High Quality Content by WIKIPEDIA articles! Ammonium perchlorate composite propellant (APCP) is a modern solid rocket propellant used in both manned and unmanned rocket vehicles. It differs from many traditional solid rocket propellants such as black powder or Zinc-Sulfur, not only in chemical composition and overall performance, but also by the nature of how it is processed. APCP is cast into shape, as opposed to powder pressing as with black-powder. This allows for manufacturing regularity and repeatability which are necessary requirements for use in the aerospace industry.