Coruscant, Heat Dissipation, and Basic Worldbuilding

Coruscant (Photo credit: Wikipedia)

Continuing along the lines of world-building for science fiction settings, I had planned a post on just how much heat Coruscant (of Star Wars universe fame) would generate and the fact that the planet would almost certainly require giant polar heat radiators or something along those lines. Trouble is, I did the math and… it doesn’t work out that way.

Coruscant supposedly has a population of one trillion, which sounds like a lot, and is, but that’s only about 125x Earth population and in the end, if you figure something like 2500 watts per person of energy (above anything but Iceland on Earth today), you end up with about 1% of the energy received from the sun. That would likely cause noticeable global warming but nothing that couldn’t be dealt with easily in the Star Wars universe (like putting out umbrellas in space to reduce solar radiation by 1%). So, no need for super-duper lasers beaming hear from Coruscant.

As with all my posts on these sorts of things, I’m not saying authors can’t use tropes, in this case, the planet-wide city. But some of the overlooked details from such tropes can make for useful technical hooks for authors. Imagine if Coruscant did have huge polar laser beams. This would give the planet a very different look, wouldn’t it? Sort of like the polar jets on a black hole. Makes for an interesting aesthetic touch you could add. But take it further: the polar jets would be dangerous to fly through, so now you have a peril for an out of control ship to deal with (drama!). Or maybe you could envision space stations that harvest this waste heat, legally, or not. Or maybe this energy can be targeted via mirrors or the like and now you have a very high power weapon.

Starspeeder 1000 flying in the planet of Corus...
Starspeeder 1000 flying in the planet of Coruscant. (Photo credit: Wikipedia)

If you have planet wide cities and don’t want to deal with the waste heat, no problem. I don’t recall anyone complaining about it regarding Coruscant (other than me of course, but I’m weird that way). But if you do want to deal with it, the possibilities range from the aesthetic to the dramatic.

But let’s turn back to why I thought waste heat would be a problem for Coruscant. There are really two reasons:

  1. In the movies, the entire planet looks like it is covered by a continuous city
  2. The various on-line Star Wars resources indicate that at times: The entire surface of Coruscant was covered by sprawling kilometers-high ecumenoplis. (Wookieepedia, which provides references). The population is given as, variously, 1 to 3 trillion.

Let’s take that data and do some number crunching, something any worldbuilder should consider doing to “kick the tires” on their premise. Coruscant is basically earth sized, which means we can use Earth data for surface area, etc. We also have Earth data that a high-rise like the World Trade Center towers in NYC had about 20,000 people in them during the day. Let’s assume Coruscant has about 20,000 people in a 100x100m area, as a starting point. Now Coruscant probably has factories and various open spaces but it is supposed to be covered with “city” multiple kilometers thick so 20,000 people for the relatively short WTC tower is spread out over a taller Coruscant structure, as partial offset. This would yield a population of: one million trillion people.

Hold on you say, the poles aren’t necessarily populated and you have too little room for factories and such. Okay, scale it back by 10x or even 100x, this is still one to ten thousand times higher population than per the Star Wars cannon. Not that it really matters, the Star Wars setting is a lot of fun regardless, but the population estimate is just way out of whack. As a check, one trillion people seems like a lot but if spread over the earth, that’s about 2 people per square kilometer. For comparison, Hong Kong has a population density of 6500 per square km and applied across the world, would  result in a population of 3300 trillion. You can scale that back for a lower population density but to get to the stated population of Coruscant, you’d have to scale it back by 1500x which doesn’t qualify as “city-wide planet” in my book since Wyoming has a population density of 2.3 people per sq. km. and the only US state less dense is Alaska, at 0.5.

Let’s assume a lot of the planet is factory and other “empty” space, it still seems like the population of Coruscant should be something more like 100 trillion or higher. Now, if you assume 2500 watts per person, and that might actually be a pretty paltry number for a super high technology society that seems to fly everywhere, the power dissipation per person is on par with the total energy received from the sun. Aside from that being a large amount of power to generate, that’s a lot of heat to dissipate: without heat radiators you are going to quickly fry the planet. And if population is 300 to 1000 trillion, now you talking about 10x solar power. The planet would burst into flames.

