Cryogenic fuel

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. rocket ships and satellites) because ordinary fuel cannot be used there, due to absence of an environment that supports combustion (on earth, oxygen is abundant in the atmosphere, whereas in human-explorable space, oxygen is virtually non-existent). Cryogenic fuels most often constitute liquefied gases such as liquid hydrogen.