Keywords:&nbsp;thermal insulation, Multilayer insulation blanket (MLI), silica aerogel, thermal conductivity,&nbsp;effective thermal conductance&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Multilayer insulation blanket (MLI) is&nbsp;one&nbsp;of the most common reliable passive thermal-control&nbsp;materials&nbsp;for&nbsp;spacecraft. It prevents both excessive heat loss from spacecraft hardware and excessive heating from environmental fluxes, rocket plumes, and other sources. Existing MLIs are typically composed of layers of high-reflectivity thin films with&nbsp;low-thermal-conductivity polyester netting or fiberglass paper as&nbsp;spacers.&nbsp;Radiation, solid conduction, and gaseous conduction, these three modes of heat transfer can be greatly minimized through the composition. Compared with other insulation systems, heat leak values for properly designed and well-executed MLI systems can be greatly reduced in high vacuum under same conditions. However, conventional MLI loses most of its insulating capability at pressures greater than 10-6 Pa.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; In&nbsp;this&nbsp;work,&nbsp;a new kind of MLI was developed with&nbsp;metalized polymer layers separated by silica&nbsp;aerogel&nbsp;sheets.&nbsp;Due&nbsp;to&nbsp;nanoporous structures of aerogel spacers, heat transfer is effectively suppressed&nbsp;inside MLI. A set of MLI configurations were designed and prepared by varying the layer thickness or layer numbers.&nbsp;Its effective&nbsp;thermal conductance keff&nbsp;has been calculated analytically, based on the average temperature difference between the MLI external and internal temperature measured at different boundary temperatures and cold vacuum pressures by&nbsp;the one-dimensional heat transfer method. With the test data, the correlation of keff was developed. The result shows significant improvement in thermal insulation for this kind of MLI, which can provide broad prospects of application for non-vacuum scenarios and extreme environmental exposure conditions.&nbsp;Reference[1] SCHOLTENS, B. E., et al. Cryogenic thermal performance testing of bulk-fill and aerogel insulation materials. In: AIP conference proceedings. American Institute of Physics, 2008. p. 152-159.[2] Fredrickson,G.O.,et.al.Ranking&nbsp;and&nbsp;Selection&nbsp;Insulation&nbsp;Systems&nbsp;for&nbsp;MNV&nbsp;Application, Special&nbsp;Report&nbsp;No. 1, Investigation&nbsp;of&nbsp;High-Performance&nbsp;Insulation&nbsp;Application&nbsp;Problems, NASA&nbsp;CR-112337, 1969.[3] MIYAKITA, Takeshi, et al. Development of a new multi-layer insulation blanket with non-interlayer-contact spacer for space cryogenic mission. Cryogenics, 2014, 64: 112-120.[4] ZHENG, Jianpeng, et al. Thermodynamic analysis and comparison of four insulation schemes for liquid hydrogen storage tank. Energy Conversion and Management, 2019, 186: 526-534.[5] FESMIRE, J. E.; JOHNSON, W. L. Cylindrical cryogenic calorimeter testing of six types of multilayer insulation systems. Cryogenics, 2018, 89: 58-75.[6] JI, Tingwu, et al. Investigation on thermal performance of high temperature multilayer insulations for hypersonic vehicles under aerodynamic heating condition. Applied thermal engineering, 2014, 70.1: 957-965.

Development of Multilayer Insulation Blanket of Aerogel With Ultra-Low Thermal Conductivity

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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