Of course, you can ignore this. The Star Wars guys do. But wouldn’t it be a cool setting that did not ignore it? You’re the author. The only limits you have are  your imagination. How would you handle that much energy? The power conduits and power plants probably not as much a problem as it sounds: the planet is after all, entirely city. Plenty of room to ship power around and plenty of space for power planets. But how do you extract the waste heat and export it into space? Maybe all over the planet there are cooling towers. But these aren’t your nuclear power planet cooling towers: these extend out of the atmosphere and are in a vacuum within their walls. They literally pipe heat out from the surface of the planet into the space. Aside from being really cool because they would be really tall and really big, imagine how the planet would look: it would be studded with cylinders. Plus intersolar space is a not a total vacuum, there would be plenty of particles to “light up” in the path of these heat export beams: the planet would have hundreds or thousands of beams of light radiating from it. In short, it would look very different from how Coruscant is shown in the movies. Not a bad way to differentiate your planet-wide city from ones your readers have already seen, right?

Just to be clear, this is not something I’m demanding science fiction writers address. Instead, I’m just pointing out that if you take your worldbuilding to the next level, you might find ways to enhance your setting, even find a cool hook for an entire novel premise.

In addition to heat dissipation, a planet like Coruscant would have interesting issues with regard to food (where does it come from, how many planets does it take to feed Coruscant, how many food freighters per day would have to arrive?) and even simple oxygen replenishment: what is converting the CO2 back to O2? Could be oxygen processors but that will take yet more power. Would make for an interesting touch on your world though, wouldn’t it: vast oxygen regeneration plants to go along with the waste heat towers. And really big freighter ships to feed the planet, star destroyer size!


Happy world building!


12 thoughts on “Coruscant, Heat Dissipation, and Basic Worldbuilding

  1. You think too much. 😉

    Joking, all good stuff to keep in mind. But, might you be over thinking some of it? Big cities in Japan and China do not have heat dissipators. That’s what the atmosphere is for. Wouldn’t the heat just pump out into space like it does now on earth? Everyone lives in climate controlled areas now anyway, so wouldn’t it be the same on that planet and damn the environment? Food could be an issue, unless it is generated like this:

    1. Cities on earth are warmer than the local areas. If everything was city, everything would be a lot warmer. On the scale of a planet-wide city, it is the same as if every spot on the planet received 1x up to 10x the current solar radiation which is clearly enough to make the non-climate controlled areas unlivable. You could go with that but Star Wars has people in the open air 🙂

      On the food- yeah there’s a whole range of things you could do. You could probably process it on-planet with the appropriate energy source. Not saying it can’t be dealt with, just that it might be an interesting thing to add to your setting.

  2. I always wondered where their food and oxygen came from, since without photosynthesis, there would be nothing to do the old 6CO2+6H2O=C6H12O6+3O2 thing. Machines, I guess, but of course they’d have to get their energy and biomass from something too. Does Coruscant have oceans, at least? Oceans would have an effect on the heat issue as well, since water is a huge heat sink.

    I tend to get knocked a bit out of disbelief in SF by things like ice worlds and desert planets for these reasons as well. I always want to know where the O2 comes from, and why (in the case of the desert planet) day-night temperature oscillations are not so extreme that they would render the surface uninhabitable for humans at least.

    1. Exactly! There wouldn’t be ice worlds (most likely) or desert worlds for the same reason: no bio-system to replenish O2. I’m glad I’m not the only one who thinks of these things.

      Single biome worlds don’t actually make a ton of sense, to me. BUt they are convenient and well accepted.

    2. I guess to continue the thought, if the population was a 1 trillion, that wouldn’t be enough to raise the temperature enough to matter a whole lot (assuming no greenhouse gas emission). However 1 trillion seems low for the type of planet-wide city as described, which might have a population of 100 trillion or more, *that* population level would be the same as doubling or even 10x the solar radiation hitting the world and that much extra energy *should* require heat dissipation, more than what you could radiate out through the atmosphere (if you wanted a reasonable surface temp 🙂 )

      Again, not saying anyone has to do anything about it in their stories. Just noting it might make a more interesting story if it was addressed. Of course, to be honest, I tend to think of Star Wars as more science fantasy, despite the fun pseudo-technical drawings and the like (really, how is a solar sailor supposed to get you anywhere fast?).

      1. Oh I see you said the same thing, re the science fantasy. I’d guess there might not be any greenhouse emissions to speak of, either, as they would have fusion or antimatter reactors or whatever they used in that universe?

  3. It would certainly be possible to have a world that’s in an ice age where there is extensive glaciation, though. And of course, there could be a very cold world that still has salty oceans which don’t freeze and may support phtoplankton like organisms that provide some free oxygen at least. Of course planets with climates that are hostile and harsh by human standards, but that support life adapted to the local conditions, are always possible. I just wonder if we could walk around on their surface and breathe their atmosphere without any special protective gear at least. Of course, that can make the “human raised by aliens” trope or “new frontier” tropes harder to do.

