Spacewalkers resume solar power system upgrade on International Space Station

Astronauts Josh Cassada and Frank Rubio floated outside the International Space Station Saturday to install a third set of roll-out solar array blankets, part of an ongoing power system upgrade, and to isolate damaged circuits in one of the lab’s original arrays.

Floating in the Quest airlock compartment, Cassada and Rubio switched their spacesuits to battery power at 7:16 a.m. ET, officially kicking off a planned seven-hour spacewalk, the 256th devoted to station assembly and maintenance and the 11th so far this year.

For identification, Cassada, call sign EV-1, is wearing a suit with red stripes and using helmet camera No. 22 while Rubio, EV-2 is using an unmarked suit with helmetcam No. 20. Both men are making their second spacewalk.

Frank Rubio, wearing an unmarked spacesuit, and Josh Cassada, wearing a suit with red stripes, prepare to install a new roll-out solar array blanket on the International Space Station, the third of six needed to augment the output of the lab’s aging original-equipment arrays.


The goal of the excursion is to install a new set of ISS Roll-Out Solar Array blankets — IROSAs — that were carried to the space station aboard a SpaceX Dragon cargo ship last month.

The station is equipped with four huge solar wings, two on each end of a truss stretching the length of a football field. The arrays rotate like paddle wheels as the lab flies through space to maximize power generation.

Each of the four wings is made up of two sets of solar cells extending in opposite directions from a central hub. The eight sets of blankets deliver electricity to eight main circuits, or power channels, during daylight to operate the lab’s systems and re-charge batteries. The batteries provide power during orbital darkness.

The first set of original-equipment blankets, located on the left end of the station’s power truss, has been in operation for more than 20 years. Subsequent wings were added in 2006, 2007 and 2009. All of them have suffered degradation from years in the space environment and they do not generate as much power as they did when they were new.

In a $103 million upgrade, NASA is installing the smaller but more-powerful IROSA blankets to augment the output of the lab’s eight older, original-equipment blankets.

Spacewalker Frank Rubio’s helmet camera captures a view along the space station’s solar power truss. Crewmate Josh Cassada is visible at upper left.


The first two IROSA blankets were installed on the left-side outboard arrays — the oldest set on the station — during spacewalks in 2021. Cassada and Rubio planned to install one of the two new IROSAs on a right-side inboard wing to augment power channel 3A.

The second new IROSA will be attached to an inboard left-side array during a December 19 spacewalk to boost power channel 4A. A final set of IROSAs are scheduled for delivery to the station next year.

The IROSAs were tightly rolled up and folded in the middle for launch. After mounting the assembly on previously installed brackets, Cassada and Rubio planned to unfold the 3A IROSA, lock it open and release restraints that will allow the blankets to unfurl to their 60-foot length.

The new blankets were to be connected to the station’s electrical grid during orbital darkness when no power is being generated.

The IROSA blankets, about half the size of the original arrays, are more efficient and will eventually generate an additional 120 kilowatts of power. They were designed to be mounted on brackets at the base of an existing wing, extending outward at a 10-degree angle to minimize the shade they cast on the array below.

“The first two arrays have been performing outstandingly well,” Matt Pickle, development projects senior manager at Boeing, said in a NASA release. “The solar cells are immensely more powerful than previous generations.”

Once all six roll-out arrays are installed, overall power generation will be boosted 20 to 30 percent, roughly matching the output of the original arrays when they were new.

The final two of the six IROSAs currently under contract will be launched next year. It’s not yet known whether NASA will buy two final IROSAs to augment all eight of the station’s original blankets.

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