Kosinski was an arrogant Starfleet propulsion expert whose warp tests sent the Enterprise across the galaxy, though the real cause was his alien assistant.
Kosinski was a Starfleet propulsion expert who came aboard from the USS Fearless in Where No One Has Gone Before to test new formulas meant to improve warp engine efficiency. He was confident and dismissive of the Enterprise engineers, and he brought along an assistant from Tau Alpha C.
His first test threw the ship into another galaxy far beyond the Milky Way, and a second carried it even further, to a realm where thoughts became real. Kosinski took the credit, but the effect was really the work of his assistant, the Traveler, whose abilities Wesley Crusher had noticed. Stanley Kamel played him.