Immersaline is a light blue, organic fluid with a viscosity approximating that of human blood. In its "natural" state, it is incapable of supporting flame or allowing explosions to proceed but, under specific conditions, it can be made to carry other gasses and has a high affinity with oxygen. In use Immersaline fully immerses the subject, penetrates the body including the digestive tract and respiratory system. It is supportive and was designed to allow humans to crew ships accelerating at up to 30G as well as manoeuvre at high stress. It was developed by JARP (the Joint Acceleration Research Program) with the final product being released not long after the end of the Amaranthine War. Five years after its first tests, JARP was able to demonstrate a ship flown by fully immersed personnel that was able to accelerate at over thirty gravities and manoeuvre with stresses in the high twenties.
Replication is a somewhat inaccurate name for what is basically a three-dimensional printing process carried out by nanotech enabled print devices. Using this technology, clients can print anything from paper reports and newspapers to components used to build spacecraft. It is one of the most important technologies developed since humans colonised the planets they now call "The Extent".
Travel through a gate, across a hyperspatial interface, is essentially instantaneous. As such, space travel, including all combat, must occur in real space and almost always within the confines of a stellar system. A system is a vast three-dimensional space and navigation within it is normally referenced with respect to that system's primary.