A team of scientists at Florida State University’s High Performance Materials Institute is using advanced nanomaterials to produce lightweight heat shields that can withstand the heat of hypersonic flight. The new experimental housing is based on a carbon nanotube sheet called buckypaper, which can be made into a very thin and flexible epidermis that can be applied to the fuselage of supersonic aircraft to provide protection and support.
For aircraft and spacecraft operating in the atmosphere at five times the speed of sound, a heat shield must be provided to avoid serious damage. This is especially true when many aerospace designs increasingly rely on carbon composites that provide strength and lightness but are susceptible to high temperatures.
Since the 1950s, heat shields made of phenolic plastic sit, known as ablation heat shields, are layered to protect returning spacecraft by layering combustion and taking away excess heat. Unfortunately, these housings are bulky, inflexible and must be replaced after one use. In the 1970s, the U.S. space shuttle used a ceramic heat shield that absorbed and reradiated heat to protect the spacecraft. These ceramic layers can be reused, but they are still large, hard and fragile.
As an alternative, the Florida State Research Group is working on a cloth paper made from pressing carbon nanotubes, a tubular carbon molecule 50,000 times thinner than a human hair, into thin sheets. When compressed into multiple layers, paper weighs 10 times lighter than steel, but is 500 times stronger.
The heat shield needs to be soaked in phenolic resin to form a lightweight material. It is very thin, but very strong, can help support the structure of the aircraft. During the flame test, the Baki paper sample, while maintaining maximum strength and flexibility, can smoothly distribute heat from the base below the shield at temperatures up to 1900 degrees C (3450 degrees F).