Technology Transfer

Protective Shuttle Tiles Insulate on Earth

A NEW CONCEPT FOR SPACECRAFT TILES ALSO can be used on Earth to make efficient, vacuum-like insulation for refrigerators, furnaces and automobile catalytic converters. The new material is a composite based on the ceramic fiber tiles on the Space Shuttle to protect the vehicle from the heat generated during reentry into Earth's atmosphere. However, the new tiles have a layer of aerogel, sometimes called "solid smoke," inside the tile's air spaces.

"Solid smoke, or aerogel, works similarly to a chunk of solid vacuum because it prevents air or other gases from transporting heat through the material," said aerogel tile co-inventor Dr. Susan White of Ames Research Center at Moffett Field, California. "It's a great insulator. The aerogel filling the air spaces inside the tiles has such small pore spaces that it traps air inside the tile's air spaces. Microscopically, it would look like clouds of smoke or strings of nano-sized pearls, tangled up. The new aerogel tiles can insulate spacecraft significantly better than today's tiles," she said. A nanometer is a billionth of a meter.

The fibers that form the tiles are mostly a mixture of silica and alumina oxides, according to co-inventor Dr. Daniel Rasky, also of Ames. The spaces inside the untreated spacecraft tiles are less than a millimeter wide.

Aerogel is a porous solid made of silica, alumina, carbon or other materials. Pure aerogel was invented decades ago and has evolved tremendously, becoming lighter, cheaper, safer and easier to manufacture, and it is useful for specialized applications. A pure aerogel can be almost invisible, or so light it nearly vanishes, whereas the aerogel tile composite is heavier because of the strengthening tile matrix.

Pure lightweight aerogel is very fragile and brittle and cannot be easily handled, but spacecraft insulation tiles filled with a layer of aerogel can be cut, machined, drilled, dropped and attached to a surface. The aerogel tile composite was developed to exploit the insulating properties of aerogel's underdemanding operating conditions, which would shatter a pure aerogel.

"The reason the aerogel tile composite will act as a great insulator for keeping freezers cold, or furnaces hot, is that the air flowing through the tile is almost completely blocked by aerogel," White said. "It is like having a chunk of solid vacuum where you need it."

Aerogel tiles can be machined into different shapes for many uses here on Earth. The aerogel space tile material could be used in commercial products that require mechanically tough superinsulation. In addition, the new material potentially could be used for furnaces, automobile catalytic converters, liquefied gas transport trucks, and liquid carbon dioxide, special nitrogen, and oxygen containers.

The new aerogel tiles also could be used to insulate future spacecraft fuel tanks. Not only will the aerogel tiles protect future spacecraft from very high reentry temperatures, the materials also will better protect spacecraft from ice formed on the extremely cold fuel tanks when the vehicle is waiting on the pad for launch.

High-temperature and environmental testing of aerogel space tiles was conducted at Ames for seven years. A patent is pending for the new material.

For more information, contact Technology Access Services at the
National Technology Transfer Center. Call: 800/678-6882.
Or contact Dr. Susan White at Ames Research Center.
Call: 650/604-6617, E-mail: swhite@mail.arc.nasa.gov
Please mention you read about it in Innovation.

The lightweight, brittle material from these cylinders fills air pockets in Space Shuttle tiles, serving as insulation. Aerogel that fills tiles can be manipulated for use in many commercial products.