Polymeric foams insulate External Tank (Credit: NASA).

In an effort to further improve the Space Shuttle’s safety and reliability, NASA’s Glenn Research Center successfully completed an External Tank Foam Thermal Structure Analysis. The Mechanics and Lifing Branch within the Materials and Structures Division at Glenn analyzed the cellular composition and behavior of the foam using a unique type of modeling.

Modeled section of foam unit cell (Credit: NASA).

Glenn’s research analysis team partnered with Marshall Space Flight Center on this project, which began in January 2005. They received contractor support from several companies including OAI, QSS and Lockheed Martin (MAF).

The foam covering the external tank is used to maintain the temperature of the cryogenic fuels stored inside. At the cellular level, each foam cell is comprised of an outer shell made of a polymer and the gas inside the shell. As the temperature of the shuttle and its external tank fluctuates, the polymer shell and gas expand at different rates and react to each other’s movements.

Glenn performed unique modeling using a physics-based, micromechanics model. This model uses an idealized presentation of the foam cell. A section of the cell is modeled using a series of beams to represent the edges of the cells. Using a combination of microstructural dimensions and physical and mechanical measurements as input, the equations for the deformation and strength of the foam were predicted.

Tear in the wall of a foam cell (Credit: NASA).

Glenn’s foam analysis work directly benefits the shuttle program by improving the reliability and safety of the external tank’s function and reducing the amount of foam debris that may be generated. The results of this work may have extended application to other areas of space research involving thermal protection systems. Also, the automotive industry or any other company working with foam material for thermal or sound insulation may benefit from Glenn’s detailed research.