Spacewalkers Thomas Pesquet and Shane Kimbrough floated back outside the International Space Station Sunday for a second attempt to deploy a balky roll-out solar array. A third excursion is on tap Friday to attach and unfurl a second blanket.
Floating in the Quest airlock, Pesquet, call sign EV-1, and Kimbrough, EV-2, switched their spacesuits to battery power at 7:42 a.m. EDT to officially begin the year’s eighth spacewalk, the 240th devoted to station assembly and maintenance since construction began in 1998.
For identification, Pesquet, a European Space Agency astronaut, is wearing a suit with red stripes and using helmet camera 20. Kimbrough is using an unmarked suit with helmet camera 22. Both astronauts also are equipped with high-definition cameras.
Kimbrough had problems with his spacesuit’s data display module and temperature-controlling sublimator when he and Pesquet made their initial attempt to install the new array last Wednesday. For Sunday’s outing, he is wearing a different suit, serial number 3015.
The new ISS roll-out solar arrays — iROSAs — are the first two of six being added to the station to offset age-related degradation of the lab’s original eight solar wings, boosting overall power output back to factory-fresh settings.
The new arrays will not replace the originals. Rather, they were designed to be mounted just in front of six of the eight original wings, tilted out about 10 degrees. While the new panels will shade a large portion of the underlying solar cells, their combined output will equal or exceed the original’s when it was new.
Each iROSA unit is made up of two blankets rolled up on spools that were folded on top of each other for launch. Before an iROSA blanket can be unrolled, the two spools must be rotated open on hinges and locked in place.
Clamps can then be released, allowing the blankets to unroll on their own, stretching out to a full 63 feet between two carbon-composite supports.
During Wednesday’s spacewalk, the first iROSA blanket was moved out to the far left end of the station’s port 6, or P6, power truss where the lab’s two oldest solar wings — P6/2B and P6/4B — are mounted.
The astronauts got first iROSA onto the P6/2B mounting fixture, but they were unable to unfold the two halves because of a mechanical interference issue.
After troubleshooting, NASA managers opted to make another attempt Sunday and to add a third, unplanned spacewalk Friday to install the second iROSA blanket on the P6/4B solar wing. The original plan called for installing the second blanket Sunday.
Assuming they get the first array deployed, Pesquet and Kimbrough will prepare the second iROSA for release from its carrier and carry out a few other “get-ahead” tasks if time is available.