Space propulsion

A vast number of different propulsion types have been fitted to Umbrian spacecraft since it first began launching objects into space, including chemical rockets, electronic thrusters, solar sails, beam-powered devices, and nuclear pulse engines. While all were capable of propelling objects through space, the most effective proved to be electric engines, such as ion or plasma thrusters. These are commonly referred to ion engines or ion thrusters, no matter their actual subtype.

These devices work by emitting a stream of ions out of their thruster nozzles, which provided the craft with thrust. Electronic thrusters were primarily powered by fusion reactors which utilize aneutronic, or non-radioactive fusion fuel sources. This greatly reduces the risk to the crew and cuts down on the maintenance and disposal costs associated with spacecraft and their power cores.

Initial challenges with scaling electronic thrusters would create barriers to the rate and extent at which the Umbrian Republic could transit through space. Even as these technologies matured, trips through the vast distances of interstellar space were measured in years or decades rather than days and months.

In these early days of interplanetary travel, half of a voyage would be spent accelerating towards the target, while the second half would be spend decelerating. Cryogenic freezing would be used to prolong the lives of the crew and passengers, making it possible for some spacers to return home to find that their children's children where now their own age.

These impediments would be removed by the discovery of supra-luminal travel. This was achieved by accident, when engineers at Serlume Stellar Engineering succeeded in creating distortions in space time while attempting to create artificial gravity. They noticed bizarre readings from their experiment, which were isolated and determined to be miniature folds in the fabric of space-time.

The initial power required to create these pockets in space time were exorbitant, but advances in the Republic's understanding of exotic particles, especially antimatter, allowed for the creation of an 'engine' which allowed for the expansion and contraction of space-time in a predefined area in proximity to the device.  This engine would contract space time in front of the craft, while expanding it behind, pushing the craft through space. Thus the first supra-luminal engine, or SLE, was born.

This groundbreaking improvement would immediately revolutionize space propulsion. SLEs became standard equipment on most starships, allowing them to pass through the interstellar medium, or space between solar systems, in previously unimaginable times.

A series of navigational buoys would be established by the Colonial Affairs Commission, creating the first star lanes which would connect the various planets of the Republic. This would greatly speed travel between worlds, ushering in a new era of interconnection between the colonies and their homeworld.

However, the pocket of space-time the SLE creates does not prevent objects within from interacting with other objects in its path. This created a lethal dilemma. If an object moving faster than light struck even a small object, the resulting collision would be catastrophic.  Jumps within a system were well within the technical capabilities of modern SLE arrays, but were considered dangerous and not worth the added risk for most purposes.

As such, ion engines remained the primary method of propulsion in the relatively busy confines of a star system. Trips requiring faster-than-light travel would begin with a short 'jump' above the system's elliptical disk, where the star's gravity would concentrate most of the system's mass, before safely travelling to the target.

The Republic's scientists continue to refine supra-luminal propulsion, slowly increasing the maximum velocities which can be obtained and shrinking the boundaries between stars.