(covers information from several alternate timelines)
The NX-class was a type of United Earth starship in Starfleet service during the mid-22nd century. The class is notable for having been the first to be constructed with the warp five engine, allowing Humanity to explore beyond neighboring star systems. The lead ship of the class, Enterprise, was launched in 2151, weeks ahead of schedule, while the second, Columbia, was launched in 2154, after lengthy delays in drydock.
The NX-class was conceived of in the early 22nd century as part of the NX Project at the Warp Five Complex: a research and development site on Earth, where Henry Archer, Zefram Cochrane and Captain W.M. Jefferies, among others, worked on the creation of the warp five engine. (ENT: "Broken Bow", "Home"; Enterprise (NX-01) dedication plaque set artwork)
Starships of the NX-class were far more formidable than the freighters that had preceded them. Following the construction of the first starship of the class (the Enterprise NX-01), three more NX-class starships were on the drawing board by August 2151. (ENT: "Broken Bow", "Fortunate Son")
Enterprise was launched from the Orbital Drydock Facility on April 12, 2151, under the command of Captain Jonathan Archer. The launch occurred three weeks ahead of schedule because United Earth needed to return the Klingon Klaang to his homeworld. The early launch was strongly protested by the Vulcans, who believed Humanity was not ready to explore space. Ambassador Soval managed to wrangle a concession from Starfleet, forcing the placement of Subcommander T'Pol on Enterprise in exchange for Vulcan star charts. (ENT: "Broken Bow")
The early launch of Enterprise meant that it left spacedock somewhat unprepared: its spatial torpedoes were uncalibrated and its phase cannons weren't even installed. The spatial torpedoes were calibrated in the heat of battle in May of 2151; the ship only survived because of the intervention of the Axanar. (ENT: "Fight or Flight") The phase cannons were not installed until September 2151, while Enterprise battled an unknown enemy. (ENT: "Silent Enemy")
After the Xindi attack on Earth in March of 2153, Enterprise was recalled home. Arriving on April 24th, the ship was refitted and upgraded with new photonic torpedoes, a universal translator update, and a new command center. She was relaunched on a new mission to the Delphic Expanse to search for the Xindi weapon. (ENT: "The Expanse", "The Xindi")
The search for the Xindi was long and perilous, taking almost a year. In February 2154, Enterprise determined the location of the Xindi weapon and arrived in the Azati Prime system. (ENT: "Stratagem", "Azati Prime") There, the ship suffered severe damage due to multiple attacking Xindi ships. The primary warp coil was destroyed, damage that required drastic actions on the part of Captain Archer to repair. (ENT: "Damage")
Enterprise accomplished its mission to destroy the Xindi weapon and was returned to Earth by a Xindi-Aquatic cruiser following the end of the mission, though it made a slight detour to an alternate timeline's 1944 with the help of Daniels, where the vessel's crew managed to stop Vosk and bring an end to the Temporal Cold War. (ENT: "Zero Hour", "Storm Front", "Storm Front, Part II")
At the time of the Xindi attack on Earth in 2153, the second NX-class starship, Columbia, was still under construction. In November 2154, Columbia was launched under the command of Captain Erika Hernandez. (ENT: "The Expanse", "Affliction")
Compared to the class prototype, Enterprise, Columbia's hull polarization was improved by twelve percent. Furthermore, the ship possessed ventral and dorsal photonic torpedo launchers as well as pulsed phase cannons. Another improvement was that the bridge stations were directly tied into the primary EPS junction. (ENT: "Home")
In November of 2154, Columbia was stuck in dry dock with engine trouble, delaying the ship's launch, and rendering it unable to assist Enterprise during a large-scale orchestrated hunt for the Romulan drone-ship. (ENT: "United")
In late 2154, the vessel's engine troubles were fixed upon the transfer of Enterprise engineer Charles Tucker to Columbia, allowing the vessel to be launched in November of that year. (ENT: "Affliction")
The NX-class consisted of a habitable saucer module that contained seven decks (lettered A through G) and a symmetrical warp field governor located just aft of the saucer section, that regulated the warp field shape that would otherwise break apart at higher warp factors. Two half-decks were inserted between D and E deck, as well as between E and F deck. These contained plasma conduits and access tunnels.
NX-class ships achieved warp flight through two warp nacelles, which housed multiple pairs of warp coils. Maximum speed was warp 5.2, and the NX-class was the first Earth vessel to achieve warp 5.06. (ENT: "Babel One", "Affliction") Standard cruising speed was warp 4.5. (ENT: "Broken Bow") A retrofitted Enterprise from an alternate timeline was theoretically able to reach warp 6.9 for short intervals. (ENT: "E²") There were two fairing impulse engines, mounted on the aft of the pylons leading to the warp nacelles. The navigational deflector was mounted on the front of the saucer module.
Initially, in 2151, the NX-class starships were designed to carry three phase cannons as the primary weapons of the ship. (ENT: "Silent Enemy") While these were powerful weapons by Human standards at the time, they were still considered to be "low-yield" particle cannons by the Klingons of the era. (ENT: "Judgment") The ship was also fitted with plasma cannons and spatial torpedoes that also turned out to be mostly less than effective in combat. (ENT: "Broken Bow", "Fight or Flight") Later on, the NX-class weapon systems were upgraded to include several more phase cannons. In 2153, photonic torpedoes were installed and improved pulsed phase cannons were developed by 2154. (ENT: "The Expanse", "Home")
The defensive systems of the NX-class were also not as advanced as those of other races at the time. Instead of deflector shields and tractor beams, the NX-class was equipped with polarized hull plating and grapplers.
