You know that feeling when you’re playing Jenga, and the blocks are stacked remarkably high, and then someone bumps the table? And as the tower wobbles, everyone just watches in wide-eyed panic, willing it to stabilize with a desperate, silent prayer: Please don’t fall, please don’t fall.
I can only assume that’s how it felt last month, when technicians were working on NASA’s new space telescope and a very important clamp suddenly unclamped, sending vibrations coursing through the entire instrument. Officials didn’t provide details about the mood in the room at that moment, but it must have been something along the lines of Oh no, oh no, oh no. This particular Jenga tower is a $10 billion telescope, and NASA has been playing the game for 25 years, carefully arranging piece after piece to produce one of the most sophisticated scientific instruments in human history.
Despite the rogue clamp, the telescope was still very much intact. But engineers had to run extra tests to make sure that the unexpected jolt had not damaged any of its components. A committee established specifically to investigate the incident eventually concluded that the observatory looked fine. The space Jenga was safe.
The space Jenga—er, I mean, the James Webb Space Telescope—is the most powerful space telescope ever constructed. The observatory will peer into the farthest reaches of the universe, revealing the stars and galaxies that formed just after the Big Bang. Perhaps no spacecraft mission has required such tender care since the Hubble Space Telescope, which famously had to be repaired in orbit when NASA realized that the observatory had left Earth with a defective mirror that blurred its view. The Webb telescope is far more complex, and the most harrowing parts of the mission still lie ahead: the rocket launch, yes, but also weeks of careful deployment in space. For Webb to do its job, so much has to go exactly right.
NASA, along with the Canadian Space Agency and the European Space Agency, started working on the telescope back in 1996, several years after Hubble launched. Whereas Hubble was designed to observe the universe in mostly visible and ultraviolet light, Webb was built to soak up the infrared, looking deeper into the cosmos to reveal even more glittering galaxies. Program managers expected the Next Generation Space Telescope, as it was known then, to cost about $500 million and launch in 2007, but over the years, the design grew far more complex than anyone had anticipated. Whole new technologies were invented specifically for the project, and they had to be tested and perfected and then tested again. The longer the project dragged on, the more money it cost. And, to put it gently, mistakes were made. At one point, engineers used the wrong solvent to clean some valves in the observatory’s propulsion system. During one test, dozens of “improperly installed” bolts broke off inside the telescope, sending technicians on a scavenger hunt. These and other errors amounted to months, sometimes years, in schedule delays.
The Webb telescope finally arrived at its launch site on the northeastern coast of South America—near the equator, where Earth’s spin will give the payload an extra boost—in October of this year. Barring any more surprises, the observatory is scheduled to blast off on the morning of December 22. “It’s just nerve-racking,” Caitlin Casey, an astronomer at the University of Texas at Austin, told me. “You don’t want it to launch yet if it’s not absolutely safe. At the same time, you just want it to go, because you know what a powerful tool it’ll be.” Casey and her colleagues have received the biggest chunk of observing time in Webb’s first year of operations, and will study thousands of the earliest galaxies in the universe, too faint for any current telescopes to spot now.
And the rocket launch to space isn’t even the most stressful move. After Webb leaves the launchpad, it will take about a month to travel to its final destination, 1 million miles from Earth. On the way there, JWST must deploy itself piece by piece. The observatory is too big to fit into any existing launch vehicles, so it will leave folded up and then unfurl in space, like a flower blooming in spring, revealing its shiny, gold-covered mirrors to the universe.
All kinds of components must deploy in just the right order, especially those that make up the observatory’s sunshield. The shield, about the size of a tennis court, consists of five layers of aluminum-coated material, which are unpredictable, Mike Menzel, the mission’s lead systems engineer at NASA’s Goddard Space Flight Center, told reporters in a press conference in early November. NASA has unfurled rigid pieces of hardware in space before, but not something as floppy as this sunshield. “We need to make sure that when we deploy, we don’t accidentally snag on any of [the] sensitive components” on the telescope, Krystal Puga, a spacecraft systems engineer at Northrop Grumman, which led the manufacturing of the observatory, said at the same press conference. The sunshield relies on 140 release mechanisms to unfurl, and each “must work perfectly,” Puga said. “They’re all single-point failures."
The observatory overall has 344 of these single-point failures, which are as ominous as they sound. About 80 percent of them are involved in the deployment sequence, Menzel said, which is one of the most complex that NASA has ever attempted. “We’ve built it, we’ve aligned it, we’ve tested it, we proved it worked. Now we’re going to have to break it up, fold it up, and actually rebuild it on orbit—rebuild it, realign it, retune it and get it to work robotically on orbit,” Menzel said. “That’s never been done before.” Engineers have, of course, practiced the various deployments over the years, on both small and full-size models. And NASA has some creative contingency plans if a part glitches in space; engineers can shimmy the observatory, twirl it, even expose it to a little bit of sunlight—anything to jolt it into working. NASA, with its failure-is-not-an-option drive, will no doubt work tirelessly to make the mission a success. But if Webb gets stuck at one of these single-point failures—really, truly stuck—and engineers exhaust all their options, then it’s game over. Unlike Hubble, this telescope was not designed to be repaired. The technology to send astronauts, packed with screwdrivers and bolts, that far from Earth doesn’t yet exist. If something goes terribly wrong, if Webb can’t unspool as planned, humankind’s most powerful space telescope becomes a beautiful $10 billion piece of space junk.
I recently asked NASA, as politely as I could, Why would you do this? Why build something so complicated, with so many opportunities for potential disaster? Menzel, the lead mission systems engineer, said that engineers simply couldn’t avoid single-point failures on a mission that essentially unpacks itself in space. “When you have a release mechanism, it’s hard to put full redundancy into that,” he told me. The final count of 344 single-point failures, Menzel said, was the lowest they could manage.
This intricate process is why the recent incident with the clamp, though alarming, also felt survivable, Johanna Teske, an astronomer at the Carnegie Institution for Science whose team will study exoplanet atmospheres in Webb's first year, told me. “My first reaction was kind of like the gritted-teeth emoji,” Teske said. “My second reaction was: This happened on the ground. This is still a place that we have access to the entire telescope and the instruments, and things can be fixed. It’s a very different story once it’s in space.”
With the unexpected shaking behind them, technicians have now begun fueling Webb’s propulsion systems, which will take the observatory to its orbit and help keep it there. Astronomers around the world are hopeful—what else can they be at this point? They have faith in the people who have worked on the telescope’s hardware over the years, putting the pieces in place. “As an astronomer, I don’t know the ins and outs of how these engineering problems are fixed. Could I tell you what the clamp is? Absolutely not,” Casey said. But the astronomy community, she said, trusts the engineers. “They know how high the stakes are,” she said.