Eventually, the fallback for a hydraulic pump or engine failure on most aircraft was the Ram Air Turbine or RAT, which was extended into and turned by the air stream to provide hydraulic (and/or electric) power. These were released by unlatching an uplock, so no hydraulic or electric power was required to bring them into play.
The F8U RAT was unusual in that it had large number of blades of high activity factor and the fan was shrouded. Most RATs now have only two blades and are not shrouded. This picture of an RF-8 with the RAT extended was taken by Joe Youngerman at the National Air and Space Museum.