Rockets
Many large rockets use liquid hydrogen as fuel, with liquid oxygen as an oxidizer. The main advantage of hydrogen rocket fuel is the high effective exhaust velocity compared to kerosene/LOX or UDMH/NTO engines. According to the Tsiolkovsky rocket equation, a rocket with higher exhaust velocity needs less propellant mass to achieve a given change of speed. Before combustion, the hydrogen runs through cooling pipes around the exhaust nozzle to protect the nozzle from damage by the hot exhaust gases.
The disadvantages of LH2/LOX engines are the low density and low temperature of liquid hydrogen, which means bigger and insulated and thus heavier fuel tanks are needed. This increases the rocket's structural mass and decreases its efficiency somewhat. Another disadvantage is the poor storability of LH2/LOX-powered rockets: Due to the constant hydrogen boil-off, the rocket can only be fueled shortly before launch, which makes cryogenic engines unsuitable for ICBMs and other rocket applications with the need for short launch preparations.
Liquid hydrogen and oxygen were also used in the Space Shuttle to run the fuel cells that power the electrical systems. The byproduct of the fuel cell is water, which is used for drinking and other applications that require water in space.
Read more about this topic: Hydrogen Vehicle, Vehicles
Famous quotes containing the word rockets:
“The Thirties dreamed white marble and slipstream chrome, immortal crystal and burnished bronze, but the rockets on the Gernsback pulps had fallen on London in the dead of night, screaming. After the war, everyone had a car—no wings for it—and the promised superhighway to drive it down, so that the sky itself darkened, and the fumes ate the marble and pitted the miracle crystal.”
—William Gibson (b. 1948)