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The YF-90 is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in a staged combustion cycle. It is China's first hydrogen-oxygen engine to use the staged combustion cycle and is expected to be used for the second stage of the Long March 9, which is a three-stage rocket with boosters.
Regenerative cooling remains the predominant method for managing the thermal loads in thrust chambers. Typically the rocket fuel acts as a coolant as it enters the engine through passages at the nozzle exit. [5] It traverses the high-heat throat region and exits near the injector face.
Liquid hydrogen can be stored and transported without boil-off, by using helium as a cooling refrigerant, since helium has an even lower boiling point than hydrogen. Hydrogen is lost via venting to the atmosphere only after it is loaded onto a launch vehicle, where there is no refrigeration.
Cryogenic fuels are fuels that require storage at extremely low temperatures in order to maintain them in a liquid state. These fuels are used in machinery that operates in space (e.g. rockets and satellites) where ordinary fuel cannot be used, due to the very low temperatures often encountered in space, and the absence of an environment that supports combustion (on Earth, oxygen is abundant ...
The rocket is launched using liquid hydrogen and liquid oxygen cryogenic propellants. Rocket propellant is used as reaction mass ejected from a rocket engine to produce thrust . The energy required can either come from the propellants themselves, as with a chemical rocket , or from an external source, as with ion engines .
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
These cryogenic temperatures vary depending on the propellant, with liquid oxygen existing below −183 °C (−297.4 °F; 90.1 K) and liquid hydrogen below −253 °C (−423.4 °F; 20.1 K). Since one or more of the propellants is in the liquid phase, all cryogenic rocket engines are by definition liquid-propellant rocket engines. [2]
The Vulcain is a gas-generator cycle rocket engine fed with cryogenic liquid oxygen and liquid hydrogen. It features regenerative cooling through a tube wall design, and the Vulcain 2 introduced a particular film cooling for the lower part of the nozzle, where exhaust gas from the turbine is re-injected in the engine. [14]