Commander Sonak was to be the new science officer aboard the USS Enterprise after it completed the refit which followed Kirk's five-year mission. He received this appointment based on Admiral Kirk's recommendation.
Sonak and another female crew member were killed in a transporter accident shortly before the starship left to deal with the V'Ger crisis in 2270s. The ship's transporter was 'temporarily' out of order that time; Janice Rand operated the transporter when she saw their silhouettes being deformed, and despite Kirk's attempts to complete the transfer, their disfigured masses ended back in Starfleet Command. The operator said they were fortunate they didn't live long. Kirk instructed him to contact Sonak's family through the Vulcan Embassy to extend his sympathies. (Star Trek: The Motion Picture)
|Science officers of the starships Enterprise|
|USS Enterprise:||Spock • Chekov • Kyle • Sonak • Decker • Saavik|
|USS Enterprise-D:||Data • Swenson|
|ISS Enterprise NX-01:||T'Pol|
|ISS Enterprise (NCC-1701):||Spock|
|USS Enterprise (alternate reality):||Spock|
The unnamed crewmember with Sonak was Vice Admiral Lori Ciana according to the novelization, and the novelization stated that the transporter inverted them: they formed with their internal organs outside their bodies. Director Robert Wise indicated in the DVD commentary for the Director's Cut edition that this woman was to be the ship's navigator, and that Ilia was a last-minute replacement.
In the script for the Star Trek: Phase II pilot episode "In Thy Image", which subsequently evolved into Star Trek: The Motion Picture, the character of Commander Ronak is virtually the same as Sonak and his manner of death is very similar (albeit significantly less gruesome).