The nose cap and wing leading edge of the space shuttle orbiter are the hottest surfaces on the spacecraft during re-entry. It is critical that these components maintain their integrity and proper thermal protection properties to ensure the safety of the spacecraft.

NASA’s Glenn Research Center is playing a vital role in understanding the chemistry of this material at high temperatures. Glenn’s Structures and Materials Division is partnering with Johnson Space Center, Kennedy Space Center, Langley Research Center, and Lockheed Martin (Dallas) on this effort.

Schematic of RCC showing carbon/carbon structure, SiC conversion coating and glass sealants (Credit: R. Czentorycki/NASA Glenn).

Reinforced Carbon-Carbon (RCC) is a carbon/carbon structure that is composed of silicon carbide (SiC) and a protective sealant for oxidation protection, as shown in the image below. Researchers at Glenn are examining the structure of RCC that has been exposed to space as well as a laboratory furnace to understand the various chemical reactions in RCC during re-entry. The goal of the current studies is to:

1. Understand the effects of the refurbishment process, which occurs after every 12-18 missions to repair coating pinholes and replace the sealant.
   
2. Understand the observed loss of sealant, which could be caused by shear forces and vaporization during re-entry and by the penetration of sealant into the RCC sub-layer. Several previous studies have developed empirical, predictive models. Glenn’s team is critically analyzing the physics behind the sealant loss.
   
3. Understand the effects of chemical reactions on the SiC coating adherence.