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| Southwest Research Institute (SwRI) has developed technology that enables spacecraft to utilize precision pointing algorithms for attitude control. SwRI is currently integrating the Parallelogram Synchronized Truss Assembly (PaSTA) technology to stabilize deployed solar arrays on the Astroscale U.S. Refueler. Image Credit: Southwest Research Institute |
Southwest Research Institute (SwRI) has developed technology to stiffen deployable structures on spacecraft, enabling autonomous spacecraft docking operations. SwRI is currently integrating the Parallelogram Synchronized Truss Assembly (PaSTA) technology with solar arrays on the Astroscale U.S. Refueler spacecraft The team is also designing two different deployable booms using PaSTA technology for another spacecraft SwRI is developing.
The Astroscale U.S. Refueler, a 300-kilogram spacecraft, will be the first to conduct hydrazine refueling operations above geostationary orbit for the United States Space Force (USSF) and will be the first-ever on-orbit refueling mission supporting a U.S. Department of War asset. SwRI has been contracted by Astroscale U.S. to build, integrate and test the refueler for the USSF. The spacecraft requires precision pointing to dock with other vehicles in space, which necessitates a stiff deployable solar array to power its movements.
“There are no bumpy roads in space, so floppy arrays typically don’t pose a problem — unless precise control and stability are needed for docking,” said SwRI Institute Engineer Randy Rose, author of a recently issued patent for the PaSTA technology. “Any vibrations can disrupt the process, making the structure’s stiffness crucial. PaSTA stabilizes the solar arrays, providing the rigid structure needed for spacecraft docking maneuvers.”
PaSTA provides a structural backbone for the solar panels, stiffening the structure once deployed. The Astroscale U.S. Refueler’s solar arrays extend four and a half feet from the spacecraft. On SwRI’s other spacecraft, each array will extend 20 feet and collectively generate 5,000 watts of power for the spacecraft while enabling the same precision pointing as the smaller refueler spacecraft.
“The Astroscale U.S. Refueler does something that is difficult for spacecraft: autonomously docking with other spacecraft,” said Ryan Rickerson, manager of SwRI’s Deployable Structures Section and lead mechanical engineer for PaSTA. “To successfully dock, all deployable structures must have a minimum natural frequency to curb vibrations. That just isn’t possible with traditional solar array designs.”
PaSTA uses a patented framework of interconnected elements in a truss structure to increase solar array, stability and rigidity. As a result, the panels don’t bend. Instead, they are stretched or compressed along their length, something known as axial loading.
“A traditional solar array has several hinged panels folded like an accordion that unfold one after another,” Rickerson said. “With each hinge operating independently, deployments can be difficult to predict and can fail potentially leading the loss of the spacecraft. By incorporating the PaSTA structure to a deployable array, the extension of adjacent panels is synchronized, and a single damper is able to control the rate of deployment.”
Solar array deployments can be challenging to test, because testing occurs on the ground under atmospheric conditions. A large solar panel experiences drag from the air, which is not a factor in space. PaSTA addresses these challenges by synchronizing the way panels unfurl, creating a smooth, controlled deployment.
Testing and integration of the PaSTA-equipped solar arrays for the refueler spacecraft are currently underway at SwRI.
Reference Number: tech100725_01
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