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Development and Validation of Cryogenic Foam Insulation for LH2 Subsonic Transports.

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Final rept.

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This experimental investigation evaluated the life of closed cell organic foams as cryogenic insulation for LH2 tanks under thermal conditions representing airline type operations. Emphasis was placed on commercially available foam materials but some modified materials and some foambarrier film combinations were evaluated also. The original objective was to determine if any available materials could survive more than a few hundred mission thermal cycles. In addition to satisfying this goal it was possible to assess the progress of degradation and to identify failure modes. The polyurethane foam insulations exhibited the best cyclic life and excellent thermal performance. Two insulations of unreinforced polyurethane foam attained 4400 thermal cycles equivalent to approximately 15 years of airline service without serious thermal or structural degradation. Fourteen foam insulation specimens were tested. Some were plain foam while others contained flame retardants, chopped fiberglass reinforcement andor vapor barriers. The thermal performance of the insulation was determined by measuring the rate at which LH2 boiled from an aluminum tank insulated with the test material. The test specimens were approximately 50 mm 2 in. thick. They were structurally scaled so that the test cycle would duplicate the maximum thermal stresses predicted for the thicker insulation of an aircraft liquid hydrogen fuel tank during a typical subsonic flight. The simulated flight cycle of approximately to minutes duration heated the other insulation surface to 316K 110 F and cooled it to 226K 20 F while the inner insulation surface remained at liquid hydrogen temperature of 20K 4230F. Two urethane foam insulations exceeded the initial life goal of 2400 simulated flight cycles and sustained 4400 cycles with only minor damage.

Subject Categories:

  • Transport Aircraft
  • Plastics
  • Air Conditioning, Heating, Lighting and Ventilating
  • Thermodynamics
  • Fuels

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