Located mainly on E Deck was the launch bay. The pressurized sector of the bay – limited to E deck – contained the launch bay control room, while the launch bay itself, on F deck, was where the two shuttlepods were docked. A magnetic docking arm extended from the launch bay's ceiling to lower or raise a shuttlepod upon arrival or departure of the craft. (ENT: "Broken Bow", "Fight or Flight")
- For deck configuration, see NX class decks.
The bridge is the nerve-center of every starship. The commanding officer of an NX-class starship sat in the center of the circular-shaped room, surrounded by the duty stations of their science and communications officers to the left, the helmsman in front, and the security chief and chief engineer (or another engineering officer) to the right. All officers faced the main viewscreen, which was mounted against the forward bulkhead of the bridge. To both sides of the viewscreen was access to a corridor that ran behind the consoles walls to port and starboard. These corridors had access to the ship's lower decks. To the aft of the bridge was the situation room, which served as an informal briefing room to the senior staff. There was also a corridor to port behind a door to the situation room which had access to the ship's lower decks. (ENT: "Broken Bow", "In a Mirror, Darkly")
The bridge of the second NX-class starship launched, Columbia, featured additional columns near the helm and behind the captain's chair. (ENT: "Affliction") These were later added to Enterprise and had been installed by 2161. (ENT: "These Are the Voyages...")
There was also a command center upgrade, a specialized room that was once a storage bay. It was created just before Enterprise went to the Delphic Expanse, for use during the Xindi mission. (ENT: "The Xindi")
NX-class corridors were made of a metallic material. They were characterized by circular section separations, for evident mechanical equilibrium reasons. They all had a pair of holders in cases of shaking or turmoil. The circular panels also had a tactical use as defenders could crouch or lean behind them as they fired upon intruders.
Sickbay was located on deck E of the NX-class. In the center of the room was an operating table, while additional beds were located alongside the walls. The sickbay facility also included a medical laboratory. (ENT: "A Night in Sickbay")
The armory was used to launch spatial or photonic torpedoes and could be used to operate the phase cannons. Although weapons were primarily kept in the armory of the NX-class, the ship possessed a total of fourteen weapons lockers. (ENT: "Acquisition")
In the time of the NX-class, the transporter was usually used for cargo transportation only, although it was capable of transporting people. Most people, however, were uneasy of the device, limiting its use to emergency situations only. (ENT: "Broken Bow")
Mess hall and theater
Located on E Deck was the ship's mess hall, which was occasionally used as a movie theater. The mess could seat approximately forty people at a time at ten circular metallic tables. Beverages and simple dishes were available from protein resequencers on the walls, while elaborate dishes were prepared in the ship's galley. A small captain's dining room was located near the galley. (ENT: "Vox Sola", "Doctor's Orders", "Singularity", "These Are the Voyages...")
The 87 crew quarters aboard the NX-class starships were located on decks B through E. Very few quarters had a view of space (usually those of the higher-ranked officers).
A list of all appearances of NX-class starships (excluding the regular appearances of Enterprise NX-01):
The prefix "NX" was formerly used for aircraft registered in the United States as experimental. If the name of this class had followed the protocols of naval tradition, it would have been called "Enterprise-class," as the first ship of a new contract provides the class' name. However, the notion that this class was to be named "NX-class" came from the producers of Star Trek: Enterprise.  Their reasons for insisting on that designation were unknown to the series' art department.  Also see Registry.
While the series of Enterprise was being conceived, the appearance of the NX-class was foremost on the minds of the creative team. Shortly before the series began airing, co-creator and executive producer Rick Berman related, "These are all things we have had to give serious thought to – the look of the ship, the look of the corridors, the transporter room, the ready room, etc." (Star Trek: Communicator issue 134, p. 14)
Along with Brannon Braga (the series' other co-creator), Rick Berman decided they would like the NX-class to look appealing and convincingly retro. "At the same time," he noted, "we had to marry a little bit of contemporary technology with what we know is going to be coming and take some poetic license and come up with a ship that is certainly a step backwards in technology from the ships we've been used to." (Star Trek: Communicator issue 134, p. 76) Braga commented on the prospect of making the NX-class seem "like something out of 1950s science fiction," stating, "I just don't think 99 percent of the audience would have bought it. So you need to take some license and say, 'We're going to make it look like a ship that would be a hundred years more advanced than something today [...]' rather than say, 'We're going to make it look like something that's a hundred years before a show that was done in the 1960s.' That's definitely a creative license that we took. But I think those kind of things are necessary." (Star Trek: Communicator issue 139, p. 51)
While admittedly making it seem slightly more advanced than the original Star Trek USS Enterprise from the 1960s, the producers still wanted to have the NX-class be similar to that ship as well as other earlier-depicted vessels. Production illustrator Doug Drexler offered, "Rick and Brannon wished to borrow from the original Enterprise, the motion picture Enterprise and some elements from other ships in the movie series." (Star Trek: Communicator issue 136, p. 34) Berman himself clarified, "We spent a lot of time studying the Enterprise from the [original] television series and then the Enterprise from Star Trek: The Motion Picture, and then the subsequent ships and a variety of other vessels. We wanted something that was reminiscent; we wanted something that people could believe would, 90 years later, evolve into Kirk's Enterprise, but obviously we wanted to make the ship with the same degree of sophistication that computer modeling can do today, as opposed to the way wooden modeling was done in the 1960's." (Star Trek: The Magazine Volume 2, Issue 7, p. 13)
Rick Berman's marching orders for production designer Herman Zimmerman to begin considering how the NX-class Enterprise would look included advice that the "new" ship should be "both retro and cool at the same time, gritty and utilitarian with space-efficient interior and hands-on equipment. A ship which shows the audience a lot more nuts and bolts than other Star Trek series while still having an incredibly futuristic look. In a subtle, very recognizable way, the ship must foreshadow the design of Enterprises to come." (Broken Bow, paperback ed., p. 259)
In the script for "Broken Bow", the NX-class is introduced with the description, "More rocketship than starship, Enterprise is lean and masculine – yet its deflector dish and twin warp nacelles suggest the shape of Starfleet vessels to come." (Broken Bow, paperback ed., p. 262) However, this statement was later revised to remove the references to both the deflector dish and the class appearing more akin to a rocket ship than a starship. 
