Astronauts install a new solar panel outside the International Space Station

NASA astronaut Josh Cassada, wearing a red-striped spacesuit, holds the ISS Roll-Out solar panel while riding the space station’s robotic arm Saturday. Credit: NASA TV/Spaceflight Now

NASA astronauts Josh Casada and Frank Rubio headed out of the International Space Station Saturday for a seven-hour flight in space to install and deploy a newly deployed solar array recently delivered by a SpaceX cargo ship.

Casada and Rubio, both on their first spaceflights, began the spacewalk at 7:16 a.m. EDT (1216 GMT) Saturday. The start of the flight was officially marked when the astronauts donned their spacesuits.

Astronauts moved from Quest in the space station’s airlock to the left or right side of the lab’s solar beam, where the station’s robotic arm placed two new ISS Roll-Out Solar Array, or iROSA, modules earlier this week after extracting them from a stump. SpaceX Dragon cargo capsule. The Dragon spacecraft delivered solar panels to the space station on November 27, along with several tons of supplies and experiments.

The new solar panel covers were wrapped around rollers and rolled like a yoga mat when attached to a mounting bracket on Starboard 4 or S4, the space station’s electrical trellis section, which measures more than a football field’s length from end-to-end.

The astronauts first removed one of the two newly delivered iROSA modules from its mount by loosening the screws and launch rails. Cassada took a position on a footstool at the end of the Canadian-made robotic arm and manually held the solar panel coils while the arm moved it toward the S4 truss.

The two astronauts placed the iROSA module on a pre-mounted mounting bracket during a previous spacewalk. They slotted the iROSA unit onto its hinge, then installed the screws to hold it in place. Casada and Rubio paired up electrical connectors to connect the new iROSA module to the space station’s electrical system. Next, they installed a Y-cable to direct the power generated from both the newly deployed solar panel and the original S4 solar panel to the laboratory’s power grid.

In this file photo, NASA astronauts Josh Casada (left) and Frank Rubio (right) prepare for a spacewalk outside the International Space Station on November 15. Credit: NASA

A stabilization bracket connects the new arrays to the station’s power channels and rotating joints, which keep the solar wings pointed toward the sun while the spacecraft races around Earth at more than 17,000 miles per hour.

The International Space Station has eight power channels, each powered by electrical power generated by a solar panel pavilion extending from the station’s grid backbone. The new solar array, which was deployed on Saturday, will produce electricity for the space station’s 3A power channel.

The original solar panels were launched on four space shuttle missions from 2000 to 2009. As expected, the efficiency of the station’s original solar panels deteriorated over time. NASA is upgrading the space station’s power system with new solar panels — at a cost of $103 million — that will partially cover six of the station’s eight original solar panels.

When all six iROSA modules are deployed to the station, the power system will be able to generate 215 kilowatts of electricity to support at least another decade of science operations. The upgrade will also accommodate new commercial modules that are scheduled to be launched on the space station.

The first pair of new solar panels deployed on the space station were launched last year and are installed on top of the station’s oldest original solar panel array in the P6 truss section, located on the far left of the forward site power plant. Two more iROSA modules are scheduled to launch on SpaceX’s resupply mission next year.

The new solar panels were provided to NASA by Boeing, Red Wire and a team of contractors.

Once the new iROSA module was mechanically and electrically integrated into the station’s S4 gears, the astronauts released the clamps holding the deployed solar array into the launch configuration. This allowed the covers to open gradually using the stress energy of the composite booms supporting the solar cover. The deployment mechanism design eliminates the need for motors to power the solar generator.

“It’s starting to move,” one of the astronauts told radio control, prompting applause from the support staff in Houston.

“It’s amazing,” Casada said. “Yeah, that’s pretty cool,” Rubio added.

Each of iROSA’s new wings will be tilted at an angle of 10 degrees to the space station’s solar panels. Credit: NASA

The carbon fiber support arms have been reverted back to their natural shape for stocking during launch.

It took about 10 minutes for the solar panel to fully unfold to its extended configuration, spanning nearly 63 feet long and 20 feet wide (19 by 6 meters). It’s about half the length and half the width of the station’s existing solar panels. Despite their small size, each of the new panels generates roughly the same amount of electricity as each of the station’s existing solar panels.

Once the blanket was deployed, the astronauts adjusted tension screws to hold the iROSA blanket in place.

Then, the astronauts returned to the space station’s gears to gear up another iROSA module, which will be installed on the left side of the P4 truss section during the spacewalk tentatively scheduled for December 19.

With their tasks complete, Casada and Rubio return to the Quest airlock and seal the hatch. They began repressurizing the air chamber at 2:21 p.m. EDT (1921 GMT), completing the spacewalk with a duration of 7 hours, 5 minutes.

Saturday’s spacewalk was the second of Casada’s and Rubio’s careers, and the 256th spacewalk since 1998 to support assembly and maintenance of the International Space Station.

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