Astronauts Install New Solar Array Outside International Space Station – Spaceflight Now

Astronauts Install New Solar Array Outside International Space Station – Spaceflight Now

NASA astronaut Josh Cassada, in a red-striped spacesuit, holds the ISS’s solar array as he rides the space station’s robotic arm on Saturday. Credit: NASA TV/Spaceflight Now

NASA astronauts Josh Cassada and Frank Rubio departed the International Space Station on Saturday for a seven-hour spacewalk to install and develop a new solar array recently delivered by a SpaceX cargo ship.

Cassada and Rubio, both on their first space flights, began their spacewalk at 7:16 a.m. EST (12:16 GMT) on Saturday. The start of the excursion is officially marked when the astronauts switch their spacesuits to battery power.

Astronauts moved from the Quest space station’s airlock to the starboard or starboard side of the laboratory’s solar power grid, where the station’s robotic arm deployed two of the ISS’s new solar arrays, or iROSAs, earlier this week after pulling them out of the cargo capsule’s trunk SpaceX Dragon. The Dragon spacecraft delivered the solar arrays to the space station on November 27, along with several tons of supplies and experiments.

The new solar array blankets were wrapped around the coil and unrolled like a yoga mat that was once placed on the mount on starboard side 4, or S4, a section of the space station’s power grid, which measures more than the length of a football field end-to-end.

Astronauts initially worked to remove one of the two newly delivered iROSA units from its carrier by loosening the launch bolts and brackets. Cassada took a position on a footrest at the end of a Canadian-made robotic arm and held the coils of the solar array with his hand as the arm moved him onto the S4 grid.

Two spacewalkers mounted the iROSA unit on a mounting bracket previously installed during a previous spacewalk. They disassembled the iROSA unit on its hinges and then installed screws to secure it in place. Cassada and Rubio attached electrical connectors to connect the new iROSA unit to the space station’s electrical system. They then inserted a Y cable to route the power generated by both the new solar array and the original S4 solar panel into the lab’s electrical grid.

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

The mounting bracket attaches the new arrays to the station’s power ducts and rotary joints, which keep the solar wings pointed toward the sun as the spacecraft races around Earth at more than 17,000 mph.

The International Space Station has eight power channels, each powered by electricity generated from a single solar array wing that extends from the station’s lattice pylon. A new solar array installed Saturday will generate electricity for the space station’s Power Channel 3A.

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 arrays degraded over time. NASA is upgrading the space station’s power system with new solar arrays being deployed — at a cost of $103 million — that will partially cover six of the station’s eight original solar panels.

When all six iROSA units are deployed on 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 include new commercial modules planned for launch to the space station.

The first pair of new solar arrays launched to the space station last year, and were installed over the station’s oldest set of original solar panels on the P6 grid section, located at the far left end of the station’s power grid. Two more iROSA units are slated to launch on a SpaceX resupply mission next year.

The new solar arrays were delivered to NASA by Boeing, Redwire and a team of subcontractors.

After the new iROSA unit was mechanically and electrically integrated into the station’s S4 grid, the astronauts released the clamps that held the retractable solar array coiled in launch configuration. This allowed the blankets to be gradually unrolled using the stress energy in the composite girders that support the solar blanket. The actuation mechanism design eliminates the need for motors to drive the solar array.

“It’s starting to move,” one of the astronauts radioed mission control, drawing applause from the support team in Houston.

“It’s unbelievable,” Cassada said. “Yeah, it’s pretty cool,” Rubio chimed in.

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

The carbon fiber support arms are wrapped to their natural shape for storage during launch.

It took about 10 minutes for the solar array to unroll to its fully extended configuration, stretching about 63 feet in length and 20 feet in width (19 by 6 meters). That’s about half the length and half the width of the station’s current solar arrays. Despite their smaller size, each of the new arrays generates roughly the same amount of electricity as each of the station’s existing solar panels.

After the blanket was unrolled, the astronauts adjusted the tension bolts to secure the iROSA blanket in place.

The astronauts then returned aboard the space station carrier to prepare another iROSA unit, which will be installed on the left side of the P4 truss section on a spacewalk tentatively scheduled for December 19.

With their tasks completed, Cassada and Rubio returned to the Quest airlock and closed the hatch. They began repressurizing the Airlolk compartment at 14:21 EST (1921 GMT), completing a 7-hour, 5-minute spacewalk.

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

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Follow Stephen Clark on Twitter: @StephenClark1.

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