Herman Zimmerman once commented that the terms "retro and cool" were "two buzzwords very easy to slip off the tongue, but not so easy to conceive on paper and then in the reality of the scenery onstage." (Star Trek: Communicator issue 135, p. 59) To assist with the concept work, he brought illustrator John Eaves onto the project. "Herman called me really early on," remembered Eaves, "and said we needed a retro Enterprise, somewhere between the Phoenix and Captain Kirk's ship, and he needed sketches for it." (Star Trek: Communicator issue 136, p. 32) Despite the numerous influential starting-points already discussed, Zimmerman gave Eaves free reign to experiment with virtually every design concept he could think of. "Orders were to try everything under the sun and don’t go for the obvious," Eaves admitted. 
An initial conceptual image John Eaves sketched took its direction straight from Herman Zimmerman. Explained Eaves, "He had found a shape he liked in one of Syd Meads’ many books and thus had me translate the shape into a starship [...] I was so glad that after he saw it on paper he changed his mind and we started to pursue a more traditional starship look." 
Another early concept for the exterior of the class took its cue from Brannon Braga having recently noticed, at a Los Angeles car show, how the then-new 2002 model of Ford Thunderbird modernized a classic design that he was very familiar with. Braga remembered, "We discussed it and we thought, Well, let's take Kirk's ship, the original Enterprise, and let's soup it up and make it more futuristic and bring it into the twenty-first century. And we worked on that for a while, but it ultimately looked just too much like the other ships." (Broken Bow, paperback ed., pp. 262-263) According to Herman Zimmerman, this version of the class especially "looked very similar to the original motion picture Enterprise." (Star Trek: Communicator issue 135, p. 60) Due to this approach making the class appear insufficiently new, the team entirely abandoned it and opted to start from scratch. "That was a really cool ship and the series would have been well served by it," Zimmerman evaluated. "But, I don't think it represented what Rick and Brannon see as the vision of this new Enterprise. So we went to work again." (Broken Bow, paperback ed., p. 263)
Ultimately, John Eaves invested much time and effort in trying to design the exterior of the NX-class. "Many many versions came and went and all were getting the boot with little to no direction on what they wanted to see from the producers end," Eaves observed. "By now, time was getting critical."  He said further, "I did lots of sketches, and they'd go too far Phoenix or too far [Kirk's] Enterprise, and it wasn't really what Mr. Berman wanted to see. He shot down almost all of the drawings and in his mind there was something he really wanted to see that was going to be different but he couldn't really put it into words, so Herman would take what he would say and translate it to me and I'd work on it." (Star Trek: Communicator issue 136, p. 32) Zimmerman himself remarked, "We went to several different styles of combinations of nacelles and saucers and engineering sections and airframes." (Star Trek: Communicator issue 135, p. 60) He also stated, "We had about a month of sketches and computer-generated images roughly showing shapes of different ships that eventually evolved." (Broken Bow, paperback ed., p. 263)
The final concept sketch that John Eaves created for the NX-class while working under Zimmerman's aegis looked far more like a typical Star Trek starship than Eaves' initial sketch had. "It was a fun piece just to [do] for concept sake," explained Eaves. 
