acres. In modern terms it’s far less, a Hide would
be well under 10 acres while a family of farmers might work thousands of acres. You can often get yields vastly higher, in
terms of space, by adding more resources or manpower. A typical heated greenhouse with a tailored
environment can produce some staggering quantities of food, typically boosting yields by a factor
of 10 or more, and going vertical or adding supplemental lighting makes this even better. This isn’t really economical yet, but it
has been getting there, particularly for things that don’t keep well and already need a
lot of manpower for harvesting, like tomatoes. As automation improves we’ll see more of
this too, as if you can have robots doing most of the construction of greenhouses and
most of the work in harvesting them, you’d hit a tipping point where it got cheaper than
keeping traditional farmland under till. It’s one of the reasons I and some others
always handwave away the food concerns about more people, we could easily support a vastly
larger population than now on existing cultivated land by going this pathway, saves a lot of
water too, it just requires a lot more manpower. So long as one person can produce the food
for several people though, this is not a bottleneck on technology. Nowadays we only use a couple of percent of
the population for farming, but if you need 20 billion people working to make food for
100 billion, that still leaves an enormous workforce for other things. You wouldn’t though, agricultural automation
can be rather tricky, especially for some crops, but we’re getting there. The same issue applies to vertical farming,
even ignoring the lighting issue, a skyscraper devoted to growing plants is flat out absurd
economically at the moment. As we get better at construction that will
probably change. That manpower issue is a big one for space
missions though. You send a team of six people to Mars to explore
the place, and you can grow some food on the ship or the planet to supplement their supplies
– particularly the ones that don’t store well or compactly – but that means one or
more of your team members is devoting a lot of their time to growing food, not exploring
or maintaining the ship or base. Hydroponics also adds mass to the mission,
you’re not saving yourself any cargo if you need more equipment and space for growing
food than simply storing it would take. At a current cost of thousands of dollars
per kilogram to escape from Earth’s gravity well, that adds up to a lot of mass when you
factor in the water requirements. Another problem, though more with quality
of life, is that your menu isn’t just controlled by what you can easily pack with you or grow
on spot, but what tastes good. Food in space generally tastes awful, and
we’ve got this problem on airplanes too. Your taste buds and smell get all messed up
by changes in pressure and humidity, and we actually pressurize planes to be closer to
sea level. On spaceships or Martian bases we’d likely
keep the pressure even lower to minimize leaking. This is not a big deal for farming, just a
little food for thought. Dietary preferences will probably vary off
Earth in unexpected ways and challenge our culinary specialists in equally unexpected
ways. However, in the long term it just makes sense
to grow your food off-Earth, so we might as well start looking at the advantages and disadvantages. The two big advantages are obvious, it cuts
down on supply costs and problems when you can grow your food near at hand, and the very
nature of extraterrestrial habitats means you have a very artificial and controlled
environment. You don’t have to worry much about disease,
pests, or invasive species ravaging your crops. You can alter temperature and humidity and
nutrient content very easily since you have to create them all from scratch in the first
place. The disadvantages though are that you have
to create it all from scratch in the first place, and this includes a lot of factors
normally not in play on Earth. I obviously can’t just toss some seeds onto
Mars or the Moon or dump them out the airlock on the ISS and expect them to grow. We should start with two things we don’t
normally have to worry about on Earth, lighting and gravity. Light itself isn’t in short supply anywhere
closer than Jupiter, but the specific spectrum and duration is another matter. The only place in the solar system with anything
like a normal Earth Day is Mars, and since that tends to be target number one for colonization,
this topic gets skipped a lot. Coincidentally Mars’ has a day just a little
longer than Earth’s, 24 hours and 37 minutes, your next closest match would be Saturn’s
Moon Mimas at 22 hours and 36 minutes, and that’s about it for anything that is vaguely
close to our natural circadian rhythm. Most moons are tidally locked to their planet,
and take a lot more than 24 hours to orbit and complete one day-night cycle, the ones
that don’t tend to be radiation blasted and have very little gravity even compared
to our own Moon. Asteroids, on the other hand, typically have
day lengths much shorter than our day, with the majority rotating several times a day. Plants don’t need much gravity, and many
seem to do just fine with none, since they mostly use it as a way of orienting themselves
and many can do that with light instead. How they handle changing day lengths is a
little harder, and varies a lot by plant. The good news is Mars at least is just fine
for plants. Stick a pressurized dome up on Mars and you
can reliably grow food there, and chances are decent the gravity will be just fine for
people and animals too though that’s educated guesswork for now. It’s possible many animals would be fine
in such environments, or even thrive, one could imagine in lower gravity chickens might
even be able to fly, which might be rather irritating for chicken farmers, but it is
possible even a small change in day length might have bad effects on things, especially
