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Space station upgrades
During the second space walk, which lasted for almost seven hours, astronauts Michael E. Fossum (center) and Piers J. Sellers (you can see his backpack right) repaired the Mobile Transporter rail car and delivered a spare pump module for the International Space Station.
Astronauts Piers Sellers and Mike Fossum took a third space walk on Wednesday to test procedures for emergency repairs. The two took infrared video to see if damage within the shuttle's reinforced carbon panels could be detected.
Applying sealant with putty knife
The space shuttle brought damaged panels to see if astronauts could repair them in orbit using a substance called NOAX--a pre-ceramic polymer sealant containing carbon-silicon carbide powder. Their tools, a caulk gun and spatulas.