Star Trek: 10 Secrets Of The USS Excelsior

In The Search for Spock, the USS Excelsior is Starfleet's newest, most advanced starship, tasked with acting as a testbed for transwarp drive.

Whatever that is.

Star Trek III never details what transwarp drive actually is, though it's clearly a propulsion technology that would theoretically allow the Excelsior to travel faster than traditional warp speeds. Future installments of the franchise wouldn't clear things up, going on to use the term "transwarp" as a catchall for numerous faster-than-warp technologies like the Borg's transwarp network. Shockingly, even 1991's ultra-detailed Star Trek: The Next Generation Technical Manual by Rick Sternbach and Michael Okuda left descriptions of transwarp drive vague.

What we can learn from The Next Generation Technical Manual, though, is that the Excelsior's "Great Experiment" was a failure but led to advancements applied to future starships, like the Enterprise-D:

While the attempt to surpass the primary warp field efficiency barrier with the Transwarp Development Project in the early 2280s proved unsuccessful, the pioneering achievements in warp power generation and field coil design eventually led to the uprated Excelsior and Ambassador class starships.

For the record, the script for 2009's Star Trek featured a reference to transwarp being used by the alternative USS Enterprise, an indication that transwarp drive had been developed among other advanced technologies in the Kelvin Timeline. This reference, however, was ultimately changed to just "warp", though transwarp beaming did play a prominent role in that film and Star Trek Into Darkness.