complex ecosystems. The light level is fine too, like Earth it
varies by latitude, but Mars is about half again as far from the Sun as we are and gets
about 43% of the light Earth gets, though its thin atmosphere means more light gets
through, including some harmful frequencies a dome would need to screen out. Ignoring the atmospheric effect for the moment,
and axial tilt, that means that Mars in its tropic band near the equator gets lighting
more like Earth’s more northern regions, Canada or Scandinavia. That’s a big deal for temperature but not
for light itself. As mentioned in the episode on Colonizing
Ceres, even out in the Asteroid Belt, where light is much weaker, most plants would get
enough light to thrive just fine. Light concentration, in the visible ranges
plants work in, is measured in a unit called Lux, some plants prefer shady light, which
can be as little as 1000 Lux, what you could get way out at Saturn, others would struggle
a bit even on the Martian equator. Possibly unsurprisingly, a lot of our key
food crops are very light-intensive, able to soak up a ton of light to power a lot of
biomass creation which we can eat. Of course Mars may be fine in lighting and
gravity but temperature is another story and so are seasonal concerns. Mars has a much longer year than us, and everything
else in the solar system further out has even longer ones. This is a pretty big deal for ecosystems,
when a lot of animals have their life cycles very tuned up to seasons, but isn’t much
of a concern for crop farming. Like a lot of magic, the trick is to use smoke
and mirrors, or at least mirrors. A lot of growing stuff in space is likely
to involve using mirrors and parabolic dishes to create the ideal lighting level and duration,
and possibly gases to absorb certain frequencies of light we don’t want, where we can’t
just filter them out easily with films on the mirrors or domes. One problem with a lot of those frequencies,
like ultraviolet, is that they damage us because of the sheer energy in those higher-frequency
photons, and generally that applies to materials as well, which can seriously shorten the life
time of structures in space. It’s one of your approaches though, you
can build something that is more of a lens than a typical dome and concentrates light
onto a smaller area, to keep it warmer and better lit, and you might be able to use tricks
like that do to farming even way out at Pluto, where only the most shade-loving plants could
even barely grow under the native lighting. One can imagine igloo-like structures made
of ice with a tiny insulated growing section in the middle, with light concentrated there. Of course Pluto is another example of very
long days, and while nowhere near as bad as Mercury or Venus, or indeed even our own Moon,
the Sun only rises there once a week. Many plants can handle perpetual lighting,
like they’d get in space, but really long dark periods is another story. You might be able to do some genetic tweaking
so something could handle the two weeks of light and then the two weeks of dark that
the Moon gets, but your alternative is supplemental lighting, either by light bulbs or orbiting
mirrors that keep a beam of sunlight on a spot. That sounds kind of high tech but isn’t,
and works pretty much anywhere in the solar system. Odds are good just about every decent sized
rock out there has enough gravity for plants to be okay, indeed a lot of taller, vining
varieties might thrive in low-gravity, but almost none have the right day length or ideal
lighting levels. But a lighting satellite is actually a very
simple device, especially around lower gravity places with no atmosphere of their own. You really just need your locations to have
a small beacon to make them easy to target and a small computer to track conditions and
relay requests to a grid of simple satellites that can rotate their big parabolic dishes
to lock onto whoever needs some light and is in their current window. It’s frankly child’s play compared to
Earth’s current satellites and launch costs are barely noticeable, after all on many of
these the gravity is so low you can chuck a cubesat into orbit like a baseball. And it’s just a mirror, probably thin aluminum
foil, with some guidance and a flywheel for power storage and attitude control. They only have to be as big as your orbital
height requires for keeping a good focus on a dome, and the only reason something can’t
orbit an asteroid a meter off the ground is that they are generally only very loosely
spherical so an orbit would be prone to running into things and getting trashed. On many of these, a precise and highly elliptical
orbit could have them fly by a given high rocky outcropping low enough, and slow enough,
you could catch one too. Strange image, we usually talk about colonizing
smaller asteroids by sticking a rotating habitat in them, but you might have one a dozen kilometers
across that started off with just a small cylinder hab embedded into it to provide spin-gravity
for some people and animals, and with the various domes scattered nearby growing food
in those domes, getting supplemental lighting from solar panels or orbital mirrors. This would be home to a family of farmers
who go out into the field in a spacesuit and rover rather than overalls and a tractor. A nice thing about smaller asteroids is their
circumference is small enough you could drive around them to get home rather than needing
to loop back, and most have a polar region where you could stick up solar panels on towers
that have perpetual sunlight. You could also do vertical farming in those
spots too, with towers under perpetual light that rotated every 24 hours. After all, in that negligible gravity, building
tall is easy, you could walk on floors made of tissue paper without ripping them. Now the mirrors can also solve another problem
