The eight-foot refit model
The studio models that represented the Constitution-class USS Enterprise were slated to be modernized and redesigned after the production of Star Trek: The Original Series and Star Trek: The Animated Series. Starting out with traditional physical studio models, digital versions were also used to represent ships of this class in the Star Trek franchise.
Ralph McQuarrie, best known to the public for his stunning production designs for the Star Wars films, was hired by Ken Adam to help develop the designs for the new Star Trek: Planet of the Titans movie, ultimately abandoned to make way for Star Trek: Phase II, the new television series. Although the design used the same elements as the original design, saucer shaped primary hull, warp engine assemblies and a engineering secondary hull, the secondary hull was flattened and wedge shaped, providing a radically different look, one not unlike the Star Destroyers McQuarrie designed for those films.
Their Enterprise design, however, was abandoned, and Roddenberry asked Matt Jefferies to update the famous starship to reflect the refit that would be part of the Phase II-series' back story. During June 1977, Jefferies' re-designed the engine nacelles from tubes to thin, flat-sided modules, and tapered their supports. He also added the distinctive photon torpedo launch ports on the saucer connector.