Some may wonder if the name Phoenix may have been more appropriate, given their early history. That history turned Excelsior's record from that of a bloated, ugly failure into a truly worthwhile replacement for the Constitution and Enterprise class ships. Their incredible design and success may be proven simply by the fact that even today they remain active.
The tale of the Excelsior starts with Starfleet beginning their early preliminary work into Faster Than Warp Propulsion. These technologies, best exemplified by modern Quantum Slipstream Drives, were an unattainable ideal for Starfleet for decades. Many drives were planned or built, but the first 4 projects were authorised simultaneously. Those drives being the Benamite-Lithium Time Warp Drive, Controlled Omega Particle Drive, Displacement Activated Spore Hub Drive and External Transporter Beam Transwarp Drive. All 4 drives took their own extreme approaches to what could possibly be done with getting a ship faster than what Henry Archer or Zephram Cochrane could ever dream of.
The Benamite-Lithium Drive was possibly the simplest of the four, at least in terms of engineering. Relying on a mixed Benamite-Lithium core feeding two warp nacelles to bend, above all else, the fabric of time rather than the fabric of the space the ship could theoretically travel through normal space at what appeared to be velocities far faster than the speed of light, matching Warp speeds whilst simply bypassing light. Their first testbed, the USS Kongo (NCC-1713), at least worked but the ship suffered a runaway, with the crew evacuating to the saucer section whilst the secondary hull sped into Romulan space. The ship was recovered in 2366 by the USS Enterprise (NCC-1701-D).
Their second testbed, the USS Enterprise (NCC-1701), worked fine, but unfortunately ran into problems with supply as Benamite is rather rare (even with modern replicators it's difficult to obtain sufficient quality Benamite in sufficient quantities for a ship to utilise the stuff) and Lithium was rather prone to exploding on contact with water, which was rather problematic for a ship with a human Chief Engineer. The project was put aside as a result, with Enterprise returning to a Dilithium core after two years.
Most of the information on the Controlled Omega Particle Drive remains classified, but what has been declassified reveals that the idea was to simply plug in a stable Omega Particle in the place of a standard warp core. This would theoretically be capable of feeding the warp drive and structural integrity fields with far more power than a conventional warp core of the day, essentially brute forcing it. Unfortunately the first experiments with a stabilised Omega particle went horribly wrong.
It is important to note that under typical circumstances Omega Particles are not stable but Metastable, able to potentially explode with a force that destroys subspace itself if poked too hard. Unfortunately the quantity housed at Starbase 81 in the Lantaru sector went critical, destroying Subspace itself across a 5 light year radius whilst the USS Soyuz, then under the command of Captain Andrew Barclay, was still present. Consequently the ship spent the years 2273 to 2278 coasting at 0.999c away from the system after neutralising the few surviving particles. It was this public, horrific failure that many believed destroyed an iconic vessel that saw the project shuttered with prejudice. On the recommendation of Admiral Kirk a detailed log of the disaster was sent out on probes to every major power the Federation had contact with to explain why the Federation had every intention of destroying every Omega particle in the known universe, treaties and borders be damned. This policy is still in active effect. One was even sent to the Borg, smuggled aboard the USS Ferrick.
Spore Drive was at least somewhat more successful. Crafted by the mind of Paul Stamets and his research partner Justin Straal the idea was to ride a subspace mycelial network around the universe, essentially a modern Transwarp drive but with more mushrooms. This saw two testbed ships constructed, the USS Glenn and USS Discovery. Glenn's first jumps were sporadic and random, culminating in the ship hitting a Radiation Firewall, causing the Inertial Dampeners to fail and the crew to be splattered. It was this unfortunate accident that saw the USS Discovery capture a Mycelial Tardigrade, initially using it as a navigator before discovering it was sentient, and thus violating anti-slavery laws . This saw immediate rectification by letting the Tardigrade (who's since gone onto a successful writing career on Ferenginar) and borrowing some DNA from it to genetically augment Stamets. This was highly illegal and ensured Stamets would be murdered if he ever set foot on Earth soil again but he did retain his commission, as he was now a core part of Discovery's FTL system. Though Spore Drive did work, the multiple deaths and violation of at least 17 different laws would ensure Discovery would retain this trait until she was lost under the witness of the USS Enterprise during the incident at Xahea.