Change of designer
Eager to collaborate on the new series, Doug Drexler was able to start participating in the design process for the NX-class about a month after it began.  "When I was brought onto the Enterprise design project it had literally reverted to square one," Drexler expressed. "Most of John and Herman's time up until that point was spent exploring very different ideas that harkened more toward rocket ships and submarines. Rick and Brannon had dutifully explored the possibilities of an entirely different direction but, and I think most wisely, decided that they were loosing something by abandoning the traditional starship configuration [....] At this point it was time for Herman to move John on to conceptualizing the new starship sets. I think Mike Okuda suggested to Herman that he might give me a call, thinking that a CGI approach to conceptualizing the ship might help break the stalemate." Thus, the fact that Drexler had been learning how to build CGI models while working on Star Trek: Voyager at visual effects house Foundation Imaging was instrumental in his invitation to participate in the design process for the NX-class. (Star Trek: Communicator issue 136, p. 32)
With the overall look of the NX-class having been somewhat decided upon via a process of elimination, Doug Drexler was tasked with working out the finer points of the class. "Rick [Berman] and Brannon [Braga] had a pretty good idea of what they were looking for," he remembered. "The devil was in the details. Our job was to take familiar geometry and restyle it." (Star Trek: The Magazine Volume 2, Issue 7, p. 30)
After receiving advice on how to proceed with the design, Doug Drexler went directly to 3d modeling of the class, preferring to model the ship digitally instead of continuing with concept drawings. He believed that working in CGI was a massive benefit to the development process, easily enabling dramatic alterations to the craft's dimensions and for the art department to show the vessel to the producers from every angle and lighting condition.  However, Drexler started designing the prototype CG model of the NX-class while under the erroneous impression that it would just be a quick mock-up, only to discover the truth as he continued to refine the model. (Star Trek: The Magazine Volume 2, Issue 10, pp. 25-26)
Doug Drexler committed to work on developing the NX-class, on the side. "I was working at Foundation during the day and thrashing out various designs at night," Drexler related. "I was doing some late nights. Herman would drop by the house two evenings a week and we would go over our leaders' reactions and make various adjustments: shorten the nacelle, raise the bottom of the saucer, more metallic, etc." (Star Trek: Communicator issue 136, p. 34) Michael Okuda pointed out, "It should also be noted that Doug worked a LOT of unpaid hours during the design of the NX-01, because he took this job very, very seriously. He started meeting with production designer Herman Zimmerman several weeks before he was officially hired. Doug, who was already working a full-time job during this period, stayed up late every night to work at home on the ship. This went on for weeks, with Doug busting his hump to capture Herman’s vision and our producers’ wishes, melding them with his own sense of starship heritage. By the time Doug was actually on payroll, he and Herman had already gone through several design cycles, buying precious time to refine the ship during the inevitable last-minute frenzy of deadline." Drexler, in turn, considers Okuda to have had considerable influence on the development of the class. "Mike Okuda and I really did spend a lot of time thrashing things out," Drexler mused. "I think Mike probably had more input into this starship than any other, due to our close friendship." 
John Eaves was thrilled to witness Doug Drexler enthusiastically evolve the appearance of the NX-class. (Star Trek: Communicator issue 136, p. 34) Eaves commented, "His work was very impressive and filling the voids of time and history with great ease [....] Sadly none of his beauties were getting anywhere either." Eaves also called Drexler's initial designs for the NX-class "perfect" and enthused, "His designs were exactly retro enough to not only compliment the [Original Series] version but made a great Starship for its century." 
Final exterior design
The producers finally determined that they wanted the NX-class to be of essentially a single hull, incapable of saucer separation. Herman Zimmerman commented, "It took us a good three months of trial and error before we arrived at the shape we now have [....] We decided to eliminate the engineering section as a separate entity and make it part of the hull. Brannon and Rick decided they didn't want a ship that would separate; that would be something that would happen some time in the future." (Star Trek: Communicator issue 135, p. 60)
The eventual twin-boomed shape of the NX-class was partly influenced by the Lockheed P-38 Lightning, an aviation source of inspiration that Doug Drexler pointed the design toward. John Eaves offered, "It was a great idea, I thought, to go with that P-38 look. Doug's first passes on that were just dead on, and exactly the shape it needed to be. He kept working on that for months and he did an awesome job." (Star Trek: Communicator issue 136, p. 34)
Given the concern that the NX-class not look so different from the typical starship layout as to seem out of place, the final design concept for the class was also heavily influenced by the look of a certain previously established starship class. Herman Zimmerman commented, "We found a ship [of the Akira-class] that was in our archives – a minor vessel that had been used in a battle in one of the features that had been created by ILM. We did not use that ship, but we took ideas from it and from those ideas eventually – and this process took about four months, all week and weekend CGI work by [...] Doug Drexler – we finally came up with [the eventual] shape." (Behind the Scenes of Enterprise) In fact, the producers at first wanted to reuse the Akira-class without any changes. Doug Drexler was horrified to be informed of this decision, which he and other members of the art department chose to oppose. 
To differentiate the NX-class from the Akira-class, the art department demanded that it meanwhile resemble the original Constitution-class. Drexler specified, "Our mission was to get it more towards the TOS ship [....] I always saw the task as not designing a new ship, but rather a 'restyling' job. I drew my inspiration from the great industrial designer Raymond Lowey [sic] who took the turn of the century steam locomotive and restyled it into the streamliner."  Drexler also characterized his agenda of injecting as many small facets from the original series design into the NX-class as he could to have been his "main mission."  He also recalled, "It was thanks to Herman that we got a blessing on going ahead with the restyle. He fought for it." 
