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Hybrid Multifoil Aerogel Thermal Insulation

Aerogel used in place of astroquartz makes lighter, more efficient insulation.

This innovation blends the merits of multifoil insulation (MFI) with aerogel-based insulation to develop a highly versatile, ultra-low thermally conductive material called hybrid multifoil aerogel thermal insulation (HyMATI). The density of the opacified aerogel is 240 mg/cm3 and has thermal conductivity in the 20 mW/mK range in high vacuum and 25 mW/mK in 1 atmosphere of gas (such as argon) up to 800 ºC. It is stable up to 1,000 ºC. This is equal to commercially available high-temperature thermal insulation. The thermal conductivity of the aerogel is 36 percent lower compared to several commercially available insulations when tested in 1 atmosphere of argon gas up to 800 ºC.

HyMATI Blends Multiple Layers of Foil Separated by Fiber Reinforced, Opacified Aerogel. Fabrication consists of: (a) stacking alternating layers of reflective metal foil and high purity quartz fiber, (b)applying slight pressure to the stack to control the spacing between metal foil layers, and (c) permeating the liquid aerogel precursor into the stack, followed by solidification and supercritical drying.
Layers of metal foil block infrared radiation (IR), which are separated by thin (100–1,000-micron) layers of opacified aerogel (see figure) The aerogel further reduces IR transport and, more importantly, significantly reduces gas and solid conduction when compared to the astroquartz used in heritage MFI (that used 7.6-micron thick molybdenum foil separated by ≈90-micron thick astroquartz with 60 layers of each forming a stack 1.7 cm thick). By replacing the astroquartz with JPL-developed aerogel, the overall mass of MFI is reduced by 36 percent. Further reductions in mass may also be had by selecting lower density metal foils, such as titanium, zirconium, or reflective Grafoil®. In addition to mass reduction benefits, HyMATI is a tunable insulation that can be tailored for use in various temperature ranges up to 1,000 ºC, and can be considered for use in space vacuum, with a cover gas such as argon or xenon or on other planets with atmosphere.

By replacing heritage MFI with aerogel, the HyMATI will reduce the mass of future RPS (radioisotope power systems) technology. Also, the aerogel has the lowest gas conductivity of any material in its class, enabling RPS operation in vacuum, cover gas, or atmosphere. This means enabling a single RPS design for all NASA missions requiring RPS as opposed to current situations where NASA has a Multi-Mission RTG (for Mars Science Laboratory, for example) and GPHS-RTG (General-Purpose Heat Source-Radioisorope Thermoelectric Generator) for deep-space exploration.

This work was done by Jeffrey Sakamoto, Jong-Ah Paik, Steven Jones, and Bill Nesmith of Caltech for NASA’s Jet Propulsion Laboratory.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, NASA Management Office–JPL. Refer to NPO-45219.