Using a series of equations, Kosinski was able to make a measurable increase in propulsion with the starships USS Ajax and USS Fearless. His warp drive efficiency upgrade experiments brought him to the USS Enterprise-D in 2364, where he was to test different ways of entering warp speed and different intermix ratios. It later was revealed that it was his mysterious assistant, The Traveler, who was affecting the upgrades and not him. (TNG: "Where No One Has Gone Before")
Some of Kosinski's theories were still valid, and Ensign Wesley Crusher tested his warp equations aboard the Enterprise while it was docked at Starbase 133 in 2367. Wesley inadvertently created a warp bubble which trapped his mother, Doctor Beverly Crusher, in an alternate universe. In this universe, Wesley contacted Kosinski for assistance when crewmembers began disappearing, but he was unable to explain the phenomenon. (TNG: "Remember Me")
Kosinski, played by Stanley Kamel, appeared in a Starfleet uniform with no communicator and did not appear to have a Starfleet rank, as he is referred to throughout the episode as "Mr. Kosinski". Kosinksi's collar featured a unique rank insignia, a small silver rectangle and a darker rectangle of the same size. It could be that he is a civilian temporarily working for Starfleet and given a uniformed position. His condescending attitude towards Picard and Riker would support the argument that he was not a part of the service or its chain of command. He is also addressed as "sir" by Riker on several occasions lending further credence to the theory that he is outside of the regular chain of command.