The impulse assembly was a part of the propulsion system aboard a 22nd century shuttlepod.
In 2153, after one thruster was damaged of Shuttlepod 2 and the hull took damage from asteroid debris in the Delphic Expanse, Commander Trip Tucker ordered Crewman Haynem to take off the engine housings of the shuttlepod and run a diagnostic of the impulse assembly. (ENT: "Impulse")