Once the plan of paying homage to the TOS Enterprise via the NX-class was approved, Doug Drexler was pleased to move the design in that direction.  "I made sure that the basic dynamic between the saucer and the nacelles was the same," he declared. Other aspects that echoed the original Star Trek ship included the placement of the join between the warp nacelles and the nacelle pylons, the shape of the saucer impulse cones at either side of the saucer section's aft, and the lower sensor dome on the bottom of the saucer section's midpoint. Drexler also horizontally squeezed the TOS Enterprise's deflector dish, moving it to the front of the saucer, and reused the idea of the ship having an airport-style control tower dome towards the aft, building such a dome into both the underside and upper side of the saucer section, rather than the singular dome that is atop the Constitution-class' secondary hull. He additionally kept spheres at the back of the nacelles, also slightly changing them by dividing both spheres in two. "If the fronts of the nacelles look like penises, I compounded that by making the ends of the NX nacelles look like a girls butt in a thong," he noted. "I thought that was fair." 
Doug Drexler wanted to make a couple of elements more clearly influenced by the TOS Enterprise than they ultimately were allowed to be; he was interested in making the nacelle pylons decidedly thin, which ultimately motivated him to highlight a thin portion of both pylons' leading edge, and the bussard collectors more orange but volatile-looking than they wound up. 
At first, the blue glow on the warp nacelles was resisted by the art department. However, they came to think of it as "fulfilling an original dream," as Gene Roddenberry had intended for a similar glow to be featured on the TOS Enterprise, a wish that had been too expensive to realize for that vessel. 
The minute detailing done to the NX-class included the paneling on its hull. "Like Andy [Probert]'s 'D', every panel was designed and fitted painstakingly to the function and form of the ship," Doug Drexler explained. "All sections have their own distinct personality and are not simply cloned and repeated." 
Doug Drexler's development of the first CG model of the NX-class was during an abundance of disputes between the art department and the producers, concerning how the ship should look. "Nearly every single detail was haggled over," Drexler recounted. "Color, texture, plating... you name it [...] The dome on the bridge was lit up originally. The producers thought the audience would mistake that for windows. I wanted a more porcelain, smooth finish. The producers wanted plating more like the TMP ship. I wanted lighter pylons, the producers wanted heavy pylons."  Eventually happy with the extent to which he affected the design, Drexler didn't take long to digitally map the surface details for the NX-class.  (The approval model can be viewed here.)
Shortly thereafter, the model was sent to Foundation Imaging, where it underwent final refinements by modeler Pierre Drolet, under the supervision of visual effects producer Dan Curry and Foundation's Robert Bonchune. (Star Trek: Communicator issue 136, p. 34) "The art department’s 'foam core' proof of concept model acted as understudy for the super-high detail version [...] in Valencia, California," remembered Doug Drexler. "This CG concept model had been through battles to rival any that the fictional ship had been through during its four year television voyage. It had been volleyed back and forth between art department and producers. It had been pulled, stretched, cut, and pounded before it had been given a go for throttle-up, and shipped off to the CG facility where it would be built with extreme attention to detail [....] Once the bloody battles between art department and production were over, the high rez version of the ship could be built in relative peace [....] The high resolution model was built with laser precision." 
Rob Bonchune noted, "Pierre Drolet was dedicated wholeheartedly to building [the NX-class]." (Star Trek: The Magazine Volume 2, Issue 10, pp. 25-26) Drolet took plenty of time over translating the art department's low-resolution approval model into the version meant for production. The earlier model continued to see service throughout the run of Star Trek: Enterprise, as the main NX-class model's digital stand-in for previsualization work.  The fact that the NX-class was built as a CG model rather than a practical studio model meant that it turned out to be more detailed than a physical model would have been. (Star Trek Monthly issue 86, p. 22) In fact, on his IMDb profile, Drolet himself referred to this digital model as "what (at least at the time) was the most detailed computer generated model in television history" and he went on to say, "Taking up 200 megabytes of RAM merely to load, the digital model consists of 500,000 polygons with 156 separate images painted on it." 
Enterprise's hull was originally meant to have only a slight bronze tint, as was favored by both Herman Zimmerman and Doug Drexler, but its appearance was changed to become more clearly bronze-colored, for reasons unknown to Drexler. It was not until the advent of Columbia that an NX-class vessel with a hull featuring merely a slight shade of bronze was depicted. 
Although the NX-class had to make the impression it was a 22nd-century predecessor to ships of the later centuries portrayed on Star Trek, everything had to be redesigned, including the vessel's interior. For instance, there was no question of simply borrowing a wall from a Star Trek: Voyager set or reusing the consoles with merely a subtle redesign. (Star Trek: The Magazine Volume 2, Issue 7, p. 48)
The cramped living conditions aboard the NX-class were influenced by an experience in which a group of the production staffers personally researched what it was like to spend a day on a nuclear submarine in 2001, about six months before the series started to be broadcast. (Star Trek: Communicator issue 134, pp. 14 & 76) "Rick and Brannon and I did a tour of a nuclear sub that was in a base in San Diego," explained Herman Zimmerman. "That was quite an interesting trip and we learned a lot about what real space you have to work with." (Star Trek: Communicator issue 135, p. 60) Deciding that they didn't want the NX-class interiors to be quite as claustrophobic as those aboard the submarine (out of concerns that such uncomfortably confined areas might be off-putting for the show's weekly audience), the group used conceptual elements from the seafaring craft in their designs for the starship, so that (for instance) the doors aboard the NX-class were made to seem like the heavy-duty hatches of nuclear submarines. (Star Trek: Communicator issue 134, p. 76; Star Trek: Communicator issue 135, p. 60)
Some of the sets and control panels were additionally influenced by NASA designs. (Star Trek: Communicator issue 134, p. 14) In fact, Herman Zimmerman researched, especially for this project, then-current designs that were in development for both NASA and the US military. (Broken Bow, paperback ed., p. 261) Rick Berman explained, "We looked at a lot of film on the various space stations – on Mir and on the [...] International Space Station – and on the interior of the various space shuttles." Berman specified, too, that – as well as wanting the interiors to be "fun" and "cool" with "a sense of excitement" – he and his collaborators tried to "find something in between" the insides of a modern-era spacecraft or submarine and the interiors of the 23rd century. (Star Trek: The Magazine Volume 2, Issue 7, p. 12)
The process of designing the inner environments of the NX-class was a struggle in which Herman Zimmerman played a key role. John Eaves offered, "The internal sets of this ship went through some pretty radical changes as it evolved [....] As much of a fight Doug had with the devilish details of the exterior, my boss had just as many with the interior." 
