Abstract: An apparatus for deploying an inflatable member, such as a safety bag in a motor vehicle, includes a hydraulic actuator for amplifying the fluid pressure in a combustion chamber, initially generated by a pyrotechnic initiator, and applying the amplified fluid pressure to continuously pressurize a liquid propellant reservoir to magnitudes exceeding the combustion chamber fluid pressure. All of the liquid propellant in the reservoir is then rapidly injected as a continuous stream into the combustion chamber for ignition and sustained combustion, thereby generating the volume of combustion gases necessary to fully inflate the safety bag.