The Andromeda Ascendant travels through Slipstream.
Slipstream, also known as Quantum Slipstream, is a method of Faster than light travel, used in a variety of science fiction franchises. While the exact mechanism behind Slipstream is unknown, it's generally portrayed as being a hazardous method of travel, and often resembles traveling through an energy tunnel of some sort.
According to the Star Trek novel "Greater Than the Sum", the scientific explanation is as follows. Rather than simply expanding the space in one region behind the ship and contracting it in one region in front, as Warp Drive does, Slipstream expands and contracts space at many points, each at quantum scale, in front of and behind the ship.
Star Trek[]
In the Star Trek universe, Quantum Slipstream is a recent technology, only developed towards the end of the 24th century. The drive is much faster than Warp drive, allowing travel across the length of the galaxy in mere days, as opposed to the decades it would take at maximum warp. In the novels, the starship Aventine was equipped with the drive, as was a fleet of ships lead by the Voyager to return to the Delta Quadrant of the galaxy.
Andromeda[]
In the Andromeda universe, slipstream is the only form of FTL travel. It's highly unpredictable and requires a human pilot; an autopilot system would fail to predict its permutations.