Cryogenic is a word that is used for a kind of component that creates an effect in which something that is treated at low temperature and the temperature is almost icy. You can find the use of the word in medical procedure also where a disease is treated by keeping it at very low temperature. In cryosurgery, the surgery is being done by creating a very low temperature at the effected area and thus killing the bacteria or virus that is affecting the part of the body.
The way you have mentioned, it seems that you are talking about the kind of engine that follows the cryogenic process. Different scientist use different kind of technology to make cryogenic engine and one of the technologies that use the system is called CECE and it uses 15,000 pound thrust-class engine and the fuel that is used in this kind of engine is the mixture of liquid form of hydrogen and oxygen.
The way you have mentioned, it seems that you are talking about the kind of engine that follows the cryogenic process. Different scientist use different kind of technology to make cryogenic engine and one of the technologies that use the system is called CECE and it uses 15,000 pound thrust-class engine and the fuel that is used in this kind of engine is the mixture of liquid form of hydrogen and oxygen.