Herman Zimmerman was interested in having the interior sets for the NX-class lightly tinted bronze. "I believe he wanted that for the interiors as well," reckoned Doug Drexler, "although that did not happen." 
The materials used in the NX-class sets constituted a more hard-edged approach to Starfleet design than what had been established in the franchise, so far. For the shipboard surfaces, the production team, under the direction of Rick Berman and Brannon Braga, used more real metal – including aluminum, steel, copper and brass – than simulated metal. This, thought Herman Zimmerman, made the painted metal surfaces seem "much more believable," as they were often situated directly next to real metal surfaces, convincing a viewer's eye that both types of surface were actually metal. The interiors didn't involve much plastic nor anything, at all, that looked like wood. The producers were also adamant for the sets not to have designer colors and that the flooring would be without carpets. (Star Trek: Communicator issue 135, p. 60)
The production team differentiated the doors aboard the NX-class by having them be non-automatic and entail more security for access. Another method that was used to relate the NX-class' highly utilitarian nature was giving the corridors an extremely basic shape. Much of the lighting for the sets was likewise made more practical; virtually every set was ninety percent lit by the set decorator and Herman Zimmerman, with the latter and his team having selected positions for the spotlights where they could be clearly viewed on-screen. (Star Trek: Communicator issue 135, pp. 60, 65 & 61)
Set decorator James Mees found that his recruitment into the project to decorate the NX-class sets was somewhat complicated. He recalled, "When we started we had virtually no prep time [....] But we had so much stuff to forget about. What we [...] had to do is to take a futuristic attitude but step back in time from the other shows." (Star Trek: The Magazine Volume 3, Issue 3, p. 86)
Much of the furniture in the NX-class interiors was bought from Europe and consisted of items that James Mees thought had been "beautifully designed." Furnishings such as sofas aboard the NX-class were from Italy. Mees noted, "We wanted to be functional, and the Europeans are quite efficient at designing furniture for very small spaces." Moments later, he recalled, "When we started I scouted out everything and showed Herman a whole lot of different pictures. When I knew the direction he wanted to go in I went back to the dealers, and when I knew how much things cost I had him come shopping with me. Then we had a show-and-tell with the producers, with a sample of every single thing; it was like a great big furniture warehouse, with all the stuff that I liked and thought we could use in different places. There was not one single item that Rick Berman and Brannon Braga didn't like, so I was very, very happy!" (Star Trek: The Magazine Volume 3, Issue 3, p. 86)
The NX-class sets were meant to complement the class' exterior. The exact whereabouts of the various shipboard areas, for example, were planned. "It's not so difficult to place the interior sets once you've got the exterior design, but it took us quite a while," stated Herman Zimmerman. (Star Trek: Communicator issue 135, p. 61) However, in their text commentary for "Broken Bow" on the ENT Season 1 DVD, Michael and Denise Okuda unofficially theorized that, based on the fact that the movement of stars viewed from Enterprise's captain's mess changed as the series progressed (seemingly indicating that that room's placement on the ship was altered during the course of the series), the NX-class had movable rooms.
The round windows on the outside of the NX-class saucer section were, upon being designed by Doug Drexler, intended to be portholes. He also hoped the production team would be permitted to include them in a set. Even though this did not happen, Drexler was highly satisfied with the interior sets that were created for the series, describing them as a "spectacular job." 
