My guess on that was that the scale changed as a result of USS Excelsior. Maybe not in Kirk's lifetime, or maybe it was, but Excelsior was suppose to be the next big leap forward for technology. While I is never confirmed or denied if the transwarp drive worked as it was suppose to, or if they went back and installed a new kind of warp drive in the Great Experiment. Only that it eventually worked as a starship and gained enough respect that the class is still being used as flagships all the way to the Dominion War about 90 years after the lead ship was launched. The other possible candidate would be the Ambassador-class starships ushering in the new design styling that would show up in the Galaxy-class and many other starships in the mid-24th century.
If the Transwarp drive had worked the Question becomes why is not on the Galaxy Class Starships the Borg have Transwarp. So the Excelsior Transwarp design must have failed at the time. And Starfleet is still trying to get it to work by the time of First Contact and Starfleet may still be trying to get it to work.
I would think that what Starfleet calls "transwarp drive" evolves as they get better technology. What was once transwarp drive in the 2280s becomes their new standard for warp drive. It not being too radically different than what pervious ships had, but was faster than before. By the 2360s and 2370s, "transwarp drive" still means a technology that is faster than current warp drives, but isn't the same as the drives used in the 2280s. Nor are transwarp drives the same across the galaxy. The Borg have one type. The Voth had a more realspace version that was closer to what I imagine Starfleet would go for more so that conduits until they acquired Quantum Slipstream drives. Once Starfleet gets to whatever tech the Voth had, that will become the standard warp drive by the time the fleet gets fitted with the technology. After that there will be a new "transwarp drive" to strive towards. Possibly a galaxy jumping drive to reach Andromeda in weeks or months rather than centuries. For all we know, the Kelvin Universe version of warp drives was just another kind of transwarp drive at one point in Federation history, and it was used on some ships, but not on others as the smaller nacelle ships started to get drives that were just as fast or faster...or perhaps just more practical.
Yeah, it's a form of transwarp, one that relies on a network of far-reaching subspace corridors (or conduits) that allows for faster-than-conventional warp travel to various parts of the Galaxy. It's not known if these conduits are naturally existing subspace phenomena, or something created artificially by the Borg, but either way it requires a vessel with the means to open a conduit and traverse it. In a way, these conduits are almost like wormholes.
The Transwarp conduits are point to point where the distance is set amount of travel and possibly is setup like a 3 dimensional map and by knowing which point in the map you are going to and knowing the point that one's starting from to figure out the programming the uses of the conduits system. But Transwarp is a speed of wrap that Starfleet hasn't any idea of how that works short of the Enterprise time in the Borg conduit in the wake of Borg ships.
USS Voyager must have returned with a dozen or so different propulsion systems that were better or at least different from Federation standard. Some they recognized, others they didn't. I wonder what scans, if any they managed to take from the Voth ships use of transwarp drive?
In the final episode, my impression is that Voyager was traveling sublight (and relative slow sublight) while in the transwap conduit.
It is possible that once in the conduit a ship might be able to reduce the level of speed on the engines and stay in the conduit without more information about the conduits system anythingpossible
A case could be made that's how it works within a conventional warp envelope as well. The ship never really crosses the speed-of-light threshold within its subspace (or warp) field, but it appears to do so--and has the same end result of doing so--to an observer in normal space.
I have an idea for a universe in which both warp-drive and hyper-drive exist. Warp-drive is slower, and you're still able to interact with normal space (thus you need to steer around stars and planets) and can communicate via sub-space radio. Hyper-drive, on the other hand, is much faster and as you're in a trans-dimensional space you can fly "right thru" stars and planets. However, you have no outside communication, and you must pre-determine the exit point where you'll drop back into normal space. Here's the kicker: dilithium, which as we all know is required to run the warp-drive, cannot exit in hyper-space and will EXPLODE if you attempt to take it there. Likewise, the jump coils in the hyper-drive engines won't survive the stresses of warp speed and will be totally useless. Ergo, no ship can mount both warp-drive and hyper-drive engines. So, when you build your fleet, do you want warp-drive or hyper-drive on your ships?? (Note: combat is done in normal space at STL speeds.)
This is all a misunderstanding of the physics at hand. Warp is based on subspace. A warp field's strength determines how deep into subspace it's merged, hence, how fast it goes. As with space there's no physical limit to depth or size. Further subspace has different domains e.g. different dimensions/universes or different frequencies if you want. The Federation and other civilization of that level have not been able to master warp in other domain as well yet. There could be domains allowing for far more efficient or faster travel. The difference between warp and hyperspace is simply a difference in naming only or the placement of the dimension. The fundamental idea for all FTL types using other dimensions for travel are the same except their naming. Only a minor number actually have different physics.
The difference between the two are whatever the author / creator of the universe wants it to be. If I want them to both exist in my world with different laws of physics, I can do that. There's no "misunderstanding of the physics".
Babylon 5 used jump drives to enter hyperspace when a ship could carry one. Otherwise species made due with static jump gates that would both make a portal into hyperspace and provide a beacon for which to locate the next gate/system so a ship could find its way out of hyperspace if it did not have a jump drive to make its own portals. I'd worked on a crossover (many years ago) for Star Trek and Star Wars, were Federation designed starships would be equipped with antique hyperdrives, because even those were faster than warp drives. With tuning of the warp field inside hyperspace, their engineers manage to get their ships up to about standard Imperial speeds, though it was taxing at first. However they did also use their warp drives in local space as they wouldn't need to chart a course with the navi computers for they hyperdrives for their few hours or day runs in some sectors. Also against Imperial Star Destroyers, since a starship that can warp can do much better hit and fade tactics locally than a hyperdrive. Also high speed photon torpedo passes are fun, when the turbolasers can't realistically track your starship.
IN the cage Captain Pike said in enage the star drive one time another said in enage the hyper-drive and said time wrap factor 5
Actually, the "time warp factor seven" (ordered by Pike) and the "prepare for hyperdrive" (ordered by Spock) are in two completely separate scenes, nearly at opposite ends of The Cage. The term "stardrive" wasn't mentioned until TNG's Encounter At Farpoint and referred to the separated saucerless secondary hull. EDIT: The term "stardrive" also got a mention in Bread & Circuses" to refer to the class of ship that the SS Beagle was