6 countries which developed cryogenic rocket engines on their own.

Cryogenic rocket engines, using super-cold propellants like liquid hydrogen and oxygen, enable powerful and efficient propulsion. Nations such as the U.S., Russia, India, China, Japan, and Europe have leveraged this technology for advanced space missions, from heavy satellite launches to manned spaceflights and interplanetary exploration. These engines exemplify the pinnacle of innovation and international collaboration in space technology.