WATCH: NASA holds pre-launch news conference on Artemis II, farthest crewed flight in decades

CAPE CANAVERAL, Fla. (AP) — After weeks of fuel leaks and other issues, NASA faced a trouble-free countdown Tuesday on the eve of astronauts' first trip to the moon in more than half a century.

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Officials reported the moon rocket was doing well on the pad, and the weather looked promising. Forecasters put the odds of favorable conditions at 80%.

WATCH: Artemis II is set to orbit the moon. Here's what to know

"Everybody's pretty excited and understands the significance of this launch," said senior test director Jeff Spaulding.

The four astronauts assigned to the Artemis II mission will become the first lunar visitors since Apollo 17 in 1972. They'll zip around the moon without landing or even orbiting, and come straight back.

WATCH: NASA holds news conference on Artemis II launch as 2-day countdown begins

It's the closest NASA has come to launching Artemis II. Hydrogen fuel leaks bumped the flight from February to March, then clogged helium lines pushed it to April. The space agency has only a handful of days every month to send the three Americans and one Canadian to the moon.

Confident that all of these problems are fixed, the launch team plans to begin fueling the 32-story Space Launch System rocket on Wednesday morning for an evening send-off.