and that is seasons. A lot of plants rely on changes in seasons
to flower, fruit and ripen. Even on a planet like Mars with a very similar
day/night cycle to that on Earth, you definitely do not get the same seasons. We can fix that, though, by simply reflecting
more or less light into the domes from our mirrors, depending on which season we are
trying to emulate. We can lengthen or shorten the days simply
enough by programming a cycle into our controlling computers. We don’t even need to keep the seasons constant
for the same planet and you wouldn’t want to do that anyway. One dome could be in the middle of summer
while another dome next door is experiencing a winter. The difference could simply be that we are
interchanging mirrors from the one dome to the other as the season changes. This means that seasonal vegetables get produced
all year round and we can condition our soil with the right mix of microbes by recreating
Earth-like seasons in our domes. Speaking of soil and microbes, you will never
take your growing soil off Earth with you. Instead, you’d make that everywhere you
go and generally, even ignoring the microbes and organic content, there won’t be a good
native mixture for growing soil and it would be toxic if you simply dumped some Martian
regolith into a dome and tried to grow plants in it. Fortunately, the key ingredients for life
are rather common, but you will have to mix them up and probably grow your soil in vats
full of microbes like you were brewing beer or yogurt. This is another reason why hydroponics tends
to be preferred, mass being arguably the bigger one, dirt is heavy. Anything we do in space is either a ship,
in which case you want to keep your mass to a minimum so it’s cheap to move it, or a
station that is getting its supplies from Earth. Let’s move onto those stations though. As we can see, most of the celestial objects
in space aren’t really suited for plant growth, it’s doable but a pain, and you
have to basically build everything from the ground up, literally, again there’s no natural
dirt to start with. So it might be easier just to build a farm
in space as a space station. Space is perpetually lit, unlike planets,
moons, and asteroids which spend half their time in the dark, and again most plants handle
perpetual light and low or no gravity just fine. However, same as you can spin a space station
to produce gravity, you can also spin it to rotate every 24 hours. It doesn’t have to spin in the same direction
either, it can be spinning fairly rapidly to produce the necessary spin-gravity, but
still rotate around once a day to provide light to each side, or just have a shutter
that closes. Space is rather big and the Sun gives off
more than a billion times the light Earth gets, plants don’t need that much lighting,
so you hardly have to be worried about wasting light, but we have a ton of different geometries
and multi-purpose paths that could optimize lighting them, which is always a good idea. And again, plants don’t need full gravity
so we’re not nearly as constrained in our structures as we are with a classic cylinder
habitat producing normal Earth gravity. You can make some very large structures, probably
donut shaped toroids, that need very little structural support since they are low gravity
and presumably only have a few people, if any, actually in them. Those folks might be wearing spacesuits inside
anyway, as those plants will likely be kept in conditions optimized to them, not people,
which would often be rather miserably high on temperature, carbon dioxide, humidity,
and so on. Or maybe they’d just be piloting robots
inside these structures instead. I would actually tend to guess most rotating
habitats would do most of their food production off-site in nearby space farms instead, reserving
normal gravity and more hardened structures for themselves and more complete ecologies
like forest and gardens, possibly even bringing in food to supplement the critters living
in those to allow higher densities of wildlife than that ecosystem might otherwise allow,
kind of like having a bird or squirrel feeder, just scaled up a bit, with robots depositing
food here and there for them. This lets you subsidize an ecosystem so it
can be smaller while still having a good amount of genetic diversity in the wildlife. For instance, an elephant back on Earth might
need many hundreds of square kilometers to feed itself, but probably needs far less to
be comfortable and happy if it’s getting additional food trucked in from space farms. The same concept applies to livestock in general. Animals need space, but they likely need as
much gravity as people, so you can minimize their living space by supplementing their
food supply rather than grazing them completely. We’ll talk more about trying to maintain
an actual ecosystem in a couple of weeks in Exporting Earth. So growing food in space for people living
in space is not an easy task but certainly doable. Economically, it’s probably going to be
a lot cheaper to build those space farms up there than to export food up there, even if
launch costs drop quite a bit. The question remains though, could we grow
food up there and bring it down to Earth? And could that ever be economically viable? Surprisingly yes, though as with doing greenhouses
here on Earth, it’s the sort of thing you do when you’re getting kinda crowded or
really want to free up farmland space for other uses. But space farming also gives us the option
of growing genetically modified crops in isolation, to prevent contamination of Earth’s ecosystem,
or because the crops have specific advantages to being grown in space. Indeed, industrial-scale bio-reactors could
be used to grow more than just food. Much of our current agriculture is already
used to produce industrial feedstocks and products, not just food. We already discussed, way back in the Arcologies
and Ecumenopolis episodes, how you could support hundreds of billions of people on Earth, in
