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Solid Rocket Boosters Space Shuttle: The rocket propellant mixture in each solid rocket motor consisted of ammonium perchlorate (oxidizer, 69.6% by weight), atomized aluminum powder (fuel, 16%), iron oxide (catalyst, 0.4%), PBAN (binder, also acts as fuel, 12.04%), and an epoxy curing agent (1.96%).[9][10] This propellant is commonly referred to as Ammonium Perchlorate Composite Propellant, or simply APCP. This mixture gave the solid rocket motors a specific impulse of 242 seconds (2.37 km/s) at sea level or 268 seconds (2.63 km/s) in a vacuum. 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. JAXA describe the fuel as "HTPB/AP/Al=12/68/20" which means, proportioned by mass, HTPB 12% (binder and fuel), Ammonium perchlorate 68% (oxidizer), and Aluminium powder, 20% (fuel). Casing The casing may be constructed from a range of materials. Cardboard is used for model rocket motors. Steel is used for the space shuttle boosters. Filament wound graphite epoxy casings are used for high performance motors. Amateur rocketry Solid fuel rockets can be bought for use in model rocketry; they are normally small cylinders of fuel with an integral nozzle and a small charge that is set off when the fuel is exhausted. This charge can be used to ignite a second stage, trigger a camera, or deploy a parachute. Designing solid rocket motors is particularly interesting to amateur rocketry enthusiasts. The design is simple, materials are inexpensive and constructions techniques are safe. Early amateur motors were gunpowder. Later, zinc/sulfur formulations were popular. Typical amateur formulations in use today are: sugar (sucrose, dextrose, and sorbitol are all common)/potassium nitrate, HTPB (a rubber like epoxy)/magnesium/ammonium nitrate, and HTPB or PBAN/aluminum/ammonium perchlorate (APCP). Most formulations also include burn rate modifiers and other additives, and also possibly additives designed to create special effects, such as colored flames, thick smoke, or sparks.
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