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liquid propellant





A propellant used in a liquid-propellant rocket engine.

Three main categories of liquid propellants may be distinguished:

Additionally, liquid propellants may be classed as bipropellants (in which a liquid fuel and a liquid oxidizer are stored separately) or monopropellants.

A good liquid propellant is one with a high specific impulse. This implies a high combustion temperature and exhaust gases with small molecular weights. However, another important factor is the density of the propellant. Lower density propellants require larger storage tanks, thus increasing the mass of the launch vehicle. Storage temperature is also important. A propellant with a low storage temperature, i.e. a cryogenic, requires thermal insulation, thus further increasing the mass of the launcher. The toxicity of the propellant yet another consideration. There are safety hazards in handling, transporting, and storing highly toxic compounds. Also, some propellants are very corrosive, however, materials that are resistant to certain propellants have been identified for use in rocket construction.


PROPERTIES OF LIQUID ROCKET PROPELLANTS
compound
chemical formula
molecular weight
density
melting point
boiling point
O2
32.00
1.141 g/ml
-218.8°C
-183.0°C
N2O4
92.01
1.45 g/ml
-9.3°C
21.15°C
HNO3
63.01
1.55 g/ml
-41.6°C
83°C
H2
2.016
0.071 g/ml
-259.3°C
-252.9°C
N2H4
32.05
1.004 g/ml
1.4°C
113.5°C
CH3NHNH2
46.07
0.866 g/ml
-52.4°C
87.5°C
dimethyl hydrazine
(CH3)2NNH2
60.10
0.791 g/ml
-58°C
63.9°C
C12H26
170.34
0.749 g/ml
-9.6°C
216.3°C


Related category

   • PROPELLANTS