Tech Briefs

Ceramic Adhesive and Methods for On-Orbit Repair of Re-Entry Vehicles

Material can be applied in space to repair damage that requires heat/oxidation protection upon re-entry to Earth’s atmosphere.

This adhesive is capable of repairing damaged leading edge components of re-entry vehicles while in space, and is novel with regard to its ability to be applied in the vacuum of space, and in a microgravity environment. Once applied, the adhesive provides thermal and oxidation protection to the substrate (in this case, reinforced carbon/carbon composites, RCCs) during re-entry of a space vehicle. Although there may be many formulations for repair adhesives, at the time of this reporting, this is the first known adhesive capable of an onorbit repair.

The adhesive is an engineered ceramic material composed of a pre-ceramic polymer and refractory powders in the form of a paste or putty that can be applied to a scratched, cracked, or fractured composite surface, covering and protecting the damaged area. The adhesive is then “cured” with a heat cycle, thereby cross-linking the polymer into a hardened material and bonding it to the substrate. During the heat of re-entry, the material is converted to a ceramic coating that provides thermal and oxidative stability to the repaired area, thus allowing the vehicle to pass safely from space into the upper atmosphere.

Ceramic powders such as SiC, ZrB2 and Y2O3 are combined with allylhydridopolycarbosilane (AHPCS) resin, and are mixed to form a paste adhesive. The material is then applied to the damaged area by brush, spatula, trowel, or other means to fill cracks, gaps, and holes, or used to bond patches onto the damaged area. The material is then cured, in a vacuum, preferably at 250 °F (≈121 °C) for two hours. The re-entry heating of the vehicle at temperatures in excess of 3,000 °F (≈1,650 °C) then converts this material into a ceramic coating.

This invention has demonstrated advantages in resistance to high temperatures, as was demonstrated in more than 100 arc-jet tests in representative environments at NASA. Extensive testing verified oxidation protection for the repaired substrate (RCC), and confirmed that the microstructure of the resulting repair leads to durability and resistance to melting or flow. Its processability and working life in a vacuum was demonstrated by NASA astronauts in glovebox processing studies, as well as on-orbit in the open space shuttle bay. All of these advantages increase the working life of NASA vehicles, as well as improve safety for any crew on a manned vehicle. The adhesive, trademarked NOAX™ or Non-Oxide Adhesive Experimental, flew on all space shuttle missions from Return To Flight (STS-114) until the final flight (STS- 135) as a crack repair material for the leading edges and nose cap of the vehicle. NOAX™ was patented under U.S. Patents 7,628,878 and 7,888,277.

This work was done by James A. Riedell and Timothy E. Easler of ATK COI Ceramics, Inc. for Johnson Space Center.

Title to this invention, covered by U.S. Patent Nos. 7,628,878 and7,888,277, has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457 (f)}. Inquiries concerning licenses for its commercial development should be addressed to:

   ATK COI Ceramics, Inc.
   9617 Distribution Avenue
   San Diego, California, 92121
   Phone No.: (858) 621-5700

MSC-23996-1/5218-1