The launch of the NASA Artemis I rocket was scrubbed for a second time on Saturday after another fuel leak.
Artemis Launch Director Charlie Blackwell-Thompson finally halted the countdown at 11:17 a.m. EDT after three to four hours of effort.
The team then started to work to de-tank the rocket.
Launch controllers were unable to troubleshoot a hydrogen leak – which was detected at 7:15 a.m. EDT – that reoccurred twice in a cavity between the ground and flight side plates of a quick disconnect.
Engineers had attempted to reseat the seal in the quick disconnect cavity where the leak occurred by applying pressure to it with helium.
Later, in a third troubleshooting attempt, they worked to warm up the quick disconnect to try to reset the seal.
Blackwell-Thompson had given the "go" to begin loading propellants in the Space Launch System (SLS) rocket four hours before the leak began creating issues.
Liftoff for the $4.1 billion test flight had been slated for 2:17 p.m. EDT from the Kennedy Space Center in Cape Canaveral, Florida.
A previous launch attempt of the 322-foot rocket on Monday was also scrubbed due to a bad engine sensor and leaking fuel.
"This is an extremely complicated machine and system. Millions of parts," NASA Administrator Bill Nelson told the Associated Press. "There are, in fact, risks. But are those risks acceptable? I leave that to the experts. My role is to remind them you don’t take any chances that are not acceptable risk."
NASA will likely try to lift off again early next week.
NASA aims to send the SLS – the most powerful rocket it has ever built – and the Orion crew capsule around the moon.
When the launch is eventually successful, Orion will travel into space for about six weeks before splashing down in the Pacific Ocean.
If the demo with test dummies works, astronauts could fly around the moon in 2024 and land on it in 2025.
Artemis, which is years behind schedule and billions over budget, aims to establish a sustained human presence on the moon, with crews eventually spending weeks at a time there. It’s considered a training ground for Mars.
An audit in 2021 predicted that NASA would spend $93 billion on the moon program by 2025.
FOX Business' Paul Conner, Lucas Manfredi and The Associated Press contributed to this report.