I am waffling over the lack of aliens, and considering uplifted Terran/etc. species: dolphins, gorillas, corvids, things of that nature.
I also feel like Gvazda would have domesticated their monkey-analogs the instant they were contacted by humans. Not sure they'd uplift them though.
Zhdez seem like the most likely to (I'm still leaning toward them having higher technology, though being reluctant to let it outside their own territory), and also to treat uplifted beings as equals. Which means you'd be less likely to encounter them outside Zhdez territory, not because they're controlled tech so much as because they wouldn't care to be treated as less-than. So they've almost certainly got catfolk of some sort, which will be interesting at first contact with the lionfolk east of the Gvazda.
Uplifted dolphins being gangsters on Melodite would be... interesting.
Jump fields/shields
I think the jump field is going to be necessary as a protective shield, much as I don't care for that idea. Naked matter in jumpspace is like blood in the water, and attracts predators. Mainly tiny parasites that nibble away at matter, so leaving the field down invites progressive etching of the hull and sensors and things. But there's also the risk of larger things.
I feel like this makes whales just another predator, though, and I'm not sure how I feel about that.
Jonah and the whale
I'm contemplating the idea that jump fields are impermeable, though that sort of starts to sound like Star Trek shields. But it allows for things like: a predator has to engulf its prey, through either a temporary or permanent opening in its own field, then break down the prey's shield. If it hasn't already, that is, though being able to grab the prey beforehand eliminates the possibility of shark/hyena analogs grabbing some of the spoils.
Which then leads me to think: what if a whale swallows a starship and then sounds?
Hmm.
Navigation
If you don't navigate via the gates, how do you navigate? I'm already at risk for "currents" being a sort of "stargate" situation, so I don't want it to be "follow the currents to the gate confluences" if I can help it.
It is possible that sensors can pick up the gates (possibly via field harmonics or something - perhaps shutting off one's drive field lets one "go dark" but also means you lose your ability for long-range sensing?)
I think aside from bioluminescent creatures, jumpspace is dark (hence "voidspace"), so that rules out visual sightings until you're close enough to a correspondence zone.
I'd like it to be something like sailing ships: compass and sextant, and if you're in a storm you might not know how far off course you are, and even if it's just cloudy you might not be entirely sure you're in the right place.
Hmm.
RIP the false star
While I think there will still be a glow from tiny organisms marking the correspondence point of each realspace mass, I think I'm going to drop the idea of the hallucinatory light and false star and so forth. This does mean I have the option of bot craft, which might be necessary in some cases: high-risk exploration and so forth.
Boy, I really need to go through the archives and mark everything that's been discarded. Which is almost everything.
Fighters vs. eldritch horrors
OTOH, if realspace mass is a treasured commodity, and sea monsters can pop out of nowhere, maybe leaving a chemical trail pointing to you is unhealthy, and chemical-rocket ships vanish without a trace? Short-term rocket weapons and fighter runs are risky but doable (hmm, stellar dogfights with a risk of attracting sharks or worse).
This does necessitate sea monsters either capable of high speed travel or of sensing things coming a long way off. Or that they are very reliably going to catch things before they hit a really high speed.
If they're not reliable in catching every ship/projectile, higher-speed communication might be possible: launch a bunch of signal rockets, one might get through. Though if you're doing a "stargate" thing, it might not be healthy to stick around afterward yourself, since there are two ends to that Exhaust Path That Points To Tasty Mass.
Hmm.
Fighters in jumpspace
If I'm back to "matter stays in jumpspace even without a field bubble around it" then it's possible to launch projectiles through jumpspace, which led me to "what about fighters in jumpspace?"
(Actually "whaling boats" but that's effectively fighters.)
Chemical thrusters would work, even if Magical Antigrav Type Stuff doesn't (though ship-internal agrav does work... hmm), which then is problematic. Because if chemical thrusters work for a fighter, it would work for the whole ship, and jet-speed-in-jumpspace starships would easily be outpaced by rocket-speed-in-jumpspace starships.
