F-1 rocket engine

F-1 rocket engine (The kind used by the Saturn V.)

A bipropellant rocket is a rocket that uses separate liquid fuel and oxidizer propellants. In contrast, solid rockets require no oxidizer, and hybrid rockets use solid propellants with a liquid or gaseous oxidizer. Bipropellant systems are more efficient than monopropellant systems, but they tend to be more complicated because of the extra hardware components needed to make sure the right amount of fuel gets mixed with the right amount of oxidizer, known as the mixture ratio.

Thousands of combinations of fuels and oxidizers have been tried over the years. Some of the more common and practical ones are:

Goddard and Rocket

Robert Goddard and his rocket

One of the most efficient mixture, oxygen and hydrogen, suffers from the extremely low temperatures required for storing hydrogen and oxygen as liquids (around 20 K or -253 °C)) and low fuel density (70 kg/m3), necessitating large and heavy tanks. The use of lightweight foam to insulate the cryogenic tanks caused problems for the Space Shuttle Columbia's STS-107 mission.

For storable ICBMs or interplanetary spacecraft, keeping the fuel cool seems to be an unsolvable problem. Because of this, mixtures of hydrazine and its derivatives in combination with nitrogen oxides are generally used for such rockets. Hydrazine has its own disadvantages, being a very caustic and volatile chemical. Consequently, hybrid rockets have recently been the vehicle of choice for low-budget private and academic developments in aerospace technology.

Small scale rocket enginesEdit

XCOR Aerospace, a California based company, is developing small scale rocket engines to power small airplanes for suborbital flights. They have tested various combination of propellants including nitrous oxide/propane, nitrous oxide/alcohol, LOX/alcohol, LOX/kerosene with success.

See alsoEdit

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