Update: There is now a wiki entry for jumpdrives, which supercedes this.
Since I'm swiping Trav hex maps, that implies a similar star drive principle: starships' capability is measured in the number of hexes it can hop. Unlike Trav, I'm capping general jump capacity at J-3. Some Chirper ships can do longer jumps, but their drives and computers are sealed-unit black boxes that the Chirpers themselves have no idea about either, so it's a good thing they're Sufficiently Advanced Tech that they (almost never) fail.
Trav explains their "flat" maps by saying that the thickness of the galactic disk isn't enough to worry about (which is silly when the the hex unit is one parsec). I'm handling this differently: the jump drives allow inter-universe travel, and there's a hand-wavy reason why you can flatten down the network into two dimensions.
There's no faster-than-light paradoxes, and you can't figure out where "adjacent" systems are with a telescope. The flat "star maps" have no congruence with physical positions, and there's a strong preference for Sol-type stars with Earthlike worlds that suggests the connections are artificial. Ancients don't answer questions about that. This gives me an excuse for a Firefly-type setup of mostly "shirtsleeve" planets, and the option for a newly discovered/linked world to suddenly upend the geography (and politics).
I hadn't actually planned to swipe this much from the Traveller Imperium but for now I'm going to label the upper left lobe the Vilani Imperium/Spinward Marches (the "default" adventuring area in canon Trav), the lower left the Solomani Sphere, the lower right the Zhodani Consulate, and the upper central/right the Vargr Extents. I think I'm going to put the Aslan in the isolated upper right part, but first contact hasn't been made yet so for now I'll ignore that area.
In Classic Trav, the Ancients seeded humaniti (they really like their ending -i) across a dozen or so worlds, and six Major Races discovered jump drive independently, three of them human. Yes, Traveller does not seem to have gone through the D&D thing of eliminating the term "race." Awkward. I am not sure yet if I'll stick with that concept though technically landrace would be correct. And funny to me, because I learned the term as related to vegetables.
Anyway.
The "Backwater" setting generates a lot of "no starport"/Red Zone systems, and some of them fell very strategically on those chokepoint systems. I'm going to declare those military-occupied systems, border checkpoints. Trade can pass through with appropriate permitting, but there is a refueling/inspection station where crews can't leave their ships, that sort of thing.
The Solomani, Vilani, and Zhodani border systems are almost sequential on the ring. The Vargr are connected to the ring via a narrow corridor, with two X systems closer to the more clustered worlds.
I'm swiping liberally from C.J. Cherryh, so my Vargr (which will probably get named Wargs to differentiate them) are going to be more kif-like, from the Chanur series. It's probably a good thing they're mostly bottled up like that.
This suggests the little cluster of worlds on the ring is not part of the Vilani Imperium, so I guess that's a politically separate area. Sword Worlds or Darrians or something, maybe, though I'm not sure I'm going to label it that yet.
Timelines
I'm further swiping from Cherryh, this time Hunter of Worlds. It's very early Cherryh and someday I am going to sit down with my ebook version and annotate all the alien words in it because it's tough to keep track of the various concepts.
Anyway, Trav has the Droyne which are (spoiler alert) also the Ancients. My Droyne are therapod-descended, so no wings (or at least only four limbs), and may or may not be the really Ancients because something probably uplifted them, but there's nothing left that isn't Droyne (or rather, Dragons or Demons or whatever the humans call them). They're also more like Cherryh's iduve or (back to Chanur) k'nnn.
The Ancients (which I think is what I'll call them for now) are entirely spacefaring; if they have a homeworld it's not around here, and they have never settled any of the known systems. Instead they have improbably large worldships, basically mobile space stations, which in times past simply showed up in a system and said "give us all your stuff." They are jump-6 at least, have unspeakable weapons and respond disproportionately to any pushback: they will wipe out entire cities if their "requests" are declined. They aren't exactly raiders, though: like the iduve, they consider it more "farming" lesser societies, and so they are perfectly willing to leave behind whatever they consider a fair trade, and also carry entire starships across otherwise uncrossable rifts.
