Ambassador class starship

The Ambassador class is a fictional Starfleet starship class that first appears in the Star Trek series Star Trek: The Next Generation.

The Ambassador class was designed by Andrew Probert to suggest a natural progression, from the older Excelsior class starships that had appeared in the third and fourth Star Trek movies, to the newer Galaxy class starship that featured throughout the The Next Generation series. The first appearance of the Ambassador-class design is as part of a sculpture depicting the five starships named Enterprise and the U.S. Naval carrier Enterprise, that hangs on the back wall of the conference room of the Enterprise-D. The sculpture appears in the pilot episode of the Next Generation and appears throughout the first four seasons of The Next Generation.

The first actual Ambassador-class starship to appear on screen is the Enterprise-C in the third season episode "Yesterday's Enterprise". The crew of the Enterprise-D encounter the Enterprise-C after it travels forward in time through a time-space rift. The sudden disappearance of the Enterprise-C in the past changes the timeline for the worse, so the crew of the Enterprise-D decide to send the Enterprise-C and its crew to restore the timeline, even though they know they are likely sacrificing the crew of the enterprise-C. For that episode, Rick Sternbach and Greg Jein expanded on Probert's design to construct the filming model, as Probert had left the production art department after season one.

Ambassador-class starships subsequently appear in two episodes of The Next Generation, "Data's Day" and "Redemption Part II") and the pilot episode of Star Trek: Deep Space Nine, "Emissary". In the episode Data's Day, the Enterprise meets with the USS Zhukov to receive a Vulcan ambassador who they relay to a Romulan starship, unaware that she is actually a Romulan spy. In the first episode of the fifth season Redemption, Part II, Commander William Riker commands the USS Excalibur as part of a blockade attempting to stop a Romulan supply convoy during a Klingon civil war. In Emissary the USS Yamaguchi appears as part of the fleet attacking a Borg vessel at the beginning of the episode. These starships have some cosmetic differences from the Enterprise-C, a result of the studio model being rebuilt to remove the battle-damaged appearance it had in Yesterday's Enterprise.

Appearance
The class design has a saucer section attached to a tubular engineering section and two warp drive nacelles attached to the rear of the engineering section. At the bow of the engineering section is the navigational deflector, while the shuttlebay is at the stern. The main bridge, lifeboats and dorsal phaser arrays are embedded into the top of the saucer section, while the ship's ventral phaser arrays, a sensor dome, and more lifeboats occupy the bottom half of the ship. The USS Yamaguchi and USS Zhukov have a modified navigational deflector, additional lifeboats, a different sensor dome and an additional shuttlebay.

Other Ambassador class starships
Although never established on screen, The Star Trek Encyclopedia written by series production staff, lists the following starships as Ambassador-class.


 * USS Adelphi (NCC-26849) : Mentioned anecdotally in dialogue in the third season Next Generation episode Tin Man, the starship Adelphi was assigned to a first contact mission and due to a misunderstanding, a conflict broke out and 47 crewmembers, including Captain Darson and two friends of William Riker's, were killed.


 * USS Exeter (NCC-26531) : The starship Exeter is mentioned a number of times in dialogue but never appears on screen. In the second season Star Trek: Voyager episode Non Sequitur, the ship is mentioned as a former assignment of Tom Paris.


 * USS Gandhi (NCC-26632) : In the Next Generation episode Second Chances, the Enterprise-D crew find a duplicate of Will Riker that was created a number of years previously. The duplicate, Tom Riker, leaves at the end of the episode for an assignment on the USS Gandhi.


 * USS Horatio (NCC-10532) : In the Next Generation episode Conspiracy, Picard meets with Captain Walker Keel of the starship USS Horatio, an old friend who warns Picard about a conspiracy within Starfleet. The Enterprise later attempts to rendezvous with the Horatio, but it has been destroyed.


 * USS Valdemar (NCC-26198) : In the Deep Space Nine episode Tribunal, the USS Valdemar is sent to the Cardassian demilitarized zone in 2370 after the arrest of Chief Miles O'Brien by the Cardassian government.


 * USS Yamaguchi (NCC-26510) : In the Deep Space Nine episode Emissary, the USS Yamaguchi appears as part of the fleet that engaged the Borg at Wolf 359.