Enterprise's scenic art department at first considered whether video playback would be required at all for the displays aboard the NX-class. Scenic Artist James Van Over noted, "We thought they [the producers] might say, 'Well, they didn't use it on [Kirk's] ship, let's just skip it.'" (Star Trek: Communicator issue 144, p. 28)
Selecting the keypads and screens for the NX-class sets proved to be challenging. "We spent quite a lot of time looking at what was available and what we could buy off the shelf, because we can't invent everything [....] We spent a lot of time looking at aircraft control panels, for instance, both ancient and not-so-ancient," recalled Herman Zimmerman, "but those things are really expensive. We would have liked to use aircraft-style LCD screens, for instance, but an LCD screen just turning it from horizontal to vertical would make a big difference, and they use them that way in modern aircraft. But those things cost about $25,000 a piece. And that's in quantity! Mike Okuda did some research and was quoted at $50,000 a piece on some screens that were 9 inches by 12 inches high. They said if we bought more than 10 they could give it to us at $40,000 a piece! [....] We couldn't afford that. We did buy about 80 LCD and plasma screens and none of them cost more than $4,000, much less $40,000." (Star Trek: Communicator issue 135, pp. 61-62)
Ultimately, there was a total of 81 active plasma and LCD screens in the NX-class sets built for the start of the series. Even though the screens were still initially very expensive, their inclusion was planned so that, over the run of the series, a lot less optical burn-ins would be required than had needed to be done for older video screens commonly used in the franchise's past. (Star Trek Monthly issue 84, pp. 28 & 29)
At the start of the series, the graphics on all the plasma screens were designed by veteran Star Trek scenic artists Michael and Denise Okuda. (Star Trek Monthly issue 84, p. 28) "Mike Okuda had the idea that the interface would be built out of boxes," said Jim Van Over, "and there would be buttons for the actors to push to give them something to do." (Star Trek: Communicator issue 144, p. 28)
All the standing sets for the NX-class had features which the production crew termed "busy boxes," and which Herman Zimmerman described as "things that can be opened up and worked on [....] Leaving so much more for the actors to do." (Broken Bow, paperback ed., p. 267)
All the standing sets for the NX-class had removable, so-called "wild" walls, to allow for cameras and equipment. (Broken Bow, paperback ed., p. 267) Director James L. Conway was very impressed with the degree of access provided for filming the smaller-than-usual sets (believing that their cramped quality made the areas feel "authentic"). Shortly after completing work on the pilot episode "Broken Bow", Conway attested, "You do have enough room because there's a crane that they use which can poke into the sets, and so in places where you normally couldn't get a Steadicam or a dolly this camera crane can reach out over the consoles and over the floor and move around, so you can actually get fantastic angles." (Star Trek: The Magazine Volume 2, Issue 7, p. 47)
Bridge and other rooms
The NX-class bridge often provided a genesis for the design of the class' other interiors. "Herman Zimmerman would always start with the bridge to set the tone for the overall architecture," remembered John Eaves, "and then branch out carrying the details through the corridors and secondary rooms, based on this master blueprint." 
Due to Rick Berman and Brannon Braga liking the bridge of the USS Defiant (NX-74205), the long and narrow shape of the NX-class bridge was influenced by that earlier-created room, as opposed to appearing (in the words of Herman Zimmerman) "elliptical as the Enterprise-D bridge was, or wide as the Voyager bridge was." ("The USS Defiant", DS9 Season 3 DVD special features; Star Trek: Communicator issue 135, p. 62) Other design facets of the NX-class bridge that took their cue from the equivalent area aboard the Defiant-class included the presence of a single helm, instead of two stations for helm and navigation functions, and detailing on the ceiling. Concerning the latter, Herman Zimmerman said, "Much of the treatment of the ceiling has overtones of the Defiant." (Star Trek: Communicator issue 135, p. 62)
Certain parts of the NX-class bridge in common with the TOS Enterprise – for instance, the room's layout featuring a sunken central captain's chair and a scope at the science station – were added at Brannon Braga's request. (Star Trek: Communicator issue 135, p. 19) Another detail of the NX-class bridge that was in homage to that of the traditional Constitution-class was an astrogator at the helm. 
Michael Okuda incorporated 1960s-style touch-tone phone buttons on the bridge consoles which seemed as if they might predate the translucent candy-colored buttons installed aboard Kirk's original Enterprise. Many of the other physical controls on the NX-class bridge were fleshed out by Anthony Fredrickson and set designer Wendy Drapanas. (Star Trek: Communicator issue 144, p. 28)
Contrastingly, one aspect of the bridge that intentionally set it apart from the equivalent areas of other ships was its inclusion of the situation room. The bridge was made to encompass this area not only so that the characters would have somewhere to have meetings close to the center of command but also because it facilitated more staging options. (Star Trek: Communicator issue 135, p. 60) Another way in which the bridge was made different, visually, from those of several past classes of ship was by not hiding the monitors under black plexiglas. (Star Trek: Communicator issue 134, p. 14; Star Trek: Communicator issue 135, p. 59) Yet another difference was that the controls were decided, by the producers, to be made essentially more hands-on, with buttons, knobs, gauges, dials, and levers, rather than touch-sensitive panels. (Star Trek: Communicator issue 135, p. 59)
The scripted description of the bridge was as follows: "Far more basic than future starships, this command center lacks the 'airport terminal' feel of Enterprises A through E. A central captain's chair is surrounded by various stations, the floors and walls are mostly steel, with source light coming from myriad glowing panels. No carpets on the floors, no wood paneling on the walls, high-tech gauges, dials." 
The interior elements of the NX-class that were sketched in concept artwork by John Eaves included the bridge viewscreen, the helm and the engineering stations on the bridge, the situation room's plotting table, the launch bay, engineering, and sickbay. (Star Trek: Communicator issue 135, pp. 60-62, 64 & 65; ) In fact, Eaves was instrumental to the design of the bridge consoles. He remarked, "In the early stages the consoles were being designed in an angled, tubular fashion; these ideas went a ways before the look changed to a more angular look." 
