The interstellar drive is a masterpiece of science. For centuries it was thought that nothing can move faster than light.
But the discovery of Exotic Matter has changed everything and now allows us to visit a large number of extrasolar Star Systems in a very short time.
Kirk: My friends, the great experiment: The Excelsior. Ready for trial runs.
Sulu: She’s supposed to have transwarp drive.
Scotty: Aye. And if my grandmother had wheels, she’d be a wagon.
Kirk: Come, come, Mr. Scott. Young minds, fresh ideas. Be tolerant.
Dialog from Star Trek III: The Search for Spock
The interstellar drive works like the Alcubierre drive, which was a speculative idea based on a solution of Einstein’s field equations in general relativity.
It has been proposed by theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve apparent faster-than-light travel if a configurable energy-density field lower than that of vacuum (that is, negative mass) could be created.
In 1994, Alcubierre proposed a method for changing the geometry of space by creating a wave that would cause the fabric of space ahead of a spacecraft to contract and the space behind it to expand.
The ship would then ride this wave inside a region of flat space, known as a warp bubble, and would not move within this bubble but instead be carried along as the region itself moves due to the actions of the drive.
Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel.
Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination faster than light would in normal space.
The mechanism of the Alcubierre drive implies a negative energy density and therefore requires Exotic Matter. In Extrasolar Origin, Exotic Matter is called "Gravium" and can be found and mined on many Planets, but it is a very rare resource.