Abstract
External Tanks (ET's) for Space Shuttle missions are coated with isocyanurate foams. These materials must perform as an insulator for cryogenic propellants and as an ablator during ascent conditions. Because of the limited high- temperature stability of conventional urethane foams, qualification of Spray-On Foam Insulation (SOFI) systems was undertaken early in the Shuttle program. The criteria used to chemically evaluate the individual components of the in sulation and the flame retardancy tests correlating composition, radiant reces sion rate and bond tension of the finished product are described in this paper. Laboratory methods to measure and control predefined component ratios for production units are also discussed.
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