HTPB Rubber
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HTPB - Hydroxyl-Terminated Polybutadiene.
HTPB was the most recent state-of-the-art composite propellant rubber binder,
manufactured by ATOChem, Inc. It is employed in a wide range of space launch
vehicles and weapon systems including: Delta II, Delta III, Delta IV, Titan
IVB and Ariane external boosters; Peacekeeper ICBM and related space launch
vehicles; the Japanese M-5 satellite launcher; the MLRS multiple rocket artillery
system; and the VT-1 missile from the Crotale surface-to-air missile system.
HTPB is a polymer of butadiene terminated at each end with a hydroxyl functional group. It belongs to a class of polymers known as polyols. It is used to react with a diisocyanate to form a polyurethane, a stable and easily stored synthetic rubber, often used in tire manufacturing.
When used in solid propellant rockets, the usual proportions are 12% HTPB (rubber binder and fuel), 20% aluminium powder (fuel), and 68% ammonium perchlorate (oxidiser). HTPB is also employed in hydrid rocket motors. These combine a solid fuel with a separate oxidiser, usually N2O (nitrous oxide gas). One of the most well known applications of hybrid motors is independantly developed SpaceShipOne, built by SpaceDev.
