I have been baffled by the statements that the ‘great experiment’ of the 2280’s ended up in failure that it was conveniently dropped like a hot plate - it reminds me of how Starfleet had to desparately erase all acknowledgement of other significantly disruptive technologies such as the S31 Time Suit, the spore drive on the Discovery 30 years prior. The theft of a battered old USS Enterprise controlled by 5 crewmen was no grounds for desparate measures i.e gambling the lives of 800+ crew members by chasing the big E into Transwarp speeds if the NX-2000’s capabilities has not yet been validated and proven. Why SF command not utilise a tractor beam from space dock? Or another ship within intercepting range? These options would have been a reasonable course of action if the NX-2000 was not tooled up to restrain the Enterprise or not fit to perform Transwarp. Something so new and game changing such as Transwarp drive would / should have yielded reliable and tangible results beforehand, only then you would make the call to commit so many officer’s lives and a new ship which is of high tactical value into a pursuit with an expectation of success. Scotty having spent reasonable time on the Excelsior must have realised by then even with a headstart the Enterprise could not outrun the NX-2000 (not when you have all speeds available through Transwarp drive!) otherwise he had not needed to go through all the trouble of tampering with the ‘complicated plumbing’ of the Transwarp drive, removing of the vital components and even trolling the Excelsior captain with an embedded ‘good morning’ message. We fast forward to the 2290’s - now with Captain Sulu, master of the ......NCC-2000 Excelsior, the most advanced and powerful ship Starfleet (not S31) has ever created - fit to publically represent the United Federation of Planets... And doing what exactly? A Fact finding mission on interstellar gasses. Surely an officer of Sulu’s experience and pedigree (ex Enterprise helmsman) coupled with the best ship should set sights at venturing beyond any other ship has gone before? Was it doubt regarding the ship among the Starfleet ranks?? The Excelsior is 5-6 years old at this point, which by such time the 2260’s era Constitution class had completed it’s primary deep exploration mission. Why has this new ship whilst in a call to arms ended up being a punch bag for old Klingon battlecruisers (VOY: Flashback) and got toyed with by a BoP? (ST:TUC) Even the bridge module looked unremarkable and unambitious, it is cramped and nothing on show to flex any ‘great experiment’ credentials, in contrast to the NX-2000 all business looking spacious bridge with black wrap around glass facias (check out the early concept art as it shows the main viewer with a wide 180 degree viewing angle with data & tactical overlays!). Instead we only remember the NCC-2000 as the only ship that sports a captain’s coffee table. I just cannot ignore the significant gaps between the depiction of the NX-2000 ship in ST3 and the NCC-2000 version in ST6. We go back to the widely accepted canon of that Transwarp drive failed so hard off the back of the failed pursuit of the Enterprise that the prototype Excelsior instead ran on conventional warp drive, end-of-story angle, this takes much suspension of disbelief to compensate for unimaginative writing. “But someone found a flaw in the Transwarp system design after undoing Scotty’s meddling, it prevented a disaster.” This would be a plausable reason, but only during early experiment and testing phases on unmanned test beds where fireworks would ensue from flawed design. Why is any significant flaw is only realised after the stage when TW is fitted on a one of a kind hull and effectively signed off for active duty? What if Scotty obfuscated the plumbing insidiously that it threw the Transwarp engineers into thinking the whole thing is fundamentally wrong? ......Scotty never believed in Transwarp afterall. In-universe reasoning tells me that based on the close observations and statements in ST3 and ST6 is that the ship that is commanded by Cpt Sulu is NOT the same ship as the NX-2000 under the helm of Cpt Styles. What happened to Styles anyway? He was regarded as unremarkable and somewhat arrogant - however deemed suitable for the plum job. What he lacked in nouse and leadership, was compensated by the promised advancements of the ship. What about his helmsman? Did the latter really end up working for OCP in the 21st century instead? Theory: The original NX-2000 Excelsior under the command of Cpt Styles acheived Transwarp speeds and in another attempt to break its previous record - just like that, the ship was gone... In 2286(?) Cpt Kirk (along with Sulu) are assigned to the Enterprise-A. The NX-2000 is seen briefly inside spacedock at that time, and again in 2287 in ST5. Was it the same ship as the one under Styles’ command? I dont know. We didnt see another Consitution refit ship (Enterprise-A) in Space dock when the original Enterprise was stolen, so there are reasons to believe some rapid construction and/or re-christening have taken place between the events of ST3 and the end of ST4 inside or near Space dock. So what happened to Styles’ ship then? If it disappeared, did it reach as far as another galaxy and was unable to make the return trip due to navigation limitations being too far out? Or ‘when’ did it go to? Was this the epic failure that only few in SF command knew about? It got so bad that Admiral Cartwright (who liked a cover up or two) gave up hope searching and had to terminate all useage of the Transwarp technology - especially if true, the worrying implication of any time travel capability. With the NX-2000 gone from 23rd century knowledge, and so did much of her prototype defence and science capabilities. Starfleet could not replicate all this in short order - so another USS Excelsior was assembled with conventional systems and bridge module design of the time - even some exterior differences to the original can be spotted easily - possibly as a result of the missing prototype systems or lack of time and resource. SF command called upon Hikaru Sulu who’s ambition to serve on the Excelsior was well noted, adding to his loyal and unquestioning character, promoting him and giving him the replacement Excelsior to go on a benign mission was the perfect smoke and mirrors they needed to fool the UFP (and more importantly) the Klingons and Romulan Empires that they are pressing ahead with plans for expansion with their next generation of multi purpose starships. The rest of what we know of the Excelsior class is history. Yet somewhere ..... or somewhen - the NX-2000 is out there living up to the great experiment billing.