Rigid polyurethane foams and rigid polyisocyanurate foams (spray-on foam insulation) used for existing space launch vehicles such as the Space Shuttle and Delta IV, and planned for use on the next generation of space vehicles, the Ares I and Ares V, can gain an extraordinary amount of water under cryogenic conditions. After 8 hours of exposure to launch pad environments on one side and cryogenic temperatures on the other, these foams gain 35% to 80% in weight. This effect translates into several thousand pounds of additional weight for the space vehicles at lift-off. A new cryogenic moisture uptake apparatus was designed to determine the amount of water/ice taken into the specimen under actual-use propellant loading conditions. This experimental study was conducted to better understand cryogenic foam insulation performance and measured the amount of moisture uptake within different foam materials. Results of testing using both aged specimens and weathered specimens are presented. The implications for the design and flight performance of thermal protection systems for future launch vehicles are discussed.
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