Encyclopedia Astronautica
N2O4/Alumizine


Nitrogen tetroxide became the storable liquid propellant of choice from the late 1950's. Alumizine was a mixture of 43% aluminum powder suspended in anhydrous hydrazine with a gelling agent. The idea was to increase the heat of combustion due to the high enthalpy of formation of aluminum oxide as a combustion product, similar to the metallized kerosene ("Kerosol") tested by Saenger in the 30's. Alumizine was never flown and was only tested in static ground tests. A drum of alumizine exploded in California when it was not disposed of safely. The fuel was proposed for some pressure-fed 'big dumb booster' designs of the late 1960's.

Nitrogen tetroxide consists principally of the tetroxide in equilibrium with a small amount of nitrogen dioxide (NO2). The purified grade contains less than 0.1 per cent water. Nitrogen tetroxide (N2O4) has a characteristic reddish-brown colour in both liquid and gaseous phases. The solid tetroxide is colorless. N2O4 has an irritating, unpleasant acid-like odour. N2O4 is a very reactive, toxic oxidiser. It is non-flammable with air; however, it will inflame combustible materials. It is not sensitive to mechanical shock, heat, or detonation. Nitrogen dioxide is made by the catalytic oxidation of ammonia; steam is used as a diluent to reduce the combustion temperature. Most of the water is condensed out, and the gases are further cooled; the nitric oxide is oxidised to nitrogen dioxide, and the remainder of the water is removed as nitric acid. The gas is essentially pure nitrogen tetroxide, which is condensed in a brine-cooled liquefier. 1959 production amounted to 60,000 tonnes per year. In carload lots of one-ton cylinders, the price was $ 0.15 per kg. By 1990 NASA was paying $ 6.00 per kg due to environmental regulations.

Oxidizer: N2O4. Fuel: Alumizine. Oxidizer Density: 1.450 g/cc. Oxidizer Freezing Point: -11 deg C. Oxidizer Boiling Point: 21 deg C.

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Associated Engines
  • LR87 Alumizine Aerojet N2O4/Alumizine rocket engine. 1960's USAF development effort for a Titan storable engine using a metallized fuel (for greater impulse density) and gelled propellants (to facilitate in-space starts after a period of coasting). More...
  • PF N204/Alumizine-1925k Notional N2O4/Alumizine rocket engine. 18,873 kN. Study 1967. Isp=280s. Used on Saturn LCB-Alumizine-250 launch vehicle. More...
  • PF N204/Alumizine-2300k Notional N2O4/Alumizine rocket engine. 22,562 kN. Study 1967. Isp=280s. Used on Saturn LCB-Alumizine-140 launch vehicle. More...

Associated Stages
  • Saturn LCB-Alumizine-140 N2O4/Alumizine propellant rocket stage. Loaded/empty mass 1,542,200/154,200 kg. Thrust 22,563.10 kN. Vacuum specific impulse 280 seconds. Boeing Low-Cost Saturn Derivative Study, 1967 (trade study of 260 inch first stages for S-IVB, all delivering 86,000 lb pyld to LEO): Low Cost Booster, Single Pressure-fed N2O4/Alumizine Propellant engine, HY-140 Hull More...
  • Saturn LCB-Alumizine-250 N2O4/Alumizine propellant rocket stage. Loaded/empty mass 1,270,100/95,300 kg. Thrust 18,873.80 kN. Vacuum specific impulse 280 seconds. Boeing Low-Cost Saturn Derivative Study, 1967 (trade study of 260 inch first stages for S-IVB, all delivering 86,000 lb pyld to LEO): Low Cost Booster, Single Pressure-fed N2O4/Alumizine Propellant engine, Ni-250 Hull More...

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