My wife is my bellwether if a concept is too technical. If I can't explain something to her, and make it interesting, a concept needs work. I spent my career in IT and Naval simulation. She spent hers in retail and conventions. Between the two of us we have a lot of very different sets of experiences in two very different lines of work.
I was struggling, yet again, with the shuttle scene I wanted to use for Chapter 1. No wait it's Chapter 2 now. And in explaining my latest brilliant idea to have the main character stopped by the Spaceguard and kept overnight because of an overzealous...
Wife: The what now?
Me: Well you know, the folks who do customs and stuff.
Wife: Why on Earth would anyone put a border up where everyone lives? You told me Psyche was one settlement. Now it's a bunch of different one.
Me: Well it's complicated by the nature of the ...(long winded explaination)...
Wife: (Patient look that tells me everything. Nods. Smiles.) I would think they would either build all the big cities in orbit, or on the planet surface, or if the real Psyche is too complicated, just make up a planet. If your main character was born on Psyche, and now in the Navy, how could she possibly get snagged in a dustup with the customs people? If you want to do that sort of story, set the scene on another planet entirely.
Me: That's why I married you!
So, needless to say, my concept for ISTO and Psyche needed a tad bit of, let's not say World Building. More like World Smithing.
We need to start with Orbital Logistics of 16 Psyche. I also need to consider that by the time this book is even published, space missions to the real Psyche will have launched. So first question: do I continue using the real Psyche?
It's a double edged sword.
16 Psyche was discovered in 1852. Given that the break between our history and the Sublight Universe occurred in 1777, I could just simply have the planet discovered by a different person at a different time who gave it a different name.
On the other hand, people loved the Expanse because it throws out the real names of real bodies. The worlds are so altered by technology that any difference between the real planetoid and the fictional one are easily explained away to the reader. My readers are either real space nuts, or like to think they are space nuts. There is a cache in making the story "real".
Not using the real planet, or calling it another name, begs the question of why bother with using the Solar system and Earth at all? I could fire up my Fantasy name generator and just go hog wild, and create "alike" planets. And that gives me a lot of freedom as an author. But I find books like that too arms length. My interest in writing this story is to get people excited about exploring the Solar System. (I used to work in a Planetarium, after all.)
I want this to be the sort of book that is educational enough that I'd be one of those guys doing book signings at the Air and Space museum. So, my die is cast. I'm going to keep using 16 Psyche, and all of my work is going to match the best science we have. If in 50 years it all sounds a bit silly, well how long has Stranger in a Strange Land been a classic? And it has native people LIVING on Mars. And Heinlein is considered a pioneer of Hard Science Fiction.
I don't plan on replicating the sexism. And I certainly plan on making fun of his politics. But I'm not going to fault a writer for having a career that was decades too early for science to catch up.
When I was a kid I would read books and dream of actually getting to a lot of these places in the Solar System by the time I had kids. That "this could happen soon" is what I loved about Arthur C. Clarke. And his science was good enough that he popularized useful ideas like the Geostationary Orbit. Did 2001 come and go without a Discovery? Yes. But do we still read his books? Hell yes.
I did hate that books and films in the 50s, 60s, and 70s would look to the year 2000 as some "Way distant future." I suspect Star Trek is going to be a lot less watchable in the 2200s when we don't have an Enterprise. For the politics in my story to make sense I need some time for civilization to have developed along a different set of lines. But I don't want to set an expiration date on my works.
For that I'm using an alternate history. As I've stated elsewhere, the date of that break is September 11, 1777.
I am also infusing the world with a concept of ubiquitous magic I call Tegic (or Tegick.) It can do somethings our Science still can't. Though, on further contemplation, there are probably things that Tegic can't do and science can. They never invented the Aeroplane. And the horseless carriage is a novelty. They have sophisticated steam plants (because Tegic can produce immense amounts of waste energy). But they never really mastered the internal combustion engine.
Because I love me some Steam Punk. And I know my audience loves steam punk.
They also haven't invented the microprocessor yet. But they have a system of computing built around holographics and analog technology. Holographics can store immense amount of data. But it's not random access. And in the process of replaying corrupt data streams they invented living computers. Artificial intelligences that can solve holistic problems. Those processors are small enough to be build into mobile platforms like humanoid robots.
But before I go off restating all of my lore manuals... again...
Psyche started off as a mining operation. As soon as the frontier opened in space with the advent of fusion powered rockets, Etoyoc Heavy Industries (a northern-pacific industrial conglomerate) set up a major extraction and metallurgical facility. Their intent was to build a major shipyard building craft that utilized a unique nickel/iron alloy steel that was cheap to produce from the material of Psyche.
At the outset, Psyche's development was purely about it's mining and shipbuilding industry. As many of the pioneers who settled it were Japanese and Korean (of the late 19th and early 20th century), there are Xenophobic elements to what we consider now "the old timers". The original pioneers of Psyche. And also the major shareholders of all of the mining companies and shipbuilding facilities.
About 50 years after Psyche was first developed, the International Space Treaty Organization was formed. ISTO chose Psyche (despite its protestations) as the new Capital. To ameliorate the concerns of the native population, a compromise was reached. Psyche would remain the property of the culture that evolved from Etoyoc Heavy Industries. ISTO's fleet and capital infrastructure would be built in orbit (and at great expense).
Psyche was a prime target when Krasnovia attacked. The Battle of Psyche was brutal. Krasnovia's fleet was massive, and cut right through the fledgling ISTO Spacey. When all seemed lost, however, missile defenses from the space platforms around Psyche made a wreck of the Krasnovian fleet.
A small "back to tradition" movement still resides on the surface of Psyche. There are also shrines and memorials from the EHI culture that people return to as part of their family, religious, tribal, or corporate practices.
