It’s the summer of new solar power on the International Space Station.
Astronauts Shane Kimbrough of NASA and Thomas Pesquet of the European Space Agency conducted their third spacewalk in just over a week and installed a second new solar array outside the space station on Friday.
The astronauts began their walk at 7:52 a.m. ET and after six hours and 13 minutes, the astronauts successfully installed and deployed the second array. Coverage was streamed on NASA’s TV channel and website, and began at 6:30 a.m. ET.
“The two space walkers executed today’s activities in flawless fashion,” said Rob Navias, NASA public affairs officer.
The entire spacewalk lasted 6 hours and 45 minutes and concluded at 2:37 p.m. ET.
A total of six solar arrays will be installed on the ISS, with the next pair arriving on a future Space X cargo flight, according to Navias.
Pesquet wore red stripes on his spacesuit as extravehicular crew member 1, and Kimbrough wore the suit without stripes as extravehicular crew member 2.
During the spacewalk, Pesquet was attached to the end of the robotic Canadarm2, which he used to grab the solar array. Inside the space station, astronaut Megan McArthur maneuvered the robotic arm and Pesquet to the location where the array will be installed.
It’s Pesquet’s fifth and Kimbrough’s ninth spacewalk overall, and their fifth together as a team. And this is the 241st spacewalk to support the assembly, maintenance and upgrading of the space station.
The duo attempted to install the first solar array last Wednesday and ran into technical issues before finishing the job. But on Sunday, they successfully installed the first Roll-Out Solar Array, called iROSA, bolted it into place and connected cables to the station’s power supply.
The solar arrays arrived at the space station on June 5 after launching on the 22nd SpaceX Dragon cargo resupply mission. The arrays were rolled up like carpet and are 750 pounds (340 kilograms) and 10 feet (3 meters) wide.
Once the array is unfurled and bolted into place by the astronauts, it will be about 63 feet (19 meters) long and 20 feet (6 meters) wide. This unfurling process takes about six minutes.
While the original solar arrays on the space station are still functioning, they have been supplying power there for more than 20 years and are showing some signs of wear after long-term exposure to the space environment. The arrays were originally designed to last 15 years.
Erosion can be caused by thruster plumes, which come from both the station’s thrusters as well as the crew and cargo vehicles that come and go from the station, said Dana Weigel, deputy manager of the International Space Station Program.
“The other factor that affects our solar arrays is micrometeorite debris. The arrays are made of a lot of small power strings, and over time those power strings can degrade if they’re hit by debris,” she said.
The new solar arrays are being placed in front of the original ones. This will increase the space station’s total available power from 160 kilowatts to 215 kilowatts. It’s also a good test for the new solar arrays, because this same design will power parts of the Gateway lunar outpost, which will help humans return to the moon through NASA’s Artemis program in 2024.
“The exposed portion of the old arrays will still be generating power in parallel with the new arrays, but those new arrays have solar cells on them that are more efficient than our original cells,” Weigel said. “They have a higher energy density and together in combination may generate more power than what our original array, when it was new, did on its own.”
The new arrays will have a similar 15-year expected life span. However, since the degradation on the original arrays was expected to be worse, the team will monitor the new arrays to test their true longevity, because they may last longer.