Modeling and experimental study on combination of foam and variable density multilayer insulation for cryogen storage

A combination of polyurethane foam and multilayer insulation is adaptive and qualified for cryogenic propellant storage application, both on orbit for long-duration mission and on earth before and during launching. A generalized layer by layer model has been proposed to predict the thermal performance of the “Foam - Variable Density Multilayer Insulation combination” (FMLI) at different vacuum levels. A cryogen boil-off calorimeter system was designed and fabricated to measure the temperature profile and the apparent thermal conductivity of FMLI samples over a wide range of vacuum level (10−3 - 105 Pa). The experimental data verified the validity of the model and indicated that the heat fluxes through the FMLI and the single VDMLI almost made no difference in vacuum of 10−3 Pa, which were both equal to 0.23 W·m−2 with the boundary temperatures of 77 and 293 K, respectively. However, at the atmosphere level of 105 Pa, the heat fluxes through the FMLI and the single VDMLI significantly differed from each other and exacerbated to 45.2 and 147.8 W·m−2, respectively. In addition, a comparison between FMLI and Aerogel-MLI was also conducted for the same thickness and weight of VDMLI and at the same boundary temperatures and vacuum levels.