Robotics work clears way for Friday spacewalk
On Friday, NASA astronauts Shane Kimbrough and Peggy Whitson will venture outside the 400-metric-ton International Space Station (ISS) on the first of two spacewalks to begin a multi-year process of upgrading the outpost’s power system.
The spacewalk, Extravehicular Activity (EVA) 38, will see the two Expedition 50 astronauts install battery adapter plates and help with the swap-out of old nickel-hydrogen batteries with new lighter and more efficient lithium ion units.
Six of the new batteries arrived in early December 2016 inside the Exposed Pallet (EP) of the unpressurized section of the Japanese Kounotori 6 spacecraft. Less than a week ago, on New Year’s Eve, ground-based robotics teams used the robotic Canadarm2 in tandem with the Special Purpose Dexterous Manipulator, also known as Dextre, to begin unbolting and moving some of the nickel-hydrogen batteries that need to be replaced.
Using Canadarm2 and Dextre to move the batteries around has actually reduced the number of required spacewalks for this task from six to two.
“When you go out EVA, you only have so much time to go out and we never have enough time to do all the things that we’d like to do,” said Kenneth Todd, ISS operations manager. “So if we can partner with the robotics [in any] capability, that’s the best solution for the entire program. It allows us to do the things with EVAs that we absolutely don’t have a choice to do [with people], but our goal would be to whittle down that number of things as we move forward in the program.”
The space station’s truss assembly, with its eight large Solar Array Wings (SAWs), contain eight power channels, one for each SAW. Each channel has three strings of batteries with each battery string containing two nickel-hydrogen units in series.
One lithium-ion battery, as well as an adapter plate, will replace two nickel-hydrogen units. A data link cable will connect the plate and lithium battery. Additionally, the top of the adapter plate can be used to store an old and depleted nickel-hydrogen battery.
Friday’s EVA will focus on the station’s 3A power channel Integrated Electronics Assembly (IEA) pallet on the Starboard 4 (S4) truss. Four nickel-hydrogen batteries were moved by Dextre last week to make way for three lithium-ion units. Three were placed on the EP by the robotics team, while the fourth was temporarily stowed on a platform attached to Dextre.
Three of the six lithium-ion batteries were then placed by Dextre in slots on the 3A IEA.
The robotic operation went almost perfectly. The only problem came when a bolt on a battery on the opposite side of the S4 truss, on the 1A channel, did not perform as expected. In one of the last acts of EVA-38, Kimbrough will finish that process to make way for robotics operations in advance of EVA-39 next Friday.
This Friday’s EVA, which will be the 196th in assistance of space station assembly and maintenance for the U.S. orbital segment, is slated to begin at 6:10 a.m. EST (11:10 GMT) Jan. 6, 2017.
Kimbrough, who is also the Expedition 50 commander, will be the lead spacewalker, EV-1. It will be his 3rd spacewalk, while Whitson will be on her 7th. Inside the ISS, the spacewalking duo will be assisted by Flight Engineers Thomas Pesquet of the European Space Agency and Oleg Novitskiy of Roscosmos.
Once Kimbrough and Whitson leave the Quest airlock, they will translate to an equipment cart on the starboard end of the S1 truss segment.
Kimbrough will grab a foot restraint and install it on the S4 truss. He will then travel back to the equipment cart and meet up with Whitson at the Mobile Base Unit, where the EP is currently being stored. They will each grab an adapter plate, connect it to their respective suit tethers and both move to the S4 truss.
When Kimbrough gets into his foot restraint, Whitson will hand him her plate to install next to a lithium-ion battery. He’ll drive two bolts and then attached a data cable from the battery to the plate.
Next Kimbrough will move a nickel-hydrogen battery to the adapter plate for storage. In its place, he’ll install his adapter plate and connect its data cable the same way as the first.
Afterward, both Kimbrough and Whitson will travel back to the EP to grab the third and last adapter for this EVA. While there, the duo will clean up the work area.
Once back at the IEA, in a similar process, the third adapter will be installed with its data cable. Kimbrough will then travel to the opposite side of the truss where the 1A channel IEA is located to drive the bolt that the robotics team had trouble with before both he and Whitson move back to the airlock.
At the end of the spacewalk, ground teams will remotely power up the batteries and verify that all is functioning properly before moving channel 3A back to a nominal configuration where it is supporting its own electrical loads again.
Sometime next week, a second round of ground-controlled robotics will prepare the 1A channel for similar EVA work on Jan. 13, 2017. This time, five nickel-hydrogen batteries will be removed and the final three lithium-ion batteries of the six brought up last month will be installed.
Once both spacewalks are finished, the EP, with nine of the 12 replaced nickel-hydrogen batteries, will be moved back into the unpressurized section of the Kounotori cargo ship in advance of it leaving the outpost.
These EVAs mark a busy next few months. On Jan. 27, the Kounotori 6 spacecraft will be unberthed before leaving the vicinity of the ISS to conduct its own post-unberthing mission to test new technologies. A couple days later, on Jan. 31, Progress MS-03 will undock and perform a destructive re-entry over the south Pacific Ocean.
Possibly as early as Feb. 8, SpaceX‘s CRS-10 Dragon capsule will launch from Kennedy Space Center’s Launch Complex 39A. The cargo ship is expected to remain attached for about one month before Orbital ATK’s Cygnus launches in March 2017.
On the Russian side, Roscosmos is still working on figuring out an exact cause of the Soyuz-U rocket failure that resulted in the loss of Progress MS-04 back on Dec. 1, 2016. Only when that investigation is complete will finalized dates for the Progress MS-05 and the crewed Soyuz MS-04 be announced.
Video courtesy of NASA
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a blog about the International Space Station, called Orbital Velocity.