Cryogenic engines are a type of rocket engine that uses cryogenic fuels, such as liquid hydrogen (LH2) and liquid oxygen (LOX), to generate thrust. Here's a simplified overview of how they work:
1. Fuel and Oxidizer Storage: LH2 and LOX are stored in separate tanks at extremely low temperatures (around -423°F and -297°F respectively).
2. Fuel and Oxidizer Pumping: The fuels are pumped from the tanks to the combustion chamber using high-speed turbopumps.
3. Mixing and Combustion: The LH2 and LOX are mixed in the combustion chamber, where they ignite, producing a high-pressure and high-temperature gas.
4. Expansion and Acceleration: The hot gas expands through a nozzle, accelerating the exhaust gases to high speeds (around 10,000 mph), generating thrust.
5. Cooling System: Cryogenic engines use a regenerative cooling system, where the fuel is circulated around the combustion chamber and nozzle to cool them before being injected into the chamber.
Cryogenic engines offer high efficiency and specific impulse (a measure of efficiency), making them ideal for space missions. However, they are complex, require sophisticated plumbing, and are challenging to handle due to the extremely low temperatures.
Some examples of cryogenic engines include:
- NASA's Space Shuttle Main Engines (SSMEs)
- Ariane 5's Vulcain engine
- SpaceX's Raptor engine
