Variable output inflator

The variable output inflator includes an injection piston assembly containing a liquid propellant chamber (22) from which liquid propellant is injected through one or more nozzles (25) in the injection piston (18) into a combustion chamber (12). The movement of the injection piston (18)is controlled by a magnetic control unit (37) employing an annular gap (41) through which the MR fluid flows in a controlled manner. The inflator is of cylindrical type and may be made of small compact dimensions.