Engineers from Boeing and a team of subcontractors have finished building the first pair of six new solar arrays to bolster the International Space Station’s aging electrical system ahead of their launch to the orbiting outpost as soon as May aboard SpaceX’s next Cargo Dragon mission.
Astronauts will begin a series of spacewalks as soon as the end of January to ready the space station’s solar array truss for the arrival of the new wings, among other outfitting and maintenance tasks.
The six new solar array wings will be installed over the space station’s existing U.S. solar panels, which were designed for 15-year service lives. The oldest of the station’s current solar arrays — built by Lockheed Martin — launched in 2000, with more pairs of wings added in 2006, 2007, and 2009.
The older solar arrays are showing some signs of degradation, as expected, according to NASA.
The space station has eight power channels, each drawing from one solar array wing mounted to the research lab’s long truss structure. Six of those channels will get an upgrade with the new solar arrays supplied by Boeing, Deployable Space Systems, and a team of subcontractors.
The six solar array wings, coupled with 24 new lithium-ion batteries launched to the station on a series of Japanese resupply missions, will help ensure the lab’s power system can support continued operations through 2030.
The six new solar panels will be one of the most visible changes to the space station’s appearance since NASA completed assembly of the outpost a decade ago. Two small commercial modules from Bigelow Aerospace and Nanoracks have been attached to the station in recent years, and new modules from Russia and the commercial company Axiom are scheduled for launch in the next few years.
“From a visual standpoint, it’s big,” said John Mulholland, ISS vice president and program manager at Boeing, which provides engineering support for the station under contract with NASA. “With the new batteries that we developed and deployed last year, that really solidifies the power going forward for at least the next decade.”
The six new solar array wings will launch two at a time inside canisters stowed in the trunks of SpaceX Cargo Dragon capsules. Astronauts will head outside on spacewalks to assist the the lab’s Canadian-built robotic arm in mounting and configuring the wings for deployment.
The new arrays will unroll like mat instead of unfurling like an accordion, as the space station’s existing solar arrays deployed.
The roll-out panels 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. A mounting bracket will plug the new arrays into the station’s existing power channels and rotary joints, which keep the solar wings pointed at the sun as the complex races around Earth at more than 17,000 mph.
“They’ll be positioned there essentially right in front of the existing solar arrays, canted at a small angle,” Mulholland said. “The existing solar arrays will still be able to feed power along with the new solar arrays, so we’re just trying them in together electrically.”
NASA procured the ISS Roll Out Solar Array, or iROSA, units through a $103 million modification to Boeing’s space station engineering sustainment contract signed in February 2018. The arrays are similar to the Roll Out Solar Array tested outside the space station in 2017.
Boeing’s subsidiary Spectrolab is supplying the high-energy solar cells for the new arrays, and Deployable Space Systems of Goleta, California, is producing the structure for the new solar wings, including the canister and frame that will extend to hold the solar array blankets in place, according to Boeing.
NASA is likely to extend the space station’s operating life from 2024 through 2028 or 2030. An extension has bipartisan support in Congress, and is expected to win approval from the incoming Biden administration.
Space agency officials want to continue using the International Space Station for biomedical research and technology demonstration experiments to gather data needed to plan long-duration expeditions to more distant destinations, such as the Moon and Mars.
NASA hopes a commercial human-rated lab in low Earth orbit will be ready to take over from the International Space Station by the time it is retired. Officials want to use the space station not only as a technology testbed, but as a vehicle to foster new markets in space, aiming to build enough demand to support a commercially viable outpost.
In an interview with Spaceflight Now this week, Mulholland said engineers have determined all of the space station’s modules, many of which are beyond their original 15-year design lives, will remain structurally sound through 2030.
“And most of that hardware has significant life beyond 2030 if required,” Mulholland said. “So there’s no cliff that we’re coming up on from a structure perspective. It was really important, I think, for us to get the batteries and the solar arrays. Getting that capability and allowing more science, and then having the capacity for Axiom and the commercial modules that we have planned to add to the International Space Station, that was really foundational to that additional usage.”
The space station’s current solar arrays can generate up to 160 kilowatts of power during orbital daytime. About half of that power is stored in the station’s batteries for use when the complex is in darkness, according to NASA.
Each new solar array will produce more than 20 kilowatts of power in orbital daytime, for a total of 120 kilowatts when all six wings are installed.
The space station will still have one uncovered pair of its existing solar arrays. Those wings, along with the arrays partially covered by the new panels, will continue generating around 95 kilowatts of power. Combined with the 120 kilowatts from the new roll-out panels, that will being the space station’s total power production capacity to 215 kilowatts.
The combination of the eight original, larger arrays, and the smaller, more efficient new arrays will restore the power generation of each augmented array to approximately the amount generated when the original arrays were first installed, providing a 20% to 30% increase in power for space station research and operations.
“The combination of the eight original, larger arrays, and the smaller, more efficient new arrays will restore the power generation of each augmented array to approximately the amount generated when the original arrays were first installed, providing a 20% to 30% increase in power for space station research and operations,” NASA said.
Mulholland said the first solar array has been assembled and completed functional testing at Deployable Space Systems, and will soon undergo vibration and thermal testing before shipment to NASA’s Kennedy Space Center in Florida for launch on SpaceX’s next Dragon cargo flight to the space station.
“So good progress,” Mulholland said. “We’re moving along at a pretty good clip.”
The next Cargo Dragon flight, currently scheduled for May, will carry two iROSA panels to the space station. The other four wings will launch on Cargo Dragon missions in 2022 and 2023, Mulholland said.
NASA said the installation of each new array will require two spacewalks by the space station crew.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.
