Dimitri Valtane was a male Human science officer of the 23rd century Starfleet. By 2293, he had attained the rank of Lieutenant commander.
From 2290 to 2293, Valtane served on the USS Excelsior under Captain Hikaru Sulu for its three-year mission cataloging gaseous planetary bodies in the Beta Quadrant. On their return, the Excelsior was hit from a shockwave. Valtane located the source, Qo'noS' moon, Praxis, and found it had exploded. (Star Trek VI: The Undiscovered Country)
Valtane was the bunk-mate of Ensign Tuvok in 2293. They worked during the gamma shift and shared common quarters with two other gamma shift officers, on Deck 7. As an eager young officer, Valtane expressed both approval and surprise regarding Captain Sulu's recklessness in attempting to rescue Captain Kirk and Dr. McCoy from Rura Penthe. When Tuvok expressed his negative outlook on Humans, Valtane did not take any personal offense and at the end of the conversation merely remarked that Tuvok's determination to resign his commission in the future would be "his loss".
Following Captain Sulu's abortive attempt to rescue Kirk and McCoy, the Excelsior came under attack while attempting to enter Klingon space. Gravely injured during the attack, Valtane, while in a state of clinical death, unwittingly transferred a memory virus to his attendant crewmate Tuvok. (VOY: "Flashback")
Appendices
Background information
Valtane was played by actor Jeremy Roberts as an adult and an unknown actor as a child.
This character had no first name in Star Trek VI: The Undiscovered Country; it wasn't established as "Dimitri" until "Flashback". The name wasn't included in the first draft of the episode's script, but was in the final draft of that teleplay.
The Star Trek Encyclopedia spells his first name as "Dmitri".
In the script of "Flashback" (both the first and final draft of the teleplay), the adult Valtane was consistently referred to as a lieutenant.
The costume worn by Roberts as Valtane in "Flashback" was auctioned off in the It's A Wrap! sale and auction on eBay. [1] [2]
Valtane, Lojur, the Borg Queen and Admiral Hayes are the only characters to debut in a Star Trek film before appearing in a Star Trek television series.
Apocrypha
He was called Masoud Valtane in the novelization of Star Trek VI: The Undiscovered Country, as well as the novel The Fearful Summons.
Peter David's novel The Captain's Daughter stated that Valtane was the Excelsior's first officer; the novelization of Star Trek VI also stated this. However, DC Comics had a story arc, collected in Tests of Courage, by Howard Weinstein in their second TOS volume that instead had Rand as first officer.
According to his biography in the video game Star Trek: Starship Creator, Valtane was the son of Nikolai and Larisa Valtane. He was born in 2259 on the Beta Niobe colony and entered Starfleet Academy in 2277. In 2280, while serving aboard the USS Malinche, he rescued two wounded crewmen from a pack of Denebian slime devils, armed only with a stick. In 2281, Valtane was assigned to the USS Gallipoli as a junior astrophysicist. In 2284, he was promoted to lieutenant and assigned to the USS Lamneth as chief stellar cartographer on a mission of exploration in the Gurava sector. In 2289, Valtane transferred to the USS Churchill as science officer. In 2291, Valtane wrote a scientific paper titled "Methods for Stabilizing Protomatter in High-Energy Matrices."