- The most senior regular line rank in Starfleet. It was most often held by starship and starbase commanders, as well as adjutants and executives serving beneath admirals. This rank was usually considered a big transition, because it was often the first rank in which officers ran a base of operation (for example, a starship) more or less by themselves. The equivalent ground forces rank to Starfleet captain was colonel. It should also be noted that there are rare cases of officers holding the Captain’s rank serving as other than the commanding officer of starship. Examples of this include Spock and Montgomery Scott, who both held the rank of Captain while serving under James T. Kirk, who also held the equal rank of Captain. Departments in rare cases could get a Captain as the superior head of that particular department such as Montgomery Scott being a ”Captain of Engineering” during the film Star Trek III: The Search for Spock. Other examples of this also include William T. Riker and Worf, both of whom attained the rank of Captain (in Worf’s case, through the Klingon Defense Force) while under the command of Captain Jean-Luc Picard. Another example of a Captain holding a position other than commanding a starship is that of Phillipa Louvois who held the rank while working as a prosecutor under the office of the Judge Advocate General.
In the modern US Navy, captain is a four-stripe officer rank. This insignia style was used in ENT all TNG era productions. During TOS and the movies, it had differing insignia. The TOS captains wore one full braid, a broken braid and another full braid. However, in the pilot ”The Cage”, Captain Pike wore only a single rank strip, so it was not clear how other officers were differentiated from captains. By ”Where No Man Has Gone Before”, Kirk was the only officer with two stripes, but that system didn’t differentiate any other officer grades below captain except for no-stripe ensigns.
- The Starfleet line rank immediately inferior to captain. Typical assignments at this rank included executive officer of larger vessels such as the Galaxy– and Sovereign-class, space station commander (such asBenjamin Sisko of Deep Space 9 prior to his promotion to captain in 2371), and commanding officer of smaller vessels. The rank of commander was also available to chief medical officers and ship counselors who passed the Bridge Officer’s Test. An officer who held the rank of commander was expected to be able to assume command of a starship should the situation call for it. Officers at this rank typically had 10-15 years of experience in Starfleet.
- Lieutenant Commander
- The Starfleet line rank immediately inferior to commander. Officers with this rank typically held positions as senior department heads on larger vessels such as the Galaxy– and Sovereign-class ships, or serve as theexecutive officer of smaller or older vessels. On most starships, the second officer held this rank (such asData of the USS Enterprise or Tuvok of the USS Voyager). In some rare cases, a lieutenant commander could also serve as the commanding officer of a smaller vessel, such as Jadzia Dax of the USS Defiant for a brief period in 2374.
- The Starfleet line rank immediately inferior to lieutenant commander. Officers at this rank typically had some command experience, and were occasionally appointed department heads on starships. Typically they were shift commanders in a department under a lieutenant commander; for example, a lieutenant commander would be chief of engineering and commander of A shift, and there would be a B and a C shift, each under a lieutenant. Additionally, some advanced Starfleet training programs, such as Advanced Tactical Training, commissioned their graduates at this rank. (TNG: ”Preemptive Strike”)
The United States armed forces have various programs for service members to begin their careers as officers in higher pay grades than second lieutenant or ensign, with commissioning in the rank of Lieutenant common for such United States Navy occupations as Judge Advocate General Corps (JAG), Chaplains, Medical and Medical Service Corps, as well as the Navy Dental Corps. Whether Starfleet utilizes a similar policy for commissioning officers in the medical and science fields is unknown, although highly likely given CounselorDeanna Troi‘s rapid rise to lieutenant commander after her advanced studies on Betazed. This may also explain how Saavik of Vulcan was both a cadet and a lieutenant in Star Trek II: The Wrath of Khan.
- Lieutenant junior grade
- The Starfleet line rank immediately inferior to lieutenant. Officers at this rank typically hold support positions on starships and starbases. At this rank, they had begun to prove their ability to perform acceptably in Starfleet, and typically began to take on more senior roles in command situations. Typical posts at this rank were conn officer, communications officer, or second officer of a shift (see lieutenant). It was also the rank bestowed on medical doctors and counselors (but not nurses) upon completion of their studies and training at Starfleet Medical Academy or elsewhere. This rank acknowledged the additional time required to become commissioned as reflected in Beverly Crusher‘s service record and Julian Bashir‘s age as a recent Academy graduate. (DS9: ”Emissary”) Assistant counselor Ezri Dax skipped her final months of training and was explicitly given ”commission as a full counselor with the rank of lieutenant (junior grade).” (DS9: ”Afterimage”)
- The most junior Starfleet line rank. It was the rank bestowed on newly-commissioned officers when they graduated from Starfleet Academy. Ensigns typically began their careers as the most junior officers in the department of their chosen specialty. Ensigns who had distinguished themselves in their academy class or on duty could be given posts as main-shift bridge officers (for example Ensign Harry Kim). A typical officer spent approximately three years at the rank of ensign. (TNG: ”Datalore”)