Propulsion systems are powered by fuel refined from tylium ore. A ship's primary propulsion systems, referred to as "sublight engines", allow it to travel at a slight fraction of the speed of light, which is sufficient to traverse the distances between planets in a solar system in relatively short timeframes. Most ships in the series also have a secondary system, called a faster-than-light drive (or "FTL"), that enables a ship to travel interstellar distances almost instantaneously, by "folding up space" in between the ship and its destination. Since, under normal circumstances, a ship that has used its FTL drive cannot be followed without explicit information about its destination, this technology is used extensively in strategic and tactical manoeuvres.