One of the construction requirements called for the Nebula class to exihibit a far greater range of functionality than any of its predecessors. After much debate, it was decided that the Nebula class would have a large upper module that could be easily removed at starbase layovers and replaced with a prefabricated module to fit the ships next assignment. Not only does 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. The adaptability and success have made Nebula class ships a powerful platform whose projected service is likely to outlast their larger, more static, counterparts.