great comfort, without having to use most of our land for farming or housing, by going
vertical. As we saw there, the big constraint isn’t
land area but really energy, or rather heat and getting rid of it when you’re done. The thing about vertical farming is that it’s
very like space farming, you are building everything, and while, on the one hand, the
construction and sourcing the resources is easier on Earth, the energy and lighting are
harder on Earth too. You also still have to use all that energy
down on Earth and get rid of the heat, whereas if you’re just importing the final product,
you don’t. Economic viability is always about your core
bottleneck. For farming, that can vary a lot. Land costs, especially good land, transport
costs and storage costs, the price of fertilizer or manpower and so on. On the extreme end of packing people onto
Earth that bottleneck is heat rather than space or even energy or money, though you
could easily end up with a system where heat was taxed to pay for getting rid of it. In that very specific context, it could be
cheaper to bring stuff down. Indeed bringing food down is cheap enough,
as you can aerobrake food pods rather than needing fuel, though that makes some heat
too. This is one of those examples where launch
systems like the Orbital Ring can demolish our traditional view of space since you can
bring stuff up and down those for transport costs reasonably similar to modern freight. And almost as importantly, return your waste
back up to space for recycling. You can harvest asteroids and comets for all
the raw materials you need, but if those are just collecting on Earth you’ve got a bit
of problem. It’s a very long term one to be sure. You shouldn’t need to import more than one
ton per person per year, and even a trillion people are only adding 10^15 kilograms a year
at that point, which would take over a billion years to build up enough waste to raise the
Earth’s gravity by a percent and you’d only be adding around a millimeter a year
to the Earth’s radius. You probably ultimately would want to lift
out as much as you take in, same as cities, farms send food to them and cities ship fertilizer
right back, but there’s no real rush or concern about a mass deficit either. It’s an interesting way to counteract rising
sea levels too, and we’ll talk about a lot of these kind of mega-engineering approaches
to Earth itself in our upcoming series, Earth 2.0, which I decided was a better name for
the topic than Downward Bound. Indeed you might even hang your farms right
down from an orbital Ring, what we call a Chandelier City or in this case a Chandelier
Farm, and such things might be pretty common in terraforming other planets too. Terraforming is a very destructive process
and you’d always start building your orbital infrastructure first, so you might grow your
way down to a planet. To fully terraform a planet, you will be pulverising
it a lot! You can’t make an omelette without breaking
some eggs and terraforming is not a gentle process. This could involve nuking it and smashing
comets, asteroids and other payloads from elsewhere into it. This would cause shockwaves, high winds, massive
dust storms, Tsunamis, and sudden and dramatic chemical changes in the atmosphere and soils. These actions would wreak havoc with any settlements
on the planet and particularly with agricultural domes, so rather than try to protect or recreate
farm space on that planet while bombarding it, it’s just easier to grow stuff in orbit. We’ll also see it’s a handy approach when
dealing with gas giants when we look at colonizing Neptune next month. A great many of our ideas today relied on
vastly cheaper launch costs, and of course that is what this series is mostly about,
how to get into space cheaper and safer and what we can do once we’re there. In this episode, and the last one on power
satellites, we’ve talked about how we can harness the power of radiation in space to
benefit life on the surface of a planet or on a spaceship. In other words, how to harness the power of
star energy — or Solar Energy as we say locally. There happens to be a great course of that
same name over at Brilliant.org that steps through everything from how much energy there
is in sunlight, to how to collect it, to how to engineer the solar energy harvesters themselves. So many of the topics we discuss here can
seem impractical or even utterly fantastic when someone firsts hears about them, but
with a solid understanding of the math and science behind them, we can see a pathway
to making them not just a reality, but the future foundations of our society. To truly understand these concepts, it helps
to have that math and science background, and at Brilliant you can pick those up, learning
at your own rate about the topics that interest you, with user-friendly graphical quizzes
and explanations. If you want to get a better and more complete
understanding of the science behind so much of what we discuss here, you can go to brilliant.org/IsaacArthur
and sign up for free. And also, the first 200 people that go to
that link will get 20% off the annual Premium subscription
Next week we’ll be returning to the alien civilization series to consider the idea of
Parasitic Aliens, like the Goa’uld from Stargate, or the alien from John Carpenter’s
film: The Thing, based on the John Campbell’s classic novella, “Who Goes There?”, our
book of the month. The week after that, we’ll be taking a deeper
look at ecology in space, as we consider how you would move large and complete colonies
on interstellar ships to colonize other worlds, in “Exporting Earth”. For alerts when those and other episodes come
out, make sure to subscribe to the channel. And if you enjoyed this episode, hit the like
button and share it with others. Until next time, thanks for watching, and
have a Great Week!

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