The Excalibur-class Space Control Ship is the single largest starship ever developed by the United Federation of Planets. Taking an inordinate amount of time, resources and innovation just to design, let alone build, the development of the Excalibur was a difficult and lengthy process fraught with challenges, revolving especially around meeting the Excalibur's overwhelming energy needs, and precisely how to generate a stable warp field around such an immense vessel. Despite the cost, however, Starfleet felt that the end results would be worth the effort, as well as the new ideas and innovations that sprung up during the development process. Launched in 2373 immediately before the beginning of the Dominion War, the USS Excalibur NX-9000 incorporated many features normally seen only on starbases. Ideally commanded by an admiral, the Excalibur carried the facilities to direct Starfleet operations across a sector, and beyond, without the inherent limitations of an immobile starbase. While initially a great, untested experiment, the onset of the Dominion War pushed the Excalibur immediately into active service, where she proved an exceptional flagship and mobile fleet command centre. The Excalibur's enormous power needs are met by not one, but two starbase-type reactor cores. A stable warp field is formed by two immense nacelles developed specifically for the Excalibur's unique requirements. When taking part in fleet engagements, the Excalibur plants herself like a tree, striking the enemy with heavy firepower in all directions and protected by almost impenetrable shields. The Excalibur further supports the rest of the fleet with repair drones, extended shields and an advanced battle network system allowing the fleet to work together more cohesively. The Excalibur prototype has proven herself so effective that Starfleet has approved the production of two sister ships, which will take a somewhat improved, more refined form in the Excalibur Mk.2.