98 percent deployed and strong enough to endure the mission
In the vast silence between Earth and Jupiter, a spacecraft named Lucy presses onward with one wing not quite fully open — a reminder that human ingenuity must sometimes make peace with imperfection. Launched in October 2021 to study the ancient Trojan asteroids, Lucy encountered a solar array that refused to lock into place, prompting more than a year of careful engineering effort. By January 2023, NASA chose acceptance over persistence, determining that the 98% deployed array already provides all the power the mission requires, and that further attempts at this cold, distant range would risk more than they could gain. The mission continues — not as planned, but as possible.
- A solar array that never fully locked has shadowed Lucy's twelve-year asteroid mission since the first days after launch in October 2021.
- Engineers spent all of 2022 running ground simulations and sending careful commands across millions of miles, coaxing the array further open — but it refused to latch.
- By January 2023, Lucy was 123 million miles from the Sun and cooling rapidly, making any new deployment attempt increasingly likely to cause damage rather than progress.
- NASA made the difficult call to stop pushing: the array at 98% deployment is taut, functional, and generating every watt the mission needs.
- A window remains — in late 2024, Lucy swings back toward Earth for a gravity assist, and the warmth of the inner solar system may invite one final reassessment of the risk.
In October 2021, NASA launched Lucy from Cape Canaveral on a twelve-year journey to study the Trojan asteroids — primitive bodies sharing Jupiter's orbit and thought to hold clues about the early solar system. Almost immediately, one of the spacecraft's two solar arrays failed to fully deploy and lock into place, setting off a prolonged engineering effort that would define the mission's first year.
Throughout 2022, the team worked patiently with Earth-based models of the spacecraft, refining their understanding of the problem and sending careful commands into deep space. They managed to extend the array further, but it still would not latch. It remained taut and generating power — just not locked as designed.
On January 19, 2023, NASA announced it would stop trying. With the array now estimated at more than 98% deployed, the mission team concluded it was stable enough in its unlocked state and already producing all the power Lucy needs for its full twelve-year mission. The risk of further attempts outweighed any benefit, particularly as Lucy had traveled 123 million miles from the Sun — growing colder and more distant at 20,000 miles per hour — conditions that ground testing showed were unfavorable for deployment success.
The decision was not a surrender so much as a recalibration. NASA left open the possibility of revisiting the question in late 2024, when Lucy returns toward Earth for a gravity assist and the warmth of the inner solar system might make one final attempt worth considering. Until then, Lucy flies on — one array open, one unlocked, and the mission intact.
In October 2021, NASA launched Lucy from Cape Canaveral on a mission to study the Trojan asteroids—primitive bodies that orbit Jupiter in tandem with the giant planet. The spacecraft was supposed to spend twelve years traveling through space, gathering data on these distant objects. But almost immediately after launch, something went wrong. One of Lucy's two solar arrays failed to fully deploy and lock into place, leaving the mission team with a problem they would spend more than a year trying to solve.
Throughout 2022, engineers attempted a series of careful maneuvers to extend the stubborn array. They worked with models of the spacecraft built on Earth, adjusting those models based on real data streaming back from space, trying to understand what was preventing full deployment. By early 2023, they had managed to pull the array out further—but it still wouldn't lock. The array remained taut and functional, but unlatched, hanging in a state of partial deployment that no one had planned for.
On January 19, 2023, NASA announced a decision: stop trying. The mission team had concluded that the array, now estimated to be more than 98 percent deployed, was safe enough in its current unlocked condition. More importantly, they determined that further deployment attempts would likely do more harm than good. The array was already generating the full amount of power the spacecraft needed. All the energy calculations that had gone into designing the twelve-year mission still held. Lucy could complete its primary objectives without ever fully locking that second array into place.
The reasoning behind this decision came down to physics and distance. Ground testing had shown that deployment attempts worked best when the spacecraft was warm and relatively close to the Sun. But by January 2023, Lucy had traveled 123 million miles from the Sun—nearly a third farther than Earth's distance from it—and was moving away at 20,000 miles per hour. In that cold, distant environment, further deployment attempts would almost certainly fail. The team saw no point in risking damage to a system that was already working.
Yet the story was not quite finished. NASA left open the possibility of revisiting the question in the fall of 2024, when Lucy would swing back toward Earth for a gravity assist maneuver. As the spacecraft approached the inner solar system, it would warm up. At that moment, the team said, they would reassess whether any additional steps might be worth attempting to reduce long-term risk. For now, though, Lucy would continue on its planned trajectory with one solar array partially deployed, generating power, and carrying the mission forward into the asteroid belt.
Notable Quotes
The current unlatched state of the array is safe enough and further deployment activities would not be beneficial— NASA mission team statement
The team will re-evaluate if additional steps to reduce risk will be needed during the spacecraft's approach to Earth in fall 2024— NASA statement
The Hearth Conversation Another angle on the story
Why did NASA decide to stop trying to deploy the array if it wasn't fully locked?
Because it was already working. The array was generating all the power the mission needed, and the engineers calculated it was strong enough to last the full twelve years. Trying to force it further risked breaking something that wasn't broken.
But doesn't an unlocked array pose some kind of structural risk during the mission?
That's what the engineering models suggested—that 98 percent deployment was safe enough. They built replicas on Earth, ran tests, and concluded the tension in the array was stable. The real risk was in the attempt itself, not in leaving it as it was.
Why couldn't they just wait until Lucy was closer to the Sun again?
They will, actually. But the spacecraft is moving away from the Sun at tremendous speed. By the time it swings back toward Earth in 2024, they'll have a chance to look at the data again and decide if it's worth trying. Right now, in the cold and distance, the odds of success are too low.
So this is a temporary decision?
More like a pragmatic one. They're not saying never. They're saying not now, not here. But when conditions change, they'll reconsider. For the next year and a half, Lucy just keeps going with what it has.
What does this say about the mission itself?
That it's resilient. The mission was designed with margins built in. One array working at full capacity is enough. That's good engineering—planning for things to go wrong and still being able to succeed.