Comparison of a Discontinuity with Various Patch Methods for Multilayer Insulation Blankets
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Multilayer Insulation (MLI) blankets used in passive thermal control for cryogenic and space applications require cutouts, slits, and features in order to conform to the shape of the structure to which they are being applied. These discontinuities negatively affect the thermal performance of the blankets. In an effort to understand what that effect is, testing was performed following the ASTM C740 Standard Guide for Evacuated Reflective Insulation in Cryogenic Service on various MLI blanket configurations placed inside a Cryostat-200 chamber. The inner chamber cold wall temperature was maintained at approximately 78 K using liquid nitrogen as the cooling mechanism, and the outer wall of the vacuum chamber was maintained at 293 K using an external heater. Seven blankets with the same material layup were tested, each containing a distinct form of aperture with the initial test case being an MLI blanket without an aperture. In the second test, a square portion of the blanket was removed from the center of the blanket. This square was then taped back inside of the cutout location for the third test. The remaining four tests were combinations of various patches covering the aperture with the square being either inserted or removed. For each feature, three tests were run at three different pressures ranging from 0.01 mTorr to 1 mTorr (0.0013 Pa to 0.13 Pa), with the pressure increasing by a factor of 10 for each test. This paper compares the various features against one another in an effort to determine the effect different apertures have on the thermal performance of MLI.