Seeded Starlane
When it comes to interstellar travel, two of the most vexing issues facing the peoples of the Sealed Kingdoms Region are the limited speed of light and the tyrrany of the rocket equation. Journeys will either take an extremely long period of time (necessitating long-term life support technologies like CELSS and cryostasis) or require powerful engines and vast quantities of fuel, the mass of which requires even more fuel to accelerate and decelerate into the desired trajectories at the desired traversal speeds. One possible avenue of escape from the latter limitation is to somehow harvest some or all of the fuel required en route. Drive systems like Bussard ramjets and catalyzed fusion RAIR drives attempt to syphon the diffuse gasses of interstellar space into accelerators to drive fusion reactions, but radiative drag and the sparseness of fusible material - even in the Soul nebula, where the Sealed Kingdoms are found - also limit the usefulness of these options.
'But,' one might ask, 'what if one could simply leave the fuel behind entirely? Surely a physical fuel or power line couldn't reach across light years... could it?' With seeded starlanes, it turns out that the answer to this question is actually 'yes.' With a little bit of preparation, the mass of a spacecraft which might otherwise be taken up with fuel can instead be put to use for other purposes.
Manufacturing
Seeding a starlane involves providing the fuel - or, in the case of light or nuclear sails, coherent light or beams of particles respectively - to a travelling vessel remotely. This can be accomplished in myriad ways, but all of them involve some degree of foresight on the part of mission planners or an understanding that a route between star systems will become a regular thuroughfare. For most spacefaring species, a seeded starlane consists of a column of fusable or fissile gas strung between the destinations in question.
A long haul automated vessel can lay a path of gas in its wake, relying on gravity to bind the gasses together. This option is simpler than most, but takes a long time and is most feasible when the destination system has no pre-established seeding infrastructure. Another option is to project the fuel at relativistic speeds along the projected flight path of a mission using particle beams or, if the gasses are charged and will tend to spread apart over time, macron beams. A spacecraft might ride the fuel beam in the manner of a sail craft until it reaches a high enough speed to gather material from the beam ahead of it. A beam coming from the destination system can instead be used to directly feed the fusion drive of a craft that otherwise requires a certain cruising speed to use its collectors, as in interstellar ramjets.
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