A third and final spacewalk to demonstrate shuttle repair techniques was carried out by Sellers and Fossum. Repairs were done on pre-damaged samples of heat shield materials brought into space on a special pallet in the payload bay of the shuttle. The repairs were expected to work best when the material has been warm and is cooling, so the actions were carefully coordinated by mission control with regard to exposure of the samples to sunlight. While the procedures, and NOAX (Non-Oxide Adhesive Experimental) material had been tested in a vacuum on Earth, the zero-G tests were required because of offgassing from the material and the potential for bubbles to form that could weaken the structure of the repair.