Afrigather Hal Levison was planning to take a nap when he acquired the dangerous information.
NASA’s Lucy spacecraft rocketed off our planet at 5:34 a.m. on October 16, 2021, so Levison and his crew had been up all night time getting ready. It was a spectacular, “image good” launch, remembers Levison, who’s the Lucy mission principal investigator from the Southwest Analysis Institute in Boulder, Colorado. The spacecraft would quickly be on its option to the Trojan asteroids, unexplored fossils of the photo voltaic system that sit roughly the identical distance from the solar as Jupiter. These small house rocks, that are thought to have shaped from the identical processes that created the planets, may make clear how our world got here to be.
However then, only a few hours after launch, the crew acquired knowledge from Lucy that exposed that considered one of her two photo voltaic arrays–which energy the spacecraft’s techniques–hadn’t fully opened. With out each photo voltaic arrays deployed, the crew wasn’t certain Lucy would make it to her meant vacation spot.
“The essential mission was in jeopardy,” Levison says. There can be no time for a nap. “It was a really exhausting day.”
The crew jumped into motion to determine what went flawed and to plan an answer. After months of sleuthing by way of the info, testing concepts on laptop fashions and spare elements on the bottom, and contemplating different trajectories for the scientific mission, the Lucy engineering crew got here up with a plan, which they set into motion earlier this summer time. Now, the spacecraft’s troublesome photo voltaic array is sort of fully unfurled–sufficient in order that the mission can proceed as deliberate.
“The state of the spacecraft is way, a lot more healthy,” Levison says, calling the feat pulled off by the crew’s engineers “completely wonderful and good.”
When the mission engineers first found the issue, they didn’t instantly know what had gone flawed. All the info confirmed them was that one of many photo voltaic arrays hadn’t fully unfurled and latched into place. The engineers couldn’t get a visible as a result of Lucy’s cameras level outward. Every thing got here by way of knowledge concerning the spacecraft’s efficiency.
Lucy’s photo voltaic arrays are like massive folding followers. When the spacecraft launched, the arrays have been folded up. To deploy them, a motor pulled on a lanyard hooked up to every array. Then, if it had reached full deployment, a latch would have held the sting of the array in place, preserving it from transferring.
“What we predict occurred is someplace alongside within the deployment, that lanyard acquired misaligned and got here out of the spool that brings the lanyard towards the latching mechanism,” explains Mark Effertz, spacecraft lead engineer for Lucy at Lockheed Martin, which constructed the spacecraft. The crew had no direct knowledge concerning the lanyard being tangled, he provides, however they extrapolated that it “began to snarl on both aspect of the spool and create a form of bundle of lanyard because the motor saved pulling.”
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With the facility provide in jeopardy, the engineers decided that they’d two foremost selections, Effertz says: They might fly Lucy as-is, and alter the course of the mission. Or, they might maintain tugging on the lanyard.
If the crew determined to maintain the photo voltaic array partly furled, Levison says, the science crew would have probably needed to choose a brand new, much less power-hungry trajectory for the spacecraft. And that will imply not going to the group of eight, hand-selected Trojan asteroids.
As a substitute, he says, the spacecraft would journey a shorter distance to 3 small Trojans. Levison doesn’t mince phrases about that different plan, saying these asteroids are “a lot much less fascinating, scientifically.”
That’s as a result of the unique trajectory took Lucy by a richly numerous group of asteroids. They vary in measurement and in coloration from grey to pink, and are shut collectively, making it attainable for the spacecraft to check many in a single journey. It’s their variety that piqued Levison and others’ pursuits, as a result of it probably implies that these asteroids shaped in far-flung areas of the photo voltaic system. Some most likely hail from the outer photo voltaic system.
Levison likes to name the Trojan asteroids “fossils,” and even named the mission “Lucy” after the well-known hominin fossil that has contributed important insights to our present understanding of early human ancestors. This mission, he explains, goals to reply questions on our origins in different methods.
“Planets don’t kind, should you’ll excuse the pun, in a vacuum,” Levison says. “Planetary techniques kind as a part of an ecosystem the place the rising planets are competing for meals, they’re knocking one another round gravitationally, they transfer round.” The Trojan asteroids are remnants of the early elements of that evolutionary course of and due to this fact home windows into our planetary origins.
[Related: A rare gas is leaking from Earth’s core. Could it be a clue to the planet’s creation?]
So the crew determined the unique trajectory for the Lucy house mission was price rescuing and devised a plan to yank the lanyard a bit more durable in an try to completely deploy the snagged photo voltaic array. The spacecraft had a backup motor constructed into its system in case the first motor to drag the lanyard failed.
“We by no means actually designed each motors to run on the similar time. However we discovered that there was a option to” inform the spacecraft to do it anyway, Effertz says. Utilizing each motors on the similar time provides it extra torque, or pulling energy, he explains. Though this maneuver doesn’t detangle the snarled lanyard, it may wind up extra of the lanyard onto the spool over the tangle, pulling the array open and holding pressure on the road.
The crew estimates that Lucy’s troubled photo voltaic array is now almost absolutely open, although it isn’t secured in place with the latch. That configuration appears to be producing sufficient energy to get Lucy to its unique goal Trojans.
The engineers are nonetheless contemplating pulling additional on the lanyard within the hopes of getting it to latch. However there are dangers related, Effertz says. The tangle would get larger and larger, which may rub towards the spacecraft and which may trigger new issues. They’ve time to determine, nevertheless, as Lucy is at the moment flying by way of a area the place the crew can’t use the craft’s antenna to obtain the required knowledge, Effertz says. So any additional tweaks should wait till round November.
