Space Shuttle Orbiter, design

Two products, PR-711 and PR-719, are manufactured by Products Research Chemical Corp. PR-711 was used for environmental sealing of structural faying surfaces of the first two flights of the space shuttle orbital airframe. PR-719 is designed to seal integral fuel tanks of aircraft. The sealant has to be a non-curing type so that the channel can be resealed without disassembling the structure. 

H2/O2 alkaline technology using immobilized electrolytes is considered to be fully developed. Confidence in the present cell technology is best represented by the fact that there is no back-up electric power on the Space Shuttle Orbiter. Further improvement of the present H2/O2 design is not considered to be cost effective with one exception maintenance cost can be decreased directly by increasing the cell stack life of the Orbiter power plant. 

Testing and verification of the ISS have involved a number of unique requirements and constraints. The major contributing factors include the on-orbit assembly process, the series of vehicle stages defining the incremental steps in the assembly process (each with unique functional performance requirements), and the requirement to operate and support human activity under the extreme environmental conditions of space. Add to this that the system is designed, built, and deployed by a consortium of 16 nations, and its parts delivered to their final assembly location by the most complex space vehicle ever built (the Space Shuttle), and the result is arguably the most difficult test and verification program ever attempted. 

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