Interstellar Travel
Interstellar travel in human society is a form of travel between different star systems. Travel often takes years, or multiple decades between systems. Antimatter jet propulsion is the most prevalent method of acceleration. Synthetics have been historically preferred as crew members for interstellar spaceflight and deep space colonisation efforts due to their low resource requirements and their lack of need for cryosleep systems; this eventually changed with the introduction of new Coalition equality regulations. Radio wave propagation takes so long between star systems that wormhole relays are often the only effective way of establishing instant communications.
Propulsion
In humanity's history, long-distance propulsion has been accomplished using two main methods. The original method, nuclear pulse propulsion, vastly increased the speed at which humanity could travel within the Solar System, but it was not until antimatter jet propulsion became available that it was possible for humanity to go interstellar.
One significant hazard of travelling near light-speed is the devastating consequences of even dust-sized grains of space debris, which can instantly tear apart a ship. This is mitigated by a large, forward-facing forcefield system, supported by superconducting capacitors capable of delivering near-relativistic impulse mitigation energies. This forcefield is in turn backed up by a second redundant forcefield and finally a heavy composite armour plate, which sometimes includes nanite-based impact regeneration capabilities. This system, known as the relativistic impact mitigation system (RIMS) is different from a defensive forcefield on military spacecraft, which wraps around the entire ship and is much less powerful than the RIMS.