Abstract: A combustion-driven hydroelectric generating system has one or more combustion cylinders that contain a liquid (such as water) and receive a combustible fuel/oxidizer mixture that is ignited and the explosive force of the combustion acts on the surface of the liquid to transfer a metered slug of the liquid to a pressurized vessel containing a pressurized gas (preferably an inert gas). The pressurized liquid from the pressurized vessel serves as a “head of water” that can be used to operate a water wheel (Pelton wheel) or hydroelectric generator and perform other useful work. The transferred liquid is replaced in the combustion cylinder, another charge of the fuel/oxidizer is introduced and ignited and the process is repeated.