A linear fluid impulse engine enables efficient conversion of the kinetic energy of large volume flows of fluid at low velocity into useful work. The linear fluid impulse engine uses symmetrically curved blades that are mounted to continuous power transmission belts that revolve on a pair of axles. The blades move in substantially linear paths on both the upstream and downstream sides of the inter-axle plane, which extends between the axes of the shafts. A linear cascade of stationary mid-plane guidevanes, located between the two sets of moving blade cascades, acts as a row of nozzles, accelerating the fluid so that it interacts with the downstream blade cascade with the proper velocity characteristics of an impulse device. Water entering the upstream blade cascade may be accelerated by stationary guidevanes to enable impulse operation.