This page discusses Rocket Motor Propellant Chemistry .

Solid propellants are classified as "composite" when made of an oxidizer and fuel, or as "Nitramine" when made up of unstable compounds, each a self-sufficient combustible. "Nitramine" refers to combining the two unstable compounds in a colloid. Additional ingredients may be added to the grain for strength, chemical stability, reduction in temperature sensitivity, and ease of processing.

Composite Propellants

The oxidizers generally employed in composite propellants are perchlorates and inorganic nitrates, such as sodium, potassium and ammonium nitrates. The reaction of the perchlorates with the fuel produces chlorine by-products which are toxic and corrosive. Potassium and sodium nitrates produce smoke, but ammonium nitrate is smokeless and non-toxic. However, it has low oxidizing potential.

Organic fuels employed in composite propellants are asphalts, synthetic rubbers, and plastics. Asphaltic fuels can be brittle unless oil is added, but this makes the grain soft and subject to deformations under its own weight at higher storage temperatures. The plastics used can be thermosetting (e.g. phenol-formaldehyde) or non-thermosetting (styrene). Rubber fuels are especially useful where the propellant grain has the potential to be subjected to a wide range of ambient temperatures as they are less likely to develop undesirable cracks in the grain.

Nitramine Propellants

The compounds generally employed in double base propellants are organic nitrates and aromatic nitro compounds. The most common nitrates are glycerol trinitrate (nitroglycerine), diethyleneglycol dinitrate and cellulose nitrate (nitrocellulose). The most common nitro compounds are ammonium picrate and TNT.

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