Nanoporous silica thermal insulation for space shuttle cryogenic tanks:
A case study
David A. Noever*
NASA Marshall Space Flight Center
Mail Stop SD48, Huntsville, AL 35812
This is an abstract
for a presentation given at the
Seventh
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
Nanoporous silica (with typical 10-50 nm porous radii) has been benchmarked for thermal insulators capable of maintaining a 150 K/cm temperature gradient. For cryogenic use in aerospace applications, the combined features for low-density, high thermal insulation factors, and low temperature compatibility are demonstrated in a prototype sandwich structure between two propulsion tanks. Theoretical modelling based on a nanoscale fractal structure suggest that the thermal conductivity scales proportionally (exponent, 1.7) with the material density--lower density increases the thermal insulation rating. Computer simulations, however, support the optimization tradeoff between material strength (Young moduli, proportional to density with exponent, 3.7), the characteristic (colloidal silica, <5 nm) particle size, and the thermal rating. The results of these simulations indicate that as nanosized particles are incorporated into the silica backbone, the resulting physical properties will be tailored by the smallest characteristic length and their fractal interconnections (dimension and fractal size). The application specifies a prototype panel which takes advantage of the processing flexibility inherent in sol-gel chemistry.
*Corresponding Address:
David A. Noever
NASA Marshall Space Flight Center
Mail Stop SD48, Huntsville, AL 35812
Phone: 256-544-7783; Fax: 256-544-2102
E-mail: [email protected]
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