Plus: if you only need a jump drive to get into space, you can have a "stargate" of a single giant hauler that pulls ships into space and lets them go, never leaving the system itself. That's (probably) not what I want.
So maybe chemical thrusters don't work? (Inertia not working feels like something that would have bigger implications though.)
I'm back to needing a field bubble, aren't I? Hmm.
Revised whaling
If whales are not sentient (or even detectibly more intelligent than a single-celled organism), it's going to be considered [more] okay to hunt them by all cultures. (Though Zhdez, for instance, are much less meat-oriented than other cultures and are not thrilled with the necessity.) This brings me back around to "no extended whaling voyages" unless:
Whales appear to migrate from map-south to north, though it's difficult to track individual whales since they avoid non-whaling ships, and whalers tend to put a permanent end to any migration for whales they find. More to the point, no new whales seem to be coming in from the south, meaning the Terran territories (terrantories) are almost whale-free.
The Inukari position is that Terrans have overfished, while the Zhdez position is that the whales are in fact moving, and that it's linked to the withdrawal of the Ancients from Charted Space. Terrans, meanwhile, have a fleet of well-armed ships who make extended northern forays to keep their ships supplied with exoplasm. On the principle that they whales are leaving, they try to fish as far north as possible, hoping to catch whales before they leave Charted Space.
The Zhdez are fairly certain it isn't overfishing, since they're seeing their own decline in whale numbers. They are focusing on alternative sources of exoplasm - both in figuring out where whales go when sounding/feeding, and in collecting less-efficient voidlife - and on finding alternative types of interstellar travel.
Terrans are, ironically, studying whales more thoroughly than anyone else (though this is one of the few areas they cooperate with Zhdez researchers).
The Inukari who take the problem seriously are working hard to figure out the link between the Ancients and whale migration - are the Ancients leaving for more whale-rich areas? Are the whales following the Ancients, who seem to have also moved north? Ancients have never demanded exoplasm as tribute, and it's not clear that's what they use to power their starships.
Great Old Ones
I've gone from thinking "maybe the realspace side of inter-system jumpspace is where the Ancients live" to "but that's also where the sea monsters are" to "hmm, maybe the ~~Ancients~~ Precursors are eldritch horrors?"
Probably not, but it's an idea I'm going to keep in the back of my mind.
Sea monsters
I'm noodling around with the idea that starwhales "sound" into some other dimension (whatever "realspace" means outside the correspondence zone of a specific system/universe). Which begs for the questions "what are they doing there?" and "what else is there?"
For the second, obviously: giant kraken. Or their analogs, at least. Something that "surfaces" out of nowhere to attack ships, possibly only in legend. After all, unless someone sees it there's no way of knowing what happened to a ship that simply disappeared. And if sea monsters only attack solitary ships, there aren't witnesses.
Trip length
Given my current parameters, there's a few limitations on how long a trip can be.
Life support is the obvious one. It's relatively easy to overcome just by choosing to, though your average passenger liner will not be equipped for an unexpectedly long trip (though it certainly will be prepared for reasonable delays).
Fuel is the big limiting factor for Traveller ships, and brightspace energy (I may have to change that name since I guess I'm waving goodbye to false stars in favor of currents) is limiting in one sense (cost) but less so in ship size/volume. (This lets whaling ships who are awash in energy keep flying where a commercial ship would find it a lot more expensive.)
A ship would have to transition between currents in order not to drop into a gate lens now and then, which again would be energy-intensive sometimes.
But if a J1 ship can just ride a J2 current for twice as long, this eliminates the isolation period of the Ancients' withdrawal. Maybe there's something about the currents that J1 ships can't manage? Too strong and it "blows out" the jump field, maybe? That does open some interesting possibilities: a J1 ship can perhaps sustain travel in a J2 current for awhile, but it's risky. And a J2 ship in a J1 current still can't go faster than the current.
So if my analogy is sailing ships, the jump field is just the sails. A storm can shred them and then you're adrift, but if you've got the canvas/energy (and are out of the storm) you can just put them up again. But a drifting hulk will eventually deteriorate. Unlike the oceangoing one, a derelict starship isn't so likely to sink (just get absorbed by a space-amoeba).
