The Nebula class is an offshoot of the Galaxy Class. Intended as a cheaper, less cost-intensive platform than the Galaxy, the Nebula was designed to supplement the Galaxys' limited numbers in the upgrade of the venerable Ambassador Class and New Orleans Class ships. Many parts of the Nebula are ripped directly from the Galaxy class: the saucer, the warp nacelles, and the warp core, along with a few of the computer systems. However, there are many more differences. For instance, the saucer section cannot seperate on the Nebula class. Many systems which are hard-locked into the Galaxys' design are included in the Nebula only as plug-in components. The large modules above the stern contain different systems and are installed modularly dependent on the Nebula's current mission. There are several different modules, each installed for a specific mission profile, for instance, for an exploration mission, a sensor suite would be installed; for an evac mission, extra living quarters would be installed; for a combat mission, a weapons array would be installed, etc. While this feature makes the Nebula class more mission-specific, it also allows for greater adaptability. Future modifications can be made with very little structural reworking or cost. While the Nebulas are seemingly less capable than the Galaxys, their adaptability and success have made them a powerful platform whose projected service will cover nearly a century.