Nob Akimoto wrote:
The Constellation class were never a back-up plan for the Excelsior. The USS Constellation itself went on a one year trail run even before the Excelsior had left the shipyard.
But in real life. The four nacelle prototype Excelsior, did lead to the idea of the Constellation.
As for the other replies, I'm sure there was plenty of internal Starfleet politicking to get the Constellation class approved and to protect it once the Excelsior with conventional engines turned out to be viable. I can also see the argument for the Miranda's popularity and the Constellation coming from their shuttle bay volume.
I think yenny
is referring to one of the early Excelsior conceptual prototype models
for Star Trek III that did happen to have 4 engines. It appeared as a background ship in the Wolf 359 aftermath, along with this
, another Excelsior concept and this
, which I think was an early Enterprise Phase II concept. It could be postulated that this ship and the Constellation shared a similar pedigree, experimenting with quad nacelle configurations before the advent of Galaxy-style (or perhaps Ambassador-style) twin-coil star-drive engines, but there is certainly no on-screen evidence to support any of this (nor is there anything to refute it, for that matter).