Sen—The Expedition 32 crew aboard the International Space Station are set to undergo their second spacewalk in less than a week, as they were unable to complete their objectives during the previous spacewalk.
Flight Engineers Suni Williams and Aki Hoshide will begin their trek outside the space station on Wednesday (September 5) at 11:15 UTC in order to finish installing a spare Main Bus Switching Unit (MBSU). The MBSU is responsible for relaying power from the space station’s solar panels to systems onboard the orbiting outpost.
The first attempt at installing the MBSU was made on August 30 in an 8 hour and 17 minute spacewalk, making it the third longest spacewalk in history. It was the first spacewalk for Hoshide and the fifth for Williams.
JAXA astronaut Aki Hoshide during a spacewalk on 30 August 2012. Credit: NASA
Williams and Hoshide removed the old unit but had trouble securing the bolts of the replacement unit in the s-zero truss. A long-duration tie-down tether was used to temporarily secure the MBSU until Wednesday's spacewalk.
Since the problem occurred last Thursday, engineers at NASA's Johnson Space Center in Houston have been trying to decipher what exactly went wrong with the power unit's installation. They concluded that the new unit was misaligned before the bolting process was attempted. They also think that there could have been thread damage on the receptacle posts on the S-zero truss.
The flight engineers spent the weekend preparing for the spacewalk, which will be the third spacewalk of Expedition 32. Williams and Hoshide revised the procedures they will need, as well as configuring the Quest airlock for the next spacewalk. Flight engineer Joe Acaba, who will remain inside the station, also assisted by reviewing the robotics choreography.
This spacewalk will last 6.5 hours, however if problems still persist with the MBSU installation after 4 hours, then Williams and Hoshide will bring the unit back inside the space station for further troubleshooting.
The Expedition 32 crew consists of three Russian cosmonauts - commander Gennady Padalka, Sergei Revin and Yuri Malenchenko, JAXA astronaut Aki Hoshide and NASA flight engineers Joe Acaba and Sunita Williams.