Derek Richardson
June 15th, 2023
A sixth iROSA is unrolled at the International Space Station during a June 15, 2023, spacewalk. This is one of six new solar arrays added to the space station over the last two years. Credit: NASA
During a pair of spacewalks over the last week, two astronauts completed installing a set of new solar arrays outside the International Space Station.
This was part of a yearslong process of upgrading the outpost’s power system to enable it to have sufficient power-generating capacity through its planned end of life in 2030.
Called an ISS Roll-Out Solar Array, or iROSA, the original plan was for six to be installed over six of eight legacy arrays. The first two pairs were delivered inside SpaceX’s Dragon cargo ship in 2021 and 2022.
The final of the initial sets was delivered to the ISS when CRS-28 cargo Dragon docked to the outpost on June 6, 2023, roughly a day after its launch from Kennedy Space Center in Florida.
The iROSA on the S6 truss being unrolled after its installation was completed. Credit: NASA
Each iROSA was in a cradle that was removed from the trunk and placed on a temporary location on the mobile base system near the starboard side of the outpost’s 356-foot (109-meter) long truss.
It would be up to two members of the seven-person Expedition 69 crew to go outside on two separate spacewalks to install the new devices in their planned locations on the starboard side of the truss.
NASA astronauts Woody Hoburg and Steve Bowen were given the task. They would alternate leadership during the outings with Bowen being the lead spacewalker during June 9’s US. EVA-87 and Hoburg during June 15’s U.S. EVA-88.
Both spacewalks would see the duo work to bring an iROSA to the work area first using the robotic Canadarm2, operated via Emirati astronaut Sultan Al Neyadi on the inside of the space station.
With Hoburg at the end of the arm and holding onto the rolled-up array, Canadarm2 would be maneuvered closer to the work area. Then the duo would pass the array back and forth to “walk” it to the final location.
For the June 9 spacewalk, an iROSA was installed on 1A power channel on the starboard S4 truss. During the June 15 outing, an iROSA was installed on the 1B power channel on the starboard S6 truss.
Each iROSA is 60 feet long by 20 feet wide (18.2 meters long by 6 meters wide) once fully unrolled. They are more advanced and efficient than the existing arrays, thus requiring less solar gathering area. Using a modification mounting kit, they were installed over the existing legacy arrays, which are 112 feet long and 39 feet wide (24 meters long and 12 meters wide).
Video courtesy of NASA
The legacy arrays were launched over the course of several space shuttle missions between 2000 and 2009, each having a roughly 15-year lifespan. Needless to say, the oldest arrays are well past that limit and have begun showing signs of degradation over the years.
With six iROSAs installed, the power capacity of the ISS has increased by about 30%, according to NASA, to about 250 kilowatts of power output. The outpost is currently consuming about 75 to 90 kilowatts.
NASA said it is working with Boeing and Redwire (the company that built the arrays) to ready two more iROSAs for launch in the 2025 time frame. Those would likely go over the remaining two legacy arrays yet to be covered, one on each side of the truss.
The location of all six iROSA devices currently installed at the International Space Station. Credit: NASA
For the June 15 spacewalk — U.S. EVA-88 — the duo was able to complete all their tasks faster than expected and get several get-ahead items done in preparation for future spacewalks.
In total U.S. EVA-87 lasted 6 hours and 3 minutes while U.S. EVA-88 lasted 5 hours and 35 minutes.
Bowen was on his 10th spacewalk, which ties him with former NASA astronauts Michael Lopez-Alegria, Bob Behnken, Peggy Whitson and Christopher Cassidy for the most EVAs by a NASA astronaut. However, his cumulative spacewalking time is 65 hours and 57 minutes, a couple hours shy of Lopez-Alegria’s record, putting him third behind Alegria’s second place rank.
The record for the most spacewalks is former Russian cosmonaut Anatoly Solovyev. He performed 16 spacewalks over his career for a cumulative time of 82 hours, 22 minutes.
For Hoburg, his two career spacewalks bring him to 11 hours and 38 minutes.
So far in 2023, there have been eight spacewalks, six of which have been performed by members of the Expedition 69 crew. There is another spacewalk expected later this month to be conducted by Russian cosmonauts.
Overall for the entire ISS program since 1998, there have been 265 EVAs in support of the outpost’s assembly and maintenance. That totals some 70 days, 3 hours and 27 minutes.
Video courtesy of NASA
Derek Richardson
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 website about human spaceflight called Orbital Velocity. You can find him on twitter @TheSpaceWriter.