    The thing about Star Wars is it was a space opera, not a hard SF story. So the planetary/space setting was a backdrop for a traditional adventure story. Having the characters in environmental suits for all the on-planet scenes would make it harder for viewers to identify who is who, of course, and possibly to relate to them as well (why the baddies wore that body armor that didn’t do anything and the good guys didn’t). It’s also why knights often seem to “forget” to don their helms and visors in fantasy movies.

    Alas, my biology background makes it a bit harder to keep all this in mind sometimes. I agree it can be fun to think about these things.

    1. We do have proof of ice worlds, to some extent: there’s some evidence for several “Snow ball” earth periods where there were glaciers at very low latitudes (and presumably altitudes, not so exciting if we’re talking very high altitude). But in the end, I don’t think the entire world was ice-bound as it is usually depicted.

      But in the end, you’re right: its space opera (or science fantasy), take your pick. Fun to watch but not hard science fiction.

      I come at this more from an engineering background. So, for instance, buzz-druids- what’s that about. Instead of a missile that delivers an explosive that immediately destroys the enemy target, it delivers a droid that slowly takes the target apart? Where’s the sense in that. But entertaining enough. Although we skip the Padmi/Anikin thread. The dialogue is too painful 🙂

  4. You raise a lot of interesting points, and it does seem like some of the “ecumenopolis” structures would be devoted to reclaiming energy and to food production. If they reclaimed a lot of heat/energy they might not have to “generate” as much energy to begin with. Then they could cover building surfaces with solar collecting material, and generate energy without creating exhaust.

    It doesn’t have to be what we think of as “solar panels;” there’s an intriguing solar roadway under development, which consists of solar collecting material sandwiched between plates of thick glass. Each module can be removed and replaced for repair. They also embed tiny lights, which allow messages to be displayed on the road surface, warning of accidents or construction ahead, etc. If similar material was used on outside building surfaces, you wouldn’t need external billboards, because you could display messages right on the buildings themselves.

    They also could install some form of windmills on high structures — although this could pose a hazard to flying vehicles. Nothing impossible to deal with, but your laws and piloting conventions would have to account for them. Another interesting flight hazard, perhaps, dodging turbine blades in an effort to elude persuers.

    As for food generation, very large greenhouses can double as air filters, and would remove some noxious chemicals while venting oxygen into the surrounding atmosphere. The better question is, can enough greenhouses be built to produce adequate food for a huge population? Some organisms do better in greenhouses than others. You could have plenty of greens, for instance, but I’m not so sure about carrots, potatoes, corn, soy, etc, and that also doesn’t consider seed production for next year’s crop, or how pollination would be achieved for crops like apples that need bees to produce fruit. And, would everyone on the planet be forced into veganism, or where are they going to get their meat?

    For me, though, the biggest obsctable to a true ecumenopolis is the oceans. As we all know, Earth’s surface is 70% water. Building a city that covered all of the water would be difficult at best, because as we all also know, water is constantly moving. Even if parts of the city were under water — nice for the aquatic races, to be sure — if substantially the entire ocean surface is covered with water, that dramatically changes the entire function of the planet. The weather would be different without exposed ocean surfaces. The food chain in the seas, which for us is based on sunlight reaching the water, would have to be utterly different. And how many terrestrial organisms depend on water life for part of their diet? The entire food web of the planet would be different without plankton, fish, etc.

    Granted, Corruscant is the is the seat of a massive empire. They certainly could import any food they wanted. But then you have the issue of garbage generated by an ecumenopolis. DON’T get me started on the garbage..!

    1. Great thoughts! as you point out, there’s many ways to address various issues. Depending on one’s story, there may be no need to address them at all but science fiction readers often read SF for the author’s view on how their cool setting could actually work so I think it is great to kick these things around.

      And besides, by thinking through some of these things, an author might find something very useful for a plot twist or even a core premise to a story.

      I definitely agree on the oceans and also wonder if it would really make sense to cover them up. In the end, it would still be a very interesting world if the oceans remained intact and all land was covered (except maybe the poles).

      As part of this exercise, I was a bit surprised to find that while 1 trillion people sounds like an awful, it doesn’t result in a very high average population density across an Earth sized world. Obviously, there is a lot of empty space on earth. I think for a trillion people, you could find ways to manage the energy and food without a lot of imports. But one trillion seems very low for an “ecumenopolis” world, where 100x or more of that seems more appropriate, in which case, I think there would have to be imports, some way to manage waste heat, etc. But again, that’s not to say it can’t be done, just that there is opportunity to work through some of the side-effects and in the process create something unique.

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