Hydraulic drive system in the context of "Working fluid"

Merlin is a family of rocket engines developed by SpaceX. They are currently a part of the Falcon 9 and Falcon Heavy launch vehicles, and were formerly used on the Falcon 1. Merlin engines use RP-1 and liquid oxygen as rocket propellants in a gas-generator power cycle. The Merlin engine was originally designed for sea recovery and reuse, but since 2016 the entire Falcon 9 booster is recovered for reuse by landing vertically on a landing pad using one of its nine Merlin engines.

The injector at the heart of Merlin is of the pintle type that was first used in the Apollo Lunar Module landing engine (LMDE). Propellants are fed by a single-shaft, dual-impeller turbopump. The turbopump also provides high-pressure fluid for the hydraulic actuators, which then recycles into the low-pressure inlet. This eliminates the need for a separate hydraulic drive system and means that thrust vectoring control failure by running out of hydraulic fluid is not possible. The engine is named after Merlin (a falcon).

A hydraulic pump is a mechanical source of power that converts mechanical power into hydraulic energy (hydrostatic energy i.e. flow, pressure). Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic. They generate flow with enough power to overcome pressure induced by a load at the pump outlet. When a hydraulic pump operates, it creates a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line to the pump and by mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement (flow through the pump per rotation of the pump) cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted. Hydrodynamic pumps are more frequent in day-to-day life. Hydrostatic pumps of various types all work on the principle of Pascal's law.

Telescoping in mechanics describes the movement of one part sliding out from another, lengthening an object (such as a telescope or the lift arm of an aerial work platform) from its rest state. Manually extended telescoping devices are common in modern products, for example they are used in umbrellas, selfie sticks, pop up canopy shelters, and (to extend handles) luggage. In heavy equipment, extension can be achieved by a hydraulics, but pulleys are generally used for simpler designs such as extendable ladders and amateur radio antennas.