US Patent 8079126 Friction stir welded bladder fuel tank

A method of fabricating a rolling bladder propellant tank assembly includes providing a pair of half-domes comprising a nanophase metallic material and a bladder formed of a ductile metallic material. A bladder support ring extends from at least one of the pair of half-domes. The pair of half-domes are positioned together to form a cavity therein with a portion of the bladder trapped between the pair of half-domes adjacent to the bladder support ring, wherein the bladder is positioned within the cavity. A seal is formed between the pair of half-domes and the bladder by friction stir welding. A friction stir welding pin used to form the seal is aligned with the bladder support ring during the friction stir welding operation.