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Larry Niven's RingWorld is supposed to do a complete revolution around its central star in a matter of days: about 9 days, assuming a ring of Earth size orbit, providing a 9.81m/s² "gravity" to its inhabitants.

But this means that its peripheral velocity corresponds to an earth orbit in 9 days instead of 365, so is roughly 40 times greater than the orbital velocity (and about 30 times greater than the escape velocity).

Until all is sections are attached together they have to be circling the sun at orbital speed. So you have to spin the ring after construction. How would you find the colossal energy for this? That would be 1600 times the kinetic energy of the Earth on its orbit.

And once the ring is in operation, how to you dock to it, given the stupendous peripheral speed?

Of course, if you find a red dwarf, you can make a smaller ring that is a lot closer to the star, and this seriously mitigates the problem, but there may be less energy available around such a star.

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    $\begingroup$ You're asking a lot of questions all at once. Please edit this to ask one question. $\endgroup$
    – sphennings
    Commented Jan 4 at 19:16
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    $\begingroup$ VTC - This is essentially asking a question about another world - which we don't do. $\endgroup$
    – TheDemonLord
    Commented Jan 4 at 20:47
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    $\begingroup$ It's worth reading this meta post regarding third-party worlds and how that relates to what we do here. Whilst we realise you're probably asking for the benefit of your own worldbuilding, it's best to make that clear when asking. $\endgroup$
    – Escaped dental patient.
    Commented Jan 4 at 21:28
  • $\begingroup$ Solar sails on the sides angled to spin the disk up, retract or turn edge up when job done, you can flip them to increase or decrease speed .. docking is no big mystery, you fly towards a target on the inner surface in a 'shallow dive' and as you enter the atmosphere the friction imparts some of its momentum, just make the dive as shallow as needed and stay in the air as long as needed to match velocity with the surface, lot of heat, good heat shielding needed, but it's no different than reentry to earth from orbit, exactly the same in fact. $\endgroup$
    – Pelinore
    Commented Jan 8 at 8:52
  • $\begingroup$ @sphennings I only see two questions rather than lots, has it been edited. $\endgroup$
    – Pelinore
    Commented Jan 8 at 8:55

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How would you find the colossal energy for this?

From the Star, you have plenty of energy right there if you can harness and control it.

Docking would be more problematic, but perhaps some sort of tractor beam that draws you in and increases your speed until it matches, perhaps over several hours.

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    $\begingroup$ one idea is mounting to the outside of the ring a giant electromagnetic accelerator, you just need to intercept an opening then the ring spin you up. $\endgroup$
    – John
    Commented Jan 4 at 21:22
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    $\begingroup$ Just use the atmosphere, reentry / atmospheric braking (in reverse?), call it what you want, the atmosphere imparts some of its momentum to a craft coming in from outside and will continues to do so until the craft matches it's velocity, and a lot of heat as it does, you need good heat shielding of course but theres nothing new there .. no special kit or tech needed @John you just spend some time flying through the atmosphere being cooked, same as we do landing on earth. $\endgroup$
    – Pelinore
    Commented Jan 8 at 8:33

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