Similar to the Borg transwarp conduits, the quantum slipstream is a narrowly focused, directed field that is initiated by manipulating the fabric of the space-time continuum using the starship’s navigational deflector array. This creates a subspace tunnel, which is projected ahead of the vessel. Once a ship has entered this tunnel, the forces inside propel it at incredible speed. To maintain the slipstream, a ship has to constantly modify the quantum field with its deflector dish. The speed of the drive is inversely proportional to the time and distance. When the crew enters the Dauntless in episode Hope and Fear for the first time and accidentally activates the propulsion system, the spaceship flies a flight of 15 light-years over a period of about 10 seconds. Thats equivalent with approximately 50 Million times the speed of light. After realizing that they would have to leave Voyager forever to get home with the Dauntless, the crew tries to match the drive of the USS Voyager to the parameters of the Dauntless. The modified Voyager is able to cover a distance of 300 light years with the slipstream modification before the system becomes unstable. The way back to Earth is stated in a fake message, created by Arturis, with 7 months aboard the Dauntless. For this period, the stocks are filled. At a residual distance of 60,000 light years at this time, this would correspond to a speed of about 100,000 times the speed of light or 500 times slower than a short slipstream jump.
However, in the episode “Timeless“, the technology proved to be dangerously unstable, resulting in the loss of all hands of the Voyager in an alternate timeline. Due to a phase variance, the Slipstream tunnel, produced by a replica slipstream drive of the Voyager, collapsed during the flight and the ship crashed on a planet near the border on the edge of the Delta Quadrant. Harry Kim and Chakotay survived, because they used the Deltaflyer, which flew ahead of the Voyager, reached the Earth safely. They used some years after this event a temporal communication device to change the timeline and rescue the ship and the crew.