Imagine a SupraWorld being built around a gas giant like Jupiter. To have a 1g gravity on the surface the resulting SupraWorld would have to be less than twice the radius of the giant (my calculation; could be wrong). I have unobtanium but it only provides impossible structural resistance and nothing else.

My civilization will start by placing a large hexagonal flat surface (where the colonists live) with very large walls to prevent the atmosphere from escaping. More will come; eventually all the hexagons will join in a ring (the walls remove periodically as two hexes join) and eventually they will "close" as a sphere(the finished SupraWorld).

How do I prevent the single "hexes" from falling into the planet? My idea was to have them at the top of a huge "tower", with the colony at one end and a large near vacuum spheroid or whatever at the other end, floating into the gas giant's metallic hydrogen ocean. Gyroscopes would stabilize the structure preventing it from flipping. How credible is that?


2 Answers 2


If you start with an open lattice, you can build a sphere with very little material. Think of chicken wire: make a form from that, then start filling in the surface a bit at a time.

You will have to use some kind of active control to keep it centered around the planet. If it has a metallic hydrogen core and thus a strong magnetic field, you can use magnetism. In fact, you can use flux pinning for the whole thing. Your unobtanium could be superconductors programmed to hover and keep station in the planet's magnetic field, without any need for super strength!

But, making flux-pinning superconductive structural elements on the nano-scale is exactly how I'd make a hard-SF supermaterial, as well.

Oh, and don't worry about the radiation. Robert L. Forward published a (real science) paper on how conductive tethers could be adapted to short out the Van Allen belts and drain the charge.

  • $\begingroup$ That's interesting! However, wouldn't you need a very strong magnetic field to keep such a massive strusture in place? $\endgroup$ May 23, 2016 at 18:36
  • $\begingroup$ The magnetic field automatically compensates for motion, and is supplied by the planet and "grabbed" by the superconductor. Or are you asking if the planet's field is strong enough? $\endgroup$
    – JDługosz
    May 23, 2016 at 18:38
  • $\begingroup$ If you have a supra-shell and just need to keep it centered, you don’t need as much strength as you would to hold up a single platform against gravity. The gravity cancels out inside the hollow shell! $\endgroup$
    – JDługosz
    May 23, 2016 at 18:40
  • $\begingroup$ yes I was wondering if it was strong enough $\endgroup$ May 23, 2016 at 20:28

Your tower idea sounds fairly expensive. Given your setup, each tower would be nearly one planet's radius (r) in height. Also, you would soon need more towers as your structure grows.

If instead you build a ring around your planet, it's circumference would be $ 2 \pi r $.

So soon after the sixth tower, your towers combined would have the same length as the circumfenrence of such a ring. I would definitely go for the ring directly.

You could build the ring segments in a stable orbit, then once completed lower them far enough so they can be join.

This will also provide a spectacular show, allowing for enormous fees for the commercial breaks...

After that, you can attach your hexagons to that ring.

As a bonus, you can completely skip the inverted pendulum problem and the gyroscopic stabilizers.

  • $\begingroup$ The problem remains: How do you prevent the hexes from falling into Jupiter when you lower them out of orbit? As soon as Jupiter's gravity takes over, you need to counteract it. $\endgroup$
    – Hackworth
    May 23, 2016 at 13:38
  • $\begingroup$ @Hackworth the ring i am suggesting will stabilize the whole setup. Gravity of the planet will hold it in place. The weight of the first hexagon will make it wobble slightly, but the force of gravity will mainly be countered by the strenght of the ring. $\endgroup$
    – Burki
    May 23, 2016 at 14:08
  • $\begingroup$ And how do you construct the ring without it falling into jupiter? $\endgroup$
    – Hackworth
    May 23, 2016 at 14:16
  • $\begingroup$ @Hackworth as mentionned, i construct it in a stable orbit. $\endgroup$
    – Burki
    May 23, 2016 at 14:17
  • $\begingroup$ Then how do you lower the ring segments so they can be joined together into a ring? Same question. $\endgroup$
    – Hackworth
    May 23, 2016 at 14:20

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