THERMAL ANALYSIS OF LOW LAYER DENSITY MULTILAYER INSULATION TEST RESULTS

Investigation of the thermal performance of low layer density multilayer insulations is important for designing long-duration space exploration missions involving the storage of cryogenic propellants. Theoretical calculations show an analytical optimal layer density. However, the appropriate test data by which to evaluate these calculations have been only recently obtained. As part of a recent research project, NASA procured several multilayer insulation test articles for calorimeter testing. These blanket-type test articles were configured to allow a layer density variation from 0.5 to 2.5 layers per millimeter. The coupon testing was completed by the Cryogenics Test Laboratory at Kennedy Space Center using the cylindrical Cryostat-100 apparatus. The results show insulation properties as a function of layer density for multiple points. Overlaying these new results with data from the literature reveals an optimum layer density; however, the value is approximately twice as high as predicted. The data also show that the transition region between high vacuum and no vacuum is dependent on the spacing of the reflective layers. These results aid in the understanding of the performance parameters of MLI and help to complete the body of literature on the topic.