The rubberlike material can take a whole lot of heat before the material starts to degrade. To increase its ability to insulate, silica fillers with high thermal properties are added. The combined material is applied to the damaged site using a 52-pound cylinder tank and a pistol grip gun connected by a hose. The silicon-based rubber and silica fillers are stored separately inside the dispenser until a cartridge of carbon dioxide is popped, pressurizing the dispenser and sending the materials flowing through a static mixer located in the gun. Once the cracks and holes in the tiles have been filled with the material, they will be placed in a sealed container and transported back to Earth in the shuttle's cargo bay and tested in simulated environments at NASA.

Kevin Wells, a NASA engineer and the project's leader, says that in-orbit testing is what's needed for NASA to be confident in the technique and in the astronauts' ability to perform the repair. "We want to make sure the mixing works and that we have addressed all the device's failure modes," he says. "We are intent and have expended a great deal of effort to make sure that we can make hardware that will increase the safety of the shuttle system so we can bring those onboard home safely."