And now, with ALL that preliminary clarification out of the way, we can finally get back to the USS Excelsior. But not yet. For first we must describe her Transwarp drive. The idea was simple, incorporating a transporter beam into the main navigational deflector to massively lower Excelsior's subspace drag, allowing for a far faster ship despite being of similar size to an old Eaves-Kurtzman vessel. However, the drive ran into problems.
The first ship converted was the USS Alkanis, a new Hercules class transport ship. Already renowned for their speed the Alkanis would make a perfect testbed when the beam… failed to make a substantial impact. This was found to be down to the ship already being of similar shape to an alligator, and so new plans were drafted. Three other ships would be converted, the Gresley Class transport USS Tornado, Nevis class surveyor USS Vantage and finally the USS Repulse. Repulse was easily the most successful vessel and so a ship based on her lines would be constructed.
Sitting at a length of 511 metres, Excelsior was a fairly large ship but resembled Repulse quite strongly in shape. Again a 140m long saucer would sit atop a ridiculously thick neck, leading into a huge secondary hull with a beautiful extended stern, trailing from the main shuttlebay to the secondary bay. In an unusual move the main shuttlebay actually suspended the shuttles in place, rather than letting them rest on the floor. The ship itself sported the best shielding one could hope to attain for the era and sported no less than 10 FH10 Phasers dotted around the hull with two dual torpedo launchers in the neck. All this was fuelled by an SSWR-XXIII-C warp core, the best the Federation had built up to that point. At conventional warp the ship could cruise at Warp 9 and potentially hit Warp 11, with Transwarp promising to double these speeds.
The day of her first test run was amidst the Genesis incident, which had seen the death of Captain Spock and decommissioning of the USS Enterprise. A few hours before Excelsior was scheduled to leave the Enterprise was stolen by Admiral Kirk, alongside Co-conspirators Montgomery Scott, Leonard McCoy, Hikaru Sulu and Pavel Chekov. As Excelsior was almost ready she moved to pursue the Enterprise, readying her Transwarp drive as the Enterprise left. Famously Captain Lawrence Styles took intense pride in his ship and hoped she would perform in style. As the ship finally engaged it all went wrong. Her plasma conduit pumps started sputtering, her engines choked and the computer systems bluescreened. The tractor beams at Earth Spacedock rapidly engaged to stabilise her orbit as Excelsior completely failed, so spectacularly that to outside onlookers it gave the impression that she coughed to a halt in the vacuum of space. This was not what had been advertised.
Following this, and taking into consideration that every other FTW project of the 2250's had been a dismal, catastrophic failure, Starfleet shuttered the Transwarp drive program. Even though sabotage had been the cause, the supreme embarrassment Excelsior caused in the middle of a geopolitical flashpoint almost saw the ship sent to Qualor II before she even entered service. It was only the full endorsement of the ship by captain Hikaru Sulu, who went on to captain the vessel for his entire captaincy, that saw the ship saved from the cutter's torch. Many ultimately consider this to have been the best decision Starfleet made in retrospect.
Whilst Excelsior wasn't a literal revolution in how starships moved, she had prompted not only a redefinition in how warp speeds were measured but how ships were constructed. Her future performance would go on to show Starfleet that Excelsior was an extremely good vessel, and over 200 more would be constructed. Reliable, easily reconfigurable and capable of punching well above their weight class the ships quickly became the most important ship in the fleet, with the Enterprise class demoted to secondary duties and the Constitution refits and few surviving Shepard class ships retired completely.
