In the old sailing days, ships set forth not knowing what they’d encounter along the way. This Jump variant (more of a re-skinning, as it leaves the core jump mechanics intact) tries to recreate that feeling by making the journey through jumpspace not just a week alone in your own pocket universe. Intended for more pulpy or mysterious games, or wherever you want a little more variety for FTL travel without changing the mechanics of your game!
Initiating a jump results in the drive generating exotic particles that are foreign to “normal” space-time–this results in our universe literally expelling the ship into an adjacent one, where the particles are native, and where the physical dimensions don’t map to those in our universe. Once this happens the clock is started—the field starts to decay, and when it destabilizes enough (in about a week), the process will be reversed, and jumpspace will expel the ship back into normal space-time. If the ship has spent the majority of its transit time moving towards their destination (by modulating the field to control its direction and speed), they’ll pop back out around where they expect. If, for some reason, the ship hasn’t moved in the direction and distance that was plotted, it…doesn’t (Jump Mishap time). This also applies to anything ejected from the ship (like, say, a space-suited person)–if it leaves the particle field, it immediately reappears in the normal universe someplace other than expected. Note that due to the nature of JS it’s impossible to predict where such premature reappearances will occur, making it impossible to weaponize.
Note that in this variant, there is only a single jumpspace that all ships travel through, instead of each ship generating their own short-lived pocket universes. However, the nature of this parallel universe is such that encounters with other ships is almost impossibly rare–if two (or more) ships coordinate their calculations they can “tandem jump” and stay in contact throughout the voyage. However, ships cannot travel together without that level of coordination, as if even a single variable is different between the two, the ships will be separated too much to detect (this removes the idea of “jump space pirates” either waiting in JS or attempting to follow a ship into JS to hijack it—unless they have inside information, of course).
There are all sorts of theories as to what JS actually /is/ (other than a parallel space-time)–however, as the normal laws of physics don’t seem to apply here, taking readings that make any sort of sense is difficult at best. What is known is that distance traveled in JS translates to much greater distance in the normal universe–and the more particles your jump drive has generated, the faster you can travel, and thus the further you can reappear from your starting point. Note that no matter the size of the field, it is usually impossible for it to survive longer than a week–no-one knows why. Legend tells of an experiment that tried to extend the life of the field—they still tell ghost stories about the spacesuited figures that are found on the edges of systems, drawing a straight line from their origin point dozens of parsecs away, each crewmember leaping into the void to escape the ship that will never stop.
Navigating JS involves a lot of math, as it appears to be an empty void full of shifting clouds of light: the astrogator is essentially plotting the correct angle and momentum for which to enter JS so that the ship reaches the appropriate exit point by the time the field wears off. This is important because there are no navigation points within JS–no stars to see, and long-range sensors just return junk data. It is possible to use short range sensors to track the direction you’ve come from, and make sure you stay “on line” (or have a way to get back to it if the ship wanders off course), as the ship’s passage disrupts the “clouds”, leaving a detectable trail behind them for a period of time–but it’s still generally a good idea to not stop or make any detours along the way.
However. There have been stories over the years of things being detected on short range sensors. Asteroid-sized masses—or larger. Smaller objects that seem to move under power. There are legends of breaks in the “clouds” that reveal structures of unknown design—stations, or megastructures. And sometimes there are transmissions–something with a pattern too chaotic to be understood, but with too much structure to be just noise. Official records don’t make mention of any of this, and you’ll have trouble finding anyone with a credible account of such encounters. But every once in a while, a strange, non-Ancient artifact will surface that the seller will claim came from jumpspace. Or maybe if you buy that crazy old spacer enough drink, they’ll tell you about the time his ship docked with one of those “cloud stations” but has no memory of what happened until they emerged from jumpspace, a parsec out from their original destination—with a missing crewmember and five crates in their hold no-one remembers loading. And of course, any ships that don’t reappear from a jump are said to have strayed “too far from their line” in order to check out one of those signals–or perhaps were overtaken by them.
Regardless, wise captains know to always “follow the line,” and most scoff at the idea of there being anything more mysterious in JS than tricks of radiation and exotic frequencies. They classify these stories and signals as just another example of the dangers of travel, in the same category as mirages in the desert, or will o’ the wisps in the swamp–tricks of the light or mind that will only lead you further away from where you should be.