External insulator for liquid hydrogen tanks

With optimized insulation thickness, tank temperatures were always below 311 K (100 F). This conclusion indicated that an aluminum tank could be used with an optimized insulation system if desired. The N2 purged systems were always lighter than CO2 purged systems. The lower condensation temperature was the controlling factor. Closed cell foam systems were lightest. Closed cell foams, in spite of their need for protective outer insulation, produced insulation systems which were lighter than systems which allowed cryodeposition. Foam system durability established for TMAX = 316 K (110 F). Tests for a subsonic application established this durability; higher temperature limit foam durability was unknown at this. An increase in foam TMAX from 316 K (110 F) to 450 K (350 F) potentially decreased TPS mass by 25 percent.