Probably the most important part of Excelsior's success, beyond sheer performance capability and an armament superior to the Atlas class, was how future-proof the design was. Whilst her predecessors, the Constitution and Shepard classes, required extensive internal and external refits to keep them up to date, resulting in no less than 4 separate subclasses within the Constitution class, the Excelsior class could accept technology without substantial alteration to the ship's frame. This made refitting the ships incredibly easy to do, allowing them to remain relevant far beyond when the quadrant should've moved past them. It also allowed them to remain the best of the best in Starfleet for a fairly respectable period of time. It has often been said that the only thing shared between an Excelsior launched in 2365 and the NX-2000 was the shape and the paint job, something anyone who's seen both can attest to.
This prestige would nominally end in 2331, with the launch of the USS Ambassador and USS Enterprise (NCC-1701-C). These ships, Starfleet's next generation heavy cruisers, were projected to wholly replace the Excelsior class within a decade, but the Ambassador class quickly ran into problems. A common criticism was that, for all their enlarged size, they weren't a massive tactical improvement. Additionally the ships ran into numerous technical problems with their more experimental warp drives, culminating in the Enterprise failing entirely over Rigel IV and requiring a tow by an Excelsior class ship. Additionally their scale ensured they could never replace the sheer number of Excelsior class ships in service (in fact the ability to produce a much larger ship en masse wouldn't come until the launch of the Inquiry class in 2383) and ensured Starfleet maintained faith in simply refitting the Excelsior class ships. A 4th batch of Excelsiors, including the famous trio of Hood, Righteous and Zelenskyy, would ultimately be constructed instead of the second batch of Ambassadors, leaving the Ambassadors to play second fiddle to the ships that they were ultimately meant to replace.
Starfleet did somewhat learn their lesson with their next attempt to replace the Excelsior class. The Niagara class essentially boiled down to an Ambassador class with the flaws ironed out, but with 1 small problem. It's third nacelle. Unique among the fleet the Niagaras were capable ships but burned more antimatter than their running mates, making them excellent first responders but poor long range vessels, leading to the Excelsiors yet again picking up the slack and maintaining their premier role, even as the Enterprise name was still carried by an Ambassador. The Narendra class, another Ambassador derivative, was never seriously considered as an Excelsior class replacement, but one was considered to carry the name USS Enterprise, with a prototype brass model even being cast.
The third attempt to replace the Excelsior class was the Galaxy Class, which can be argued to be a poor idea done well. Carrying everything including over 5,000 Kitchen Sinks the Galaxy Class was frankly too much to build in the necessary numbers, as whilst a Galaxy could replace 5 Excelsior class ships there were only 4 Galaxy Class ships at their peak in the 2360's and at least 400 among the Excelsior class, with the final batch of 40 ships being constructed in response to the initial order for 12 Galaxy class ships being halved. In service. In truth the ship that pushed the Excelsior out of the spotlight would ultimately be the Sovereign class, but it's hard to say they don't do remarkably well in secondary roles.
Notably, even in the face of these many attempts to retire the class, the Excelsior class has maintained a constant presence in Starfleet's battle formations since 2290. Three, the USS Melbourne (NCC-2043), USS Hood (NCC-42296) and USS Righteous (NCC-42451) were present at Wolf 359 and two, the USS Atlantis (NCC-72507) and USS Sodor (NCC-72545) were at the battle of Sector 001. This is on top of presence at key flash points from the Khitomer Accords to the battle of Cardassia, as well as leading the fleets through the battles of Chin'Toka and Anlace VII. One ship, the USS Potemkin, even holds the honour of being the first Starfleet ship to beat the Borg in straight combat, beating a Probe back as civilian transports fled during the Borg incursion of 2369. Whilst they may have been older ships at their core, it's hard to deny their success.
All in all, with numerous victories and discoveries under their belt the Excelsior class is looking to remain the backbone of the fleet. Starting with the USS Righteous a complete refit, the Excelsior II class, underway to keep these ships ready to face anything well into the future. There are even rumours that the Excelsiors will remain active as far into the future as the 32nd century, but we'll just have to wait and see.