Research and Technology | NASA Glenn Research Center

As part of the Crew Exploration Vehicle (CEV) Thermal Protection System (TPS) Advanced Development Project (ADP), researchers from the Tribology & Mechanical Components Branch Seal Team developed and evaluated a sealing system for the interface between the heat shield and the back-shell on Orion.

This effort included formulation of a design for the sealing system and subsequent testing of the seals at representative operating conditions. Compression, leakage, bond integrity, and thermal exposure tests were performed by the team on sub-scale seals at NASA Glenn Research Center.

Glenn also conducted extensive arc jet tests at NASA Ames Research Center using a unique test fixture that simulated reentry heating conditions on the interface. These tests demonstrated the ability of the GRC seals to prevent ingress of hot re-entry gases into the heat shield to the back-shell interface.

For their contributions and commitments in leading this effort at GRC, Bruce Steinetz and Pat Dunlap were honored by the CEV Project Office and CEV TPS ADP during a ceremony on September 10, 2009 at NASA Ames. Dr. Pete Worden, NASA Ames Center Director, presented the awards.

U.S. Patent No. 7,497,443 (LEW 17,166-1) was issued to Dr. Bruce Steinetz and Mr. Pat Dunlap of the Structures and Materials Division for their invention entitled, “Resilient Flexible Pressure-activated Seal.” The patent describes a structural seal that combines both metal and ceramic materials to achieve greater levels of temperature, resiliency and compliance characteristics relative to conventional formed C-shaped metal seal designs.

Greater compliance and flexibility is achieved by fabricating the C-shape jacket from sheet metal segments fashioned in a “comb-like” structure and “nested” together. Internal and external laminates are indexed to “cover” and therefore seal the gaps of the adjacent layer. Added flexibility is desired to seal variable gaps that may occur between adjacent structures due to either mechanical or thermal loads. The opening of the “C-shape” is positioned toward the high pressure zone allowing the pressure to aid in seating and therefore sealing the seal against the sealing surfaces.

For higher temperature applications, the open cavity of the “C-shape” is filled with either simple ceramic insulation or braided/woven textile structures fashioned of high temperature ceramic fibers to insulate the metal segments from the high temperature gas. Combining the insulating element with the metal seal element allows higher operating temperatures for the metal seal than otherwise would be possible.

Applications of this seal include high temperature structural joints in either aerospace structures (airframes, propulsion systems) or industrial components (furnaces, other) requiring high temperature seals. This work was originally funded by NASA’s Next Generation Launch Technology Project (NGLT).

On November 20, astronauts Heidemarie Stefanyshyn-Piper and Shane Kimbrough conducted what is most likely the world’s most extreme lube job, greasing the Canada Arm’s Latching End Effector (LEE) and the failed starboard Solar Alpha Rotary Joint (SARJ). Both of these mechanisms began to fail when their original solid lubricants unexpectedly wore out. Since solid lubricants cannot readily be replenished, the on-orbit addition of grease was seen as the best recovery plan.

In late 2006, Drs. Christopher DellaCorte and Phillip Abel consulted with the Canadian Space Agency (CSA) to help them troubleshoot sticking cable end bearings observed on the LEE. Lab tests confirmed that the addition of grease to the SARJ contact surfaces reduced friction and was a viable recovery option. Coincidentally, both the LEE and the SARJ were greased during the same EVA.