Composite propellant used in the space shuttle solid rocket boosters that consists mainly of ammonium perchlorate as the oxidizer, powdered aluminium as the metallic fuel, and PBAN, polybutadiene-acrylic acid-acrylonitrile terpolymer, as the polymeric fuel binder. A small amount of iron oxide is added to increase the burning rate. The final product is a rubbery material not unlike a typewriter eraser.