10 Unused Star Trek Ship Designs We NEED To See
6. Klingon D-4 Class Battlecruiser
The story behind the D-4 Class Battlecruiser is a heartbreaking one. In 2001, a new design of Klingon ship was requested for Enterprise's first season episode Unexpected. Though the design team were exhausted from their work on the pilot, they got to work on the new/old design.
John Eaves started a retro look at the Klingon D-7 class Battlecruiser. He based some of the ideas on the Golden Gate bridge, particularly the wiring that is visibly holding some of it together. This design was then sent to Foundation Imaging, where Rob Bonchune was responsible for rendering the ship in CGI. Despite the animator Koji Kuramura staying up for 36 hours to get the model over the line, the producers ended up not using it - as there were maybe four or five windows out of alignment.
This resulted in the re-use of the CGI K'T'Inga Battlecruiser that had been used in Deep Space Nine and Voyager, though in both Voyager and Enterprise this presented serious continuity issues. The K'T'Inga had not debuted until The Motion Picture, over 100 years after the events of Enterprise. The model was called a D-7 in Voyager, though retained the detailing of the latter ship.
The D-4 is well overdue for its debut in Star Trek, ready and waiting as it is to be seen.