Clarke Habitats, Clarke Rings
|The Clarke Habitats around Zarathustra are loosely connected to a low tension orbital ring|
Unlike other habitat types, which each have an identifiable form that is usually (but not always)named after the sophont or group that designed it, a Clarke habitat is identified by its location and named after the orbit it is placed in. A Clarke orbit (or a Clarke belt) is defined as the stationary orbit for a particular planet; the semimajor axis of such an orbit is determined by the gravitational pull of the world and the rotation period. For Old Earth the gravity is one standard gee and the rotation period one standard day; this gives a semimajor axis of 42,164 kilometres. Planets with fast rotations have smaller Clarke orbits, planets with longer rotations have wider ones. Tidally locked planets such as Twilight and Dante have no true stationary orbits available, and it is not possible to find stationary orbits around most moons because of tidal locking or interactions with the primary.
Usually, the habitats found in Clarke orbits are limited to the smaller habitat types such as Freespheres, Stanford tori, Bernal Spheres, and rarely - O'Neill cylinders and Bishop rings. However there is plenty of room in this orbit for many such habitats and often a planet will be surrounded by an orbital cluster or band. These swarms can become quite dense and visible from the surface, often competing with the stars in the 'Milky Way.'
This band can become (or be designed from the start to be) quite extensive, forming a physically connected ring around the planet. Unlike Orbital rings, which are placed in lower orbits, a Clarke ring does not need dynamic compression members or space fountains to resist the pull of a planet's gravity. It may however need to be stabilized from drifting by tethering the structure to the planet below with multiple beanstalks. A Clarke ring can be a quite sizable megastructure and is often able to house as many citizens as its planet. This, and the constant transport of beings between the two, necessitates that the space elevators be very robust and on some worlds the beanstalks themselves can house millions, especially in the base towers that are typically tens of kilometres high. Linking the habitats loosely together in this way helps to prevent the ring from clumping together because of self-gravitation.
|The Clarke Ring around Jensan forms a continuous structure, linked to the planet by beanstalks|
The first Clarke band was built around Earth during the Late Interplanetary age, as an incomplete ring of unconnected habitats accessed from the ground by the orbital towers. During the Great Expulsion this ring was increased massively in size by the Agents of GAIA, until there were thousands of large and crowded temporary habitats holding billions of refugees. Social problems in these habitats were extreme, and several habitats became lawless territories, making the dangerous flight to the stars a more appealing prospect.