#propulsion  a propelling force
  supertype:  force  the physical influence that produces a change in a physical quantity; "force equals mass times acceleration"
  subtype:  nuclear_propulsion__nuclearpropulsion  the use of a nuclear reactor either to produce electricity to power an engine (as in a nuclear submarine) or to directly heat a propellant (as in nuclear rockets)
  subtype:  reaction_propulsion  propulsion that results from the ejection at high velocity of a mass of gas to which the vehicle reacts with an equal and opposite momentum
     subtype:  jet_propulsion__jetpropulsion  propulsion by means of the discharge of a jet of fluid toward the rear
     subtype:  rocket_propulsion  reaction propulsion using stored oxygen for combustion; used where there is insufficient atmospheric oxygen

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