Transwarp

Voth ship traveling at transwarp speeds

Transwarp is a generic term for some speeds that exceed traditional warp drive limits. Species such as the Voth employed ships that were equipped with transwarp drives. (VOY: "Distant Origin") Similarly, the Quantum slipstream, developed by Species 116, was a method of propulsion not unlike transwarp drive. (VOY: "Hope and Fear")

The Federation attempted to develop a transwarp drive in the USS Excelsior in 2285, termed "The Great Experiment". However, the effort was ultimately unsuccessful in achieving infinite velocity. (Star Trek III: The Search for Spock) In 2374, the USS Defiant studied a rare subspace compression anomaly in the hopes of collecting data relevant to the development of transwarp corridors. (DS9: "One Little Ship")

In 2372, Tom Paris of the USS Voyager managed to break the transwarp barrier in the shuttlecraft Cochrane, after discovering a new form of dilithium. Although this form of travel was found to have severe, unanticipated side effects, Mr. Paris was the first person in Starfleet to cross the transwarp threshold. (VOY: "Threshold")

The Borg transwarp drive was based on generating transwarp conduits. This technology was first encountered by the Federation in the 2350s by the USS Raven. This encounter remained unreported at the time. (VOY: "Dark Frontier") In 2370, the ship used by the rogue Borg that were under the control of Lore used a conduit during an attack on Federation space. Geordi La Forge of the USS Enterprise-D likened this form of transwarp to "falling into a fast-moving river and getting swept away by the current." (TNG: "Descent") In 2374, Seven of Nine attempted unsuccessfully to modify Voyager to create a transwarp conduit. (VOY: "Day of Honor")

In 2375, USS Voyager used a transwarp coil stolen from a Borg sphere to traverse 20,000 light years closer to the Alpha Quadrant, thus cutting about fifteen years off of the trip. (VOY: "Dark Frontier")

In 2376, the Pathfinder Project wasted 6 months attempting to develop a transwarp probe, based on simulations made by Reginald Barclay. (VOY: "Pathfinder")

Background

In 2267, the term "ultrawarp speeds" was attributed to the velocity of approximately Warp 15. This was obviously before Warp 10 was a reference to infinite velocity. Warp 15 was at that time beyond the limitations of the conventional warp drive of the Enterprise. It is therefore possible that ultrawarp is a synonym, or rather an older term, for transwarp. (TOS: "The Changeling")

According to the Star Trek: Deep Space Nine Technical Manual (page 14), the Cardassian Union predicted a breakthrough in energy-field stability for transwarp computation speeds in computer core technology, during the 2370s.