I'm not sure of the exact timeline, but like the iduve, they pretty much vanished from known space at one point, off on their own inscrutable business. At their peak they were not exactly scheduled service but they regularly crossed the J4-J6 lanes connecting the isolated system and cluster between the Vilani and Vargr. And then they disappeared, fairly abruptly, leaving behind a fair number of their Sports/Praytsirv: individuals created (they're big on genetic engineering) to bridge human thinking to Ancient thinking, and considered disposable animals. Animals with J4+ starships that only they can operate, and who have formed something of their own community in the absence of the Ancients themselves.
(Or near-absence. I am thinking a worldship pops in now and then to check on the status of the sector. But they really aren't something that would interact well with player-characters directly. Something that gives absolute orders and will vaporize you and the entire station if you talk back to it? That's a TPK every time.)
The Ancients and their hive-minds are a big reason for anti-psi sentiment in Vilani and Solomani space. Zhodani have embraced it, but are still well aware of the dangers of too much telepathy collapsing into a hive-mind (which humans are very unsuited for). Although the Vilani/Solomani view might have come from pre-compliance to the Ancients, who probably burned out any hive-minds they came across - either because it tended to consume and collapse entire communities/worlds, or because they would pose a threat to Ancients, take your pick.
Anyway: in the absence of Ancients and their ferry service (and subtle depressing of technological increase), humans made the improvement from Jump-2 tech to Jump-3, mostly reconnecting everything. Not sure exactly how long the isolation lasted, but there are probably some dependent worlds whose population collapsed. (Oof, I will try to avoid any parallels with Current Events but they may be unavoidable.)
They also started arming starships, which of course the Ancients didn't permit, and going to (low-key) war. Geography kind of makes it self-limiting, though there may have been some Reunification Wars within each current empire's territory. The Solomani, not getting along with Zhodani or Vilani, basically barricaded themselves in. The Vilani had settled that now-isolated cluster at the top of the Ring, while the Zhodani held the right side of it and explored the spur leading toward the Warg.
Meanwhile the Vargr only had J2, and while they had contact with the Ancients, the Ancients didn't let on to either humans or Vargr about the others' existence. So it was a surprise to both parties when the Zhodani found the Extents at the end of the spur. The doggies were very "friendly" toward the superior-tech-having Zhodani, until the sudden but inevitable betrayal once the Vargr had access to J3. It was more a schism within the Vargr, and like the Solomani they mostly barricaded themselves in. There's plenty of trade along the corridor, which are more or less shared worlds.
But those J4 Chirpers went "oh yeah, we've been shortcutting through the Extents to get to the whatever the isolated blob in between is called, we just didn't mention that the interim system was occupied because you weren't allowed to know about that species, but now that you do we can run trade and passengers in between." So there's a limited amount of interchange between the hinterlands of the Vilani Imperium and the Vargr extents, though the Chirpers won't faciliate an invasion.
Charted Space
Update: There is now a wiki entry for Charted Space, which supercedes this.
In the same way that fabric collecting is a separate hobby from sewing, worldbuilding is a separate hobby from gamemastering. I like to do the former even without any real plan for the latter. (If I had treated my ADHD earlier in life I'd probably be an author, but I never developed the skills for making characters to live in my worlds. That was for the players to do!)
Traveller tends to be a game of vast scopes, where the idea of players visiting the same world more than once can be completely, er, alien. The tiny two-subsector map of Trillion Credit Squadron was a revelation to Young Me, and the idea of a little "pocket empires" campaign was suddenly fascinating. I am not planning this to be specifically a Traveller gameworld, but the maps are comfort food, plus there's random-gen tools out there already.
I really like randomly generating a map and then extrapolating from the geography. My charted space is a compromise between the Imperium and TCS map: one Sparse, Backwater sector.
To get a 30,000-foot view, I popped the maps into Inkscape, set a hex-friendly grid, and set up layers. Top layer is Systems, which has just the starport code filling a white hex. Next layer is J2, which is a light blue hex in any space passed through by a J2 ship.
Next layer is J3, and so on. The gradient is good for visualization but so is the ability to simply turn off layers, and it turns out that if you turn off everything J4 and above you get really promising geography: there is a ring of systems in the middle, and four lobes connected to the ring by only a single system. That's four discrete empires right there. I can work with this.
