
Here's a ship I'm working on for my Starfleet Museum website.
This is a heavy cruiser introduced in the late 2170s. After the successful conclusion of the Earth-Romulan war, the newly formed Starfleet had few large cruisers, being mostly an exploratory force of long-range, lightly armed ships (like Daedalus). Ex-United Earth Stellar Navy admirals thought that Starfleet needed a large, fast, heavily armed heavy cruiser to defend against a possibly resurgent Romulan Empire, deter other potential rivals, and show the flag in a muscular way. They pushed for the development of the Dragon class, which turned out to be a technically overambitious white elephant. It was fast and well armed, but was something of a hanger queen because of all the extremely advanced (for the time) technologies that didn't quite work together well. Dragon's overreliance on weaponry also meant that it didn't have much to do when another war with the Romulans failed to break out.
(Note: As with all histories for my website, I'm ignoring the existence of a series called Enterprise.)