Multiple realities(covers information from several alternate timelines)
Microfusion thrusters were a type of thruster that were incorporated into the propulsion system aboard various Federation shuttlecraft types.
Both the Type 6 shuttlecraft and Type 15 shuttlepod employed microfusion thrusters. (TNG: "The Outcast", "In Theory")
The Yellowstone-class runabout had twelve microfusion thrusters. (VOY: "Non Sequitur")