Composite Boss Technology

Composite tank technology has now been developed to contain liquid hydrogen and liquid oxygen without use of a liner. This advancement will significantly reduce the inert component of propulsion system weight. The thrust to weight ratio performance factor and the pressure X volume/weight pressure vessel performancce measurement will both be increased as a result of this development. The metallic boss fitting/ closure assembly now becomes the critical weight component in a cryogenic tank assembly. This Phase I SBIR proposal has as its goal the adaptation of composite materials in place of metals in tank boss structure. In addition to structural loads, the boss assembly is designed to provide an effective seal arrangement as the primary inlet/outlet/vent system for cryogenic tankage. An innovative concept will also be evaluated for the potential integration of a composite boss design into the composite dome structure of the vessel. Designs of composite bosses will be tailored to fit tanks from 4' up to 12" diameter. This will effectively cover the size range of cryogenic tanks used as research and sub-scale assemblies for currently emerging systems, such as the Air Force Expendable Launch Vehicle and the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) program. An 18" diameter composite tank will be filament wound with integral bosses and layed up closures will be fabricated and assembled onto the tank. IM7/977-2 materials will be used based on successful demonstration in the LH2 program. Surface treatment of the composite structure may be required to meet the requirements for cryogenic sealing techniques being submitted under a parallel SBIR proposal.