Composite propellant

Overview

Ammonium perchlorate (AP) composite propellant is a composite propellant, meaning that it has both fuel and oxidizer combined into a homogeneous mixture, in this case with a rubbery binder as part of the fuel. The propellant is most often composed of ammonium perchlorate, an elastomer binder such as hydroxyl-terminated polybutadiene (HTPB) or polybutadiene acrylic acid acrylonitrile prepolymer (PBAN), powdered metal (typically aluminium), and various burn ratecatalysts. In addition, curing additives induce elastomer binder cross-linking to solidify the propellant before use. The perchlorate serves as the oxidizer, while the binder and aluminium serve as the fuel. Burn rate catalysts determine how quickly the mixture burns. The resulting cured propellant is fairly elastic (rubbery), which also helps limit fracturing during accumulated damage (such as shipping, installing, cutting) and high acceleration applications such as rocketry. This includes the Space Shuttle missions, in which APCP was used for the two SRBs.