This idea actually originated with @Karko in a different thread but since I heard it I can’t stop thinking about it so here is a huge brain dump for you all 
DISCLAIMER: all info in this thread is hypothetical and invented by me, I have had no communication with the devs regarding whether any of this would even be technically possible
What are they?
Orbital settlements are as the name suggests, settlements established in orbit around a planet. It’s like the Sanctum, but player-built!
Just like in the Sanctum, the planet you are orbiting appears above you in the sky, and you can whip out your totem to see player locations and landmarks, use warp augments to set a destination, etc.
How do I make one?
Orbital settlements are pretty epic, so they require end game progression to establish one. First you need to craft a space beacon, which requires epic crafting skills and access to exotic materials like Blink and Darkmatter. You also need to craft a special space beacon fuel, which requires (TBD exotic materials). Finally, you need the high-level epic skill Space Engineer, which is required to place and fuel space beacons.
Once you have all this, as well as at least one free plot, simply place the space beacon anywhere on the planet where there is open sky, open the interface, fuel it, and then press the Launch button. Your beacon will shoot off into the sky like a rocket, letting everyone around you know of your accomplishment! (I picture it looking like a meteor landing, but in reverse).
After the launch, your space beacon will appear in your beacons list, allowing you to warp to it and begin building your station!
How do other players get there?
Other players can follow you through a warp conduit, or share location tokens for your station and warp there on their own. You can also establish portals to the surface, or even other stations!
Perhaps your station will even appear on the surface as a twinkling star in the sky, allowing players to use a totem and warp augment to set a warp destination to your station.
What about interplanetary travel?
One of the advantages of being in orbit is that you’re already on your way to other worlds. Portals from the surface to your station are a one blinksec hop, and in turn, portals to other worlds cost one blinksec less than they would on the surface! And portals to stations around other worlds cost TWO blinksecs less than a surface-to-surface portal! This makes stations ideal locations for constructing interplanetary portal hubs.
Can I expand my settlement?
Yes! Space is truly boundless; you can use plots to expand your settlement in orbit as large as you want!
Other players can join your settlement too, simply by building their own space beacon in a plot adjacent to yours.
Can I craft and run shops in orbit?
Of course! Space has no resources, so you’ll have to bring everything with you, but anything you can do on the surface you can do in space as well
Can I access my station when the surface world is full?
Yes, and this is one of the great things about stations, is that they run on a separate server to the surface world and can be accessed even when the world is full.