Yesterday I mentioned that astronauts had run into a problem attaching a power unit to the outside of the international space station. The problem was that a bolt had been cross-threaded and astronauts were unable to tighten it to secure the power unit it held to the outside of space station. NASA engineers came up with multiple options to repair the damaged bolt and secure the power unit.
Space station astronauts Sunita Williams and Akihiko Hoshide performed the second space walk yesterday and were expected to spend about 6 1/2 hours working outside the space station to secure the replacement power unit. The pair of astronauts first attempted to install the power unit last week during a space walk that lasted eight hours and 17 minutes. That made it the third longest space walk in history, and the single longest spacewalk performed by the space station crew.
The two astronauts spent the weekend getting ready for their space walk and preparing custom-made tools used to clean and lubricate the bolts and the receptacles the bolts going to on the space station's main truss. This main truss is sort of like the backbone for the entire space station. The astronauts had 15 pages of options and procedures to choose from in the repair of the stripped bolts.
If the second spacewalk is unable to properly attach the power unit the outside of the space station, the astronauts were going to remove the replacement power unit and bring it inside for more study. The astronauts had to be able to turn the bolt 15 turns to secure the power unit, and the defective bolt has so far only turned nine times.