Two astronauts stepped outside the International Space Station on Thursday for the first of two spacewalks, one week apart, to install a final pair of roll-out solar blankets that will complete a complex, years-long upgrade of the lab’s aging power system.
Floating in the station’s Quest airlock, NASA’s Anil Menon and Canadian Space Agency astronaut Joshua Kutryk switched their suits to battery power at 7:57 a.m. EDT, officially kicking off a planned six-and-a-half-hour spacewalk, the eighth so far this year and the 285th since ISS assembly began in 1998. The excursion began in orbital darkness, prompting Kutryk to observe that “the night is dark and full of wonders.”
The goal of Thursday’s excursion and a follow-on spacewalk scheduled for next week is to complete an overhaul that began in 2021 when the first of eight ISS roll-out solar arrays, or IROSAs, was installed. The IROSAs are smaller than the station’s original solar panels but feature state-of-the-art solar cells that deliver significantly higher efficiency.
Before the first IROSA was installed, the original arrays generated about 152 kilowatts of power. The six IROSAs installed to date have boosted that output to approximately 200 kilowatts. With the final two sets in place, the station will have roughly 215 kilowatts of available power to sustain operations, life-support systems, scientific research, and visiting vehicles through its planned retirement and de-orbiting in 2030.
The final two IROSA units were delivered to the station earlier this month aboard a SpaceX Cargo Dragon capsule, with each folded in half and stowed in the ship’s unpressurized trunk section. The station’s robotic arm, operated remotely by flight controllers at the Johnson Space Center in Houston, pulled the arrays out of the Dragon and stowed them on the left side of the laboratory’s power truss to await installation.
Menon, a veteran of three spacewalks earlier this year, and Kutryk, undertaking his first extra-vehicular activity, planned to mount the seventh IROSA on a previously assembled support fixture at the base of one of the station’s left-side inboard solar wings. The flight plan required Kutryk and Menon to unbolt one of the stowed arrays so Menon, anchored to the end of the station’s 58-foot-long robot arm, could carry it to its mounting point farther outboard along the power truss.
Garrett Hehn, a spacewalk flight director, noted the physical demands of the hardware. The units weigh around 750 pounds in their folded configuration and measure about 10 feet long. Flight controllers devised an elegant series of maneuvers to move Menon and the array on the robot arm by rotating around the actual center of mass of the arrays rather than the crew member, a lesson learned from previous excursions to reduce fatigue.
Once in position, the astronauts planned to mount the IROSA on its support frame, unfold its two halves, and bolt them together. Working while the station is on Earth’s night side when the arrays do not generate power, the spacewalkers intended to make the electrical connections tying the new array into power channel 2A before unrolling the blankets.
The IROSAs deploy much like a reverse tape measure, utilizing built-in stored energy that allows the blankets to unroll without motors or other drive mechanisms. Hehn compared the deployment mechanism to a snap bracelet, explaining that a series of magnets along the sides allows the blankets to roll out steadily over a period of about 10 minutes.
Menon and Kutryk plan to float back outside on November 5 to install the final IROSA on a solar wing at the far right end of the power truss. Because the robot arm lacks the reach to carry Menon and the blankets to the far end of the truss, the astronauts will hand the hardware off to each other in a leapfrog fashion to reach the waiting support frame. Gaurang Patel, a senior manager in NASA’s Low Earth Orbit Program, confirmed that the upcoming November excursion will conclude the station’s major power augmentation upgrades.
