In my previous two questions regarding temperature regulation and Rotations I set up the idea of creating a multi-layered shell world consisting of planetary crusts stuffed inside one another creating multiple planets in the space of one. In this continuing series, I'll be looking at sectioning the layers to be most efficient.

In a galaxy far far away, the Imperator of a Stellar Civilization decides to create a monument to his empire's technological achievements by creating a multi-layered shell world. He designates a convenient portion of empty space along a proper orbit around their star as the site for this world. They dedicate an astounding amount of resources and energy to complete this project. But as always, another issue occurs.

How would a shell world like this be best sectioned to utilize the energy from its core and the incoming solar energy?

What I'm looking for is how to be most efficient between layers baring in mind that some of these layers will be used for habitation while others will be used for industry and so on and so forth. For reference, habitable temperatures for this species are between -5 and 40 degrees Celsius and to stick with a nice solid number we can assume 7 layers will be created on this project.

Image for Reference: The world of Septerra Core

  • $\begingroup$ I think 7 layers would be a lot, the temperature increases about 25 C per km down (granted, it would be lower because of the airflow but still), you'd have to end up with extremely thin shells to stay within your defined temperature ranges. $\endgroup$
    – Nathan
    Nov 15, 2018 at 20:44
  • $\begingroup$ This is the primary reason why I started the series of questions with Temperature regulation. And it is linked in this question to provide context and reference. $\endgroup$ Nov 15, 2018 at 21:41
  • $\begingroup$ Then I misunderstood your question, appologies $\endgroup$
    – Nathan
    Nov 15, 2018 at 21:59
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    $\begingroup$ What distinguishes your 7 layer planet from other megastructures, such as Couruscant. In Star Wars, Couruscant technically had a single "ground layer," but it built vertically thousands of feet up. Some of Paolo Soleri's more extreme Arcologies also permitted one to live without ever setting foot on the ground (though I don't think he's recommend it) $\endgroup$
    – Cort Ammon
    Nov 16, 2018 at 5:03
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    $\begingroup$ Hmmm, I actually can't provide a good answer for that. I mean there are obvious differences but structurally they represent the same concept of having a world that fits far more than its surface area would state. On a functional level, the only difference between this is that far more people would live under artificial skies. That and how this world functions must necessarily be different because of the whole going through layers bit. $\endgroup$ Nov 16, 2018 at 16:23

1 Answer 1


I don't think utilizing the core temperature or the solar flux is of any importance: building a planet is in no sense an efficient usage of resources, so why should the final product be efficient? Temperatures can be controlled with giant nuclear powered fans or huge glass domes and so they should not be the leading factor in designing such a planet.

Instead the real question is, what could be done on this planet? It's a monument so it should be beautiful and impressive, so heavy industry definitely is a no go. I personally would use the planet for:

  1. Diplomatic center
  2. Rememberance activities
  3. Holiday destination
  4. Trade center
  5. University
  6. Library
  7. Bank

It goes without saying that the bank should be the lowest level: there is no safer place to store gold than miles underground. It also does not need much interaction with the surface. A single shaft all the way to the outermost layer with an impressive building should do the trick.

Similarly, a library is in no need of sunlight. Scholars can happily study using artificial light. At the lower levels the enviornment changes are minimal, allowing the books to be kept in good condition. Placing the university on the level right above the library then makes sense as well.

Since this is a beautiful planet and a huge amount of wealth will be gathered here it makes sense to allow a complete layer for the trading of goods. However, the trade center needs to be completely underground so that all trade can be checked (and taxed) while it's lowered down.

Of course, what's the point of a monument if nobody sees it? Everybody in the universe should come by and spend some time here. The third layer has quite a bit of space open to the outside allowing it to become a beautiful holiday destination. Most people won't stay long so there will be a lot of traffic so 'airports' could be placed here as well.

Rememberance activities are always a core aspect of monuments. The second level is already considerable smaller than the lower levels, but it still has plenty of room for huge structures commemorating the fallen and honour our glorious leaders.

The diplomatic center should be the jewel that tops the crown. The most beautiful shell is obviously the one that can see the entire outside universe. It also allows emperors to leave the planet quickly if this is required, or to flee down to the lower levels if it is an outside threat.

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    $\begingroup$ An interesting way to set up the world. It leads me to the idea that you could also have a conspiracy theory around a hidden 8th layer that's a government blacksite. $\endgroup$ Nov 16, 2018 at 16:24

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