ISS Crew Will Have to Manage Power Usage While Devising Fix for Bolt Problem

The six-person crew aboard the International Space Station (ISS) will have to manage how it uses electrical power for an indeterminate period of time while ground-based experts determine how to fix a recalcitrant bolt that thwarted a repair operation today.

NASA astronaut Suni Williams and Japanese astronaut Aki Hoshide had three main tasks plus one “get ahead” assignment when they began their spacewalk this morning at 7:16 am CT (8:16 am ET).   By the end of their near record-setting venture of 8 hours and 17 minutes, they had completed only one and a half of those tasks.  The problem was a bolt they could not drive into a box containing a replacement Main System Bus Unit (MSBU) that connects the ISS’s solar arrays with the station’s electric distribution system.

There are eight solar arrays, two connected through each of four MSBUs.   With one MSBU out of commission, the three Russians, two Americans and one Japanese aboard will have to be careful about what systems they have running at any one time.

Williams and Hoshide succeeded in removing the faulty MSBU, which had been supplying power, but could not be commanded.   When the astronauts went to install the new one, however, they were unable to drive one of two bolts into the assemby that secures the MSBU to the station.  

Japanese astronaut Aki Hoshide at the end of the space station’s robotic arm during today’s spacewalk.

Photo credit:  NASA TV.

During a late afternoon press conference after the astronauts were safely back inside the space station, ISS program manager Mike Sufferdini praised them and their ground-based colleagues for trying a number of work-arounds.  In the end, however, the astronauts had to secure the replacement to the ISS with a long duration tie-down strap until a solution is devised.

A timeline for another attempt is up in the air, but Sufferdini said ideally it would occur while NASA astronaut Joe Acaba is still onboard.  He is scheduled to return to Earth on September 16 (Houston time) along with two of the Russian cosmonauts.   He worked closely with Williams and Hoshide from inside the ISS today — operating the robotic arm — so keeping that team together for a second attempt will save crew time, Sufferdini said.   First, however, the technical experts will have to determine what to do.  He said hopefully another EVA could take place next week, but could not make any commitment.

Williams and Hoshide did succeed in one of their tasks:  re-routing cables associated with a Russian module that will be launched next year.  They were not able to replace a camera on Canadarm2 or perform a “get ahead” task of placing a cover on the docking port that previously was used for the space shuttle.