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So I'm making a post-FTL world in which humans are the first, and so far only, species to explore the stars. It's thousands (if not millions) of years in the future, and we've become post scarcity. Antimatter, Antienergy, Fusion, Fission, genetic engineering, molecular 3D printing, and FTL light travel have all been developed and perfected. Basically the only thing we can't do is manipulate gravity freely.

What form does my space habitat take to house the largest population of humans in a world where the limiting factors are only the forces of gravity vs structural integrity?

Restrictions:

  • No Handwavium material, but feel free to create structures completely out of carbon nanotubes, gallium, gold, or any other material provided it won't decay fast enough to hurt structural integrity or irradiate people to death.

  • Structure should be made to last 1,000 years minimum.

  • Any given enclosure need to be connected to another enclosure with a walkway that can be walked through in a manageable amount of time, like an hour or less. It's a quirk that future humans have, wanting to be as closely together as possible.

  • It should be expandable when possible.

Assume:

  • Logistics such as food, water, and electricity are all self contained in any given structure using '(S)ignificantly (A)dvanced (T)echnology [that it] appear[s]to be magic.' No need to worry about it I'll work around whatever.

  • Any size planet, black hole, or other astronomical body can be found and moved or made using S.A.T., so long as the body can exist at all. I.E.: Any star with enough mass to collapse into a black hole will, but any star below that size can be found and used.

  • Radiation coming from space is neutralized. However, if you use something radioactive like a sun in your design, you need to account for the mass of appropriate radiation shields.

  • Construction time is no object.

Given these perameters, how do I make the larges livable habitat possible?

Some possible forms the station could take:

  • An orb that encircles a black hole to use for gravity.

  • A series of super dense planetary cores that creates gravity for each consecutive floor building outwards in layers that encircle the entire planet until gravity is too weak, and then the outermost layer is connected to the outermost layer of another structure build around a planetary core.

  • A hollow cylinder surrounding the barycenter of a series of planets that all give off ~1g.

I am only looking for the calculations regarding structural integrity, and maximizing size of living space. It doesn't matter how I'm going to make it, I just want to know what shape I should make it in.

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This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

closed as primarily opinion-based by Mołot, Raditz_35, Separatrix, Gryphon - Reinstate Monica, RonJohn Sep 6 '18 at 10:48

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ There is no way to answer a question about what could be done millions of years into the future, especially if you throw physics out the window with ftl. Also, constructing the largest possible maximizes one and only one thing: size. There are other important parameters. Making the largest one physically possible makes no sense. But that's just a side note, it doesn't have to make sense to be fun $\endgroup$ – Raditz_35 Sep 6 '18 at 8:19
  • $\begingroup$ Hard science can't apply when you've given a situation that isn't possible by what we currently consider hard science. $\endgroup$ – Separatrix Sep 6 '18 at 8:29
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    $\begingroup$ While this question says "a couple of million years in the future" it's not opinion based nor unanswerable. It's not asking us to invent new materials, but that given todays knowledge of future materials and construction methods, what could we build? The million years in the future is there only to take away any grievances like "we cant build that in the forseeable future" or "we need power generation from a Black hole and that's not feasible within x-thousand years". The best answer would be extremely simple to determine: it combines construction and materials to build the biggest habitat. $\endgroup$ – Demigan Sep 6 '18 at 12:22
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    $\begingroup$ Just put an "infinite" cylinder in deep space held together by carbon nanotubes. Rotate about the center of the cylinder and have everyone live on the inside edge. Now you just need to know the end "gravity" you want and CNT tensile strength and you can find the cylinder radius. Even then it doesn't matter much because your cylinder is so long. $\endgroup$ – svenvo7 Sep 6 '18 at 14:08
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    $\begingroup$ @Clay Deitas What you need to do is to look up Larry Niven's article "Bigger than Worlds" (1974) for ideas. - isfdb.org/cgi-bin/title.cgi?133302 - And I remember an article sometime later about building a ring around Jupiter at the right height to have one Earth gravity. One could also build a ring around The Sun at the right height to have one Earth gravity. As for building planets see planetplanet.net/the-ultimate-solar-system $\endgroup$ – M. A. Golding Sep 6 '18 at 14:40
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Order a planet from Amazon

You said you can move planets. You have FTL. 3D molecular printing means you can build anything. That means, you can terraform planets.

I believe there would exist a company that makes them in your future. There could be one whose headquarters would are on Magrathea.

Just - don't order a Weyland-Yutani one.

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  • $\begingroup$ Although the references are nice, this doesn't really answer my question at all. $\endgroup$ – Clay Deitas Sep 6 '18 at 11:56

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