Cryogenic material is held at very low temperatures (the word cryogens comes from the Greek “kyros”, which means icy cold). A cryogenic liquid with which many are familiar is liquid nitrogen but other materials are also widely used in science as cryogenic liquids. It is used as a rocket fuel as well as for other industrial purposes.
3. How is a cryogenic engine different from a conventional rocket engine?
The solid-propellant engine is the oldest and simplest form of rocketry, dating back to the ancient Chinese. It is simply a casing, usually steel, filled with a mixture of solid-form chemicals (fuel and oxidizer) that burn at a rapid rate, expelling hot gases from a nozzle to achieve thrust. Unlike liquid-propellant engines, though, a solid-propellant motor cannot be shut down. Once ignited, it will burn until all the propellant is exhausted.
4. How are rocket engines different from jet engines?
A jet aircraft operates on the same principle, using oxygen in the atmosphere to support combustion for its fuel. But a rocket engine has to operate outside the atmosphere, and so must carry its own oxidizer. The gauge of efficiency for rocket propellants is specific impulse, stated in seconds. The higher the number, the “hotter” the propellant.