The sail analogy doesn't go too far though, I don't think I want solar-sail looking starships (even if it's just the field and not a physical structure.
Revising the jump field
There are two competing uses of the jump field, at this point in my theory: getting into jumpspace, and moving through it. I initially thought of this as being the same use: you're maintaining a bubble of realspace in an alternate universe, and shaping that bubble to convince jumpspace to squeeze you along like a watermelon pip.
If dropping out of jumpspace only happens in the lens of a gate, that changes the purpose of the jump field. If there aren't laws-of-physics differences between the two spaces, such that jumpspace life is basically normal matter (albeit with some handwavey magic energy fields), then a ship can stay in jumpspace indefinitely, permanent structures can be built in jumpspace, and so on, and I'm not quite sure that's what I want, and yet.
Maybe the problem is just that the alternate universe has normal laws of physics, but no native matter (hence: the void). Jumpspace creatures (or plants) are hungry for realspace matter and a stationary structure will get chewed to bits. Plus here's a strong enough current piped through the gate that turbulence will mean "stationary" around a system isn't doable. A ship could stay in jumpspace indefinitely but it needs to keep maneuvering even to stay in one place, and then you'll have to keep scraping the space-barnacles. But it miiiiiight be possible to build pirate stations in the doldrums. They'll need defended from wildlife and maneuvered to stay in position, just considerably less so.
Currents
Okay, here's my thought: the "currents" that pass through a correspondence zone all go the same direction, twisting and braiding into a bundle that fills the correspondence zone at right angles to the invariable plane. Planets (or any mass of sufficient size) cause a distortion in the correspondence zone, pulling it up or down out of the plane in a sort of dimple.
The correspondence zone is a big lenticular shape, and ships have to get far enough out of the way below the plane to enter jumpspace outside the zone, because once you cross the "lens" you are dumped out. The lens is incredibly thin, compared to its diameter; a 1G ship will take 12 to 16 hours to reach the edge of it. Attempts can be made sooner but one runs the risk of wasting field energy only to be dumped back insystem.
The current curves up and out from the lens and then branches, taking off in all directions, braiding, and corkscrewing around others. There are hundreds that go between any given J1 pairs, declining to tens between J6 pairs.
Currents shift over time, and where opposing currents encounter each other, cause turbulence. So does the ever-moving distortion of a planet in its orbit, meaning ships drop into the compressed but not yet turbulent current ahead of their destination. A ship that loses its jump field to turbulence may have a great deal of trouble reestablishing it.
Outside the prevailing currents, a ship can still find current to ride, though sometimes less predictably. Changing currents mid-trip is thus possible, though it will add time to the journey.
There are occasional doldrums, of varying size up to the great rifts between systems. Whales can cross them, because they can "swim" as well as passively use currents. Starships can do some of this, but it is incredibily power-hungry - though the whales' field manipulation is clearly less energy-intensive, a rift-crossing journey will still deplete their exoplasm reserves.
Circulation cells
Maybe there are the jumpspace equivalent of Hadley cells circulating above and below the map plane, and converging in (and through) each gate/correspondence zone. If you want to go the opposite direction, you have to "rise" or "sink" in the plane, to catch the current going the right direction. The current is strongest in the exact line(s) between the two gates, but if you want to sneak or avoid pirates or whatever, you follow a little (or a lot, if you have enough sail to still get to your destination in time) out of line.
And maybe you have to have enough sail (J2+) to get around the pull of the gate if you want to keep going... though this means a J1 ship could sail through an empty hex... unless it's an unformed correspondence zone that would wreck a ship. (And maybe an extremely skilled pilot can pull it off with an underpowered ship.)
And maybe this is why a jump can't just be initiated from a planet? You have to have enough escape velocity (perpendicular to the jump plane/system ecliptic) to get away from the gate in jumpspace? Or it's the correspondence pull of a planet that actually drops you out, I guess, though that changes the "it's the jump charge decaying that drops you out" which, to be honest, I'm starting to think I'll get away from.
