design from Star Trek: The Motion Picture, Alan Dean Foster & Robert Wise

        In 2269, the Constitution Class cruiser USS Enterprise returned from its last 5-year mission, the only one of the original 13 remaining in service, all others having been lost or destroyed. She was publicly hailed as the 'Champion Of The Federation', and, shortly afterward the vessel began a scheduled overhaul that would lead to one of the most interesting conversion/modifications in recent history. What began as a scheduled overhaul of a Constitution Class cruiser turned into the Enterprise Class cruiser.
        While in drydock for upgrade to the Mk IV version of the Constitution Class, the Chief of Engineering, Commander Montgomery Scott, proposed that the vessel be fitted with FWG-1 warp engines, which would give the ship 33% more operating power and would increase its range. The proposal was endorsed, and the vessel was fitted with the newer engines. Once the engines were tested, it was found that the mounts would not withstand the forces exerted by the higher speeds, and so new pylon assemblies were required. A new lower or secondary hull assembly was designed that not only supported the new engines but also incorporated several major changes in appearance.
        The secondary hull was enlarged, giving room for larger shuttle bays, larger and more efficiently arranged engineering compartments and work stations, enlarged and improved research facilities, and an enclosed sensor array instead of the older-style extended dish. Furthermore, the photon torpedo bay was placed in the upper forward area. These changes also meant that the primary hull had to be replaced with a larger dish able to house the new fire-control, life-support, and computer systems. The vessel's final appearance was so drastically changed that Star Fleet Command decided to make it a new class entirely.
        The Enterprise Class ships are the most powerful in known space. Since their introduction in 2271, they have been the UFP's most effective deterrent to aggression. Their combat abilities are equaled by their capability to perform extensive research duties, and this makes them the most versatile of all vessels in service. Despite the dual capabilities, however, the class is being used more and more in its combat role due to the increased border activities of both the Klingon and Romulan Empires.
        Like many ships, the Enterprise Class has been modified. The first modification was made to house the FIF-1 impulse drive system, giving the Mk II 7% more operating power. The Mk Ill, likely to replace both the Mk I and II, mounts the FIF-2 impulse drive system, giving 15% more power than the Mk I and 6% more power than the Mk II. Also incorporated into this design is an additional bank of FH-11 phasers and an additional FP-4 torpedo bay, both systems firing aft, giving the class much needed protection there. These modifications have been ordered on several existing Mk Is and Mk Iis, and they may be required on all vessels of this class in the near future. Only two Mk Is are under construction; both are believed to be undergoing the modifications to Mk III.
        The Enterprise Class cruisers are produced at the Sol III and Salazaar shipyards at a rate of 4 per year. The number under prodJction varies and should only be used for reference.