Integrated MLI: Advanced Thermal Insulation Using Micro-Molding Technology

Current Multilayer Insulation (MLI) technology is over 50 years old, and is typically comprised of 10 to 120 layers of metalized polymer films separated by polyester netting. MLI is the best thermal insulation in a vacuum, and is the insulation of choice for spacecraft and cryogenic system insulation, but has problems relating to density control and performance, application labor, and difficulty covering small and large scales. An innovative concept for improved cryogenic insulation, Integrated MLI, is proposed based on a micro-machined or micro-molded substructure. Thermal conductivity will be lower than conventional MLI, layers would be inherently attached to each other and support one another, construction would be easier, and the vacuum shell could be supported by the IMLI, greatly reducing the mass of the insulation system with vacuum shells used to insulate cryogenic dewars or tanks. An improved insulation should provide lower thermal conductivity, lower specific thermal conductivity, vacuum compatibility, layers inherently attached to each other that support themselves, efficient assembly and provide structural reliability. Recent advances in injection molding has resulted in the ability to mold structures with very small features, comprised of materials with low thermal conductivity and low outgassing. Integrated MLI will consist of small micro-machined or micro-molded structures that support radiation barrier layers, and will offer significant advantages. Preliminary analysis of several potential designs indicates IMLI has a theoretical thermal conductivity less than half that of MLI, allowing improved long term cryogenic propellant storage and spacecraft thermal performance. It may provide improved structural assembly, strength and integrity over current MLI. This proposal is to work on the design, material selection, assembly processes and preliminary physical property testing of a prototype of this innovative new thermal insulation.