14 DAY TRIAL // Today, September 5, NASA TV will broadcast a new extravehicular activity (EVA) taking place outside of the International Space Station (ISS), in low-Earth orbit. The spacewalk is scheduled to begin at around 7:15 am EDT (1115 GMT).
NASA TV coverage will begin at around 6 am EDT (1000 GMT).
This will be the third spacewalk taken by members of the Expedition 31 crew aboard the orbital station. The main goal of this maneuver will be to install a new power unit on the outer hull of the ISS.
This was attempted during an EVA carried out last week, but astronauts from NASA and the Japanese Aerospace Exploration Agency (JAXA) failed to complete all the objectives on their checklists.
A new spacewalk was therefore programmed for today. JAXA astronaut Akihiko Hoshide and NASA astronaut Sunita Williams, both flight engineers with Expedition 31, will go outside the station again, and attempt to finish the job they started last week.
A series of stuck bolts prevented them from replacing a defective power relay box, located on the long truss rod making up the ISS' backbone. During their previous EVA, then spent a total of 8 hours trying to get the job done, even though they were supposed to spend just 6 ½ hours in space.
According to Mission Control, a stubborn bolt stood between the astronauts and their objectives. Located on the main bus switching unit (MBSU), the bolt refused to budge despite attempts to pry it loose. The electrical connections could therefore not be attached to the unit, Space reports.
The four MBSU on the ISS are responsible for centralizing the electricity produced by the massive solar panels on the orbital outpost, and for distributing it across all modules. Now that one of the units is broken, two of the eight panels powering the station are useless.
NASA experts held a meeting yesterday, September 4. They analyzed the MBSU situation, and set up a series of procedures that should theoretically cover all possible scenarios.
“The most probable cause is likely a combination of a slight misalignment in the positioning of the spare unit for its installation prior to bolting and possible damage to the threads of the receptacle posts on the S-zero truss to which the MBSU must be bolted in place,” NASA experts said yesterday.