Astronauts Thomas Pesquet and Shane Kimbrough floated outside the International Space Station Sunday on a spacewalk to complete deployment and unrolling of a new solar array blanket after encountering spacesuit glitches and an interference issue during a previous excursion Wednesday.
Pesquet and Kimbrough switched their spacesuits to battery power at 7:42 a.m. EDT (1142 GMT) Sunday to begin a planned six-and-a-half hour spacewalk. Pesquet, a European Space Agency astronaut, is designated EV1, or lead spacewalker, and is wearing a suit with red stripes. Kimbrough is where a white spacesuit without any markings.
The astronauts planned to move from the space station’s Quest airlock to the far port, or left, side of the lab’s solar power truss. Once in place, Pesquet and Kimbrough will complete tasks they started during Wednesday’s spacewalk.
The astronauts lost time while ground teams evaluated an issue with the controls and display module on Kimbrough’s suit Wednesday. Then mission control discussed momentary glitch with a sublimator, part of the cooling system on Kimbrough’s suit.
The astronauts continued the spacewalk and moved a new ISS Roll-Out Solar Array, or iROSA, unit from a temporary mounting fixture to the far port side of the station’s truss. Once at the P6 solar array work site, the astronauts attached the iROSA to a mounting fixture installed on preparatory spacewalk earlier this year, then attempted to unfold the unit like a book.
But the astronauts ran into some interference as they tried to unfold the iROSA unit. With Pesquet and Kimbrough already running behind schedule due to the earlier spacesuit issues, mission control called it quits and told the astronauts to head back inside the space station.
The spacewalk Sunday was originally planned to install a second iROSA solar array on the other side of the P6 truss, but now Pesquet and Kimbrough will try to complete the tasks they didn’t accomplish Wednesday.
Kimbrough, a former U.S. Army helicopter pilot making the eighth spacewalk of his career, swapped spacesuits for Sunday’s excursion after the troubles with his suit Wednesday.
The International Space Station has eight power channels, each fed with electrical power generated from one solar array wing extending from the station’s truss backbone. The original solar panels launched on four space shuttle missions from 2000 to 2009.
As expected, the solar panel efficiency has degraded over time. NASA is upgrading the space station’s power system with the new roll-out solar arrays, which will partially cover six of the station’s eight original solar panels.
The first pair of iROSA wings will go on the oldest solar panel module — named P6 — on the far left, or port, side of the space station. They launched to the space station on a SpaceX Cargo Dragon capsule earlier this month. The new solar arrays were supplied to NASA by Boeing, Redwire, and a team of subcontractors.
The roll-out solar arrays will stretch 63 feet long and 20 feet wide (19-by-6 meters), about half the length and half the width of the station’s current solar arrays. Despite their smaller size, each of the new arrays will generate about the same amount of electricity as each of the station’s existing solar panels.
A mounting bracket will plug the new arrays into the station’s power channels and rotary joints, which keep the solar wings pointed at the sun as the spacecraft races around Earth at more than 17,000 mph. The new arrays will be angled 10 degrees from the old solar panels.
On Sunday’s spacewalk, Pesquet and Kimbrough will work to unfold the iROSA solar array on the 2B power channel at the P6 truss segment. The astronauts will drive bolts to secure the array in place, then mate power cables to connect the new array to the space station’s electrical grid.
The cables must be mated when the space station is flying over the night side of the Earth, when the old P6 solar array is not drawing any power. Then the astronauts will release clamps keeping the roll-out solar array spooled in its launch configuration.
The array will unroll using strain energy in the composite booms supporting the solar blanket, eliminating the need for motors to control deployment. The carbon fiber booms are rolled back against their natural shape for storage during launch.
If the astronauts complete their work with the first iROSA unit, they will head back in-board on the truss to prep a second iROSA for attachment to the 4B power channel on the opposite side of the P6 truss during a future spacewalk.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.