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

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

Casada and Rubio, both on their first flights to space, began the spacewalk at 7:16 a.m. EST (1216 GMT) on Saturday. The start of the excursion was officially marked when the astronauts switched their spacesuits to battery power.

The astronauts moved from the space station’s Quest airlock to the starboard, or starboard, side of the lab’s solar power farm, where the station’s robotic arm placed two new ISS Roll-Out Solar Array, or iROSA, units earlier this week after removing them from the trunk of a SpaceX Dragon cargo capsule. 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 pulleys and unrolled like a yoga mat after being mounted on starboard mounting bracket 4, or S4, a section of the space station’s power truss that measures more than the length of a football field from the end to the end.

Initially, the astronauts worked to remove one of the two newly delivered iROSA modules from its carrier by loosening the launch bolts and restraints. Cassada took a position on a footrest at the end of the Canadian-made robotic arm and held the pulleys of the solar array with his hand as the arm moved him toward the S4 truss.

The two spacewalkers positioned the iROSA device on a mounting bracket previously placed during a previous spacewalk. They unfolded the iROSA device on its hinge, then installed bolts to secure it in place. Cassada and Rubio attached electrical connectors to connect the new iROSA device to the space station’s electrical system. They then placed a Y cable to direct the energy generated by both the new solar array and the original S4 solar panel into the lab’s electrical grid.

The mounting bracket includes the new arrays in the station’s power ducts and the rotating joints that keep the solar wings pointed at the sun as the spacecraft races around Earth at more than 27,000 miles per hour.

The International Space Station has eight power channels, each powered by electrical power generated by a single solar array wing extending from the station’s truss spine. The new solar array, deployed on Saturday, will produce 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 deteriorated over time. NASA is revamping the space station’s power system with new deployable solar arrays — 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 deployable solar arrays were launched to the space station last year and were installed on top of the station’s oldest set of original solar panels in section P6, located at the far left end of the outpost’s power farm. Two more iROSA units are scheduled to be launched 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 device was mechanically and electrically integrated into the station’s S4 truss, the astronauts released clamps keeping the deployable coiled solar array in its launch configuration. This allowed the blankets to gradually unfold, using the tension energy in the composite booms supporting the solar blanket. The design of the deployment mechanism eliminates the need for motors to drive the solar array.

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

“It’s amazing,” Cassada said. “Yeah, it’s great,” Rubio chimed in.

The carbon fiber support booms were coiled back against their natural shape for storage during firing.

It took about 10 minutes for the solar array to unfold to its fully extended configuration, stretching about 63 feet long and 20 feet wide (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 any of the station’s existing solar panels.

Once the blanket was deployed, the astronauts adjusted the clamping bolts to secure the iROSA blanket in place.

The astronauts then headed back aboard the space station truss to prepare another iROSA device that will be installed on the left side of the P4 truss during a spacewalk tentatively scheduled for Dec. 19.

After completing their tasks, Casada and Rubio returned to the Quest’s airlock and closed the hatch. They began pressurizing the airlolk compartment at 14:21 EST (1921 GMT), ending the 7-hour, 5-minute spacewalk.

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

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Follow Stephen Clarke on Twitter: @StephenClark1.