The Nebula-class was developed along-side the Galaxy-class in the 2340s and 50s. While Starfleet firmly believed in the feasibility of the Galaxy-class, they wanted a more cost-effective ship that would be able to perform much of the same missions as the larger, more expensive capital ships under construction.
Part of the design that was approved by Starfleet included a multi-mission module that could easily be exchanged within days at a certified facility. The first of which consisted of a sensor dome attached to the rear of the ship. Designed to aid in long-range reconnaissance and search-and-rescue operations, the sensor pod quickly proved its usefulness, so much so that several Nebula-class vessels were allocated to border patrols.
With the flexibility given to it by the replaceable pod-module, the Nebula-class has quickly become one of the most produced and utilized Starships of the 24th century.
Shortly after the Galaxy-class Project was approved in 2343, it was realized that the expense of building such a large capital ship, both in resources and time, would limit the number of ships being constructed. Starfleet, however, was impressed with the design of the Galaxy-class, and wished to adapt it for use in a smaller, less expensive class of starships.
In 2345, the Nebula-class Project was officially approved after designers worked for nearly seven months side-by-side with the Galaxy-class Project team at the ASDB.
The Nebula-class proposal used the same basic design as the Galaxy, with two major differences: the stardrive section was approximately 12 decks shorter than the Galaxy’s, and the warp nacelles were situated facing “downward” as opposed to the “upward” placement on the Galaxy.
Another design incorporated into the Nebula-class Project was the “rollpod” used in previous classes, such as the Miranda. In fact, as the prototype USS Nebula was being built, one of the chief designers referred to it as a “24th century Miranda,” a nickname that would later be transferred to the Akira-class Project.
By leaving seventy-percent of the interior unfinished, the USS Nebula (NCC-60202) was able to leave the Utopia Planitia Fleet Yards – minus the roll-pod – under her own power in late 2353. Around that time the Akira-class Project was approved, and some of the design team members were transferred to that Project.
Starfleet did not feel the need to have two starships with “rollpods”, and wished to try something different with the Nebula-class. The multi-mission modules used on the New Orleans-class vessels had proven useful, and a variant was designed for the Nebula. The original module was elliptically-shaped and connected to the stardrive section by the use of two support pylons. The design proved sound, and when equipped with specialized sensor pallets it greatly increased the range of the Nebula’s sensors.
The original module design, however, would not last more than a decade. Years after the debut of the elliptical pod, reports were received claiming that micro-fractures had developed in the support pylons connecting the pod to the ship while at high-warp for durations longer than 48 hours. All Nebula-class ships were restricted to a speed of warp factor five, or warp seven under extreme emergencies, until the problem could be resolved.
The replacement pod came in the form of a triangular module, connected to the stardrive section by a single pylon. This design, however, partially blocked the main shuttlebay, making docking and launching of shuttles difficult. The second shuttlebay, located on deck 22, was expanded to carry more auxiliary craft and act as the primary launchpad for shuttle craft.