this was the generic term used to describe the starship engine and its components which allowed the ship to travel at supralight speeds through hyperspace. It worked with the ship's navigational computer to ensure that any direction and course changes necessary to maneuver through hyperspace were executed without encountering gravity shadows. Most hyperdrives required a fusion generator to propel a ship through space. The hyperdrive was built from a titanium-chromium compound that could withstand the forces needed to push through the space-time fabric of realspace into the hyperspacial continuum. The hyperdrive used modified gamma radiation to create electromagnetic energy that, when ejected from the hyperdrive, caused the realspace time-space matrix to ripple. The hyperdrive continued to eject electromagnetic energy to push against these ripples, propelling the ship into hyperspace. However, the hyperdrive system could only work in the near-absense of gravity. This meant that a ship had to escape from a planet's gravity well before it could jump into hyperspace. Each hyperdrive system was equipped with a cutoff which returned the ship to realspace if a gravity well was discovered in an unspecified location. This principle allowed for the of gravity-well generators - such as those used on the Imperial Interdictor-class cruiser - as a way to drag starships out of hyperspace at a specific location. It was rumored that the hyperdrive was invented eons ago by a space-faring race from outside the known galaxy. When this race encountered the known galaxy, shortly before the formation of the Old republic, it first came upon the Corellian System. There, the aliens sold the secrets of the hyperdrive to the Corellians, who studied it for decades before producing their first, working hyperdrive. Interstellar exploration and unification began in earnest. After about 20 years, the Corellians began selling their ideas to other star systems, and a huge galactic community was born, which later evolved into the Old Republic. Although none of this was ever proven, the presence of planetary repulsors inside each of the Corellian System's planets showed that there was a more technologically-advanced civilization in the system at some point in its history. Hyperdrives were grouped according to their ability to exceed the speed of light, and ware categorized by classes. The lower the class number, the faster the hyperdrive could propel the ship. For example, the Millennium Falcon could make ".5 past lightspeed," an indication that it had a Class .5 hyperdrive. This class was considered twice as fast as Class 1 hyperdrive, and could attain speeds of 127 light-years per hour. Note that Dark Force Rising indicates that .5 is faster than .45, which seems to contradict this description of relative speed. Interestingly enough, although a hyperdrive needs a near-absence of gravity in which to operate, any open area of space that lacked at least some form of matter was also to be avoided. In these areas, where there was no resistance on the ship's shields, a hyperdrive could operate at such incredible levels that it could literally tear itself apart. Thus, starship owners often had to recalibrate their hyperdrives on a regular basis, to account for the areas of space in which they traveled most often.