Throttle assembly
The throttle assembly was a component (or series of components) of the propulsion system of Earth's first warp-capable vessel, the Phoenix.

Integrated into a Titan II nuclear missile by Zefram Cochrane and his team of engineers in Bozeman, Montana in the mid-21st century, the throttle assembly utilized theta radiation. On the evening of 4 April, 2063, the Phoenix rocket was damaged in its silo by a Borg attack, launched from the 24th century. Large doses of theta radiation leaked from the damaged throttle assembly, causing severe radiation poisoning in Lily Sloane, a member of Cochrane's team. 

The throttle assembly was ultimately repaired and the Phoenix flew on the following day, 5 April, 2063. ()

Propulsion technology