Question: In [Iain M. Banks'](https://en.wikipedia.org/wiki/Iain_Banks), fairly rockin' [Culture novel](https://en.wikipedia.org/wiki/The_Culture), [*Consider Phlebas*](https://en.wikipedia.org/wiki/Consider_Phlebas) a good third of the book takes place on what is called the **"Vavatch Orbital"**. An orbital is apparently a massive artificially created megastructure, similar to the [Death Star](https://en.wikipedia.org/wiki/Death_Star) or the titular [Halo](https://en.wikipedia.org/wiki/Halo_%28megastructure%29).

At one point in the book the Vavatch Orbital is described as a minor orbital, not as big as a ring or a sphere. Then later it is almost directly described as having a ring shape. Still earlier in the story it is described as a bucket being swung in circles, though this description maybe used only to describe how the orbital uses centrifugal force instead of actual gravity.

Whatever the size, the orbital has to have enough sea space for a Megaship (a city sized ocean ship) to travel for more than a century before reaching land again.

[Wikipedia tends to suggest that all orbitals are rings](https://en.wikipedia.org/wiki/Orbital_%28The_Culture%29), but then why the mention of a sphere, or that Vavatch is not big enough to be a ring?

Answer: 
There's an illustration (by [Mark Salwowski](https://www.salwowski.com/)) of Vavatch on the cover of the 1988 Orbit (UK) paperback edition of the novel:

![The flat plane of the orbital, tilted at an angle to the right, fills the foreground with a blue sea under white clouds, with the blue haze of atmosphere fading to the black of space above.  In the distance the orbital curves off to the right, a band of blue-white against the star-flecked black of space.](https://i.stack.imgur.com/WMS6F.jpg)

The first description of the Orbital in the book also gives its dimensions:

> 
> Vavatch lay in space like a god’s bracelet. The fourteen-million kilometre hoop glittered and sparkled, blue and gold against the jet-black gulf of space beyond. As the *Clear Air Turbulence* warped in towards the Orbital, most of the Company watched their goal approach on the main screen in the mess. The aquamarine sea, which covered most of the surface of the artefact’s ultradense base material, was spattered with white puffs of cloud, collected in huge storm systems or vast banks, some of which seemed to stretch right across the full thirty-five-thousand-kilometre breadth of the slowly turning Orbital.
> 
> 
> 

So it's 35,000 km wide and 14,000,000 km in circumference (4,500,000 km in diameter), giving it a surface area of 4.9 × 1011 km2, about 960 times the surface area of Earth. A ship taking an (Earth) century to circumnavigate Vavatch would need to travel at an average speed of about 16 km/hour (8.6 kt).
"Consider Phlebas" calls Vavatch a hoop on page 255:

> 
> Vavatch, that fourteen-million-kilometre hoop, was starting to
>  uncoil. A chain, it had been cut
> 
> 
>