Gas giants are the most valuable real estate in any given solar system. Their rings, moons, and Trojan asteroids are immense stores of easily-accessed and easily-extracted resources - everything you need to start up a permanent colony. Delta-V costs are cheap, plenty of volatiles and fusion fuel, there's a convenient gravity assist right next door. If a solar system has any permanent habitation, even if it is only an automated refueling depot, it's going to be orbiting a gas giant.
Terrestrial worlds, in comparison, are more or less worthless: you'll be trapped launching material out of the gravity well in order to build the infrastructure necessary for a functioning colony, and you could build all that infrastructure far easier and cheaper by just using asteroids. The cheap way, the sensible way, is to start outwards and go in - orbital habitats first, then surface - especially if terraforming is on the table.
For an interstellar civilization, like the ones we would find in everyone's Mothership homebrew, this will lead to an interesting dual society: the dominant culture groups will be concentrated in the lunar and orbital habitats around gas giants, as they serve as the hubs commerce hubs for both in-system and inter-system trade. Inner-system terrestrial worlds (those that might get terraformed) will be relative backwaters and their inhabitants will be, if not legally, practically segregated from the greater interstellar community, simply because it costs more, both time and money, to get to where you need to go. Imagine if you transplanted the modern US interstate system on top of the bronze-age Mediterranean, gas giants serving as the cities where routes meet. It's like that.
For PCs traveling between stars, any given gas giant hub is going to be relatively similar. The companies, factions, and people present will still vary on a sector-to-sector basis, but system-to-system things will be familiar. If you've got one feature, you'll get most of the rest. It's the terrestrial worlds where the weird people are, where the poor people are, where the excitement and conflict and diversity is. They're the dungeon, to the gas giant's town.
The secret here is that since gas giant hubs are variants of the same city, you don't have to worry about fleshing them out. You're playing Mothership! Your PCs are the poor people who get to visit the spaceport for a bite to eat at Great Googly Moogly's and a sleep shift in a coffin hotel before you're back to work.
Shore Leave in the Distributed City
Your typical visit to the Distributed City will work go something like this:
- Your ship emerges from hyperspace. If all went well, she'll be arriving in one piece and with minimal spatio-temporal error. Essential crew are brought out of cryo.
- The ship's communication officer (or another individual serving as such) will contact the relay buoy at the jump point and declare a destination. The buoy will update the public ship registry and Orbital Control with the ship's information.
- Days to weeks pass as your ship moves from the jump point to its destination.
- Upon entering the planet's magnetosphere, your ship will discharge the exotic energy buildup from its warp core.
- With the destination in sight, Orbital Control will guide you to an open docking arm. This is a slow, delicate process, and agonizing to wait through.
- With the ship docked, everyone up for shore leave will pile in the little people-mover and be shot down the magnetic rail towards the main station. You typically won't bring much with you - no more than a light bag. The ship will be unloaded, restocked, refueled, and repaired while you are away.
- You'll disembark in decontamination, where you will spend the next several hours getting a thorough scrubdown and a medical screening. Anything remotely suspicious will see you either sent back to your ship or thrown in quarantine. Your belongings will go through a security check in addition to cleaning (if you have cybernetics, those are checked after decon. They tend to hold things up.) before they are returned to you. Most stations will do a rudimentary scan of any computers brought aboard, to check for malicious programs.
- After decon and security is customs check-in. Your visitor's credit account gets activated, you are logged as temporary inhabitant, you're free to go. The spaceport is your oyster.
Your average spaceport in the Distributed City will be recognizable to anyone who's been in an airport before, if extremely compressed. It's a space meant for people to pass through, not for them to live long-term. There's a thin layer of shops, restaurants, hotels, overtop all the machinery and infrastructure that keeps the place running - space stations are mostly plumbing by mass, after all.
You'll more than likely end up hot-bunking in one of the public-use coffin hotels, unless you decide to drop some of your pay on luxury accommodations. Food will be limited to big chains (overpriced), but after months of ship rations some unidentifiable greasy slop is still welcome - if you want something actually good, you'll have to pay through the nose or cook it yourself. The further you go from the main causeways (or the Core) the more variety you'll find, the more lived-in it will be, as you transition away from the port proper into the parts where people actually live (if there are any to be found)
There are always plenty of ways to reduce stress available, and if you're creative you can invent a few more. Psychological strain is the #1 cause of human-origin spacing accidents so even corporate agrees that you should enjoy yourself. Reduces the insurance premiums.
If you really want to visit another station in the City, or go dirtside if it's available, you'll need to hop on a shuttle or elevator. Your decon and security clearance will be valid, but it's still transit time eating into your R&R.
Shore leave will always be over too soon, and when that time comes you'll end up going in reverse. You'll go back through customs and security (likely nursing the hangover from the pre-launch party the night before), back through decontamination, back to the ship. You'll have a mass budget for your personal possessions, so anything physical you've bought better be under that limit or it's staying behind. Orbital control guides you out, and then it's back to work until you reach the jump point and have to hit cryo.
And then it all repeats and you arrive in a new node of the City, same-but-different.
What About Terrestrial Worlds?
While terrestrial worlds are not very important in-universe, they are very important for actually playing the Mothership - people like weird planets, horror loves isolation, and with everything I've been babbling about above you naturally get both. Always comes back to the cosmic rust belt.
You'll arrive at a terrestrial world in much the same way as the City, though it'll take longer to get there given the distance between the inner system and the jump point. You might have already stopped off at the City, or at the very least done a slingshot orbit to discharge your warp core and change velocity. There'll be a station to dock with (usually), shuttles or an elevator down to the surface (hopefully), all the same procedures before going ashore. Everything's just smaller and poorer - if it isn't, that's a sign that you're probably not welcome here.
When designing planets for scenarios, bear in mind that they will more than likely be settled for one of the following reasons:
- Rich people want to go there.
- Rich people want to send poor people there.
- Poor people want to get away from rich people.
- Poor people think they can get rich, and / or rich people think they can get richer.
- There isn't a better option in this system.
- It's a 1st generation colony, settled in the years before the City really got off the ground.
No matter what the case is, you will be weeks away from the City by ship, and any communication (if you have something fit for interplanetary transmissions) will have tens of minutes up to over an hour in terms of lag. It's not a convenient trip out here, or back. There are fewer people spread out over more space. You'll step into the economic and cultural shadow of the City.
Start writing down specifics, add something weird, and it practically writes itself.