Quantum slipstream drive is a propulsion system not too dissimilar to transwarp drive developed by the Borg, in which it takes ships at speeds higher than those permitted by even the most advanced warp engines, producing what is called slipstream velocity.
The technology was created around the 2370s by a species in the Delta Quadrant. The USS Voyager was the first Federation vessel to achieve slipstream velocity, but as they had little experience with it they could not keep up with the rapidly changing quantum field.
In 2381 following the defeat of the Borg, Starfleet was beginning to install quantum slipstream drives on its vessels. However due to the nature of the technology,not all ships were compatible with the upgrade. Later, a small contingent of Starfleet vessels, including Voyager, were outfitted with the drives in order to explore the Delta Quadrant in greater detail, and to learn any information available of the Borg. Unknown to Starfleet, at the same time in 2381, B'Elanna Torres had managed to recreate the technology from memory and outfitted a small vessel with the drive, for the purpose of evading groups pursuing her daughter.
Many starships on deep space assignments were equipped with the drive, in order to facilitate a quicker journey back to port, and in case of emergency. Originally, the drive was kept solely within the Federation, and with the Romulans and Klingons struggling to duplicate this success, a joint scientific research project was launched, where other possibilities were thought of including transwarp drive.
Ultimately, transwarp became impossible to achieve, so the Federation and her allies reverted back to quantum slipstream, due to their advanced knowledge of it. It was so successful in fact, that ships continued to use it up to 200 years later, when it was installed on the USS Pioneer in 2597.
The widespread availability of quantum slipstream drive enabled distant Federation allies, such as Natrix, to finally join the Federation proper.
Vanguard Command timeline
By 2385, only starships of the Vesta-class, Invincible-class, Suzerain-class and Dauntless-class are equipped with working quantum slipstream drives. However, with the exception of the Vesta-class, the other classes are only able to use their quantum slipstream drives for about 24 hours before reverting to warp drive. Cool down time is at least another 24 hours before the slipstream drive can brought online again. Although these class of ships have been designed to be the most receptive to this type of propulsion system, Federation technology simply was not compatible to slipstream technology.
The capital starships of the Vanguard Fleet are the only vessels of that division equipped with the quantum slipstream drive. With the size of the slipstream tunnel produced by their drives, the rest of their respective task force could travel along with it at slipstream velocity as long as they are in tight formation.
Slipstream velocity is attained when energy produced by a starship's quantum drive is coursed through the deflector array to create a slipstream tunnel that allows it to travel at faster-than-warp speed.
As recorded by the crew of the USS Voyager, a starship in slipstream velocity could cover fifteen light years in just three minutes, or 300 light years in one hour. This calculates out to 9,467,280,000 times the speed of light.