(covers information from several alternate timelines)
"It is a historical irony that Doctor Cochrane would use an instrument of mass destruction to inaugurate an era of peace."
The Phoenix was an Earth spaceship constructed during the mid-21st century. It was the first man-made, manned spacecraft to achieve light speed using warp drive. The Phoenix was remembered as the ship that instigated Earth's First Contact with Vulcans.
Dr. Zefram Cochrane, the inventor of warp drive, built this warp ship inside a missile complex in Bozeman, Montana. The ship was initially a United States Air Force nuclear missile with a titanium casing. It took six months for Lily Sloane to scrounge enough titanium to build the four-meter cockpit of the Phoenix. Dr. Cochrane was the pilot, and Lily Sloane was initially intended to be one of the co-pilots. However, William Riker and Geordi La Forge (both of the USS Enterprise-E, from 2373) served as the crew.
On April 4th 2063, less than forty-eight hours away from launch, a group of Borg from the 24th century attempted to destroy the Phoenix. They managed to cause significant damage to various sections of the fuselage and the primary intercooler system. The throttle assembly was damaged, leaking dangerous levels of theta radiation. There were temperature variations in the fuel manifold, the intermix chamber needed to be reconstructed, and there was a damaged warp plasma conduit that needed to be replaced. All damage was repaired in time for the launch, with the help of the crew of the Enterprise, which had pursued the Borg from the future.
On April 5th, around 11 am, the Phoenix was launched. The first stage of the craft used traditional chemical engines. First-stage shutdown and separation was performed in orbit. The nacelles were extended, the warp core and plasma injectors were brought on-line, and the nacelles were charged. It took several seconds to accelerate to critical velocity. Light speed was then achieved by the craft. (Star Trek: First Contact; VOY: "Year of Hell")
The first flight of the Phoenix attracted the attention of a passing Vulcan ship, the T'Plana-Hath, causing the Vulcans to decide to make First Contact. First Contact Day was celebrated annually to commemorate this First Contact between Humans and Vulcans. (VOY: "Homestead")
A model of the Phoenix was kept in Travis Mayweather's old quarters aboard the ECS Horizon. (ENT: "Horizon") Admiral Maxwell Forrest kept a similar model in his office on Earth. (ENT: "The Expanse", "Home")
By the 24th century, the Phoenix was an exhibit in the Smithsonian Institution. Jean-Luc Picard saw the exhibit many times as a boy, but was never allowed to touch it. The blueprints of the Phoenix were available on Federation starships. (Star Trek: First Contact)
In 2259 of the alternate reality, a model of the the Phoenix was included in a historic display of miniature space and aircraft inside Admiral Alexander Marcus' office on Earth. (Star Trek Into Darkness)
The Phoenix is described in virtually all non-canon reference sources as the prototype of warp drive. Dialogue in Star Trek: First Contact and subsequent episodes, however, leave room for the unmanned prototype test of warp drive, prior to the launch of the Phoenix, as described in Star Trek: The Next Generation Technical Manual. If such a test took place, it would have also been in 2063, as this was the year Dr. Cochrane tested his first warp engine. Cochrane described the launch as his "first warp flight" and Kathryn Janeway included Dr. Cochrane in her list of legendary pilots. It is safe to assume this was at least the first manned warp ship of Earth. (ENT: "Regeneration"; VOY: "Friendship One", "Threshold"; Star Trek: First Contact)
For the reference book Star Trek Chronology, Michael and Denise Okuda, together with Rick Sternbach, came up with what they thought the Phoenix might look like. A model of this design was even built for the project, constructed by Greg Jein. This was the Bonaventure (C1-21) model. (Star Trek: The Official Starships Collection, issue 64, p. 12)
At one point during the writing of First Contact, the writers of the film considered what might power the matter-antimatter reaction chamber aboard the Phoenix, in lieu of dilithium crystals. Co-writer Ronald D. Moore later recalled, "We had talked about it being from something modified from the thermonuclear warhead – that somehow setting off the fission reaction was what kicked it off." (Star Trek Monthly issue 45, p. 46)
The assignment of designing the Phoenix was given to concept artist John Eaves. The task immediately presented him with several challenges; he had to devise a configuration that could convincingly be portrayed as mankind's first faster-than-light vessel, that looked like it had been designed in the present, but would also suggest the design of Starfleet craft from the future. (Star Trek: The Official Starships Collection, issue 64, p. 10)
