liquid hydrogen (H2)
Liquid hydrogen (H2) is hydrogen in its liquid state, used as a cryogenic rocket fuel. Hydrogen gas turns to liquid under standard atmospheric pressure at -262.9°C. When oxidized by liquid oxygen, liquid hydrogen delivers about 40% more thrust per unit mass than other liquid fuels, such as kerosene. Molecular weight: 2.016; density: 0.071 g/ml. Commonly referred to in rocketry as LH2.