Of all the NX-class sets created for the pilot episode "Broken Bow", James Mees once characterized the bridge and engineering as "the easiest and hardest, all at the same time" and explained this opinion by commenting of the two selections, "They're monumental, and although you do have a little bit of room for growth, you pretty much have to get it right." The basic design of the bridge was mostly decided upon when Mees joined the project to decorate the sets. "Herman had already developed the general idea of the bridge, so a lot of it was there and in working order," Mees explained. Virtually all the chairs on the bridge were from the aforementioned European showroom, except for the command chair. After receiving the sketches of the room's work stations from the art department, Mees put together the intricately detailed consoles. (Star Trek: The Magazine Volume 3, Issue 3, pp. 86 & 85)
Many of the NX-class sets were built on Paramount Stages 8 and 9. However, the bridge and armory sets were constructed on Paramount Stage 18. (Star Trek Monthly issue 84, p. 25) The bridge and situation room were the most costly sets of the NX-class interiors to build. (Star Trek Monthly issue 84, p. 29)
The NX-class bridge displays were run at a nearby video control room which, like the bridge set, contained many screens, with rack upon rack of monitors that kept quality control over the images on the set, such as previewing displays that were to be switched. Rather than utilizing videotape playback, the displays on the bridge were fed to the set's monitors from Apple G4 Cube computers (of which there were about fifteen to twenty) using CD playback. (Star Trek: Communicator issue 135, p. 62; Star Trek: Communicator issue 144, p. 29) Rick Berman referred to the array of plasma screens on the NX-class bridge as "beautiful." (Star Trek: Communicator issue 134, p. 14)
In total, the process of designing the NX-class took almost a year. (Star Trek: The Magazine Volume 2, Issue 7, p. 13)
Shortly prior to the launch of the series, Rick Berman cited the standard crew complement of the NX-class as being "around 65 crew members." (Star Trek: Communicator issue 134, p. 76) In Star Trek: Communicator issue 135 (p. 23) and Star Trek Monthly issue 84 (p. 6), the crew complement was said to be 78 and 87 respectively. Star Trek: The Magazine Volume 2, Issue 7 (p. 30) gave a rougher estimate of "between 70 and 80." "Strange New World" established the total of eighty-three crew members, a number repeated in later episodes, such as "Silent Enemy", "Oasis", "Singularity", "The Catwalk", "The Expanse" and "These Are the Voyages...".
Repeatedly asked to devise the best shots of the NX-class, Foundation Imaging viewed the ship from almost every possible camera angle, early in the series run. They found that the class was highly photogenic. "We were really trying hard to find a bad camera angle," mused Foundation's Aram Granger. (Star Trek Monthly issue 86, p. 22)
Rick Berman was ultimately delighted with the look of the NX-class. Not long before the series began airing, he contemplated the design, saying, "We have designed a ship which is very cool while, at the same time, is not as streamlined as the Enterprise has become [....] The whole layout and feel of the ship is different – I don't know if 'retro' is the right word but it certainly is not the ship Captain Kirk was on. However, in every way, it signals and telegraphs what in 90 years will be Kirk's Enterprise [....] [but] the interior design of the ship is, I think, dramatically different than previous Enterprise bridges specifically [....] There is definitely some of that submarine feel to [the NX-class bridge] compared to the bridges of the D or E or Voyager." (Star Trek: Communicator issue 134, pp. 14 & 76)
Jonathan Archer actor Scott Bakula was also pleased with the realistic feel of the NX-class interiors, believing that it helped ground the actors in their work. "I love that it's small," he enthused. "I love that it's based on a submarine [....] I think it has a great feel to it. Sometimes I do feel like I'm in a submarine, banging around. But it feels right." (Star Trek Monthly issue 84, p. 32)
There were several fan complaints that the NX-class looks more advanced than both the original variant of Constitution-class and even the Intrepid-class, due to the creative license the producers originally took with the design of the NX-class, as they preferred not to reduce the appearance of the ship's technology to being limited more than modernity. (Star Trek: Communicator issue 139, p. 51)
Doug Drexler ultimately wished that the overall exterior of the NX-class had been brighter than it ultimately was, stating, "The NX appeared dark and dingy on actual show. Against space it was often hard to see. Not to my taste." 
In the video game Star Trek: Elite Force II, a computer on the Enterprise-E had information on the NX project on display.
The Pocket ENT novels Kobayashi Maru and Beneath the Raptor's Wing have depicted the manufacture of four additional NX-class ships, all named for American space shuttles: Challenger (NX-03), Discovery (NX-04), Atlantis (NX-05), and Endeavour (NX-06). Beneath the Raptor's Wing further depicts development of the NX-class being suspended due to Earth's war with the Romulans, owing to the high costs and time involved in building an NX-class ship. Starfleet's shipbuilding efforts were refocused on the older Daedalus-class ships, which were comparatively faster and cheaper to construct.
The Pocket TNG novel Indistinguishable from Magic establishes that production on NX-class ships resumed after the Earth-Romulan War, and that, according to Jean-Luc Picard, the total number of NX-class vessels rose to "fifteen or sixteen" before the class was finally retired. One such vessel, Intrepid (NX-07), featured prominently in the novel.
In the game Star Trek Online, new player captains are able to purchase a replica of the NX-class to fly as their starter ship from the in-game C-Store. The NX-class ship is similar to the Miranda-class starter ship, but is classified as a Light Escort rather than a Light Cruiser.