The complex cultural easements and structural planning mean that the planet is harvested exclusively by a cult of EHI traditionalists. Most reside on the orbital settlements, and spend a few weeks at a time on the planet. Their output, while not as fast as the some industrialists would like, is still quite sufficient for maintaining an active industry. The rates for the metal they produce is not as high as they would like, but just low enough to keep shipyards from sourcing their materials from elsewhere.
The people who are responsible for safely and sustainably harvesting Psyche are known as the Sikto. They are considered cultural elites in Psyche society. Something like the Kohen in Jewish culture. Sikto have special rules about what the are allowed to accept as payment. They also must maintain (at least the appearance) of social propriety. On the planet's surface, their word is law. They are the people ultimately responsible for worker safety. In orbit, they can indulge in a less stringent lifestyle, but if a Sikto brings dishonor to the order, they are cast out.
Living under such a stringent safety/taboo culture on the surface means that very few people live on Psyche's surface full time. In the Pre-ISTO days, traders and contractors had to live in special "barbarian" settlements, or reside primarily on a ship in orbit. When the ISTO started developing on Psyche, they were built exclusively in orbit. Over time the native population of Psyche (so much as they can be a distinct culture in only 50 years) migrated up to orbit.
The orbital settlements are one of several standard designs. Psyche has a special mega-projects graving platform which was manufactured on the planet, and thrust into orbit. It acts as a scaffold for producing city-sized construction projects. The facility is towed to where the new city is to be built, and acts as a base to attach the first few cables between the new settlement and the planet surface. These first few cables act as a a space elevator to hoist the bulk of the material that will comprise the structure of the settlement. After the basic frame is assembled, and the entire settlement can rotate to produce gravity, the construction cables are replaced by more durable tethers.
In the original plan, there were to be 12 Project Perseus settlements. Each housing about 250,000 people. Project Perseus settlements are large drum-shaped vessels, that can be stacked to add more capacity. When a city's population expands beyond what one module can support, additional modules are added.
The design board looked at several different designs that stressed different "ideals". The problem being that optimizing for one made the settlement impractical for other reasons.
A settlement can't be below 225m in radius, or it spins so fast the people on board have to live with excessive Coriolis forces. Well, the people will adapt, but the plants, not so much. This design was thrown out because, while viable on its own, if the city ever needed to expand stacking a additional units leads to an unstable shape.
Make a station that minimizes Coriolis forces, and maximizes stack-ability, and you end up with a ribbon of land that is entirely too narrow to be of use.
In the end, they picked a "tuna can". Design:
Up to 4 modules can be stacked end-to-end, allowing for cities of up to 1,000,000 people. The interior volume provides amble space, but with sufficient useful area to provide generous port facilities for large vessels.
If you want to play with my math, I adapted my colony ship spreadsheet for fixed stations.
Our story will start in the Capital of New Franklin (on anchorage 1):
There are 7 decks in the outer shell. The middle deck is where most of the people are clustered. Locals call it the "Metropolis" level. The city center has an area of about 2 million square meters / 484 acres. Almost 90 city blocks (assuming you are using Manhatten's blocks as your reference.) Underneath the outermost inhabited ring is a massive water reservoir that also doubles as a radiation shield.
One side of the inner cylinder opens to space. This provides the port facilities for the city. The other side mates with a hub and anchorage. The anchorage is elongated to allow large ships (who maintain their own rotation) to dock with the colony and exchange goods and people in microgravity. New Franklin's anchorage
Do keep in mind that the A row and the P row are next door neighbors. This city is on the inside of a cylinder. In keeping with Japanese tradition, the block are named, the streets are not. There is no column I. People have their own legends. But the fact of the matter is that I looks too much like a 1, a J and a lower case L.
New Franklin started off as a single module. It was only ever intended to be the seat of Government and a military HQ. In the decades since they have added 2 new modules, which begets more office buildings, which begets more housing, which ... well they are talking about adding a fourth.
The Project Perseus stations were the first 6 installations.
The growing pains experienced during the construction of the first 4 cities led to a revision of urban planning in the 1960s. Advances in space construction (and the infrastructure provided by the first 4 cities) allowed for larger radius structures to be constructed. With vessels on the drawing boards that were 800m in diameter, it was thought best to provide facilities with at least an internal radius of 410m. These new cities would house 750,000 right out of the gate, and like the Project Perseus, these new cities would be built with expansion by modules.
Four project Gilgamesh stations would be built.
When ISTO started evaluating its needs for building interstellar craft, it found it needed even larger facilties. Estimates projected the vessels would be upwards of 1200 meters in diameter. While many of the modules could be constructed in Project Gilgamesh yards, they needed a final assembly bay.
Three project Iliad stations would be built. For my first book (Sublight Frontier), Project Iliad isn't even on the drawing books yet.
If you want to visualize what the ring of settlements around Psyche looks like:
And the pattern I am using is the Golden Angle. Essentially I can repeat this pattern for quite a while without repeating AND keep the distribution relatively balanced. To place a new station, take the longitude of the previous station and add 137.5077640500378546463487 degrees.
All of the settlements are kept at their assigned longitude in psyche-stationary orbit by tethers to the surface.
Mining operations are gradually lowering the mass of Psyche itself. At the same time, the building boom is lobbing more and more of that loss mass into orbital distane around Psyche. This has the same effect as stretching your arms out when spinning. Psyche's rotation is slowing. To compensate, each settlement can adjust the length of their tether. But, as they pay out more cable to keep in a stable orbit, that effect slows Psyche's rotation even more. More cable is more mass that has to be held up by the station, which makes the problem even worse.
For now, it will take a few centuries for Psyche's rotation to slow enough that operating the space elevator system will be impractical. But the possibility is on planner's radar.