September 9, 2022 4:54 PM EDT

For the past 23 days, the Space Launch System (SLS) moon rocket has been more monument than machine, standing 32-stories tall on launch pad 39B at the Kennedy Space Center, the most conspicuous object for miles around as it towers over the flat Florida landscape. On Aug. 29 and again on Sept. 3, the rocket was supposed to take off on an uncrewed mission around the moon—kicking off NASA’s Artemis program, which aims to have Americans back on the lunar surface by 2026. Both launches came to nothing as serial technical glitches kept the engines quiet and the hardware motionless. But engineers are hardly giving up.

As NASA reports, work is taking place out at the pad that could see the SLS at last take off in one of two upcoming launch windows: on Sept. 23, during a two-hour stretch beginning at 6:47 a.m. ET; or on Sept. 27, during a 70-minute period that starts at 11:37 a.m. ET. It is during those two time frames that the moon will be in a favorable position to make the planned mission possible. First, though, come the repairs.

The biggest challenge the engineers face is fixing leaks that have formed around two fuel lines that feed liquid hydrogen to the rocket. The first leak involves an 8 in. (20 cm) wide cable that is used for filling the SLS’s massive tanks. The second involves one of four 4 in. (10 cm) cables that cool the rocket’s main stage engines, conditioning them to the proper temperature so that they can withstand the head of ignition.

It’s a good thing the work can be carried out on the launch pad, since if the SLS had to make the 4 mi. (6.4 km), 12-hour creep back to the Vehicle Assembly Building (VAB) aboard its mobile launch platform, the September launch windows would likely be missed. Even so, the SLS may be headed back to the hangar anyway. That’s because the fuel lines aren’t the only problem the massive rocket faces. There’s also the matter of its self-destruct system.

The rocket is equipped with on-board batteries that would trigger a controlled explosion over the Atlantic Ocean if the SLS went awry during launch and threatened to veer back over land. The batteries are certified for 25 days—a period that ends this Sunday—and can only be serviced and recharged in the VAB. NASA, however, has confidence that the batteries will remain operational well into and past the two upcoming launch windows. But it’s not up to NASA to green-light extending the certification. That’s up to U.S. Space Force officials, who have not yet responded to the space agency’s request for an extension.

“We did submit our waiver package to them,” Jim Free, NASA’s director of exploration, told CBS News. “They’ve been very gracious and understanding of what we’re trying to do. … It’s our job to comply with their requirements, so we will do that.”

For now it’s a waiting game—both for the space agency and for moon enthusiasts hoping that the SLS candle will at last be lit. America’s era of crewed lunar exploration will eventually resume. The question remains when.

This story originally appeared in TIME Space, our weekly newsletter covering all things space. You can sign up here.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.

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