Eaves was aware that the Phoenix would additionally have to be adapted from a Titan missile. Since a decommissioned Titan II missile had actually been found by the production staff, Eaves began the design process by studying the missile. The first sketch he produced for the Phoenix was the nose cone, one of several parts of the real missile that had been dismantled. After the film production company filled in the other parts which had been missing from the missile's exterior (so it could be used as the Phoenix's "launch vehicle"), the Phoenix's nose cone was constructed. "We built a cone to go over the existing one, or at least what remained of it," Eaves recalled. "I actually made the new cone longer than the original one and give it an outward curve as well as adding four riblets that ran from the wider base right up to the nose." Eaves wanted the capsule to seem like its creators had initially used existing technology that happened to be available but had also gradually attached extra bits when required. After he consequently added a "bubble" window to enable the crew to look out and around, his design for the nose cone was approved. Eaves also designed the cone's interior, producing a concept sketch of that area which was dated March 1996. (Star Trek: The Official Starships Collection, issue 64, pp. 10, 11-12 & 13)
Once Eaves' design for the nose cone was approved, a model of the cone was built by Clete F. Cetrone, using sketches which demonstrated the top, side and three-quarter view, along with the actual specifications of the original nose cone. It was meanwhile obvious that the Phoenix was essentially to change shape following its launch. (Star Trek: The Official Starships Collection, issue 64, p. 12)
Originally, the First Contact art department began toying with the idea of having the Phoenix, as depicted in the film, match the design from Star Trek Chronology, built years earlier. "But, after some thought," Eaves continued, "(VFX producer) Peter Lauritson decided it would be a struggle to fit that ship into what was obviously a pretty confined place. For me it was a real wrench as the stuff they'd done was beautiful but in the end we agreed it just wasn't going to pan out." (Star Trek: The Official Starships Collection, issue 64, p. 12)
Returning to the drawing board, John Eaves then specifically focused on determining precisely what size the Phoenix would be, how the vessel, which the script of First Contact described as having nacelles, would fit inside a missile and how, having broken loose of its launch vehicle, it would subsequently convert into a craft capable of warp drive. "I took the [real] plans of the missile and tried to work out what a good length of rocket versus a solid rocket fuel base would be. From there I pulled the Phoenix idea out and tried to figure out the details." Eaves arrived at a design much like the ultimately used one, featuring large thrusters on the bottom of the craft as well as a solid fuselage with an open framework and nacelles that folded out of the sides of the missile during flight. Production Designer Herman Zimmerman was of the opinion that the ship should look as though it had been built from parts which had been salvaged, resulting in areas of the craft looking virtually skeletal. Finally, Eaves worked on both a longer and shorter version of the Phoenix. (Star Trek: The Official Starships Collection, issue 64, pp. 12-13)
John Eaves made a conscious effort to make the Phoenix's nacelles as big as possible. While he was working on the two sizes of the ship, he concentrated specifically on the warp drive. Its design was influenced by him having seen a documentary about the atom bomb which showed that one of the early atom bombs had a ring of triggers which all had to be activated simultaneously in order for the triggering mechanism to work. "I thought wouldn't it be cool if that is the premise behind this unit – that all these triggers needed to fire to make the warp action come into play." The only thing thereafter left to do was to fashion the nacelles so that they appeared similar to those of the Constitution-class USS Enterprise, in an attempt to create a visual link between the time periods. (Star Trek: The Official Starships Collection, issue 64, p. 13)
After the designs were submitted to Herman Zimmerman and Producer Rick Berman, the latter member of the production personnel selected the shorter version of the Phoenix. He also moved the nacelles slightly forward to give the craft a more balanced (if mechanically challenging) design. (Star Trek: The Official Starships Collection, issue 64, p. 13)
A method of returning the Phoenix to Earth intact is illustrated by the artist in Star Trek: The Art of John Eaves. Eaves depicts a flight pattern chart that shows the Phoenix landing by way of a feathered reentry configuration and parachutes.