The Aerogel-Based Super-Insulation was developed by Aspen
Systems, Inc., of Marlborough, Massachusetts. This technology was developed
under a NASA Small Business Innovation Research (SBIR) contract for KSC.
This superinsulation is an innovative, flexible cryogenic insulation with
extremely low thermal conductivity. The design of this product takes advantage
of the low thermal conductivity of the ultralow-density aerogels (ULDAís)
and incorporates a flexible, durable matrix to maximize applicability.
The core of the superinsulation technology is aerogels formed at the fiber-fiber
contacts, forcing solid heat transfer to occur through the aerogels. This
configuration both improves the ease of handling aerogels and reduces the
heat transfer rate through the fiber materials. The close-packed structure
of aerogels also eliminates the open structures in the fiber matrix and,
thereby, minimizes convection heat transfer. Therefore, improved thermal
resistance can be achieved for both evacuated and nonevacuated systems
while maintaining good flexibility. In addition, by producing the aerogels
in an opacified fiber matrix, the structure also significantly inhibits
radiation heat transfer in the infrared range. This technology can be easily
adapted to a broad range of commercial applications.
The basic form of the super-insulation system is a blanket composed
of aerogel-based radiation shield layers and low thermal conductivity aerogel/fiber
matrix composites. The final product can be a blanket, sheet, sleeve, or
clamshell unit, depending on the application (see the photograph). The
blanket alone can be employed as an alternative to multilayer insulation
or perlite powder in vacuum-jacketed systems. The configurations of the
sheet and sleeve units are similar to the blanket but add outer skin and
backing material. The outer skin provides (1) a weather barrier to prevent
condensation of moisture or air, (2) safety and strength during handling
and installation, and (3) durability for protection from harsh environments.
The configuration of the clamshell unit is similar to that of the sheet
or sleeve but is custom-sized to piping, pipe flange, or piping components
(see the drawing). In this case, the superinsulation can be relatively
rigid (not brittle) for insulating simple objects such as piping or can
be flexible for insulating complex-shaped objects.
The thermal performance of the aerogel-based superinsulation has been
measured by both transient heat flux and liquid nitrogen boiloff methods.
The apparent thermal conductivity of the plain blanket super-insulation
is lower than 1 milliwatt per meter-kelvin (R-value per inch greater than
140) at high vacuum (below 10E-5 torr) with cold and warm boundary temperatures
of 77 and 280 kelvin. Most importantly, the thermal conductivity has been
shown to be insensitive to residual gas pressure up to a vacuum level of
10E-1 torr. The thermal conductivity in ambient pressure nitrogen is below
10 milliwatts per meter-kelvin (R-value per inch greater than 14).
Currently, Aspen Systems is producing aerogel thermal insulation
products for a variety of customers. Prototype super-insulation systems
are being field tested at KSC.
KSC
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